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0.0 Fuel pressure while on cross country

Rrhsch

Active Member
I think I need a new fuel pressure sensor. Shortly after a refueling stop with 100LL, the fuel pressure started to swing rapidly from 1.1 to 5.0 psi at 5400 RPM and suddenly stopped at 0.0 psi. Engine was running fine. I made a precautionary landing to check out the problem.

On the ground I determined that I had fuel pressure that wasn't registering on the G3X. I could hear the electric pump running and tested the flow from the gasolator to confirm the pump was indeed working.

It was very hot out and I decided to let the engine cool for a couple of hours. When I powered up the G3X the fuel pressure showed max fuel pressure 14+ psi. As soon as I started the Rotax, the fuel pressure started to swing up and down and stoped at 0.0 psi.

I unplugged the sensor, removed the rubber seal and reattached the plug with no change in the reading.

After extensive taxi testing and run-ups I finished the flight.

I will order a new sensor unless some one has had the same symptoms and resolved it using a different method.
 
Could be the sensor or the wiring. My money is on the wiring having a loose connection -- check that first, its cheaper!
 
Sometimes I think these sensors cause more problems than they solve. Over the years I?ve owned 7 aircraft and 4 had no fuel pressure indication. I never missed it, and the response to any engine stumbling always included turn on the aux pump. Never needed it either fortunately!
 
Check the ground wire and surface its attached to. So many of my problems early in flying my airplane were poor grounding.

Chris
 
Sometimes I think these sensors cause more problems than they solve. Over the years I?ve owned 7 aircraft and 4 had no fuel pressure indication. I never missed it, and the response to any engine stumbling always included turn on the aux pump. Never needed it either fortunately!

If you have a gravity fed fuel system no pressure gauge is required.
If it is not a gravity fed system, a gauge is required.
 
Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let?s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it?s nice when it works, but it really doesn?t add any value.

Rich
 
Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let’s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it’s nice when it works, but it really doesn’t add any value.

Rich

Well, I guess you could carry that logic a little further and say the engine will tell you it looses oil pressure when it seizes up or no engine noise might mean you have exhausted your supply of fuel.

If for no other reason, the fuel pressure gage is necessary to verify that both fuel pumps are running while performing a pre-takeoff check (you do a pre-flight check?). With master switch on, and engine not yet running, the fuel pressure should be ~ 2psig. With engine running the fuel pressure increases to ~ 5psig signifying that both electric and engine driven pumps are both working and it is safe to proceed.

It’s really hard to believe that anyone would advocate that a fuel pressure gage doesn’t add any value. I never thought I'd have to defend the necessity of having fuel pressure displayed for safe operation of an airplane. Maybe its like Trumped-up Government where you just get rid of everything and fly by the seat of your pants...
 
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If you have a gravity fed fuel system no pressure gauge is required.
If it is not a gravity fed system, a gauge is required.

Scott,

I am not familiar with any requirement for a fuel pressure gage unlike the minimum FAR required instruments. If you are saying it is good practice I would agree, but let?s face it if your fuel pressure really is low the engine will tell you, and if you have a back up pump you will turn it on.

On my 12 I switch the electric pump off after climb out. That does not result in a low fuel pressure alarm, so what difference does the indication make in the response? My point is that it?s nice when it works, but it really doesn?t add any value.

Rich

Bad choice of a word without clarification.
I did not mean that FAR 91 requires it..... common sense (which established it as standard practice) requires it.

A carburated engine will easily run on only .5 psi pressure.
No pilot would takeoff with a pressure gauge indicating only .5 psi.
Short of an indication failure, it shows that there is something wrong in the fuel delivery system, but if there was no pressure gauge, the engine would have started fine but that in it self doesn't assure that the flight will end well......

That means a lot of added value in my opinion.
 
