M939 Lift pump, AKA transfer pump priming pump part numbers : M923A2 M925A2 5 tons

[actionpaintball]

Poor 1st attempt at recovery:

Well....it took me forever to find these and did not see much history. We needed a new lift (transfer) pump for a M923A2, could not prime it and was sucking air. The pick-up tube seemed good and we could power prime it with an electric pump. Checked all fittings, new fuel, and tank switch; all seemed good. Truck is getting delivered and we will try a new pump.

FYI: Part numbers for pump went like this: TM # 3917999, equal to 3936318, updated by new Cummins part number 4988749. The 4- series Cummins part number was in stock for $55. Cummins makes two different kinds of pumps that look the same from what I understand. There is a low pressure and high pressure pump,and we need the high pressure version. I believe the only difference is the pump diaphragm and pump spring.

I will let everyone know if the 4988749 Cummins pump works out. We were really close to getting the truck running and ran out of govliq sand in the hourglass.

On a side note, the larger primary fuel filter was missing from the truck (frame mounted, driver firewall), but it did not look like it was removed (no paint or brackets ect...). This truck just had the smaller soda can sized fuel filter. Is this normal? The TM shows two filters.

 

[Speedzilla]

Hey, funny I should see this posted this morning. Just last night I was looking all over for the part number for the lift pump. I bought a -A2 with similar symptoms and was going to replace the lift pump. I'll post back if I have any luck!

 

[Scar59]

My buddy is in the same fix for his M923A2. He just picked up the pump from local Cummins, his truck has been right since he brought it home. Please post your results
JC

 

[chadande]

My A2 has the big primary fuel filter. Post a pic of yours, I'd like to see it.

 

[actionpaintball]

That was the ticket, plus a bad rubber line supplementing the air leak. That is the correct part number.

 

[HASSON1911]

FYI for those of you wondering if you need to change your pump, thinking it is wearing out or already wore out(i.e. me!) Cummins states to unhook fuel supply line after pump and insert into container, pull fuel shut off, and crank for 30 sec. continuous. If you have under 150ml in your container your pump is bad!

 

[harleyboy1]

That was the ticket, plus a bad rubber line supplementing the air leak. That is the correct part number.

After sitting about day or so my 923 refuses to crank. I have to crack bleeder on IP and hand pump lift pump to purge air out to solid fuel. Just wondering if lift pump has a one way check valve in it to prevent drain back.

 

[jwesley74]

After sitting about day or so my 923 refuses to crank. I have to crack bleeder on IP and hand pump lift pump to purge air out to solid fuel. Just wondering if lift pump has a one way check valve in it to prevent drain back.

Yes, my 925A2 was losing prime after a few hrs. Yes the primer pump has a check valve in it. My understanding, you cant get just a new check valve. Have to buy the whole primer/transfer pump. My buddy says can get at Napa too. Don't know part number yet. But I'm searching. My truck came from DRMO with algae in the tank. Took primer pump apart to clean screen in it and clean check valve. Didn't help much. Now primer pump leaking at the hand pump. So just gonna get a new pump. In process of soaking tank in gasoline now to kill algae and drain/flush. Then running algae X in full tank. Thinking of bypassing cartridge filter and putting inline spin on filter for quick filter changes and cheaper filters until tank & system is clean & clear of algae. Good luck.

 

[Rusty Nut]

Anybody have complaints about the chinese copies of this pump? I ordered off fleabay as seller offers $58/ delivered. Replacing this pump will be much cheaper than changing my priming thumb or starter.

Any other tips to make this change go smoother?

Thanks.

 

[PureMayhem]

I had the same symptoms with my primer pump. It was leaking out of the hand pump and I was losing prime immediately after shut off. I purchased a new pump from a Cummins dealer in Houston and ever since the engine starts in under 1 revolution. The removal and install was very straight forward. I did also have to replace the hose between the large filter and the primer pump as it was cracked so make sure you examine all your hoses also.

 

[maccus]

Poor 1st attempt at recovery:

FYI: Part numbers for pump went like this: TM # 3917999, equal to 3936318, updated by new Cummins part number 4988749. The 4- series Cummins part number was in stock for $55. Cummins makes two different kinds of pumps that look the same from what I understand. There is a low pressure and high pressure pump,and we need the high pressure version. I believe the only difference is the pump diaphragm and pump spring.



View attachment 441030

Some trivia on the part numbers for the M939A2s transfer pump. Actionpaintball is 100% correct on his tracking the numbers. The 4988749 is the correct number at this time. There were previous numbers used and many are still out there and will probably work ok but are not the latest and greatest. Cummins does not change numbers unless there is an improvement/change in the part.

I called the Cummins district distributer today and got a knowledgeable parts guy to talk to. He said often when a part is upgraded and new numbers are generated Cummins will sell the stock that they have under the older number to after market dealers. As I said the parts will work but do not have the latest upgrades. I ordered #4988749 and the parts guy said I should also order the two seals that are used on the tube leaving the pump as they will probably get destroyed when I change out the pump. Good information. Also he had available the date of mfg and the Cummins Build List (CBL) for my engine serial number. The CBL tells you exactly what every part number is on all the parts used in the MFG of your serial numbered engine. Also can give you the date of MFG to the day. Very nice info to have for use in the future. Cost of the pump for me direct from Cummins was $52.00 so why go to eBay etc..

 

[Jlprober]

Since i cleaned all of the algae from the fuel system there was a pin hole stream of fuel coming from this connection which attaches on top of the pump within this discussion. It is spraying from between my left thumb and index finger. I would like to know this part number if anyone has a clue please. I briefly (2 hour search lol) researched the TM to no avail. Thank you in advance to your kind consideration and saving me the lambasting of not having my TM memorized. PS the number on the part seems to be a SN for the part but did not produce any results from a google search.

Peace my brothers.

 

[simp5782]

Since i cleaned all of the algae from the fuel system there was a pin hole stream of fuel coming from this connection which attaches on top of the pump within this discussion. It is spraying from between my left thumb and index finger. I would like to know this part number if anyone has a clue please. I briefly (2 hour search lol) researched the TM to no avail. Thank you in advance to your kind consideration and saving me the lambasting of not having my TM memorized. PS the number on the part seems to be a SN for the part but did not produce any results from a google search.

Peace my brothers.
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It's a pressure switch for the diagnostic unit. You don't need it. Just put a pipe plug in it and roll on.

 

[Jlprober]

NICE! Thanks!,,,,,,,that sure wasn't in the TM.