Engine/Transmission (1998.5 - 2002) Uh, sounds like maybe the VP44 ?

[John - K5AWO]

My son, PJ just got his truck back together.

-98. 5 ISB 3500 DRW 2x4 93000 miles. 2nd owner since 77,000 miles.



The lift pump died (down to six psi) but he didn't know that until the truck started to have stumbling problems when it was hot.



At first it would just stumble and die when throttle released. Then it got to where it would start to stumble in cruise.



Tonight, on the first run after the new lift pump (moved to the fuel tank and now a pusher) it ran super fine until about 5 minutes after it reached operating temp, 190*.



He turned around and headed for the house and made it just fine although he was getting a bit anxious that it might stop altogether a mile from home.



Fuel pressure is holding 14-15 psi all the time. He didn't do any WOT, just normal up ramp to the freeway and go.



I was wondering if it might be a wiring issue somewhere, but we also thought it might be something effected by heat soak.



My question is: Since it works fine cold, why the problem when at operating temp? I feel it is electrical but maybe not.



John

 

[lcoblentz]

Mine is acting the same way. Runs fine when cold, but stumbles when warmed up. It's going to the dealer on Monday, and I'll post results. BTW, I am showing a P0216 code.

 

[A Johnson]

I can't remember the exact terminology, but the early pumps had a problem with the VP's computer loosing a connection when they get warm.



A Johnson

 

[lcoblentz]

Just got home from the dealer. The service advisor came over to me and said, "Looks like you need an injection pump. We'll get started on it, and call you later today when it's finished. " I was impressed! They checked the lift pump, and said it was good. I may replace it anyway, just for my own peace of mind. Very amazing that they had the VP44 in stock. Or, perhaps that's a message... .....

 

[John - K5AWO]

Definitely add a new lift pump to the job. I would also install a pusher pump at the tank to be sure the lift pump doesn't have to work so hard. The Holley RED pump is sized right with about 5-7 psi push pressure.



mallory makes some good pumps, and the carter pumps.