Me too

I am also having a new low pressure indication on my RV12. I have a switch for the electric pump, so I can see what the fuel pressure measures at different power settings. I get low fuel pressure warnings on the Dynon 180 if I turn off the electric pump with the plane in level flight at anything over 4800 RPM. A replacement engine pump didn't change anything, so I'm wondering what could be wrong; the sensors, the fuel lines, etc. Any suggestions beyond ignoring it and using the electric pump if the engine falters? Mark
 
I am also having a new low pressure indication on my RV12. I have a switch for the electric pump, so I can see what the fuel pressure measures at different power settings. I get low fuel pressure warnings on the Dynon 180 if I turn off the electric pump with the plane in level flight at anything over 4800 RPM. A replacement engine pump didn't change anything, so I'm wondering what could be wrong; the sensors, the fuel lines, etc. Any suggestions beyond ignoring it and using the electric pump if the engine falters? Mark

The RV-12 fuel system was designed for both pumps to be operating at all times (the standard per plans build has no switch to turn off the electric pump in flight)

Depending on the fuel being used, OAT, etc., it is possible for the measured fuel pressure to go below the set limit if both pumps are not operating.
 
How do you know it is telling the truth? The pressure sensors are notorious inaccurate.

These fancy electronic systems are fantastic; and after seeing 2.3 or 2.4 psi with both fuel pumps operating during decent from altitude. I "wil be" installing both machanical fuel & oil gauges during next annual.

Call me insecure...but I start looking for someplace "immediately" to land when pressures are not what they should be. Likewise, an operational Garmin 796 w/remote gps...(had pito tube break @ clamp block) on way home from OSH loosing airspeed indication (nothing like landing with indicated 30 knot forward and 135 knot tailwind)..
 
Fuel Pressure Loss

I have a similar issue with my Zodiac 601 HDS with a Rotax 912 and leading edge wing tanks. Since several weeks the fuel pressure in cruise started to slowly drop from 5 psi to 2 psi (with the electrical pump and the mechanical pump running). When reducing RPMs the fuel pressure comes back. The situation has worsened over time; the fuel pressure now drops down to 2 psi during take-off. The engine runs without any issues, though.
I have tried almost everything: replaced the fuel pressure sensor (connected to Grand Rapid EIS), replaced electrical pump, replaced mechanical pump, replaced fuel hoses in engine compartment... so far no success.
I will now hook up a mechanical fuel pressure gauge.
Anybody with an idea about the root cause? I'm completely on a loss...

Thanks
 
2 PSI is equal to about 2 meters of head pressure in a gravity fed fuel system. That is plenty. The maximum pressure is set by an internal spring inside of the engine driven fuel pump. Pressure drop is caused by fuel flow. That flow can be to the carburetors, a leak, or return to the fuel tank.
 
Copy and paste from Rotax Owner forum:

"In the Installation manual it does say the re-circulation line restrictor is .35mm or .014".

Actually that is a misprint that should have been fixed. The restrictor should be a #35 Mikuni pilot or slow jet. It is actually based on fuel flow and not hole size from Rotax. The new pump really needs a re-circulation line or it can give erroneous readings and have high fuel pressure."
Looks like the .014 may work.

From what other 12 owners have told me that some 12 owners didn't use the restrictor in their re-circulation hoses. This allowed to much fuel to bypass and caused low fuel pressure and even engine stumbling at take off.
 
From what other 12 owners have told me that some 12 owners didn't use the restrictor in their re-circulation hoses. This allowed to much fuel to bypass and caused low fuel pressure and even engine stumbling at take off.

Roger,
The RV-12 Rotax power plant kit comes with a pre-made hose that already has the proper restrictor installed. The only potential problem is if someone installs the hose backwards with the restrictor path routed to the fuel pressure sensor instead of the return line. It is rather obvious when this happens because the fuel pressure will not get into the normal pressure range with just the electric pump operating on the ground.
 
These fancy electronic systems are fantastic; and after seeing 2.3 or 2.4 psi with both fuel pumps operating during decent from altitude. I "wil be" installing both machanical fuel & oil gauges during next annual.

Call me insecure...but I start looking for someplace "immediately" to land when pressures are not what they should be. Likewise, an operational Garmin 796 w/remote gps...(had pito tube break @ clamp block) on way home from OSH loosing airspeed indication (nothing like landing with indicated 30 knot forward and 135 knot tailwind)..

Regarding a mechanical oil pressure gauge backup system..... We worked with an RV-12 owner who wanted to do this exact thing. I really like how he installed everything.

It is detailed on page 5-7 of the following installation manual.

http://aircraftspecialty.com/PDF Documents/Rotax 912 Remote Oil Sender.pdf

We have not yet worked with anyone on a secondary fuel pressure gauge, but if you need anything fabricated, we will be happy to help out.

