Engine/Transmission (1998.5 - 2002) Bumping the lift pump.....won't

[SSovaiko]

99 2500 24v w/3000miles on new lift pump



I recently noticed that the lift pump will not cycle when turning the key 'on'. Does the ECM, or other timer circuit, control the lift pump pre-start key-on cycle?



In recent months, I noticed that I sometimes didn't hear the pump cycle before start. But now that I added the Superchip stage 1 ECM program, the pump rarely ever cycles on at key-on. When starting, the engine will die or stumble until lift pump builds pressure at engine crank/start. Once the lift pump is running, the engine runs fine - but the trick is to crank it to get the lift pump to run. Occasionally, the lift pump will bump cycle for 1/2 second or so at key-on, but it's rare.



Any ideas other than removing the Superchip program? I guess I have no fuel filter changes for awhile as I can't easily refill the filter... ...



Oh, Idle pressure on the pump is 15psi.

Thx



Steve in CO

 

[RAJohnson]

SSovaiko Welcome to the TDR. Oo.



Did this problem occur before or after the superchips . I think the ECM does provide the start signal to the LP. Hopefully others with more knowledge will chime in.



This should Bump it back to the top.

 

[Bob Cochran]

I changed my lift pump with one I was carring as a spare purchased from Cummin's about 5,000 miles ago. Scary because fuel pressure when to zero half way between La Junta Co. and Taos NM pulling a 14,000 lbs 5er!!!! Also program with Super Chips heavy program when towing, high performance when not. I have not had the problems you described. Wish I could help accept to say I am not having the problem.

 

[Jetson]

Check this: turn the key on but do not crank it for 6 or 7 seconds and see if the lift pump is delayed.



Mine does this occasionally and I did not notice at first but the Wait to Start light and the lift pump both are delayed. Sometimes it comes on right away like it is supposed to. This may be a problem with the ECM.

 

[SSovaiko]

The lift pump almost always seemed to cycle prio to the SUperchip load. Now it never cycles... I've resorted to bump-cranking the starter to get the pump to run for 30 secs or so. It will not pump, no matter how long I leave the key 'on', unless I bump the starter, so it doesn't seem to be delayed - it just isn't there until the starter gets bumped.



Related note - the grid heaters also seem erratic - they seem to stay on just as long and cycle on/off just as much at 70F as they do now at 5F... . are these timers located together in one box somewhere?



Thx



Steve

 

[Jetson]

Try resetting the computer. Disconnect the battery cables for at least 30 minutes. Then turn the key on and connect the negative then the positive cables. This is supposed to reset the computer. It sounds like the ECM is not initializing like it is supposed to.



I think the IAT sensor (intake air temp) sends the signal for the heater grid. You can try removing it and cleaning it with carb cleaner. Also use some electrical contact cleaner on the connectors.