Interesting issue…

[Stretch2126]

So I’ve recently come across what I think is a stuck open injector on an LNF. Everything was running fine until after a pull I let off and idle stumbled real rough the first day and cleaned up after a second. Afr was around 10-1 or .69 lambda. Next day start it and do some logging and after the WOT pull it misses like crazy and barely runs, puffing one smoke out of the exhaust. First I thought something let go finally but it smelled like raw gas. Plug was not hurt but soaked in fuel. Idle was at .66 lambda or somewhere in the 9-1 range. Going to do a compression test later and check piston height but I think it’s ok.
Mostly wrote all this to see if anyone else ever heard of a stuck open injector on a LNF. Didn’t see much online. Maybe time to look at opels.

 

[Desert Sasqwatch]

All injectors are electro-mechanical and subject to wear and tear, so having one fail open is not unheard of - but this is the first reported failed LNF injector I recall seeing on this forum. As we know the LNF injectors are a 'set'. Assume your donor had some miles on it? Since one has failed it's probably best to replace all. If planning more HP or E85 use the Opels are a good investment, otherwise the stock LNF injectors are good to 400+ HP with gasoline. Gives us a follow up for what you find, will be good info for the other LNF builders to know.

 

[Stretch2126]

Yeah my engine and transmission have 143k so it’s likely it was just its time. It was absolutely a dead miss so that didn’t feel great but on the tow home I was thinking on how the previous run the fuel pressure would drop and jump around 200 at idle. My minimum is set at 400.

 

[SmsDetroit]

If I run mine to redline in first I get a dead miss and have to get out of it. If I push the clutch in a rev it several times it clears out and runs fine. Only does this at the top of first gear. If I shift around 5500 rpm’s no issues.

 

[Stretch2126]

I found out the fun way. I turned the key on and watched fuel dribble in past the injector just with the low pump. I’m off to find a new set lol. On the tow home I had the key on so I’m sure that wash gave me lower compression, but the rings are hopefully alright cause it didn’t run long with the miss.

 

[Stretch2126]

Ran a compression test after it aired out a little. Not sure if some of the gas was still in the rings but I got 150psi on the problem cylinder and 175ish on the others. I put a little oil in it and let it set for a couple days. I’m really hoping the rings and chamber are still usuable.