Have a great week,
Steve
 
Tom and I are very interested in this data point as the AIRCRAFT SPECIALTY/TS FLIGHTLINES fuel setup utilizes different components than the stock kit. We eliminated the banjo bolts and fuel block and replaced it with an AN cross and Tee setup.

If any customers of ours are experiencing a similar issue with low fuel pressure, can you please email us at [email protected] and let us know? We build Rotax kits for a variety of aircraft, but the RV-12 represents the largest data point. To date, we have not had any reports of low fuel pressure in any of the Rotax kits, but we would like to hear from anyone who has been flying with our fuel hoses.

Thanks so much for your help,
Steve
 
Tom and I are very interested in this data point as the AIRCRAFT SPECIALTY/TS FLIGHTLINES fuel setup utilizes different components than the stock kit. We eliminated the banjo bolts and fuel block and replaced it with an AN cross and Tee setup.

If any customers of ours are experiencing a similar issue with low fuel pressure, can you please email us at [email protected] and let us know? We build Rotax kits for a variety of aircraft, but the RV-12 represents the largest data point. To date, we have not had any reports of low fuel pressure in any of the Rotax kits, but we would like to hear from anyone who has been flying with our fuel hoses.

Thanks so much for your help,
Steve

Steve,

Did you make provision for the metering orfice in the return line?

And yes...would like info on both fuel & oil mechanical gauge set up (realize the fuel gauge set up would need to be beta)...
 
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Steve,

Did you make provision for the metering orfice in the return line?

And yes...would like info on both fuel & oil mechanical gauge set up (realize the oil gauge set up would need to be beta)...

Yes, the restrictor is necessary in the fuel return line. We place it in a different location than in the stock kit. It is not installed in the fuel line, but rather screwed onto a fitting. That way all of our lines are field replaceable if any one ever gets damaged.

Here is a link to the fuel kit installation manual

http://aircraftspecialty.com/PDF Documents/Fuel Hose Install 111013.pdf

The remote oil pressure sender includes a provision already for the backup mechanical gauge. That is what the images on page 5-7 of this manual show.
http://aircraftspecialty.com/PDF D...l Sender.pdf

The only item that would be completely beta is the mechanical fuel pressure sender installation, but that would be fairly easily accommodated.

Steve
 
Just as a point of reference==

Our .015 restrictor fitting threads on the return side of our cross fitting. It is Black in color--so instantly noticed if it is missing.
For those of you that dont know how small .014 really is, its a number 79 drill bit. .015 is a 78 drill bit. Maybe a little larger than the hair on your arm---well kinda.
library


This pic shows the size of the restrictor. Yep is tiny. We sized this after consulting with Rotax several years ago.

Tom
 
Tom,

I installed your system last March, and have had no problems. I usually run a fuel pressure of 3.9 psi with the electric pump on and 3.6 on just the mechanical pump. The only pressure issue I?ve had was due to vapor lock using some old fuel on a hot day, and turning on the electric pump fixed that.

I notice that your picture shows the restrictor on the cross fitting, but the instructions I had were to put it on the bulkhead return fitting. Is that a change or did you just put it on the cross in the picture for sense of scale?

Rich
 
Rich,

We put it on the bulkhead return fitting as per the installation manual. It technically could go in either location but putting it on the bulkhead return gives us a bit more room.

Glad you like your kit!!!

Take care
Steve
 
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Rich---I put it on the cross for photo purposes.
Tom

BTW---Steve and others did most of the beta work on this package. We knew the guidelines we wanted, and then had to design a package to integrate it all together. Teflon hose, AN hardware, etc.
We havent heard from anyone with this package having a pressure issue. Alot of them flying worldwide, not only on RV12's but others with the 912 Rotax.

Tom
 
Back to sensor wars

I think I need a new fuel pressure sensor. Shortly after a refueling stop with 100LL, the fuel pressure started to swing rapidly from 1.1 to 5.0 psi at 5400 RPM and suddenly stopped at 0.0 psi. Engine was running fine. I made a precautionary landing to check out the problem.

On the ground I determined that I had fuel pressure that wasn't registering on the G3X. I could hear the electric pump running and tested the flow from the gasolator to confirm the pump was indeed working.

