What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Replace Engine Fuel Pump

J

jersey

Well Known Member
Has anybody experienced a leak on the engine driven fuel pump. I received a "low fuel pressure" alarm yesterday and noticed a gasoline smell while decending. Additionaly I noticed large fluctuations about 30 minutes before I received the alarm. I was able to locate the leak with the engine off and the electric fuel pump on. Fuel is leaking from the engine driven pump where the diaphram housing is crimped together. I got a total of 46 hours on the engine.

Would appreciate any help and info on how to replace the pump. It appears as though there is a special crimped clamp that attaches the fuel lines to the pump.:confused:

Thanks,
Gary Eldridge
 
The fuel pump should be covered under warranty, but you'll have to buy the replacement, send in the old one, and wait a month for a check.

The low pressure alarm is pretty common. Do a search under RV-12 and there are several threads about a leaking pump, warranty claims, and low pressure alarms.
 
Last edited:
Hey Gary - -

I had a pump problem. Was a very slight leak at the mounting area. Under warranty, they replace the pump AND hoses as an assembly. You have to pay for it, then wait for your money back. Takes a month maybe. They told me they have had several pump problems.

John Bender
 
Geez,...

...another show stopper to worry about. And a potential fire hazard to boot :eek:
I thought these motors were supposed to be reliable :rolleyes:.

I think the warranty period is six months after the dealer receives the engine, but there is that waiver that refers to 1st engine start, does anyone know how long they will honor returns of fuel pumps and oil pressure senders? Maybe, if I'm lucky, I won't have any of these problems :p
Tony
 
Last edited:
Thanks for the info.

Thanks for the info guys, I've got a plan now.

Happy new year y'all!

Gary
 
Rotax Warranty

Lets get this Warranty stuff straight right out of the Gate shell we.;) See this link and this document came with your engine.

http://www.rotaxflyingclub.com/tech...les/SL-912-012_914-010_2ST-006_R2_English.pdf

Stuff of importance:
See page 3 of 6 and read when coverage begins. Then read same page 4.1 A.Engines: (a) That is you coverage period, 18 months or 200 hrs.

Continue onto next page at the top and see parts coverage, 18 months or 100 hours.:eek:
 
Warranty

They do honor the warranties. I lost a $1000 electronic module and they replaced it. Paid me back 8 weeks later...a nervous two months.
 
Another Fuel Pump Failure!

I recently had a fuel pressure problem to. On takeoff roll after reaching full power the engine started to lose power and run ruff. When power was reduced all readings returned to normal. On the ground during a full power run-up I received at first, a fuel flow alarm showing fuel flow exceeding Max red line then Second, the fuel pressure reduced to the yellow arc. Again when power was reduced all readings went back to normal. After inspection of the engine driven fuel pump we noticed a very small amount of fuel (less than a drop)leaking out of the weep holes on the back of the pump. Per the new video on Rotax-Owner.com web site this indicated that the pump was bad. A new Pump was ordered and installed. All engine ops returned to normal. Twelve hours and still no problems. Here is a picture of the fuel pump.
P2140018.jpg

P2140021.jpg

I run premium unleaded, no ethanol, 110 hrs on engine. You can see a small brown fuel stain on the weep hole. Premium unleaded turns brown when it dries. Here is a picture of a typical fuel system and fuel pump schematic from a Rotax maintenance manual.
RotaxFuel010.jpg

