Engine/Transmission (1994 - 1998) Lift Pump

[Buck88]

So I think my lift pump is going out. There is a ticking noise coming from that area, and I've heard people say it's the lift pump. Would poor fuel economy be a sign of a bad LP? I'm getting about 14 around town with the mods listed and a 3K GSK, 4:10's. If I do need a new LP, where is the best place to get one? I looked on E-bay, but no luck. Appreciate it guys! - Buck

 

[EKlem]

The lift pumps rarely die. Many people have the ticking that you are talking about with pumps that still seem to run fine. The drop in fuel economy that you are seeing could well have to do with winter fuel.



Do you have access to a fuel pressure gauge? That would give you a better answer.

 

[Greenleaf]

Test the pressure of the supply system. Use an adapter fitting. The one Geno's Garage sells is a fit all, though it is advertised to fit only the ISB engines. Duh. Called the tapped banjo bolt.



If you get a gauge on that, you most likely need a pinch valve of some sorts to dampen the pulses. Otherwise the reading will bounce 17-22 psi.



Look for 20 psi at idle speed. If the overflow valve is going out, you will see much lower than that. To test the LP, simply pinch off the return line near the injection pump with the engine at slow idle speed. If the LP is sound, it will build pressure rapidly. If not, you likely need a new LP. The LP's are superceeded many times over, so the new one will likely look different but will work just the same.



I buy mine from a Cummins Branch (supply) House and skip/bypass the middle man. Save about 60. 00 per lift pump that way.



I alway feel like I have to explain I have 1st gen trucks, but also have a fleet of 12 valve school buses

 

[Timebomb]

Mines been ticking as well. Ive gotta check FP as well. It breaks up a bit above 2600 like theres a lack of fuel, with the pumps mods there shouldnt be... lol

 

[BigPapa]

Better watch out! Timebomb's ticking!



My LP was ticking, too. Read here:



https://www.turbodieselregister.com/forums/showthread.php?t=170443



I changed my fuel filter and it quit ticking. Now, 1000 miles later it's ticking again. My personal opinion is that this ULSD is knocking all the gunk loose in the hauling equipment, pumping equipment, and our fuel systems and that stuff is clogging up our fuel filters.



Scott

 

[FDavid]

I had a bad ticking sound and thought the lift pump was going out too. While I was at TST I had the guys there check my fuel pressure and it was right on spec. I went to Cummins anyway and purchased a new overflow valve AND lift pump and guess what... . the ticking is still there. I called cummins and the employee there said that its normal and just a result of the way the cam hits the plunger on LP.

 

[Timebomb]

Well here is my story.....

I replaced everything one at a time. Pressure was 16psi to start with at idle and droped to 0 under load by 25 psi. of boost so I replaced the overflow valve first with the updated one (has a smaller hole in it) that took it up to 20psi but no change under load. Then bypassed fuel heater, no change. Then new lift pump, that took idle to 22psi. but still 0 under load. At that point I felt like a dumb***** because I had not changed the filter yet. I didnt think to change it cause I thought I had changed it not long ago. Well by the looks of the filter I was wrong. A new filter netted 30 psi at idle and no less than 20psi under full load. So you may want to check the filter first.



Oh and the ticking is gone. But there was nothing wrong with the stock lift pump after all, so I wouldnt let a little ticking worry you.