It was very hot out and I decided to let the engine cool for a couple of hours. When I powered up the G3X the fuel pressure showed max fuel pressure 14+ psi. As soon as I started the Rotax, the fuel pressure started to swing up and down and stoped at 0.0 psi.

I unplugged the sensor, removed the rubber seal and reattached the plug with no change in the reading.

After extensive taxi testing and run-ups I finished the flight.

I will order a new sensor unless some one has had the same symptoms and resolved it using a different method.

The fuel sensor was replaced and all is well. I never intended to start a war of sorts. This is definitely not in the same league an tail wheele or primer wars.

I now show a 0.5 PSI increase in fuel pressure. I like to know that everything is working within normal ranges. The one minuet warning before the engine quits is one more minuet I have to react to a potential issue. Just my view.

Now back to thread drift.
 
Was running up the engine with out top or bottom cowl and notice a low fuel pressure warning which stopped when closing throttle and changing relative position to 10-12kt surface wind while turning around the apron. My carb vent lines are the prescribed length 3 or 4 inches and are tucked behind the carb bowl clips. Could being cowless and direct wind pressure and turning prop wind pressure impact fuel pressure?
 
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Could being cowless and direct wind pressure and turning prop wind pressure impact fuel pressure?
Yes, the fuel pressure sensor compares atmospheric pressure to fuel pressure. If the air pressure at the sensor changes, then the displayed fuel pressure will change too, even though the fuel pressure remains constant. Who knows how much the air pressure actually changes with cowl removed?
 
The fuel sensor was replaced and all is well. I never intended to start a war of sorts. This is definitely not in the same league an tail wheele or primer wars.

I now show a 0.5 PSI increase in fuel pressure. I like to know that everything is working within normal ranges. The one minuet warning before the engine quits is one more minuet I have to react to a potential issue. Just my view.

Now back to thread drift.

What?
You didn't have to replace all of your FWF fuel hose system with an after market kit to have normal fuel pressure readings? :rolleyes:
 
What?
You didn't have to replace all of your FWF fuel hose system with an after market kit to have normal fuel pressure readings? :rolleyes:

Of course not. Why would anyone replace an entire fuel system due to an erratic sensor? That would make no sense. There are a lot of reasons to utilize the aftermarket fuel hose kit, but an erratic sensor is definitely not one of them.

Keep in mind the history of the development of the aftermarket kit. It started shortly after Vans issued service bulletin 13-3-21 in March of 2013.

"Rotax has recommended a 5 year replacement schedule for rubber hoses and fittings in their engine."

After reading that, Tom and I were wondering why ANY aircraft should be utilizing rubber hoses in any portion of their fuel system. We also were wondering why RV-12 owners should be paying more for a rubber hose setup than a much higher quality conductive Teflon setup would cost.

We set out to offer RV-12 owners a better option. Originally, we utilized the same banjo fitting and fuel block design to keep the system exactly the same. The difference was that we utilized conductive Teflon hose assemblies with no life limit and a resistance to damage from any fuel additives.

After building several systems like that, we realized that if anyone ever suffered hose damage (physical damage to a hose from not being secured properly, etc...), they would not be able to field replace the hoses. We decided to source adapters to change the entire fuel system over to aviation standard type hoses. Now, all hoses utilize 37 degree flare fittings so any mechanic can make a up a field replacement hose quickly and get a customer on their way. No longer would a rotax owner need to order a specially sourced hose to repair an issue. This is especially true in the case of the restricted return hose.

So, you are 100% correct that ordering a different fuel system to fix an erratic sensor makes no sense. Potential reasons to replace the fuel system include:

1. Our package is lighter weight than the stock hose setup. (with early rubber hoses....I am not sure of the weight of the current setup being sent)
2. All hoses are field replaceable in the event of any physical damage.
3. No life limit on ANY of the fuel system components
4. 10 year warranty on all components.
5. Less expensive than Rotax provided Teflon
6. Every hose is pressure tested prior to shipment.
7. All stainless steel fittings on hose ends.
8. Just as a random side benefit...no known reports of low fuel pressure for undetermined reasons.

With that said, if someone's current fuel hose system is working great, there is no reason to replace it. But, if/when it requires replacement, all options should be considered.

Since you are actively monitoring this thread, here are a few questions...

