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First start- no start.

Dave Bernard

Active Member
What I had hoped would be a milestone day yesterday ended in disappointment...

I've got a new o-360, Dynon Skyview on my rv8.

We did the pre-oil procedure, put the plugs back in and out some gas in and prepared to start- the first interesting thing was the fuel pressure. Fuel pump came on and you could hear the fuel being pumped into the carb, but once it was full the pressure indication shot up to 17 psi or so. This seemed super high so I chalked it up to an indication problem, and shut off the pump. I have the facet pump from Vans which should only put out 6psi. The fitting from the engine fuel pump has the restrictor fitting installed.

We cranked multiple times, normal start, hot/flooded start, fuel pump on, fuel pump off, no dice. Not even a sniffle came from the engine, no indication of firing at all.

We drained the carb to see if it was contaminated with the preservation oil still, no dice, just fuel.

Pull the plugs, the bottom plugs were super oily which I suppose is normal for this new engine. Top plugs were wet but not oily. Cleaned and reinstalled. Not convinced the cylinders are getting fuel.

I didn't check the mag timing- the engine ran at the factory for a few hours before it was shipped, so I can't imagine the timing is wrong. My mag wiring goes from the Acs switch with pickoffs installed for Dynon tach indication to the mags with a shield ground pigtail there. I pulled the pickoffs to see if that was interfering, no luck.

The Dynon also showed 0 RPM during the start cycle, is that normal- do the RPMs not show until the engine is running?

Thoughts?
 
The fuel pressure is easy enough to verify with an cheap fuel pressure gauge plumbed in, although an indication error seems much more likely. An ignition issue would be my guess.

I would not take it for granted that the magnetos are timed correctly, as I recall some past posts here indicating that their engines arrived from Lycoming incorrectly timed or maybe even not at all.

Have you verified all the magneto wiring (p-leads properly grounding, leads to proper cyclinders, etc)? A timing check would help with this, and certainly be worth it. I was sure I had timed mine right the first time, and I was wrong :D

Chris
 
Spark

When the grandson was 6, I would always have him hold the spark plug wire while I cranked the mower.....if he jumped or cried I was getting fire.:D
 
Of the 14 possible causes for hard starting listed in the Lycoming Trouble Shooting Guide, http://www.lycoming.com/node/17944 , 10 deal with the ignition system. My advice, look at the guide and methodically check and rule out systems as the culprit in a linear fashion. For example start with fuel and once that's ruled completely out as a problem, then and only then move on to the next potential item.
 
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You need to confirm that fuel pressure! If you mistakenly got a high pressure pump installed that is putting out 17 PSI, that is your problem. The needle / seat in the carb cannot hold back anywhere near that pressure level and the carb bowl will overfill, causing a very rich mixture. The wet upper plugs (assuming it is gas and not oil), likely confirms the overly rich mixture.

Larry
 
comments in line below

What I had hoped would be a milestone day yesterday ended in disappointment...

I've got a new o-360, Dynon Skyview on my rv8.

We did the pre-oil procedure, put the plugs back in and out some gas in and prepared to start- the first interesting thing was the fuel pressure. Fuel pump came on and you could hear the fuel being pumped into the carb, but once it was full the pressure indication shot up to 17 psi or so. This seemed super high so I chalked it up to an indication problem, and shut off the pump. I have the facet pump from Vans which should only put out 6psi. The fitting from the engine fuel pump has the restrictor fitting installed.

We cranked multiple times, normal start, hot/flooded start, fuel pump on, fuel pump off, no dice. Not even a sniffle came from the engine, no indication of firing at all.

We drained the carb to see if it was contaminated with the preservation oil still, no dice, just fuel.

Pull the plugs, the bottom plugs were super oily which I suppose is normal for this new engine. Top plugs were wet but not oily. Cleaned and reinstalled. Not convinced the cylinders are getting fuel.

What leads you to this conclusion? Did you smell gas when you pulled the plugs? They typically are only wet due to either oil or gas

I didn't check the mag timing- the engine ran at the factory for a few hours before it was shipped, so I can't imagine the timing is wrong. My mag wiring goes from the Acs switch with pickoffs installed for Dynon tach indication to the mags with a shield ground pigtail there. I pulled the pickoffs to see if that was interfering, no luck.

