Engine/Transmission (1998.5 - 2002) LP pressures at start up.

[Ncostello]

This should be an easy one. When my truck is running, I see anywhere from 15 to 17 psi on the lift pump pressure at idle. WOT under load never sees below 14psi. Maybe I got a good one when I bought this one.



When I first turn on the ignition without starting, the LP runs for about 3 to 5 seconds, the pressure goes up to 15 psi. Then the LP stops and the pressure starts dropping to basically 0 again, until I start the truck, at which point it goes right back up to 15psi.



Is the system supposed to retain any pressure at all. I mean when the lift pump runs for a few seconds when I turn on the ignition switch, should it drop to say 5psi and hold until I start the truck. Just wondering if its normal to drop down to 0 psi again.



I didn't put on new banjo washers on when I installed the new LP. Schied didn't tell me I'd need any. And I couldn't wait another day for them. The old ones looked fine. And It doesn't leak. I was just curious as to where my pressure is going... unless its going right back to the tank.

 

[Shovelhead]

Mine operates the same... ie Fuel Pressure drops off after lift pump cycle.

 

[Steve St.Laurent]

Completely normal. Fuel pressure will go back to 0 after the lift pumps stop running.

 

[Ncostello]

Thanks...

Thats what I needed. If I install a low pressure pusher, the VP should be fine with 7psi or so on startup even if the pusher continues to run, as long as I wait for the OEM lift pump to stop and its pressure to back off after turning the ignition to the on position.



I'm getting the parts I need to use a low pressure Carter, along with a bypass and checkvalve, and also looking at a low restriction Raycor Filter setup, like so many are using.



I couldn't be responsible for how the previous owner took care of his lift pump, filters, and consequently the VP injector pump, but when I get my new VP (in the works), I will make sure its taken care of.



All I feel I need is a fresh clean supply of fuel at the right pressure, a permanent guage to monitor it all, and everything should survive fine.

 

[kaptn]

Wow I have been checking your posts lately and you sure are the busy bee arent you. (LOL)

 

[Ncostello]

Yes, more like a swarm of bees. I've wanted a Dodge Cummins for 10 years and now that I finally have one, I've got some problems. But they will be resolved. And when I get done, I'll know this thing inside and out, bottom and top. I'll be able to diagnose and fix about anything that commonly goes wrong. I look at it as post-warranty training. hehe. I'll have to admit though, I've owned 7 different trucks, Dodge, Chevy, GMC, Ford... all of them, both 4x4, 2x4, manual, automatic, V-8, 6-cyl, ranging from an 84' to a 98', and this truck is by far the best... and the worst in many respects. I didn't work on all the other trucks combined as much as what I have with this Dodge. But I still like it. When I get all the little bugs worked out, I'm sure it will run great and I'll keep it that way... for a long time.

 

[WadePatton]

If the ECM ever gets reflashed, the LP will cycle on for about 1/2 second at key-on and won't build more than 5# pressure.



I think it's the "hard start-warm" update, but it was piggybacked with my "intermittent stumble" TSB.



I like it, less work for the LP.



I too, wanted one for years, but just got mine this June. Very glad I waited for a 24, and EXTREMELY happy I didn't wait until 3G's dominated the market.