1. Are all rv-12 hoses currently being shipped made of conductive Teflon, or just the carb hoses?
2. Are all fittings currently stainless? Or are they a combination of CR Steel and Brass?
3. What is the current replacement schedule for firewall forward hoses? Are they all on a 10 year replacement schedule?
 
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Rich---I put it on the cross for photo purposes.
Tom

BTW---Steve and others did most of the beta work on this package. We knew the guidelines we wanted, and then had to design a package to integrate it all together. Teflon hose, AN hardware, etc.
We havent heard from anyone with this package having a pressure issue. Alot of them flying worldwide, not only on RV12's but others with the 912 Rotax.

Tom

Of course not. Why would anyone replace an entire fuel system due to an erratic sensor?

Steve,
Tom was the one that originally inserted an infomercial promoting the idea that users of your hose kit haven't had any low fuel pressure indications....
In this thread about an instance that clearly looks like a sensor problem.
 
Scott---no infomercial here. No Alex Trebek, no buxom blonde in stillettos, no toll free phone number, no add a second order for free, just pay the shipping and handling. Quite the contrary. NOT selling anything. In fact, we've helped alot of RV builders WITHOUT selling them anything.

As far as the Rotax fuel pressure issue, it does NOT have anything to do with Vans hoses, or our hoses. YES, most of the low pressure warning issues ARE instrument related. (We actually advise owners to check the pressure with a known good mechanical gauge to verify the results.) Some were from an actually failing mechanical fuel pump. Rotax, put out the SB on the 5 year hose replacement, we didnt. We just make them from teflon. YES the carb hoses from Rotax are Stratoflex 101 teflon. BUT the other hoses WERE SAE 100R30 rubber at the time we were working on this kit. The effects of an ethanol additive fuel on the rubber hose is well known--gee thats why most all the automotive companies have gone to teflon, thermoplastic, and nylon hose in their systems instead of using rubber hose. Begs to ask why Vans didnt use it, but thats not for me to say.

Minor history lesson here--Page 46-08 of the 11/10 powerplant install instructions of the RV12. I'm sure its been updated now, but thats what we were working with back then. Step 1, RTV seal the end of the rubber hose, the firesleeve, and the band area at the banjo fitting. Well gee, we KNOW of builders that were PULLING the firesleeve and the HOSE off the banjo barbs (pretty easy with Oetiker clamps), and actually pulling the end part of the hose liner with the barbs.) They replaced the Oetiker clamps with screw clamps and finished the install. The question arose was Why Vans didnt do all that before hand? They were supplying the hoses. No telling how many early 12 builders just forced the hose back on the barbs and left it at that. Yeah, 2.4 to 5 lbs isnt much pressure, but you would think your planes fuel system would be slightly more substantial than your Briggs & Stratton mower. THATS where all of this started, NOT fixing a low fuel pressure WARNING issue. It was about using a teflon hose for the other hoses in the system to MATCH what ROTAX had put on the carbs.

WE checked with several Rotax service centers and Rotax engineers that told us the 912 would run at full power at the reported low pressure of 2.2 psi. YEP it will, but certainly most guys would appreciate more fuel pressure than that. So I assume thats why Vans designed the system to run the boost pump all the time, to maintain the constant flow and elevated pressure to the system. Yes, some builders have put their pumps on switches, and have been spanked because of it. I'm thinking that its because Vans wants the pumps on to make sure there isnt a fuel starvation issue, JUST IN CASE there actually was an issue. BUT, if the Rotax runs at 2.2 psi, then why run the boost pump all the time?

Steve and I didnt take on this project on our own. In fact we were asked to do it by some RV12 builders. They didnt want a rubber hose fuel system. The originals we built did use banjo fittings. We still do some like that. It wasnt to FIX a low pressure 'issue', it was to provide a hose that didnt need to be changed every 5 years.

OH--IF its just a sender issue thats creating this illusion of a real pressure loss, then why not solve that problem? Oh gee, every time someone goes out and gets a warning of low pressure lets throw another sender on the plane. It might be fun to find out how many guys have had to put multiple senders on their planes. Is it an interface issue with the sender and the EFIS? Is it a plumbing issue for the sender? Can it be duplicated so the root cause can be established?

I'm all for getting to the bottom of the cause for this. Instrumentation or real pressure loss. Either way, its a problem. The solution isnt in an infomercial.

