m939a2 wont start after fuel filter change

wheelspinner

Well-known member
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North Carolina - FINALLY !
You guys are making this waaaaaaaayyyyyy too hard. There is a VERY SPECIFIC bleeder (PLease look at the TM!) Loosen that, pump pump 20-30 times. Get a good flow of solid fuel (let it drip down, not hurting anything) tighten up the bleeder and get going. I have run my truck COMPLETELY dry TWICE (yeah dumb I know!) and fueling, bleeding and leaving took a grand total of 5 minutes, maybe.
 

captain

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South Eastern PA
I tried that bleeder per the TM and earlier posts. pumping the primer on the lift/transfer pump did not produce any fuel from the bleeder. Neither did cranking the engine for some time. Pumping the primer did produce fuel from the banjo fuel inlet to the injection pump.

I don't know why it is not working. The truck ran perfectly fine 5 minutes before I changed the fuel filter. Cracking the bleeder and priming until fuel comes out is what I do on the 5.9. Works well. I ordered some fram filters (what was originally on the truck) to replace the new napa one. I might order a new lift/transfer pump too.

The only time so far since the filter change that I was able to get the truck to run on #2 was after adding some air pressure to the fuel tank. It ran very poorly for about 30 seconds then quit.

Maybe I just have no idea how to change a fuel filter. Is the filter mounting stud supposed to be run up hard into the engine block or just up to the gasket notch before the filter is screwed on?
 

86m1028

Active member
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Murphy TEXAS
Please explain how the tractors are different from the cargo's.
I have an m923a2, I changed my large filter under the fender, gave it a few pumps on the primer
& she fired right up
 

Tornadogt

Member
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7
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Location
Adkins, Texas
Please explain how the tractors are different from the cargo's.
I have an m923a2, I changed my large filter under the fender, gave it a few pumps on the primer
& she fired right up
Tractors have Duel Tanks and a Switch valve just to the left side base of the Drivers seat (sometimes this is where air can get in the system on tractors)

On topic IF you are not getting fuel out of the Bleeder at the side of the injection pump when you pump the hand primer and you know that pressurizing the tank does get fuel to the bleeder I would say the fuel pump is bad....

With that said it may of been working fine before you changed the fuel filter.. THEN when you went to hand prime the pump after the filter was changed if anything was dry rotted inside the pump that action my of torn or broken a seal/diagram in the pump and now it is not working..

Just one possibility, not unheard of or impossible

good luck and let us know when you do get it solved..
 

acme66

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Plains, Montana
Is there an inlet screen in the tank? I ask because you said it worked for a bit after pressuring the tank. Seems to me I had an old jeep that would pull fuel fine but when it ran out it was buggered. Turned out the pickup screen in the tank was gummed up. Maybe without the fuel in the lines the pump/prime pump can't suck hard enough to pull fuel? Maybe some low air pressure backwards into the tank, maybe it knocks the stuff loose long enough to test the idea. If the TM isn't working thinking outside the box might be in order.

Ken
 

captain

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Location
South Eastern PA
Thanks all for the help so far. I did try cracking the injector lines. The injector lines and the bleeder provide no fuel when pumping the primer or cranking the engine. The only time I got fuel to the bleeder was with air pressure into the fuel tank. Before I pressurized the fuel tank I did remove the fuel line to the lift/transfer pump and blow that back out into the tank. It sounded free and clear. Tomorrow some new fram filters will arrive. I will try replace the new napa filter with a fram like was originally installed and working on the truck. Next I will try to run the truck with constant pressure in the fuel tank. If that does not work then I will call cummins and order a new lift/transfer pump. They do die. I have changed them three times now between my two 5.9s. I hope they can get me the right one based off the engine serial number. The cummins part number in the TM does not appear to be correct. The primer on the lift pump on the a2 seems to be less standard in that it sits between the inlet and outlet. Most of the lift pumps the primer is below/above both fittings.
 

Tornadogt

Member
724
7
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Location
Adkins, Texas
I searched and found this:
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.

Others seem to confirm the 4988749 part number

link to thread:
http://www.steelsoldiers.com/showth...riming-pump-part-numbers-M923A2-M925A2-5-tons
 

captain

Member
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0
6
Location
South Eastern PA
I got back to it this weekend after letting the truck sit for a week. I ordered a new lift pump and a bunch of new filters just to insure I would not need any of them. I pressurized the fuel tank and cracked the bleeder on the pump. No fuel. I cracked the inlet banjo on the pump and fuel came out of that and the bleeder banjo. When I closed the inlet banjo fuel stopped leaking from both locations. I closed the bleeder. I started up the truck and it fired off nice and smoothly. I kept the tank pressurized for a few minutes. The truck seems to run ok. In short I have no idea why fuel does not come out of the bleeder without the inlet banjo cracked. Now I'm off to resolve my low power issues and it will be a truck I can drive! Thanks for the help everyone. I'm sure I would still be beating my head against the block with out it.
 
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