BILTIT

Just installed my LP piston pump today since i was seeing 0psi with the diaphragm frequently. Fired it up and had 9-10psi, drove it around and it doesn't get under 5psi. Cool i thought. Went on a 2hr road trip and am seeing 0 at times and up to 8psi other times, strange.

I am going to verify my pressure sensor isn't shot, anything else that could be causing a low pressure? Fuel filter may have 1000km on it.

jimbo486

You didn't buy a Delphi pump did you? The Delphi pumps run at a lower pressure than the Cummins or Carter lift pumps.

BILTIT

Yes it is a Delphi, got it from dieselautopower. Didn't know they run lower pressure, can the spring be shimmed?

autocar56

Fuel restriction , something in the tank or plugged fuel line. If it is running good, no noticeable power loss or hard starting issues I would thing bad sensor or gauge,

BILTIT

It runs fine, maybe even better than before.

j_martin

Any rhyme or reason to the low and high pressure readings, ie low at full throttle?

bgilbert

DAP sells the wrong one. It's not an equivalent to the 3936320 low pressure Cummins pump. It's really no better than a stock replacement diaphragm pump. Also 9-10psi is normal for their pump. 12-18psi is normal for 3936320.

d22019

That is good to know. I was getting ready to buy on of those kits but didn't like the fact that there was no info who who makes the pump. I'll just get the correct one form cummins.

JBradley500

yeah that pumps not great. my cummins pump would run over 20psi.

bigjohn92

I have the cummins low pressure lift pump it runs between 12-20psi good upgrade. It's not an equivalent to the 3936320 low pressure Cummins pump. 12-18psi is normal for 3936320. This is by far the best up grade I've made to my 92 dodge cummins. I also was going to order this kit dap sells.

I'm thinking u may have a fuel restriction my only guess.
john

BILTIT

No rhyme or reason, its all over. I will start with a mech. gauge to prove the sensor. Thanks for everyones info, i might just purchase the proper cummins pump.

NJTman

How does having greater fuel pressure benefit the IP ?

EDIT:

Never mind. It prevents fuel starvation with larger injectors....

Good OLD thread for part #'s, BTW.....

https://www.dieseltruckresource.com/...mp-t84412.html

BILTIT

Yikes, called local cummins shop and they want $382.37CAD for the 3936320 (new #4988751).

jimbo486

I only paid about $186USD for mine. Maybe a Cummins dealer across the border can sell you one and send it to you.

BILTIT

May have found one here, will see when it arrives.

http://www.cumminspartsdirect.com/Ca...ift-pumps.aspx