Engine/Transmission (1998.5 - 2002) Lift Pump Change and Pressures

[DavidC]

After installing a Westach 0-16 PSI fuel pressure Gauge and new fuel filter and noticing a slight power decrease towing 32' 5th wheel (which started all this).

Original Fuel pump, truck only 33000 miles. All readings post filter.

Idle = 11psi

Cruise = 8-9psi

WOT = 5-6psi



After a visit to Cummins Rocky Mountain in Phoenix (formerly Cummins Southwest).

New pump installed,truck only.

Idle = 14psi

Cruise = 13psi

WOT = 10psi



Will be interesting when the 5th wheel gets connected what it will do now.

Parts breakdown include,

1 each 3990105 pump @ 145. 95

1 each 4025182 wiring harness @ 7. 48

1 each 3935171 sealing washer @ . 96 (Bag contains 4 washers)

1 each CPB discount @ 15. 45

Total cost after taxes = 150. 19



The complete change was done from the top, did not remove anything except the pump assembly. Taking my good old time it took about 1 hour and 30 minutes. Now the idle pressure at 14psi I think coincides with the fuel return pop off that the service manual states is set at 14psi to open. If I am right about this I should not expect to see anything above 14 unless the return valve gets stuck closed or cannot handle the volume supplied to the valve or associated plumbing back to the tank. Am I correct in this ?

 

[jwinnie]

I see 14 psi 90% of the time with my new lift pump, 13 psi on the highway. every couple of days it spikes to 15 or 16 psi, not sure why, could be my cheap Nordskog guage

 

[AKostman]

Just had a new pump installed 3 months ago, installed a westech gauge at the filter. Idle 16lbs cruise 15 wot 12. Gauge seems to be acurate. Pump # is nothing like the ones I've seen on forums?

 

[Jack in Alaska]

Lift Pump

I had a new lift pump installed, under warranty, about 800 miles ago at 93,800 miles. Old one,original, was erratic.

It now idles at 15 psi, cruise at 13 psi & wot at 11 psi. using my Westach gauge at the filter.

Truck seems to have more "get up & go" since it was changed although that may just be my imagination.

 

[RustyJC]

I have the Westach combo dual fuel pressure gauge measuring pre-filter and post-filter. At idle, I see 16 psig on both gauges. At WOT, I see 12-13 pre-filter and 11-12 post-filter. The truck has about 8,600 miles on it; still on the original lift pump.



Rusty