Engine riddle for you..... Two dead cyl on left Side?

[N941WR]

I'm with the others, this doesn't sound like an ignition issue. Two mags, four wires, or four plugs just don't go bad all at the same time.

That leaves the primer, induction, and exhaust.

The fuel puddle is a new clue. Remove and inspect everthing, starting with the primer.

[RV10inOz]

And maybe don't reinstall the primer!

[WA85]

I had a similar problem years ago on an O-320. Out of the blue, I had two of the hydraulic lifters/ tappets on the same side fail due to the internal check valves getting stuck open due to blockage, preventing the valves from opening all the way. I think I had one intake and one exhaust, could have been both intake. The symptoms were two rough running / dead cylinders on the RH side. Since the both lifters were not "pumping up", the valves didn't open properly, thus it passed a compression test easily. I did everything you did until I pulled a valve cover and found the two valves were barely opening. I removed the push rod tubes / rods and attempted to remove any debris from inside the lifter by squirting solvent into the center hole and sucking the debris out with a vacuum. I then re-installed everything except the valve covers and rotated the engine over until oil pressure was indicated. I measured the valve action at the rocker arm and they worked OK after that. Whatever I did, it worked and the engine ran OK afterwards. Your issue may not be related to this at all, but it might be another idea to help you in your troubleshooting.

[abnranger69]

Well, winner winner, chicken dinner!

It was a primer pump issue. Had a failure in the primer pump solenoid that was allowing max fuel to be pumped into the L side cylinders, thereby "drowning" them out/over rich. Totally makes sense now.

Sure appreciate everybody's input, definitely helped me sort through things. Start simple and work from there..... learned a lot!

Thanx again!

Dave

[turbo]

[humptybump]

Thanks for the update Dave. Good sleuthing!

[n82rb]

glad to hear that you found it and it was a easy fix.

bob burns
RV-4 N82RB

[dave4754]

I was looking into the primer issue as I am now into the QB fuse and doing my fuel system.

This reinforces my opinion that I think I will use the manual piston primer and keep it simple.

When I phoned Vans they asked why I needed one, of course they rarely see -20 C flying days like we do here in Canada. Nothing like a crisp cold day of flying over a white landscape eh?

Thanks again.

[Walt]

Better yet just go with fuel injection, no primer, no carb ice

[ao.frog]

I'm impressed: this guy was right on! Way to go Paige!

Originally Posted by PaigeHoffart

This is a bit of a reach, but do you have primer lines to the left cylinders only? A stuck primer solenoid causing them to run way over rich at idle?

Paige