M818 fuel knock in Cummins

[gem1410]

My M818 has 48k miles--starts fast--idles at 625 rpm--comes up to running temp--it has low power and is very slow getting up to 50mph. It has what sounds like a fuel knock all the way up to 45mph--Over 45mph the noise goes away and the engine sounds OK--The noise comes back as soon as I go under 45mph--Any ideas what this might be--Thanks

 

[WillWagner]

Any unusual smoke?

 

[PorscheTech911]

Did you check for water in the fuel or the condition of the fuel filter?

 

[gem1410]

Seems like some unburnt fuel is going out the exhaust

 

[gem1410]

The fuel looks clean although I will check the filter on monday

 

[gem1410]

may have a bad injector--will try cracking each line to find the bad one--I have never worked on these engines--how hard is it to get at the injectors----Thanks

 

[bigmike]

may have a bad injector--will try cracking each line to find the bad one--I have never worked on these engines--how hard is it to get at the injectors----Thanks

cracking the line will do what? what are you looking for when doing this?

 

[gem1410]

find which injector is not working--I am looking for the engine to run rough if the injector is good with the fuel line cracked and for the engine to run the same with a bad injector cracked at the fuel line

 

[WillWagner]

may have a bad injector--will try cracking each line to find the bad one--I have never worked on these engines--how hard is it to get at the injectors----Thanks

If you have an 818, you have an 855...no injector lines to crack. Does it miss at start up? The N/A 855's do have a rattling sound on acceleration. You say you see unburnt fuel out the pipe. What color is it?

 

[bigmike]

find which injector is not working--I am looking for the engine to run rough if the injector is good with the fuel line cracked and for the engine to run the same with a bad injector cracked at the fuel line

got it...thanks

 

[gem1410]

Yes it misses at start up--gray--it seems to puff--

 

[Floridianson]

The fuel looks clean although I will check the filter on monday

Don't forget the fuel screen on the TP under the big flat head screw on top.
Could your emergency shut down valve not be reset all the way. How are the rubber lines on the transfer valve?