Mags could get bumped in shipping or installation. I would confirm the timing.


The Dynon also showed 0 RPM during the start cycle, is that normal- do the RPMs not show until the engine is running?

I would expect the Dynon to show RPM at cranking speeds. A 0 here could indicate incorrect EMS setup, wrong resistors installed or nothing being sensed on the P lead, which would mean the mag is not firing. You may want to consider wiring your P leads through mechanical switches until you confirm that your mags are firing. Bad switches and incorrect wiring seem to happen frequently with the keyed ign switch. P-lead switch should be open when you want a spark and closed (short to ground) when you don't.

Thoughts?
 
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Check your ignition (mag) switch and make sure that you are not grounding your impulse mag also as you are cranking the starter.

As far as the high fuel pressure goes, it will need to be resolved later. Just run the pump till you see pressure (3#) then shut it off. The motor will run fine on the mechanical pump.

Do double check the timing.
 
172: nothing led to that conclusion- I just don't know. I assume it's getting gas to the cylinders but I'm not ruling out something weird with the carb.

The Fuel pressure deal was what I expected: the Dynon thought it had the 50psi sensor, which is why it was showing bad info... Switched to the 15psi sensor in hardware mapping and now showing 5 psi.

On to the ignition....
 
172: nothing led to that conclusion- I just don't know. I assume it's getting gas to the cylinders but I'm not ruling out something weird with the carb.

The Fuel pressure deal was what I expected: the Dynon thought it had the 50psi sensor, which is why it was showing bad info... Switched to the 15psi sensor in hardware mapping and now showing 5 psi.

On to the ignition....

If you did not smell gas and have it dripping out, you can not be sure. Did you purge/test the fuel flow to the carb? One system test I worked on, 2 quarts of contaminated fluid came out. It was injected, so maybe a carb would be less. I would not just assume to have fuel, you need a positive indicator. Even to walking off with a wet plug and putting a match under it. Even 90% oil and water can smell like gasoline. Be sure, then move on. Pretty basic.

Keep at it, debugging is part of the process. It is necessary to a safe aircraft.
 
My first start was also a nonstart. It was due to my misunderstanding of how to wire the mags as gasman suggested. When switch is in the "on" position or circuit is closed, the mags are grounded and won't fire. Open circuit equals not grounded and mags will fire
 
no fire

From past experience, disconnect the "P" leads at the mags, then try the start.
A friend had the same problem first start, he swore he had pinned the ignition switch out correctly. He pinned the switch out again with help from others and it seemed fine, I asked him to just disconnect the leads but after pinning them out again decided to have them rebuilt, the engine was mid time off of another RV, but the mags had not been touched. When he got the mags back he put them on and it wouldn't start again, I again asked him to humor me and remove the "P" leads from the mags. He did and it lit in 2 blades. He did have the switch wired correctly, but when he put the leads on the mags the shielding would ground out, so when he pinned them out off of the mags they would pin out correctly then ground out when they were put back on the mag. I'm sure it's something simple. Make sure that the mixture goes to full ICO, before you do this.

Rt
 
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From past experience, disconnect the "P" leads at the mags, then try the start.

Just be careful here...this is a dangerous condition (although you might already have one if your wiring is messed up so that "on" = grounded, but "off" = ungrounded). With no way to ground the mags, the only way to stop the engine is via idle cut-off and if, like a friend of mine, the control was not *quite* able to reach idle cut-off on first engine start (it was easily fixed), the only way he could stop the engine was via grounding the mags ("off"). If you have disconnected the p-leads, AND the mixture won't reach full ICO, you won't be able to stop the engine. (I suppose you *could*, by pulling mixture all the way back and then pushing the throttle forward until the mixture reached on incombustible ratio, but...)
 
