Engine/Transmission (1998.5 - 2002) New lift pump behaves different

[RDBuck]

Installed a new lift pump-Cummins part#3990082,susposedly the latest upgrade?-but it does not do anything when I bump the starter. It puts out good pressure when the truck runs-14# at idle and 8-10# at cruise. The "old" pump(6 mths) was totally erratic but it would put out 12-14# when the starter was bumped with engine not started plus you could hear it run. With engine running the pressure would drop to 0-1# then bounce to 10-12,sometimes stay there and other times drop back to 0 and stay there until the truck was shut down and restarted and then the presuure would go through its' routine again.

My question-is anything different about this "new" pump? It seems to operate exactly opposite from the old one-no pressure when "bumped" but fine with the engine running.

 

[nps]

The pump running when the starter is bumped is a function of the ECM - not the pump. The ECM supplies the voltage to turn the pump on and off. So what you describe doesn't have anything to do with your new pump.

 

[sethAdams]

Installed a new lift pump-Cummins part#3990082,susposedly the latest upgrade?-but it does not do anything when I bump the starter. It puts out good pressure when the truck runs-14# at idle and 8-10# at cruise. The "old" pump(6 mths) was totally erratic but it would put out 12-14# when the starter was bumped with engine not started plus you could hear it run. With engine running the pressure would drop to 0-1# then bounce to 10-12,sometimes stay there and other times drop back to 0 and stay there until the truck was shut down and restarted and then the presuure would go through its' routine again.

My question-is anything different about this "new" pump? It seems to operate exactly opposite from the old one-no pressure when "bumped" but fine with the engine running.

I just purchased a new LP from cummins today and it charges as soon as you bump the starter.

 

[RDBuck]

The pump is behaving normally all of a sudden. It charges when bumped and holds 14# for 25 seconds just as it should. Have no idea what happened.



Seth, what was the part # of your pump?

 

[sethAdams]

it was 3990082 was the pump and wire combo.

 

[BrysonSmith]

cummins lift pump

I put a new cummins lift pump on 3 weeks ago. I get 16 when I bump the starter, 14-15 at idle, and 11 at 70mph.

 

[cromptrj]

2002 2500 4x4 6 speed HO 4:10 gears 70,000 miles on truck it has had 1 new lift pump and also a TPS ran really good for a while then it just started pulsing at highway speed dont matter what gear or throttle position or how hard its running it just pulses RPM is swinging all the time it has a edge comp on it but still the same problems with or without the box

 

[Joe Mc]

A few years back I purchased an LP from Cummins and it was 10# @ idle and dropped to 4 @ WOT - this is before sticks and comp. The parts counter guy told me he'd give me another pump but I'd have to pay full price and deal with the warranty Manager for refund??? I went to Cummins web site and blasted them (nicely) mentioning TDR and (at that time) the other 15k members with same pos LP. Received a call the next day asking where to send the check - no questions asked about wanting the pump back either. Guess I got lucky.

 

[mhenon]

2002 2500 4x4 6 speed HO 4:10 gears 70,000 miles on truck it has had 1 new lift pump and also a TPS ran really good for a while then it just started pulsing at highway speed dont matter what gear or throttle position or how hard its running it just pulses RPM is swinging all the time it has a edge comp on it but still the same problems with or without the box

That pulsing you hear is probably the early spasms of death for the VP44. It's just what mine did before I had the dealer change out the VP and LP.

Mike