Tom


Tom
 
WE checked with several Rotax service centers and Rotax engineers that told us the 912 would run at full power at the reported low pressure of 2.2 psi. YEP it will, but certainly most guys would appreciate more fuel pressure than that. So I assume thats why Vans designed the system to run the boost pump all the time, to maintain the constant flow and elevated pressure to the system. Yes, some builders have put their pumps on switches, and have been spanked because of it. I'm thinking that its because Vans wants the pumps on to make sure there isnt a fuel starvation issue, JUST IN CASE there actually was an issue. BUT, if the Rotax runs at 2.2 psi, then why run the boost pump all the time?

The RV-12 has a tightly cowled engine and when you shut it down the heat is retained for a long period. The residual heat after engine shutdown can cause the fuel to boil off in the carburetor float bowls.

What you have to watch out for is restarting a warm engine that has been sitting for some time. In this case there is likelihood that fuel has vaporized from the float bowls and the carburetor bodies are still warm. That is why it is best practice to allow the electric fuel pump to operate for approx. 5 minutes to recirculate cool fuel through the upper distribution manifold and return to the fuel tank. If for no other reason this is why the electric fuel pump should be run in continuous mode. Why take the chance of switching the electric pump on/off and perhaps some day forgetting to turn it on. If Vans says it should always be powered, that?s plenty good enough for me.
 
Yes, the fuel pressure sensor compares atmospheric pressure to fuel pressure. If the air pressure at the sensor changes, then the displayed fuel pressure will change too, even though the fuel pressure remains constant. Who knows how much the air pressure actually changes with cowl removed?

Thanks Joe, had only half that picture.
 
Roger,
The RV-12 Rotax power plant kit comes with a pre-made hose that already has the proper restrictor installed. The only potential problem is if someone installs the hose backwards with the restrictor path routed to the fuel pressure sensor instead of the return line. It is rather obvious when this happens because the fuel pressure will not get into the normal pressure range with just the electric pump operating on the ground.

I guess after reading this, I really need to investigate my restrictor installation. I typically allow the electric pump to run for a bit before starting, particularly after a breakfast or lunch stop. The idea is to circulate the warm fuel out of the engine compartment, and back into the tank, and thus reducing the chances of vapor lock. I never get all the way up to normal with only the electric pump running. Typical it settles at about 2.4 psi, whereas after starting the engine, it goes immediately up to 4.6 psi. If I am reading Scott's post correctly, my 2.4 psi with just the electric pump running is not satisfactory. It would be nice to hear what others are seeing with just the electric pump running.

Thanks.......Tom
 
I guess after reading this, I really need to investigate my restrictor installation. I typically allow the electric pump to run for a bit before starting, particularly after a breakfast or lunch stop. The idea is to circulate the warm fuel out of the engine compartment, and back into the tank, and thus reducing the chances of vapor lock. I never get all the way up to normal with only the electric pump running. Typical it settles at about 2.4 psi, whereas after starting the engine, it goes immediately up to 4.6 psi. If I am reading Scott's post correctly, my 2.4 psi with just the electric pump running is not satisfactory. It would be nice to hear what others are seeing with just the electric pump running.

Thanks.......Tom

The electric pump by it self will not produce normal in flight pressure value that you get with the engine drive pump operating.
2.5 PSI is about right, and is more than enough to operate the engine at cruise power.
The design philosophy of the lower pressure pump is that with an in flight engine drive pump failure, the pressure will drop into the yellow range and que the pilot that something is not as it should be.
 
Thanks Scott. That sure eliminates my worry. I was certain that I had installed the restrictor according to plans, and have never had a fuel pressure issue that I was aware of. I really appreciate you chiming in.........Tom
 
Hey Tom----thats sort of what all of us are looking for---actual fuel pressure numbers. And you say you havent had a pressure issue that you know of.
So my question would be is there something different about your 12 that others having the pressure issue dont have on their planes?
NOT fanning a flame war here, but trying to understand why some are having issues and others are not, in a supposed plans built package. Also trying to compare apples to apples.

So if you had 2 planes in the same area, flying at the same time, 1 had a pressure issue and one did not, both supposedly built to plans, then whats creating the pressure issue----IF in fact it IS an actual low fuel pressure and not and instrumentation issue?
Thats something I think we all would like to know. Are any of the SLSA RV12's having a pressure warning issue? We've been trying to fins out.