As you can see the Rotax fuel pump is not a impeller type fuel pump but Diaphragm pump. Any crack or leak in the diaphragm or case will cause the pump to go bad. There are two pumps you can buy, Part #892-546 comes with the fuel line attached $511 and part #892-542 one with no fuel lines attached $168. After the warranty runs out I will be switching over to the cheaper one if I need a new one. LEAF says they sell 3 to 4 pumps a month. Not a good sign of how dependable these pumps are. I don’t think the engine would stop running in flight if your pump starts to fail but you probably will not get full power. As in this thread and others on the form about this subject engines continued to run. I am also not sure why the fuel flow would increase to the red line as fuel pressure reduces. I believe that for some reason as air is induced into the system through the pump flow increases back to the tank via the return fuel line. Maybe someone with more experience with diaphragm pumps could explain this phenomenon which is why I included the fuel diagram. Some people who do not run Rotax engines seem to diagnose this high fuel flow fuel indication as fuel Vapor lock. The new fuel pump fixed my problem so that wasn’t’ the case. I also think that the Rotax fuel pump could be bad and not indicate a fuel leak. It’s an insidious problem because even at a 4000RPM runup before takeoff the engine ran fine, only at Max power did I begin to have problems. Several times back at the hanger we did max power runups after the aborted takeoff and the problem didn’t occur. Maybe on the takeoff roll as airspeed increased and RPM slowly increased as a result and the demand for fuel increased in the carb jets the pump couldn’t keep up with demand as it started to induce air into the system through a possible crack in the diaphragm. The builder in me would have loved to cut open the fuel pump to inspect the inside to see why it leaked(it’s a sealed unit). But because it was a warranty item I had to send it back intact. I really like the Rotax engine but some of the accessories seem to be weak. It’s hard to know the exact data on failures of these types. As with the Honeywell oil sensor failures sometimes the things last for hundreds of hours and then sometimes they fail right away. Hey Larry G in your past have you had any problems with the fuel pump? It would be great if all three Rotax dealers in the USA would request a Rotax Tech Rep from Austria to attend OSH and give a talk about these Accessories and any improvements that maybe down the line. It was quite a coincidence cause recently a new Video on Rotax-Own.com came out about this very problem so maybe Rotax knows about this problem. I would think that the USA is one of the largest users of the Rotax engine. It would seem that the dealers walk a fine line with Rotax in their marketing agreements as far as feedback they can give them on these problems. The remote mounting fire wall kit that Lockwood sells for the Honeywell oil pressure sending unit would be an example of this dilemma. Lockwood knows that having the pressure unit out on the front of the engine causes it to fail vs having it mounted on the firewall, but they are unable to get Rotax to change it. Anybody who has owned a BMW would understand how precise the standards are with the Germans and how hard it is for them to change things. Well I guess it not a perfect world anyways. Still love this little bird and am having a great time flying it. See you at OSH.
 
Last edited:
Hey John - -

Maybe I missed it, but do you have the aux. pump running all the time ? Would not seem you would run out of gas flow ? Leak, ok, but the aux. pump should make up any flow loss in the mechanical pump. Hmmmm ?

John Bender
 
Jetguy said:
Yes the Aux fuel pump is wired on all the time in Plane.
Click to expand...

I wonder if this is not the problem. Over pressurization / volume? I have not had the problem and I have my electric pump off (switched) unless I am landing or taking off.

Marty, try pulling the fuse after take off and go flying again. Let us know what you find.
 
Last edited:
Fuel pump test

Be careful pulling the fuel pump fuse. If the engine pump fails, there is no backup. The master switch should be off when pulling or replacing the fuse to prevent the fuse from accidentally blowing. It is safer to do troubleshooting on the ground.
I thought of a test for the engine driven fuel pump:
1. Disconnect the fuel return line from the firewall shelf and plug the hose end.
2. Disconnect the fuel supply line from the gascolator and apply 5psi air pressure to the fuel hose. (The Rotax_912_HeavyMaint_Manual.pdf says the maximum fuel pressure allowed is 5.8 psi.)
3. Watch the engine fuel pump for leaks. If no leak is observed, try turning the prop by hand to flex the pump diaphragm.
I have never tried this test but it seems like a good idea.
Joe Gores
 
Air can leak through a hole that is too small for liquid to leak through. I imagine that when the engine driven pump first starts to fail, the hole in the diaphragm is very small. It is possible that air could leak into the pump on its intake stroke.
Joe Gores
 
Possible, but on the intake stroke, the diaphram is not really working as a suction, since the electric pump is forcing the cavity full of fuel as it becomes larger. Full of fuel or vapor, depending on the heat to the fuel line from gascolator to that pump. Assuming the check valves operate like most every other mechanical diaphram fuel pump, in fact when diaphram is on the "intake" stroke, fuel would be easily pushed thru all the way to the carbs by the electric pump. In a perfect world, the engine pump quitting would be a non-event, probably signaled only by a reduction of fuel pressure.
 
