M939A2 lift pump replacement - part number 3936316

[Flea]

When I brought my 923A2 home recently, it ran like a top. I got the thing parked, and it promptly died. I thought I ran it out of fuel, so I filled it using cans and reprimed the system. When I was priming, I noticed the fuel primer had some fuel weeping around the priming button. I decided to order a new lift pump.

I checked around and was surprised at the price of lift pumps. I checked 8.3 lift pumps at just about all of the retailers I could think of, and found at least 6 or 7 part numbers, multiple brands, etc. One thing I noticed was that 5.9 pumps looked identical and were far cheaper. I found an eBay auction for a 5.9 lift pump that appeared to be the same as was on the truck for about $25. It was NIB and US manufacture. The price was good enough for me to take the chance on it not fitting.

Part number 3936316, and it has a 30 mm plunger vs the 26mm in the stock pump. It appears to be of good quality and comes with the appropriate gasket for the block. The fitting from the supply side of the pump was a different size, so I had to buy a flare fitting adapter from Lowe's (about $5). I also replaced the supply hose from the fuel filter to the lift pump to be sure that I have eliminated all air contamination.

The truck now starts with no issues. I spent a long time searching the part number on the site, and I couldn't find anything. I thought I would post up in case anyone else needs a lift pump and needs the part number. It is compatible between the 5.9 and 8.3 blocks.

 

[Jbulach]

Bumping this up with my experience, and some more info. So after reading this thread I bought the Chinese 3936316 pump for $23, and was unable to find any lift pumps that claimed to be made in the US. The size difference on the inlet can be resolved by simply adding a bushing.
The big difference between the pump for the B vs C motor is the height of the outlet check valve. Fortunately I was able to swap them out so I didn’t have to modify my rigid fuel line. After the fact, I did some more digging, and found the 3936318 pump, that was meant for the 8.3, for the same price and should be a direct bolt on, with no extra parts, or swapping necessary.

 

[tobyS]

Have a 3936318 on the way....thanks.

 

[Jbulach]

Thanks Toby, let us know what it looks like.

Also most of the cheap $25ish pumps of varying part numbers get 3-4 star reviews. Most of the bad reviews are due to immediate, or quick developing external leaks, so you might want to throw it on ASAP, that way you can send it back if you get a junk pump.

Also another trick for anyone searching through the pile of cummins part numbers for a pump, or most any other part, especially for the B and C engine’s, if you replace the first digit of the Cummins number and replace it with the letter j, it “usually” makes the Case-IH part number, and a lot of times the Case parts are much cheaper.

 

[WillWagner]

The cap on the inlet is interchangeable. You can swap the 3/4 pipe one to the new pump, just be careful, big spring pressure there. Also, there is a screen inside the cap that is the inlet. I have seen it plug with debris and give the symptom of a failed lift pump but in reality, there is just a giant restriction that you can't measure, it shows up as a low flow/pressure lift pump.

Just went and worked on the guy that does my trees truck. He has a Ford Cargo with a B in it, that's what his issue was.

 

[Jbulach]

Have a 3936318 on the way....thanks.

Hey Toby, I’m trying to tie up some of my open ended post. Did you ever get this pump and have a chance to put it on or visually compare it to the one on your truck?

 

[Flea]

FWIW, Almost three years on this pump, and I am still trucking right along (no pun intended). I have put almost 5K miles on it with no issues. Still fires on the first hit of the starter, hot or cold.