1991 M931A2 fuel issues wont start loses prime in Arizona

[ArizonaGasMonkey]

My 1991 M931A2 will not prime up with manual pump and will only start with starting fluid.

I was told that it could be the fuel valve by the drivers seat that wont hold fuel in place.

I do not know if that is true or not.

After it is started it runs awesome. After it sits longer than 45-minutes it wont start again. I cannot even prime it up.

Any ideas or suggestions?

Thanks in advance

Aaron
four 8 zero 8 eight 8 six 7 three 8

 

[Suprman]

The cab floor valve can be rebuilt with new o rings. Common a2 truck issue is the fuel line from the big canister to the lift pump. They wear thru. Gotta be an air leak somewhere. Can't be that big of a leak if the truck runs ok once you do get it primed. Might as well replace the filters while you are working on it.

 

[M35A2-AZ]

Sounds like you are sucking air from some place. I would start at the lift pump and put a hose on it and put it in a can for fuel and see if it will prime, Then just start working to the tank. Good chance it is the fuel tank valve, or old hoses. Does it do it on both tanks?

 

[MuleMac01]

Check the hard rubber fuel lines from tank to filter. Mine showed no leaks what so ever but kept loosing prime. replaced em now air leak is gone. Starts right up 3 cranks.. Any hose shop can make you new ones for about 100 bucks or less.

 

[Csm Davis]

Yes before you change or rebuild anything else replace all of the non metal fuel lines, that fixes 90% of the problems. Then do as M35A2-AZ has instructed above.

 

[silverstate55]

At least your draw tube didn't break off at the solder joint & fall off inside your fuel tank while you're on a 2-lane highway with no shoulder...that was exciting!

 

[MtnSnow]

At least your draw tube didn't break off at the solder joint & fall off inside your fuel tank while you're on a 2-lane highway with no shoulder...that was exciting!

I had this exact thing happen to me on my M925a2. I knew it wasn't my fuel hoses as I had just replaced them a few days earlier and when the primer pump wouldn't get me any fuel went straight to the tank and looked with a flashlight and Yep...no suction tube was attached to the fuel line bung elbow!

 

[M35A2-AZ]

At least your draw tube didn't break off at the solder joint & fall off inside your fuel tank while you're on a 2-lane highway with no shoulder...that was exciting!

My draw tube did not fall off but it cracked and would not hold a prime or run very good. I had a hard time trouble shooting that.

 

[VPed]

If your M931 loses prime in Arizona, can you just move out?

 

[74M35A2]

As all said above. Put new O rings and lube into fuel selector valve, pull and check your fuel tank dip tube (suction elbow and straw), replace all soft fuel suction lines (they won't leak to outside due to suction, they will suck air instead), and then once there is air in the line it still will not actually prime with the manual primer until you open the bleed port on the injection pump, or at least anywhere after the lift pump. You could also crack one of the banjo fittings to the small engine mounted fuel filter or after it, but bleeding at the injection pump is best. That is a 10mm head, on the engine side of the pump, front section. Between the pump body and engine. Common issues. Easy and low cost to solve.

 

[86m1028]

Im having a fuel problem on a recently acquired m936a2, it looses prime.
I have replaced all lines from tank to pump (bypassed the selector valve & large frame mounted fuel filter).
Replaced small engine mounted fuel filter and checked pickup tube.
Prime truck, it will run fine, shut it down & within 20-30 min truck will not restart without priming again.
What am I missing ?

I guess my 2 questions are 1 can/will an IP bleed down internally ?
Engine oil is not showing any high fuel levels (have not done oil analysis).
2 The prime pump on the engine does pump fuel to reprime but can it allow fuel to drain back into the tank ?

 

[MtnSnow]

You might have a return fuel line check valve that has a weak spring or it has a dirty seat and not sealing well. This was one of the problems on my M925a2 along with a pickup draw tube that had a cracked solder joint both allowed the system to bled down


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[86m1028]

You might have a return fuel line check valve that has a weak spring or it has a dirty seat and not sealing well. This was one of the problems on my M925a2 along with a pickup draw tube that had a cracked solder joint both allowed the system to bled down
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Thanks
Ill check the return check valve.
Didnt mention in my first post that I even used the 2nd tank with no luck.
1st tank, I did pull the tank & check the pickup tube (with the wrecker bed you have to pull the tank to gain access).