Engine/Transmission (1994 - 1998) 94-12v Hot Missfire

[MartyAdams]

My 94 runs great cold however I began to notice an uneven idle last fall when the engine was hot. I changed the fuel filter and checked the lift pump pressure and all seemed fine. Recently when the engine is hot and shut off then restarted a short time after there is a distinctive miss and a loud clicking noise from the injection pump. The symptoms goes away only after the engine stalls and I let it sit for a few minutes. I thought it was air however I checked for signs of leaks and I cannot find any. When I do a hot brake stall in the driveway to wot and then ramp the engine back down to idle it surges for about 20 seconds and then returns to idle. The engine also seems to flutter at idle unlike the usual rock stable rpm. I suspect the flutter and surging is due to missfire however the clicking from the injection pump has me stumped. Any ideas or help would be appreciated. Also note that this engine has been installed as a repower with the complete dodge drivetrain and computer. I have been driving it for 1. 5 years now and this is the first trouble I have seen over the last 3 months.



Marty

 

[Signal73]

Any ideas on how many miles the Overflow valve has on it?

 

[MartyAdams]

The engine has 77 000 kms on it. Is the overflow the valve that which controls the return of fuel to the tank? Also I should have mentioned that when I changed the fuel filter I notice a pick up in power so the filter was more than due for a change.



Marty

 

[Signal73]

Yeah, Thats the one. I only threw it out there because when its bad, I recall it makes a clicking noise, And will cause low power symptoms. But if your FP is ok, and it runs good cold, Im not sure if thats it. Have you checked and cleaned the Pre filter bowl strainer?

 

[ALehman]

The best thing to do with the prefilter assembly is bypass it. Its known for sucking air.

 

[MartyAdams]

I pulled the overflow valve tonight and I could not find anything wrong with it. The spring seem strong and it does not appear to stick in anyway. Also cleaned the prefilter and there was a few bits in it however overall not bad. I tried to make it suck air by leaving the prefilter loose and when it did such air the engine would just quit. This is a different symptom than what is happening when the engine miss fires. I am thinking I may have an injection pump barrel piston sticking although with lots of fuel nothing should be getting hot. Any ideas? Any fuel injection pump experts who could help me diagnose the injection pump?

Marty

 

[Matthug]

I have a similar problem, not the clicking though but the miss. I think an injector is gummed up, but I have a set of brand new 300's to install soon.

 

[Andy Redmond]

I confer injector, delivery valve and maybe governor issues.



Run some good injector cleaner through it for a few tanks and then each 10K or so as a preventive measure.



Let us know what you find. .