Understand---we dont have a 12 here that we can do some testing with. Sure would be awesome to get some data.
Any volunteers? Email me.

Tom
 
The electric pump by it self will not produce normal in flight pressure value that you get with the engine drive pump operating.
2.5 PSI is about right, and is more than enough to operate the engine at cruise power.
The design philosophy of the lower pressure pump is that with an in flight engine drive pump failure, the pressure will drop into the yellow range and que the pilot that something is not as it should be.

I would sure like to know why my fuel pressure drops to around 2.1 psi following a cross-country flight (4 gals remaining in tank) during decent from altitude? Engine @ 4900 rpm....up to that point it had been in normal range (this has happened many times...

Edit: this next annual, I intend to install a mechanical oil & fuel psi gauges..will report back on findings when able to compare data..
 
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trying to understand why some are having issues and others are not, in a supposed plans built package. Also trying to compare apples to apples.

To add some clarity....

There are now 563 (that are known about) RV-12's competed and flown.

I realize there are some that have had low fuel pressure indications but it appears to still be a small percentage of the total fleet.

I don't have an answer for those that are having low pressure indications but work is still being done to try and find an answer.

Tom has previously promoted that none of the RV-12's that have incorporated his aftermarket hose kit have had low fuel pressure indications. Perhaps if someone that does have low pressure indications was interested in changing out their hoses, we could find out if his hose set does make a difference and possibly have some additional info that could be used to solve it.
 
To add some clarity....

There are now 563 (that are known about) RV-12's competed and flown.

I realize there are some that have had low fuel pressure indications but it appears to still be a small percentage of the total fleet.

I don't have an answer for those that are having low pressure indications but work is still being done to try and find an answer.

Tom has previously promoted that none of the RV-12's that have incorporated his aftermarket hose kit have had low fuel pressure indications. Perhaps if someone that does have low pressure indications was interested in changing out their hoses, we could find out if his hose set does make a difference and possibly have some additional info that could be used to solve it.

Scott,

Tom and I would be happy to try that to see if there is any change. It would be an interesting data point. In all actuality, nothing might change....or it might. Our kit is flying on about 50-60 RV-12 aircraft, which is only about 10% of the flying fleet. So, it is a lot smaller sampling than the factory hoses.

As Tom mentioned earlier, I did the prototype work on the RV-12 fuel retrofit kit along with some awesome beta testers who really helped us out making it a smooth installation. None of the beta testers we worked with wanted to replace the factory kit due to low fuel pressure issues. They wanted a hose installation that would last for the life of the airframe. So, we weren't working to "fix" a problem, but rather create a package that didn't have hose components that needed to be replaced at 5 year intervals.

We know that a lot of people purchased our kit at the 5 year replacement point for the rubber hoses, but we don't know if anyone has purchased our kit to try to get rid of a low fuel pressure problem. All we know is that no one has come out and told us that they are experiencing low pressure with our hoses. That could be for one of two reasons. One reason is that maybe they are not experiencing low pressure. The second is that maybe they are still experiencing low pressure but have not mentioned it because it is not a completely uncommon occurrence.

I am presuming that the factory RV-12 is not experiencing any low pressure indications? If it ever does, we would be happy to work with engineering to see if the fuel kit makes a difference.

As a matter of fact, if Vans would like to install our fuel kit, thermostat kit, and remote oil sender kit on their factory -12 and then consider approving it as an option for SLSA owners, we would be happy to provide whatever data is necessary. We have had a number of SLSA owners approach us about the kits, ESPECIALLY the Oil Thermostat which is very nice in cold climates. However, we are unable to sell them these packages because the factory has not tested/approved them for SLSA aircraft. Contact me offline if you are interested in discussing.

Based on the fact that some users have experienced low pressure with lower fuel quantities in their tank, is there any possibility of a venting issue? Or any data that exists for the vented cap versus the secondary vent?

Steve
 
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Was running up the engine with out top or bottom cowl and notice a low fuel pressure warning which stopped when closing throttle and changing relative position to 10-12kt surface wind while turning around the apron. My carb vent lines are the prescribed length 3 or 4 inches and are tucked behind the carb bowl clips. Could being cowless and direct wind pressure and turning prop wind pressure impact fuel pressure?