Fuel Valve

Just be careful here...this is a dangerous condition (although you might already have one if your wiring is messed up so that "on" = grounded, but "off" = ungrounded). With no way to ground the mags, the only way to stop the engine is via idle cut-off and if, like a friend of mine, the control was not *quite* able to reach idle cut-off on first engine start (it was easily fixed), the only way he could stop the engine was via grounding the mags ("off"). If you have disconnected the p-leads, AND the mixture won't reach full ICO, you won't be able to stop the engine. (I suppose you *could*, by pulling mixture all the way back and then pushing the throttle forward until the mixture reached on incombustible ratio, but...)

All RV's should be equipped with a fuel selector that has an off position. This can be used to shut down an engine if the mixture won't reach idle cut-off.

Skylor
 
P-Lead Adaptors?

In 2013 I decided to replace my homemade P-leads with Bogerts. One of the pair wasn't long enough and caused the mag to short out. Just a possibility...

6pwTzq.jpg
 
On my first start attempt, the engine would occasionally fire but not start. I checked and cranked at intervals until the battery was getting weak. No start.

When I was climbing out of the aircraft, I noticed the mixture lever in the idle cutoff position. Idiot!

I put the battery on charge and went to lunch. Next try it fired up on the second blade...

Of course all my helpers who had come to hold fire extinguishers and see the engine run had great fun at my expense...
 
First engine start

Dave,

Probably a silly question but did you perhaps look up the lower intake and see if there is a plug just above the throttle body/carb?

Engine manufacturers and rebuilders sometimes put a rubber cap in the lower opening at the throttle body to keep debris & foreign matter out during shipping.

Might be worth a look, sounds like the appropriate symptoms if everything else checks OK. That would definitely prevent a start since there is no air going into the engine, (fuel, air & spark req'd).

I had my 1991 engine recently rebuilt by Poplar Grove Engine rebuilder up in Chicago. While installing it we did a thorough inspection and found a red rubber plug right at the bottom of the engine intake at the throttle body attachment so it was fairly easy to pull it out. And no, they said nothing about it so I assumed it might be standard procedure. It would have definitely prevented a start. Except for that remission of information they did a superb job and the engine has been running flawlessly.

Hope this is your start problem because it would be a super easy fix.

Good luck!
 
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Confirm, plug wire firing order?
There was an RV-10 at my airport that wouldn't catch on the first start; It just popped and coughed. The problem turned out to be what you said: plug wires were crossed. When he fixed that, she fired right up and the engine purred like a kitten.
 
There was an RV-10 at my airport that wouldn't catch on the first start; It just popped and coughed. The problem turned out to be what you said: plug wires were crossed. When he fixed that, she fired right up and the engine purred like a kitten.

Ya...don't ask how I know this......:rolleyes:
 
Just be careful here...this is a dangerous condition (although you might already have one if your wiring is messed up so that "on" = grounded, but "off" = ungrounded). With no way to ground the mags, the only way to stop the engine is via idle cut-off and if, like a friend of mine, the control was not *quite* able to reach idle cut-off on first engine start (it was easily fixed), the only way he could stop the engine was via grounding the mags ("off"). If you have disconnected the p-leads, AND the mixture won't reach full ICO, you won't be able to stop the engine. (I suppose you *could*, by pulling mixture all the way back and then pushing the throttle forward until the mixture reached on incombustible ratio, but...)

Or turn the fuel selector off...
 
Or turn the fuel selector off...

Ah, yes...I should have thought of that, too... doh!

But with the mags ungrounded, the engine is always "hot", so just watch that prop and don't touch it lest it decide to fire :0 Plenty of videos out there of what can happen.
 
Thanks for all the replies gents:

Turns out it was a P-lead issue. Disconnected them today and it fired 3rd blade. Taxied around for a bit too, a huge milestone!

Next session will be to figure out where it's grounding. I'm suspect of the switch- I've been through the diagrams 100 times (I'm sure I wired it correct) and we verified it wasn't the shield ground. Rumor has it these ACS switches are prone to this issue....

Will report back!

Cheers,
DB
 
Thanks for all the replies gents:

Turns out it was a P-lead issue. Disconnected them today and it fired 3rd blade. Taxied around for a bit too, a huge milestone!

