blueflyer

blueflyer

Well Known Member
OK, this is not a problem on my unfinished RV, but to keep it RV related, this will help me when installing the engine in my RV.....so here goes:

I am trying to start my engine and cylinder #1 will not fire. I have 2 slick mags, the left is the impulse mag. I have the #1 cylinder hooked to the primer. 0 SMOH engine, 0 time mags. Both are about 3-4 months old. The engine and mags were test run at the engine facility.

I have wired my panel with all toggles: master, alternator, L mag, R mag.
When I start the engine, everything cranks up just fine, but #1 isn't firing. It stays cold. I removed the plugs from #1 and the bottom plug had fuel in it. So, I know fuel is getting to it.

I switched the plugs with another cylinder, and restarted. Same thing. No fire to #1 and the other cylinder ran/started good. CHT on #1 stayed at 95 degrees.

I would doubt that since the top and bottom plug isn't firing that both mags are bad, or both wires are bad. I know its getting fuel.

I have my mags grounded at the panel, not the magneto.

I believe its likely I have a wiring problem somewhere from my panel to the magneto. Would anyone agree or disagree with starting there? Also, could I be flooding my cylinder somehow (since its the only one with primer)?
 
Pull your plug harness caps and pull the prop through by hand. See If #1 has any compression. Normally I'd just say make sure the mags are off, but pull the caps anyway.
 
Switching plugs rules them out, but not the wires. I know, slim chance, but a chance. Yes, you could be flooding it, but after a few seconds of running, that should clear. Perhaps an intake leak? That is the first thing I would check. The engine has been handled since it was tested, and those hose connections can be moved. I would pull a plug from all cylinders and see if you get fire to each plug, and double check to see you have compression by pulling it through by hand. A valve could be stuck. All of these seem unlikely, but easily checked.

Bob
 
that reminds me.....there is oil coming out of the exhaust that is attached to #1 cylinder. No oil coming from other exhaust pipe. This doesn't bother me too much since the rings aren't seated and #1 isn't firing, but more information for you to know.

aerhed said:
Pull your plug harness caps and pull the prop through by hand. See If #1 has any compression. Normally I'd just say make sure the mags are off, but pull the caps anyway.
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You could have the plug wired running to the wrong plugs, but probably pretty low on the probability list.

First off, I would look for compression issues, then spark plug wiring. If the engine is running at all, I doubt the problem is in the 12v side of the ignition wiring.

You need only three things for the cylinder to run------compression, combustible mixture in the cylinder, and a properly timed spark.

Have you done a mag check with the engine running???? if both sides drop badly, and makes the engine shakes a lot, I suspect your plug wiring is mixed up.
 
I'd guess that even with low compression, the cylinder would fire and heat up.

If I had this, I'd probably verify the sparking on all the cylinders. To do that, you might have to pull the mag and spin the mag with a drill and a home-made fitting to engage the drive. (Something like a socket extension with a hose over the end to line up with the drive.) A paper clip in the distributor block that arc's around to near but not touching the case should do the trick.

That would, for sure, rule out the mag. Then, wires, to plug, etc. That would rule out ignition.

The other thing you might do is to do a compression check with an automotive type compression gauge. In contrast to the typical leak down check that is common the automotive type test gives an indication of how well the engine is breathing. (For example, in say the cam lobe was completely gone - worn down to nothing. In a leak down test, all you know is that the cylinder holds pressure. But, it may not be taking in any fuel/air mix - in this example, the auto type test would show the problem.)

Dan
 
Make sure the primer is actually hooked up. If it's not the big leak there will suck in so much air that the cylinder will be tool lean to fire (ask me how I know!).

Not likely a mag problem since other cylinders are okay.
 
Bob,
that sounds like the simplest solution yet, so I hope you're right.

I did not do a mag check during the 2-3 minute ground run. I wish I would have. I will begin the troubleshooting tomorrow and use everyone's suggestions until I get this thing figured out.

I too doubt its an internal mag problem since the other cylinders are purring like they should. I also doubt that one wiring harness coming off 2 different mags, both coincidentally going to cylinder #1 are bad....but I will check them as I go down the list of "things to check."

BobTurner said:
Make sure the primer is actually hooked up. If it's not the big leak there will suck in so much air that the cylinder will be tool lean to fire (ask me how I know!).