I'm one of the 50-60 12's sporting the TS Flightlines fuel line system. On the contrary, regarding the discussion about low fuel pressure, mine is normal to borederline yellow (occasionally blinking a few times-then normal range) when fully configured for flight.
 
Gents,

I too have had sporadic low fuel pressure issues that I have never been able to correlate to anything. Just yesterday, on climb out on a full tank, my fuel pressure dipped to a bit below 3 lbs. A minute or two later, it returned to normal with the same power settings and angle of climb. The previous incident was about a month ago while in cruise at 8500 feet with approximately an hour of fuel used from the tank. It also cleared up by itself in a few minutes. There have been many more of these occurrences in the past. I have a stock fuel system installed per the KAI with the new venting system (undrilled fuel cap).

My fuel pressure sender is not one of the ones that were effected by the improper venting issue, so I have ruled that out as a possible cause. None of my past conditional inspections has revealed any foreign matter in the tank screen or the gascollator. Engine performance never changes during these episodes, but it still tends to make me a bit nervous.

Alex
 
Gents,

I too have had sporadic low fuel pressure issues that I have never been able to correlate to anything. Just yesterday, on climb out on a full tank, my fuel pressure dipped to a bit below 3 lbs. A minute or two later, it returned to normal with the same power settings and angle of climb. The previous incident was about a month ago while in cruise at 8500 feet with approximately an hour of fuel used from the tank. It also cleared up by itself in a few minutes. There have been many more of these occurrences in the past. I have a stock fuel system installed per the KAI with the new venting system (undrilled fuel cap).

My fuel pressure sender is not one of the ones that were effected by the improper venting issue, so I have ruled that out as a possible cause. None of my past conditional inspections has revealed any foreign matter in the tank screen or the gascollator. Engine performance never changes during these episodes, but it still tends to make me a bit nervous.

Alex


Same issue here. Exactly. It is sporadic, maybe more often when cruising at higher altitudes. Engine runs fine, no smell of fuel.
 
Morning all----
WE have a request--and we realize that its asking alot. WE would like to know those of you that are having an actual pressure issue---seemingly a real pressure scenario and not instrumentation. WE know that some of you have tested things with a mechanical gauge and have verified a drop in pressure. WE would like to know the details and the data of this. Of equal importance, we would like to know if any of the SLSA RV12's are experiencing this issue.

Obviously a pressure drop is a serious issue. But, some of you have stated that the engine maintains power, no skipping or sluggishness. Several of you have stated that you get the indication after cruise, decending. What I would like to know is if of you have had an engine power loss, and what the fuel pressure was indicating----if you know that. (You might have been alittle busy and not noticed.)

In all fairness, we would also like to know if any of you with the TS Flightlines/Aircraft Specialty fuel hose kit are experiencing similar issues. Seems that about a year and a half ago I asked that question, and got zero answers. That lead to my statement about our kit. So CERTAINLY, we would like to know.

For those of you that wish, you can contact me by email at tsflightlines@gmail, or Steve at [email protected]. I'm available by phone also.

Thanks to the members for the help!
Tom
 
I have a switched pump. The biggest flag to me that I left it on after leveling off is fuel flow. In cruise with just the engine driven pump running I see 4.5 GPH, but when I turn on the electric pump it goes up to 5.5 GPH.
 
S-LSA

Scott,

SNIP

... They wanted a hose installation that would last for the life of the airframe. So, we weren't working to "fix" a problem, but rather create a package that didn't have hose components that needed to be replaced at 5 year intervals.

SNIP

. . . As a matter of fact, if Vans would like to install our fuel kit, thermostat kit, and remote oil sender kit on their factory -12 and then consider approving it as an option for SLSA owners, we would be happy to provide whatever data is necessary. We have had a number of SLSA owners approach us about the kits, ESPECIALLY the Oil Thermostat which is very nice in cold climates.

SNIP

Steve

Hi Steve:

As the operator of an S-LSA RV-12 used in a flight school in SE Wisconsin I would dearly love to have lifetime fuel hoses and an oil thermostat - our winters are long and cold.

Since you and I are in the same locale Steve I wonder if Van's would allow you to install those items on our aircraft, periodically inspect them and send the data you collect to the factory so blanket S-LSA approval can be given?

Just a thought. I think I'll call Gus this coming week and ask him about this idea.
 
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