fuel pump trouble

[bigsix]

hello folks. i am having starting trouble on a cummins 5 ton. i have read it could be an adjustable overflow valve. i have been looking for the tranfer pump nut no joy.starter winds for

two minutes or so before it picks up fuel to start. can anybody point me in the right direction?

 

[porkysplace]

Welcome to SS . First off you will get more reply posting in the correct forum (
[h=2]5-ton and up ) And listing what model truck and engine.[/h]A few related threads ( maybe).
[h=3]M923/A1 Fuel system common issues[/h]
[h=3]M939A2 Adjustable return fuel check valve.[/h]
[h=1]1991 M931A2 fuel issues wont start loses prime in Arizona[/h] [h=3]M923 fuel problem[/h] [h=3]5 ton not holding fuel prime problem[/h]
[h=1]M939A2 fuel lift/transfer pump[/h]
[h=2][/h]

 

[gringeltaube]

Moved.

 

[WillWagner]

And, you cannot guess or just throw parts at things and expect to make things work. You need to troubleshoot things.

 

[74M35A2]

They don't have an adjustable overflow valve. That is typically an aftermarket part.

Have you replaced the soft fuel lines on the suction side of the system? Fuel filter(s) together correctly? Tank have fuel? Pickup tube removed and checked?

What's up with the new guys shift (caps) key not working? We'll help you, but don't make it difficult for us to do so by guessing vehicle/engine/etc....

If you are cranking the starter for 2 minutes straight, you will need a new one soon. They are really only rated to be cranked 30 seconds continuously at a time, and then a several minute cool down.

 

[bigsix]

hello . its a big cam cummins 1985 model. changed filter and had a new fuel hose made. full of fuel pickup tube is good. the only damp place i can see is on the hand pump and it is barely damp no drips. when it starts it runs good but not a snappy rev on the throttle. when you cut it off and immediately try to restart its the same thing again.

 

[porkysplace]

hello . its a big cam cummins 1985 model. changed filter and had a new fuel hose made. full of fuel pickup tube is good. the only damp place i can see is on the hand pump and it is barely damp no drips. when it starts it runs good but not a snappy rev on the throttle. when you cut it off and immediately try to restart its the same thing again.

It is sucking air in somewhere.
Some ideas where in this thread
[h=1]M931 Fuel prime problem[/h]

 

[bigsix]

what about pressurizing the fuel tanks ? would that make fuel come out of an air leak on the return side?

 

[bigsix]

also thanks in advance for all the help.

 

[bigsix]

also do they not have any kind of check valve on the system?

 

[98G]

hello . its a big cam cummins 1985 model. changed filter and had a new fuel hose made. full of fuel pickup tube is good. the only damp place i can see is on the hand pump and it is barely damp no drips. when it starts it runs good but not a snappy rev on the throttle. when you cut it off and immediately try to restart its the same thing again.

I believe it's a small cam Cummins NH250 unless it's been swapped out..

 

[WillWagner]

The only check valve is the pump. You can drop a line into a clean bucket of fuel and go directly to the pump. if it starts better and will restart easily after shut down, your issue is somewhere in the lines up to the pump or in the tank.

 

[bigsix]

hello folks. a little catch up on the fuel problem. it was the hand pump and line. no visible leak. i put 5 pounds of air pressure through my tank vent tube and it showed up bubbling fuel out. i just took it off and plugged the outlet for it. the truck runs really good now. thanks for the help.

 

[Captaincarrier]

hello folks. a little catch up on the fuel problem. it was the hand pump and line. no visible leak. i put 5 pounds of air pressure through my tank vent tube and it showed up bubbling fuel out. i just took it off and plugged the outlet for it. the truck runs really good now. thanks for the help.

Every major problem has a simple solution.

 

[WillWagner]

Right on, easy fixes are the best!

 

[parklandtrans]

FYI....very common for fuel lines (rubber) to deteriorate from the inside out and either clog up system further down the line or the line totally collapses in on itself....NOT SOMETHING YOU CAN SEE FROM THE OUTSIDE LOOKING AT THE LINE..
This is a very common problem on caliper hoses on regular vehicles, tires are "locked up" until you release the pressure at the bleeder screw...99% of the time higher mileage vehicles get these hoses....even if they look awesome..!!
So in closing....do everybody a huge solid by making brake hoses part of your complete brake service job..!!
bob (parklandtrans)