Not likely a mag problem since other cylinders are okay.
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Either you don't have fuel or you don't have spark. Is the engine fuel injected? If so, you might have a clogged injector. The mag/wiring check you're doing is important too, but I can't imagine both ignition systems failing on the same cylinder. The odds are low.

A really odd failure would be an intake valve that isn't opening. You can check that by pulling a valve cover and verifying that the intake valve is doing its thing.
 
Probably not oil

What's running out is maybe fuel mixed with carbon, looks like oil. I'm guessing its flooding from the primer. You mentioned (only?) #1 was plumbed to the primer. If manual plunger type make sure it's closed and locked, or disconnect it at the cylinder, plug it and see what happens.
Unlikely both mags are bad.
Tim
 
I think you're right...its fuel, not oil.

The engine is carbureted with only primer plumbed to cylinder #1. After sleeping on it last night, my father called early this morning and said he woke up at 4 AM and came to the same conclusion as others on this forum. That "stuff" coming from the exhaust pipe is excess/unburned fuel, not oil. Once he said it, it made sense. We'll go test this theory today. I am optimistic this will solve our problem.

I enjoy experimental airplanes, but I really like the fact that my father and I work on our things together. That's what its all about. While I'm at it, I have learned so many things on this board as well. This forum is truly an irrreplaceable resource.


tim2542 said:
What's running out is maybe fuel mixed with carbon, looks like oil. I'm guessing its flooding from the primer. You mentioned (only?) #1 was plumbed to the primer. If manual plunger type make sure it's closed and locked, or disconnect it at the cylinder, plug it and see what happens.
Unlikely both mags are bad.
Tim
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If electric solenoid primer, make sure it is plumbed in correct direction, I think port #2 is input, #1 output.
 
Yes, that will be my first check. I feel like I'm flooding the cylinder with the primer, but I cant see how that is happening (I haven't gotten to the airport this morning to investigate yet). I assume the primer solenoid is stuck in the open position and continually flooding that cylinder. Its possible its plumbed backwards, but I seem to recall double checking that issue.

The primer is plumbed as follows:
Fuel flows from main tank through the Vans electric fuel pump, then to the gascolator. The gascolator has a fitting in the top of it where the primer solenoid is attached, then out the solenoid to the cylinder.


647jc said:
If electric solenoid primer, make sure it is plumbed in correct direction, I think port #2 is input, #1 output.
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Yes, your plumbing sounds correct. My understanding of the solenoid is that the device will not close and stay closed if plumbed backwards. The pressure (or suction) can open the solenoid valve if plumbed backwards.
 
Simple test: remove the primer line from the port on the cylinder and cap it off.

That said, if it were me I would take every bit of the primer system and remove it from the airplane permanently. In my -6 I originally installed one and removed it because I never used it.
 
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rocketbob said:
Simple test: remove the primer line from the port on the cylinder and cap it off.

That said, if it were me I would take every bit of the primer system and remove it from the airplane permanently. In my -6 I originally installed one and removed it because I never used it.
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+1 with RocketBob :)
 
This reminded me when I tried to start my engine I found that someone had crossed the plug wires. The engine builder test ran the engine and I just took it for granite that the wires we correct.

Dan
 
And the results are in.....

I'm glad it was something so simple, but just goes to show you how easy a little thing can cause trouble.

A few months ago, I swapped the placement of several toggle switches on my panel. While swapping the primer solenoid switch into another hole, I inserted it upside down. So, that meant that what I thought was the off position, was actually on. So I was flooding the cylinder. One quick 180 degree rotation of a toggle switch and all is working perfectly.

Man, oh, man......
 
Thanks.

JR, thanks for getting back to us on the cause, and also congrats on finding it and getting the engine happy:D
 
Spring Loaded switch

My primer switch is spring loaded to the OFF position. I have to hold it up against the spring to actuate the primer solenoid.

YMMV, but I like this arrangement.

blueflyer said:
I'm glad it was something so simple, but just goes to show you how easy a little thing can cause trouble.

A few months ago, I swapped the placement of several toggle switches on my panel. While swapping the primer solenoid switch into another hole, I inserted it upside down. So, that meant that what I thought was the off position, was actually on. So I was flooding the cylinder. One quick 180 degree rotation of a toggle switch and all is working perfectly.

Man, oh, man......
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Good idea. I even have a spring loaded switch in my switch bin.

PCHunt said:
My primer switch is spring loaded to the OFF position. I have to hold it up against the spring to actuate the primer solenoid.

YMMV, but I like this arrangement.
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