Next session will be to figure out where it's grounding. I'm suspect of the switch- I've been through the diagrams 100 times (I'm sure I wired it correct) and we verified it wasn't the shield ground. Rumor has it these ACS switches are prone to this issue....

Will report back!

Cheers,
DB

I'm glad you found the problem, this is about the 10th time I've heard of this! When you hear the sound of hooves, think cows; not camels. There was a few years ACS had an incorrect dwg in the their catalog and supplied with the switch. Locate an old Bendix drawing for the proper pin-out.

First start on a new plane is indeed a big milestone; congratulations.
 
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Welp, I'm still miffed over here.

I pulled the switch out and checked it's continuity and didn't find anything wrong as far as I know. With the key off, both mag terminals ground. In L, the right terminal grounds. In R the left terminal grounds. In Both, neither ground. In the start position, the right terminal grounds itself through the jumper, the left does not ground. The body of the switch does not ground to itself from the rear ground terminal.

My ground wire grounds to the fuselage.

Neither p lead wires nor their shields ground while disconnected from the switch and the p leads. I have verified the p leads go to correct wire that connects to the switch.

The P lead terminals on the mags both ground while disconnected from the p leads.

Could it still be the switch even though it tests as I expected? What am I missing?
 
This is confusing to me as well. With no pleads hooked up, the plead terminal on the magneto has some continuity to the airframe- i.e. I get a beep from my ohmmeter. I understand this is because of the inner workings of the magneto, but that's the extent of knowledge here!!
 
The P lead terminals on the mags both ground while disconnected from the p leads.
Not so fast, my friend. With the points closed, the resistance will only read 0.5 ohms - not a direct short but close enough to make your continuity checker beep. (Ask me how I know...)
 
Return grounding...

My ground wire grounds to the fuselage.

Hi Dave, Great to hear you got her running! :D

It sounds to me that wiring your ground terminal on the switch to the fuselage ground would be a problem. From what I gather, it should be sent back thru the wiring shield, by the starter contacts, to ground out at the mags. Electrical radio interference would also be an issue...

Hopefully this wiring diagram will clarify as well as this thread link...

http://www.aeroelectric.com/articles/MagnetoSwitchOptions.pdf

Thanks to Gil Alexander.

http://www.vansairforce.com/community/showthread.php?t=36272

Sorry......don't know where that bottom quote link comes from..... :confused:




Best Regards,

T.C.








 
Thanks for the reply tommy.

I know this is a can of worms, but here goes:

The ACS switch diagram says the center ground post grounds to "nearest structural member", not the shielding.

I have read in numerous places that the shielding is only grounded at the ground post on the magneto. My shielding ends prior to the connection that hooks up to the mag switch.

The Lycoming mechanic I had here yesterday asked me specifically if my shielding was only grounded on the mag side, he was happy that it was.

Perhaps this is the problem... But I'd hate to rewire the leads just to find out it wasn't.....
 
Haha- no not "that is the solution" - that is the switch I am using!

Gotta keep troubleshooting tomorrow.


Rats! Forgot my own question...Doh:eek: Thought that response was way to quick!


Well, to make it up I found this helpful. :)

10ace518_347.jpg




Good luck tomorrow.




T.C.
 
I "may" have figured the solution (fingers crossed):

The ACS switch diagram does not show the ignition wires as shielded (and has not been revised since 2001...). With the ACS switch wired with shielded wires connected only at the magneto end, and the ground post wired directly to the airframe ground, I ASSume that I may be grounding the mags in all switch positions.

If I were to ground the shields on the switch end to the switch ground post, and not directly to the airframe, I would be getting the desired grounding action through the shields back to the magnetos.

I'm thinking of disconnecting the ship ground from the ground post of the switch, and running some temp wire from the switch ground post out to the shielding ground post on the mags, strictly for test purposes before I mangle up my P-lead wires switch side.

Thoughts?

I found this thread helpful.

SECOND EDIT:

I am concerned that wiring both shield wires to the center ground post could inadvertently ground both mags when you only desire one- thus not allowing a mag check or even starting. Should the right P-lead shield ground to the jumper terminal, and the left p-lead shield ground to the center post on the switch?? Am I over-thinking?
 
