My Lift-pump has been loosing pressure over the past several months and it is down to 12psi at idle and 10psi full throttle. When should I say enough and replace the pump?

 

Well if it were me, I would do it now and not risk it failing early. I wouldn't want to risk losing the fuel pump as well.

 

Just replaced mine had 5 psi at idle and 2 psi at 2000 rpm no load saw something on the diesel doctor about pressure, have a gauge ordered so I can monitor the pressure and when it gets low will change if I remember right 12-10 is not real bad.but I sure ain't no expert

 

I haven't seen one with only 2 PSI difference between idle & WOT.
Usually it's more like 5-7 psi difference.


I'd change it now, and keep the old one for a "middle of the night in the middle of nowhere" spare.

You KNOW it's dying, don't wait until it leaves you stranded.

 

Yeah I guess I will go ahead and change it out I already have a new one so I guess there is no reason not to. I was just trying to get as much life as I could out of the old one since these things go out so much. Thanks for the help on this guys I'm going out to the barn to change it now.

 

I have learned the hard way about having a fuel pressure gauge. My original lift pump lasted 70k and at 71k I got a freebe from a good dealer, on Warranty. At that time I had 3 gauges,boost ,EGT and tranny temp. ( on a A pillar pod) now I also have a isspro 0/30psi fuel pressure gauge mounted in the cubby next to the radio,and just below the air bag switch. Before I installed the gauge, the only way I could test the pressure was with a test tool that would hook up at the schrader valve on the VP44 . So after I hooked up my gauge yesterday, I used the afore mentioned tool to bleed off the air before starting up the truck. On startup,I was happy to see 15psi. but after starting off on a test drive, I saw the gauge drop to 4psi. After installing the test gauge on the vp44 I saw 4psi also
Well tommorow I go to the local stealler for a new lift pump.(on warranty) I still have 18k on my 100k extended warranty.

 

I'm sure my lift pump is starting to fail, Just recently when starting from cold it reads anything from 3-9 psi, and then slowly goes upto 11 psi, wot is about 7-9 psi, and cruising is 10-11 psi one question i would like advise on is which replacement to get, an OEM, or Carter 4601HP, as i can't afford a FASS system, or are there any other suggestions. Thanks....

 

FYI-
Bad lift pump presure=major injector pump problems!

 

If you go with the Carter pump you will have to lose the banjo connections for a pair of 3/8 barbed fittings with 1/2 NPT thread. Not a bad thing since they flow better than the stock fittings.
I would also suggest that when replacing the pump that you move it down on to the frame rail, you will just have to extend the factory harness to get power to it. It should live a long, long life in it's new home.

 

Just get the Fass or the Rasp now and be done with it, 4 lift pumps for me($700) in 76k, shoulda went Fass long time ago, would have been money ahead, now with the Fass I have 4 yr warrenty or 100k.

As soon as the lil womans 04.5 shows any weakness in the pump a Fass is goin on.

 

Thanks guys, unfortunatly as i said FASS is out of the question for the time being, so it looks like it's going to have to be the Carter for now and then save some serious dosh for a better system in the future. Thanks again..........Ade

 

Check your local Cummins part house.
Their price is usually $100 or better LESS than the dealer for the exact same part.

 

10 psi at full throttle is a great pump under most any condition. If you can not get it to go below 10, leave it alone. 12 psi at idle is also a "good pump". Until you see something around 5- 6 psi at WOT. I personally say don't fool with it. If you need security, buy the new pump, change it out and keep the one you have now as a spare.

 

I went ahead and replaced the pump since I already had a new one. I am taking yalls advice and I threw the old pump in my toolbox (wrapped up and in a box ) so if I have any trouble I can pull over and 30 minuets later be hauling again. Thanks for the help with this.

 

Now you have one less thing to worry about.

My 1st pump is sitting on the shelf.
About the same pressures you saw @ 37,000 miles.
Pump 2 is now @ 76,000 and still 15 psi idle, 10 @ WOT


It's sure nice to be able to glance over and see how it's doing at any moment with a full time gauge.