Engine/Transmission (1994 - 1998) Rough running 12 valve

[JTeague]

A buddy of mine has a 95 5spd 2wd Dually that misses and runs rough after driving for about 10 miles or so at above 60mph. The truck will begin to miss and lose power while driving at a steady speed. There is not smoke of any kind from the tail pipe. THe truck will start to run right when the throttle is wide open after the missing starts. After the throttle is released from wide open, the engine will bump the governor for a couple of seconds and then die if clutch is depressed. The engine will restart after about 5 seconds of cranking and then will run properly for a couple of miles before acting up again. I first checked the fuel pressure, it was low due to a dirty filter and a broken overflow valve spring. After that we had 22 psi at idle and 28psi at WOT. The problem was still there. After that I checked the obvious things like fuel lines and preheater for air leaks, fuel shutoff solenoid, pre filter, and for a clogged sock in the tank. All were o. k. He then decided to replace the transfer pump, this also did not fix the problem. I am running out of ideas as to what is wrong and am beginning to think the injector pump is the culprit. It just doesn't make sense to me why the problem is intermittent. BTW the truck has ony 144k. Any thoughts would be appreciated.

 

[scramblin]

Originally posted by JTeague

A buddy of mine has a 95 5spd 2wd Dually that misses and runs rough after driving for about 10 miles or so at above 60mph. The truck will begin to miss and lose power while driving at a steady speed. There is not smoke of any kind from the tail pipe. THe truck will start to run right when the throttle is wide open after the missing starts. After the throttle is released from wide open, the engine will bump the governor for a couple of seconds and then die if clutch is depressed. The engine will restart after about 5 seconds of cranking and then will run properly for a couple of miles before acting up again. I first checked the fuel pressure, it was low due to a dirty filter and a broken overflow valve spring. After that we had 22 psi at idle and 28psi at WOT. The problem was still there. After that I checked the obvious things like fuel lines and preheater for air leaks, fuel shutoff solenoid, pre filter, and for a clogged sock in the tank. All were o. k. He then decided to replace the transfer pump, this also did not fix the problem. I am running out of ideas as to what is wrong and am beginning to think the injector pump is the culprit. It just doesn't make sense to me why the problem is intermittent. BTW the truck has ony 144k. Any thoughts would be appreciated.

My last truck did the same thing. It was the injection pump. But my truck had 375kmi.

 

[Jim Fulmer]

JTeague Sounds like you covered all the bases except timing but I doubt it would help, next thing I would do is contact a know pump guy... . hum... . Piers comes to mind!



Jim

 

[PUMPERDUDE]

What is the fuel pressure doing when the problem occurs?Sounds like you're catching air. At 144k miles the fuel lines are probably toast if they havent been changed already. One other thing to check (long shot ) is your pickup tube in the tank. I've read here that a few have had pinholes chaffed in them causing intermittent problems at certain tank levels. Good luck.

 

[Piersol]

Does the 1995 have a catalytic converter? Maybe its plugged.

 

[JTeague]

Thanks guys for the responses. I have already replaced the fuel lines from the body to the engine and checked the lines from and in the tank. The timing is at 15 deg and the cat is gone. The only thing left is the injector pump and injectors. The fuel pressure remains constant between 25 to 30 psi when the problem occurs also. I guess the next step is to pull the pump and have it checked out on a test bench. I guess the P pumps break too

 

[Jeff H]

Any strange noises? My pump made loud ticking noises when it went bad. Had a bad barrel. I was told that 1995 trucks have a higher failure on inj pumps than the others.

 

[JTeague]

Jeff, It does start ticking also when the problem occurs. I bet it has the same problem as yours did. Thanks.





Jason