New Fuel Pump From Rotax

I understand that Rotax is replacing these old fuel pumps that we have, with a new, and better unit, which will be on all of there new engines soon. Sure hope we can retrofit our engines with the new pump when the old one starts giving trouble. If anyone has additional info about these new pumps, please chime in!!

Tom
 
For What It's Worth...

I have a friend who has been running a Rotax 912 on a Zenair Zodiac since about 1995. He has replace more than a few engine driven fuel pumps.
Several times he has been told, "This new design pump shouldn't fail!"
 
Last edited:
My fuel pump began leaking from the forward weep hole at around 50 hours on the engine. I have ordered a new fuel pump with lines and hope to receive them next week. My question for those of you who have put on the new and improved pump is this: Did you install a check valve as recommended per SI-912-020 R5? Exact verbage is: "If a auxilliary electrical fuel pump is used a check valve (part no. 874532) should be used." I did not think that this was necessary with our installation but I don't remember anyone discussing it.

Any feedback would be appreciated. Thanks.

Doyle
 
Doyle,

I replaced my pump many moons ago. I remember being intially confused by that "requirement", but somewhere found information that the check valve is not needed in the RV-12 installation. Can't remember exactly where I got the info. Hope this helps.

John
 
Thanks for the info John. If one were required I'm sure that Van's would have let us all know since they are shipping out engines with the new pump installed. But I find it best to check with those that have alrready done this in the field.

Doyle
 
If I had a rotax I think I know where that mechanical pump would be going..And it wouldn't be anywhere near the airplane that for sure.

I know of a couple of rotax owners who "saw the light" and junked the fuel pump in favour of two electric pumps put in the hydraulically correct place in the fuel system. This was after I showed the them the elctric only ste up on my Soob powered Zodiac with the same carbs as the Rotax.

I don't now if you RV12 guys can do that legally but this is a poor fuel, system design (mechanical pump in the wrong place) and electric pumps can be made perfectly reliable,,for a lot cheaper to boot.

Frank

Zenair Zodiac electric only fuel pumps..currently 700+ hours
RV 7a electric only, FI'd currently 500+ plus hours.
 
frankh said:
If I had a rotax I think I know where that mechanical pump would be going..And it wouldn't be anywhere near the airplane that for sure.

I know of a couple of rotax owners who "saw the light" and junked the fuel pump in favour of two electric pumps put in the hydraulically correct place in the fuel system. This was after I showed the them the elctric only ste up on my Soob powered Zodiac with the same carbs as the Rotax.

I don't now if you RV12 guys can do that legally but this is a poor fuel, system design (mechanical pump in the wrong place) and electric pumps can be made perfectly reliable,,for a lot cheaper to boot.

Frank

Zenair Zodiac electric only fuel pumps..currently 700+ hours
RV 7a electric only, FI'd currently 500+ plus hours.
Click to expand...

As in everything with airplane design (and modification), any design choice is usually a compromise or trade off.

An RV-12 modified to use two electric pumps would require changing a very simple to operate airplane (systems wise) to one that required electrical power to keep in the air (and the dual redundancy power system and pilot management of that system, that would go with that requirement).
The current RV-12 design will stay in the air with a total electrical failure. It will also stay in the air with a single mechanical or electrical fuel pump failure.

The new pump design looks very promising, and hopefully it will make fuel pump failures on ROTAX 912 a thing of the past.
 
Don, not exactly but close.

Magnetos do not require a battery to make a spark.

While the he Rotax ignition system does not use magnetos it also does not require a battery to make a spark either.

With either system you get spark even with an electrical system failure. This is very different from other non-magneto systems that will fail with an electrical system failure - like some auto engine conversions. (sorry could not resist the tease)

A guy from Lockwood explained to me how it worked a couple of years ago at sun'n'fun. I've forgotten the explanation but the abov is the short answer.

Sort of magical!

- Dave
 
OK, did the research, Scott was correct, it is a CDI system that needs no battery power to keep running. Truly this is a very good system for an aircraft, coupled with mechanical and electric pumps gives a good redundancy for sure. Mine has some of that, it will run on the alternator if the battery fails, and will run on the battery if the alternator fails, and I have a spare fuel pump and a spare ECU to engage with the flip of a switch..
 
You must log in or register to reply here.
Back
Top