woodchuck2

my truck starts great and will idle till warmed up.Then will rev way up and stop when warm.I,cleaned the tank,replaced the lift pump,cleaned prefiltre and new fuel filer.Doesn,t always rev up,may just sputter and die.any suggests be appreciated

azblazor

Maybe the OFV?

Required_Field

See my current thread "On the Road Again ..." in this forum. I am being told it could be the IP, but I'm getting a fuel pressure gauge and OFV for better diagnostics.

woodchuck2

yes, i read your posts and it sounds very similar to my problems,btw thanks blazer ,haven't cheked out ofv yet.

gorms

3 things that can cause the motor to rev up by itself are engine oil getting into intake (turbo usually), internal governor problem/sticky rack on injector pump, or throttle cable getting hung up.

If it takes longer for it to act up on a fresh full tank, or runs better by pouring cool water on injector pump it is rebuild time.

I would lean towards this, but check the intake horn or intercooler for oil to check for turbo leak. Carefully check throttle cable and linkage for fraying etc. Woul not be a bad idea to make sure shut down solenoid is pulling all the way up too.

Required_Field

I initially thought that the revving (which I don't have as much) was caused by fluctuating fuel supply to the IP, and/or by my foot trying to compensate for the stumbling engine, which then catches and revs, so that I let off, and then it stumbles ... repeat. If I understand what folks are saying about the IP, (not sure I do, would welcome correction) the plungers are sticking in the barrels, so that fuel isn't delivered in the right amounts at the right time to the injectors -- which causes the stumble, but I'm not sure why the rev. That would seem to require extra fuel getting delivered. ???

woodchuck2

a buddy thinks it may be electrical,,say fuel pump relay.I can,t see how a mechanical pump should be affected.Can someone enlighten me on this? I haven,t tested fpr yet.

Required_Field

It is surprisingly difficult to find a good clear explanation, or I am using the wrong keywords. Have a look at the links below. The Truck Trend article is great, but doesn't mention how the P7100 provides different amounts of fuel in response to throttle input. The answer is that the throttle moves a rack & pinion which rotates the plungers in the barrels, which have a helix cut into them. So the guy at the Allis Chalmers forum (sorry, I looked anywhere!) says when a plunger sticks, it'll hold the rack wherever it was, which might be open enough to cause revving/surging from the other five cylinders.
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Bosch P-Pump Fuel Injection - Diesel Tech - Diesel Power Magazine

What happens when the rack sticks or hangs up? - AllisChalmers Forum

p7100 pump problem - Dodge Cummins Diesel Forum

woodchuck2

I cracked the i,pump lines after a cold start,fuel comes out on all 6.However when it warmed up the usual hissing,I cracked no,1 but no fuel on 2.the truck stopped so I repeated,this time it revved way up so I cracked no.2 again no fuel.the stopped and I heard a ping.I fire up again and crack no.2 again and the fuel comes out but the truck stops.I,m convinced now it,s time to rebuild.Can,t think of anything else to try.