5 ton not holding fuel prime problem

[dezrat]

Help, I have a 1990 bmy 5 ton 6x6 cargo truck. if the vehicle sits for more than a day the truck will start then die after about 2 mins. of running. I have replaced the fuel filter (large) and the water seperator also the lifting pump. finally if i reprime the system by pullling a vaccume on top of the large fuel filter with the schrader valve removed then reprime to the injector pump the motor will run all day.
Any help would be greatly appreciated.
thank you
Dezrat

 

[smittyjr355]

If you havent done already replace the rubber hose that runs from the fuel canister filter to lift pump.

 

[jcappeljr]

Like smitty said ,I have replaced that rubber line that he said on about 10 trucks, and that solved the issue.

 

[74M35A2]

There are 2 hoses in this area to replace. One is from the tank to large filter (tank has hard lines for the first few feet), and the next is from the large filter to lift pump. It is a vacuum only system, so when they leak they suck air only and do not push fluid out. Mine was starting to do the same, no signs of leakage, I replaced both hoses, and the issue disappeared. This issue is so prevalent that some people just replace them before evening starting a truck from auction. Take your off and to a hydraulic shop they can easily replicate them.

There have also been cases of fuel tank dip tube fractures where the tube is connected into the fitting at the tank. Would not hurt to pull that and check it also while you are doing so, it is all easy work.

Make sure the square washer at the top of the large filter is orientated correctly so it sits down in its recessed area squarely and is not sticking up.

 

[trooper632]

Im having the same issues with my 923a2, messed with it for an hour yesterday. But I unhooked the hose from the top of the big fuel filter that runs to the lift pump and put air to the fuel tank and got fuel running out of the hose, but then it stopped flowing even while the air was still being put into the tank, don't know why. I figured tat fuel should flow as long as air is being supplied. Fixing to push it off a cliff with a running truck. Guess ill try replacing the top hose to the lift pump first

 

[Coffey1]

Check o ring on fuel filter bolt.

 

[Floridianson]

Check o ring on fuel filter bolt.

I also when having to canister off and doing the filter replacement take a sharp tool and clean out the square where the square washer fits. Some seem to get a poor fit after a long time.

 

[tractors0130]

If your filters, hoses and tank dip tube are all OK, double check your lift pump or just replace it. I've had a couple with bad check valves on the 8.3's that would't start well and would lose prime. Problems went away after installing new Cummins lift pump.

 

[74M35A2]

=====Threadjack=====

Hey, tractors0130, today marks the 2nd anniversary of my heart valve replacement, of which the very first trip I took after getting back clearance to drive was to head down your way and buy my M925A2 from you! Survival present to self if I woke up after it. Thanks again, truck has been a total riot, makes people go crazy when they see it pulling up at Tim Horton's. Here is a pic of her a month back, just after fresh paint:



=====Threadjack End=====

 

[tractors0130]

=====Threadjack=====

Hey, tractors0130, today marks the 2nd anniversary of my heart valve replacement, of which the very first trip I took after getting back clearance to drive was to head down your way and buy my M925A2 from you! Survival present to self if I woke up after it. Thanks again, truck has been a total riot, makes people go crazy when they see it pulling up at Tim Horton's. Here is a pic of her a month back, just after fresh paint:

View attachment 594854

=====Threadjack End=====

What a difference a little paint makes, looks good.

 

[RobertoGatos]

check valve at the IP

 

[MuleMac01]

Mine had the SAME prob few weeks ago when it started to get colder in Las Vegas replaced both filters didn't work then replaced the both rubber hoses and that fixed the issue...

 

[silverstate55]

Mine had the SAME prob few weeks ago when it started to get colder in Las Vegas replaced both filters didn't work then replaced the both rubber hoses and that fixed the issue...

Glad to hear that the new hoses worked for you!