tomd

Quick question...
How does one know if their lift pump is going bad?

I'm looking into upgrading my stock lift pump. I remember somewhere/someone in the past was talking about a piston type lift pump which is better than the diaphragm type? Also, I looked on eBay and didn’t see any piston type lift pump, but there is one for my truck, just not sure if its the one I am looking for. Anybody have any part numbers so that I might be able to find one at one of the auto part stores here in town, or that they can order one?

I think I might need a new one...

Thanks much for any help,

Regards,
Tom

Bob Beauchaine

Here are the part numbers for the piston style lift pump. They are all Cummins numbers. You will find a wide range of prices so shop around.

1 - Pump 3036320
1 - Fuel tube - pump to Fuel filter 3914753
2 - Gaskets 3939258
2 - Sealing washers for banjo bolts at fuel filter 3963983
1 - Spacer to move pump out 1/4" 3914284
2 - New pump mounting bolts 3900631

This pump looks like the 2nd Gen lift pumps but it operates at a lower pressure that is safe for your VE.

Bob

tomd

Bob,

Thank YOU!

I couldn’t ask for a better reply.

I had no idea that there was other pieced needed in order to replace with a piston type lift pump. Awesome that you gave me the nomenclature and part numbers for everything!!

tomd

Cummins was not able to find a lift pump with the number...3036320

I found out that it was actually a 3936320!

Still working on it!

Bob Beauchaine

Could be my fat fingers re the pump number - I will double check. Just make sure it is not a 2nd Gen pump. You will also need to remove some of the lifter cover noise deadener(sp) to get it to fit I used a die grinder to cut enough off.

Bob

wannadiesel

Bad lift pump symptoms are usually hard starting, fuel in the oil, or low power.

If your plans for the truck include big injectors, I suggest skipping the piston lift pump and going straight to a Walbro electric. The electric is a little more expensive, but it will keep up with big injectors. Before I went to the Walbro, I could pull my piston pump down to 5 psi. The Walbro won't go under 15 psi.

tomd

Thanks guys

I went to cummins located in San Leandro and bought all the parts. I took the old one out, and just now bolted the new one up... Harder job than I thought.
The top of the pump (Large brass nut)seems to hit the side of the block and I'm hoping that the it bolted flush and that there are no oil leaks. Its tricky pushing in the pump and turning the bolt through two gaskets and a spacer trying to thread while doing yoga on top of the engine with arms, legs etc cramping up. Just now had to take a break. Will try either tonight to finish or tomorrow. By the way...

"lifter cover noise deadener"?? Where or what is this? Is it the side of the block?


Thanks again!

tomd

Well this sucks.. I see I'll be having to take out the pump and cutting around the area noted in this thread! No wonder it was hard puting this in.

https://www.dieseltruckresource.com/...ft+pump+piston


I see that this is what you were talking about Bob! Wish i would have came here to check replies before starting!

BC847

Oops!



Somethingtomakepostlongenough

tomd

Well, I did some grinding and then some carving with the knife. I didn’t realize that the piece that needed cutting away was plastic. It all went on very easy when all was in order.

I hooked it all up, opened the bleeder screw and went to pump it, but nothing! No fuel going up. I disconnected the line into the lift pump and pushed it aside. Then I grabbed a turkey baster and carved it so that it would fit over the nozzle going into the pump and poured fuel into the plastic baster piece. Then went to pumping and it sucked fuel up to the bleeder screw. The pump needed to be primed. The turkey baster worked like a charm with no spillage!


The truck seems to run a little better when putting my foot into it, but the egt's are the same and the 20psi max is the same but it seems to build up boost a little quicker. So this means that the old lift pump is still good, but would like to tear it apart and see what it looks like inside.

Would the truck still run ok if there is air in the lines near the injectors? Should I go ahead and bleed the lines?

I think my next step will be new injectors.

BC847

If you had enough air in the lines to cause a problem, you'd know right away. It'll miss most noticeably. If that's the case, with the engine idling cool, wearing gloves, crack the nut on each injector just enough to burp some fuel out. If there's air in there, it'll come out then.

It's my understanding that small amounts of air will be passed back to the fuel tank within a short time.

tomd

Thank You BC847!

I really like your helpful threads. I just went over your BHAF thread showing your great fabrication project! Nice! https://www.dieseltruckresource.com/...ad.php?t=63169

Must be that good air out in NC!
I love that State.

Regards
Tom

BC847

Yup!