Engine/Transmission (1994 - 1998) Injection Pump Problem?

[Jschafer]

The last three times that i have driven my truck for any length of time (over one hour) on the highway running around 70 75 mph I have gotten a slight vibration in the engine and it will come and go in a cycle maybe 15 seconds or so then run smooth again. It runs and starts perfect around town no problems, it will do this for ten minutes or so then quit, also twice when I started it after running a while it has really serged at idle like a gasser with a BIG cam.



The last time I checked my pressures they were a little low and I new I needed a new lift pump. Sunday I installed a new Lp and filter and found the check valve to be bad on the old one plus 350 k on it.



Today I pulled the dump trailer about 40 miles to the dump then 5 miles from home the truck starts to shake like a bad tire or something I let off the throttle and it stops then i get back up to 70mph and it happens again, after the 3-4 th time I let off and the engine stays at rpm for just a second with my foot off of the pedal I get off at my exit and all is well again.



I looked everything over for fuel leaks but every thing is dry



I havn't checked the pressure on the new pump yet but will try to get to it tomorrow



Any Idea's



Joe

 

[Vaughn MacKenzie]

How many miles on the injectors? Sounds like an intermittent slight miss. If they're original time to have them checked out or replaced. You might try a double dose of fuel conditioner as well as a can of Sea Foam to see if that helps.

Another thing if you haven't done a valve adjustment in the last 50-100k might give that a shot too.

Vaughn

 

[Jschafer]

Thanks Vaughn



I replaced the injectors this past fall with a set that were cut like a marine 370 probally 10 k ago they have been fine, they only had a few miles on them, I was told.



The valves probally have around 50 -70k since adjusted, I did put conditioner in this last tank but just the minamum also I put a new rubber supply line on as the old one had a few crackes, the return line was new last year and looked perfect.



What is sea foam is that like a dry gas?



I was wondering if it could be the return valve loosing its seat?



I will have to check the Valves and maybe switch the injectors if the pressure checkes out

 

[MMcCallie]

Gosh, actually sounds exactly like the last time i had a loose driveshaft. Are you sure it is an engine problem? Maybe next time try keeping the RPM where you feel the vibration and put the gear shift in neutral.

 

[Jschafer]

also twice when I started it after running a while it has really serged at idle like a gasser with a BIG cam.

Not a driveshaft

 

[JTEdieselram]

Ha Ha, check to make sure your gas cap is good! I had a similar problem, what happened was that the gas cap would not vent, causing an extreme vacuum to occur in the tank starving the injection pump, it would only do it to me on the highway, and it actually caused the truck to flat out die several times. Cheap fix if thats all it is,