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I had the same issue. Turns out there were a couple of very small wires from the shielding that were grounding out at the back of the key switch. Very hard to see. cut back the shielding to be sure no wires grounded the key switch.
thanks,
Mark
 
Deja vu all over again....

Yep it seems this issue has been around for a bit. I mean 4 different wiring options in this thread alone, and of few more in the forums...But it seems to me that the most recommend one is the return ground thru wire shield. As per this diagram...

http://www.aeroelectric.com/articles/MagnetoSwitchOptions.pdf

So Dave, I'd eventually wire it as per the diagram above. No, the double wire shields will not be an issue.( see the switch contact points operation above... Note: R and the ground next to it are jumped together at the terminals, so the diagram is a bit skewed.)

Now that being said...they all try and I believe do achieve the same basic end results. But some with unwanted and possibly damaging effects. I'll leave the debate about good, best, and better, for another time. Which I think Dave alluded to with his can of worms....;)


So leaving your wiring as is ....it should still work.




Back to troubleshooting...


First...Is L terminal at the switch REALLY grounding out whilst starting. (Wiring or switch problem)

Secondly... Will the Left mag start the engine on it's own.
(Mag issue)

I leave it to your expertise on finding the results but if I were asked to recommend something...

For 1) Take out the starter fuse. (no power to the switch, and starter contactor) and check for continuity between L terminal on switch, and ship ground with the switch turned to the start position. Note...engine should not turn over, and I don't believe that any voltage will be present at the terminal with all wiring as is. But perhaps removing L plead from L terminal would be wise. Replace fuse...

For 2) Leave Left mag plead disconnected from terminal L on starter switch, and see if it starts!

Regards,

T.C.
 
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Another possibility

I thought mine was wired per Vans diagram, I cranked and cranked. About when I gave up and let go of the key the engine fired. Turned out I had the left and right p-leads reversed grounding the left mag for starting. How did I do that? Vans diagram shows the p-leads, J3 and J4 to the right and left mags, right on the left, left on the right. I looked at the diagram instead of reading.
 
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.But it seems to me that the most recommend one is the return ground thru wire shield. As per this diagram...

I'm not one pf those people.....
The long term durability of the P lead shield is vulnerable depending on how it is actually completed (There is strong evidence that first time builders don't always have a good idea what to do here). This then makes it highly likely that at some point in the future the airplane will have an unsafe mag because of a failed grounding path. It is for this reason that I promote sheild connection at one end only and then use an airframe connection to the switch ground as the grounding source.

None of this is relevant to the O.P.'s problem though because the ground is used to disable the mag, not enable it.
Even if the ground it hooked up incorrectly, as long as each P lead is connected to the switch properly, the mags should fire the plugs (but it may cause an unsafe condition by not disabling the mags when the ignition is off).
 
I'm not one pf those people.....
The long term durability of the P lead shield is vulnerable depending on how it is actually completed (There is strong evidence that first time builders don't always have a good idea what to do here). This then makes it highly likely that at some point in the future the airplane will have an unsafe mag because of a failed grounding path. It is for this reason that I promote shield connection at one end only and then use an airframe connection to the switch ground as the grounding source./QUOTE]

^^^ I live in this camp too. 5 EXB, all wired this way, 7,000+ trouble free hours.
 
Well guys this whole process has been humbling, educational and now embarrassing.

This whole thing was my fault all along. Mlew in post #39 had it right- I had cut my shielding too short on the switch side, and just a few strands were enough to ground out both (yes, I screwed up both of 'em) P-leads.

30 minutes later, I had the engine running with correct ignition. Mag check and grounding check went as expected.

My wiring is: ACS switch diagram wiring, Dynon pickoffs and resistors for the RPM, ONE end ground shielded at the mag.

Reading/using the ohmmeter better was a valuable lesson here.

I sincerely appreciate all the help and time from everyone who has chimed in on this thread- and I apologize to those who are rolling their eyes at me from behind their keyboard!

Time for some liquid reward, and time to email the DAR!!!

Dave B
 
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