Lift pump is dead and the truck runs fine

[OO]

Don't know what to make of it but I just checked out a guys '98. 5 and the lift pump doesn't seem to run at all. Bumped the starter and still can't hear it run. I asked the owner about it and he says it's been that way since he bought it a couple weeks ago. The truck doesn't seem to care about the situation. Do those '98. 5 have some magic injector pump or the worlds quietest lift pump?

 

[Hombre]

I had the same problem. Put 5000 miles on the truck with zero pressure from the lift pump. I dont understand how the thing was running??? Its amazing how much better it runs with a new lift pump!!

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Y2K 3500 QC,SLT,AT,3. 54,4X4,DK GARNET,AGATE,LOADED,

 

[Steve Campbell]

How long will it run without adequate return flow for cooling of the injection pump?

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1999 Qcab 4x4 Driftwood
Steve

 

[mikel]

I believe there are two pumps inside the "injection pump". A kind of high volume low-pressure rotary pump and the high-pressure low volume piston(?) pump. The rotary pump MAY be able to draw hard enough to get fuel and keep the engine running, but I don't think it was designed for that. I believe it is supposed to be fed with a positive pressure so that there is excess fuel to cool the "injection pump" as a whole. I think that there is a thread that does a much better job of explaining this than I am dooing, I'll see if I can find it.

Mike

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'99 QC 2500 SLT Driftwood 2wd SB 24v Auto 3. 55 LSD
ISSPRO pyrometer, Walker 21468, 20,000 miles 12-19-00

-- email address removed --

Howdy Agg's!

 

[highland]

My lift pump went out also, and it seemed to run fine. The dealer checked pressure and replaced the lift pump under warranty. Although the truch did seem to run fine without the lift pump, it ran smoother and harder when the lift pump was replaced. I am not sure but I think the injector pump is designed to be "fed" fuel from the lift pump under slight pressure to operate as designed. Better get it replaced or risk damage to the injector pump.

 

[Chad Sheets]

The injection pump will pull enough fuel to inject. However it will not pull enough excess for cooling and lubrication. The truck will run until the injection pump dies, which could be a month or a year, or next week.

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Always ready to help!
2000 2500 Red Sport quad cab, 4x4, K&N, DDI's, straight piped, boost, pyro and fuel pressure gages, Hot Power Edge, EZ box, mean looking set of 33. 5" tires, Snap On diamond tool box, Marine Corps window sticker, Semper Fi!

1972 340 Cuda'. Original tripple Black, 340 car w/air. Good clean car, super stock springs, Weld Prostars, shaker hood, strong 340 with a 727/4000 stahl, 4. 56... . Bombs away!
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[Steve St.Laurent]

I've had two bad lift pumps on my truck - neither time did I notice any driveability problems. Although once a good pump was in there it did seem to have better throttle response. Like the guys above said - what you lose is cooling and lubrication, your fuel pressure has to go very very low (I've heard around negative 5 psi) before you'll see a driveability problem. This is the very reason that I highly recommend having a full time fuel pressure gauge on any 24 valve truck - or at a minimum checking it regularly (driving down the road under load - not sitting in a driveway at idle).



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-Steve St. Laurent - President of the Great Lakes TDR
'98 QC LB (CMNSPWR), 4x4, ISB, 5sp, 4. 10 LSD, TST Powermax, 275hp RV injectors, SW fuel pressure gauge, BD exhaust brake, Isspro turbo temp monitor, front Draw-Tite receiver, rear Draw-Tite class V receiver, BFG 285/75R16 AT KO's, (all the common stuff clipped)

 

[icarus33]

Yeah, and just wait till he has to change the fuel filter. Even refilling the cannister with fuel before reinstalling, it will probably not start. Once the prime is lost, the truck is done. Happened to a guy I know and after the lift pump was replaced, bumped the starter a couple times to run the lift pump and started right up.

icarus

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'98. 5, 2500, 4x4, LB, QC, AUTO, 3. 54 rear, Snugtop, Rhinoliner, ISB, non Cummins enhanced ECM, DDIIIa injectors, K&N, Transgo Diesel shift kit, KJones TC, Autometer boost, transmission temp, digital pyro, Mag-Hytec diff/transmission cvrs. , Redline lubed.

 

[OO]

Did the fuel filter change along with draining a completely full tank. Had to use another electric fuel pump and a lot of cranking to get it going again. The reason I walked over and looked at the guys truck is it sounded like it was running on either. Popped the filler cap and O baby did it smell like gas. These trucks don't run to smooth on unleaded. Sounded like a PSD cackling on all 8 cylinders.