I see, but I don't know what the wiring from these LPG emulators internally looks like, so maybe that is why the ECU doesn't recognize an error?

 

That is entirely possible. I have no idea how the LPG system actually works... .as I have never had to play with one. Would it be overly difficult to completely bypass the LPG system, see if the problem goes away??

 

Basically it is a 2nd set of injectors with a seperate control unit. I already tried it and bypassed/shorted the emulators (they emulate the fuel injectors when on LPG) and pulled the fuse of the controller. But the wiring is still in between though.

 

Yeah, try swapping injectors. That will at least tell you if the injector is at fault, or the wiring.

 

Yeah, I will try that for sure.
Will have some time on thursday, the plan is to:
change the other spark plugs now they arrived
swap the injectors 5 <-> 7
follow the whole wiring from the injectors to the ECU and check the wiring to the LPG emulators there

I already did renew (shrinking soldering connector) the wire from the ECU to injector #7, but it seems that this was not the cause.

I also have a leak down tester here, but haven't tried it on a big engine like that though. Will have to go into further reading how it works on a V8. Have been using it on an inline 4 only.

If all this fails I will take it to a shop though for better inspection with some Chrysler testers (there is a workshop who has been a Chrysler service department a while back).

Thank you again for your help!
I hope I can figure this out.

 

Works the same way. Turn the cylinder you are testing to top dead center, in firing position, (both valves closed) and test away. On these engines, supposedly, "up to" 25% leakdown is 'acceptable'.....

 

Yeah, will try that or a compression test first maybe?
But I don't think it is something mechanical that is wrong. That would be present at all times, not only on petrol?

And I read a lot about broken lifters and stuff, but wouldn't that throw more codes? At the moment I don't have any code at all, the P0307 I had in the morning was gone when driving home.
Very odd really.
I still think it is some electrical problem, but I'll have to see...

 

I think it's an electrical problem as well. If it were mechanical, what you were trying to burn wouldn't matter.

 

I will have a major go at it tomorrow when I can use a friends' workshop so my fingers won't freeze too fast.

Will replace the spark plugs, remove the injectors, check and clean them, check the whole injector wiring circuits and test it.

I hope that the problems will be solved then, but if they aren't I think I will have to remove the cam covers maybe.
Even though I can't think of any explanation at the moment why it would run different on LPG with a e.g. broken valve spring or worn cam lobe or broken lifter or something...

 

I agree with ya, I really don't think this is a mechanical issue......