8.3 cummins fuel issue

[Pipevine]

I've got an 8.3 mechanical cummins in a 95 L8000. It sat for about a decade before I got it. Drained the tank, fresh fuel. Replaced the check valve on the back side of the injection pump as it wasn't holding pressure. Everything was great smooth idle, good throttle response etc.....then it just started to sound like it was running out of fuel, giving it some throttle seemed to help for a couple seconds then it died. Took the fuel line from the tank loose at the lift pump and attached a short hose to the lift pump and ran it into a jug of diesel, primed with hand pump, truck started, ran a couple minutes then died like it was out of fuel. Anybody have any ideas?

 

[Wytruckwrench]

The lift pump has a screen in the suction side maybe. I have had fits with those sometimes.

 

[RZucker]

Sounds like bad check valves in the lift pump. Is this the style with a pushbutton primer on the lift pump? No screen in that type. It should have an inline strainer between the pump and tank. Sometimes if it has crap in the check valves, you can blow air from the inlet to outlet and clean them out. But as long as it has sat, I would say the rubber seats in the checks are no good. Cummins used to offer a rebuild kit for those pumps. Not sure if they still do.

 

[thepumpguysc]

IF u replaced the overflow valve already, I would suspect the lift pump also..
What # ovflo valve did u get.??
Have u checked PRESSURE at the pump inlet yet.??

 

[Pipevine]

Yes it's the pump with the pushbutton primer.

Overflow valve:
Bosch Part number 2 417 413 101

Havent checked pressure yet bc its hard lined all the way from lift pump to Injection pump

Could it possibly be something in the fuel heater that is right before the LP

 

[Pipevine]

Sounds like bad check valves in the lift pump. Is this the style with a pushbutton primer on the lift pump? No screen in that type. It should have an inline strainer between the pump and tank. Sometimes if it has crap in the check valves, you can blow air from the inlet to outlet and clean them out. But as long as it has sat, I would say the rubber seats in the checks are no good. Cummins used to offer a rebuild kit for those pumps. Not sure if they still do.

Please explain which inlet and outlet you're referring to.

 

[thepumpguysc]

The threads on those banjo bolts are 14x1.5 mm Just go to the parts store & get 1.. drill it & tap it to fit a pressure gauge.. replace the original B. Bolt w/ the 1 u made & take a pr. reading..
Once u get the reading, swap'm back..
Theres an inlet & outlet on BOTH the supply pump AND the injection pump..

 

[Pipevine]

Ok will do. Thank you

 

[Pipevine]

I came to the realization that every time I start the truck it is running until the fuel in the filter is gone and then dies. Even went so far as to put an electric lift pump before the mechanical one just to see what would happen, same results, runs for a couple minutes then dies. If I open the filter drain at that point, nothing comes out.

 

[Birken Vogt]

What if you run said electric pump back to the tank off the battery for a couple minutes? Does it lose prime then?

 

[BigWrench55]

If you are emptying a filter then you either have a restriction or sucking air. Check the line that feeds the filter that is running dry.

 

[thepumpguysc]

YUP.. if your emptying the filter, then the lift pump is sucking.. but cant get any more..
Take the cap off the fuel tank & see what happens..??

 

[Pipevine]

Unbeknownst to me the electric pump I hooked up was running but not pumping. Been having hell finding an m14x1. 5 banjo bolt to drill and tap for pressure gauge. (never dreamed one would be so hard to find.)
Am I correct in my understanding that there are also two check valves in the banjos on the filter head that can stick open?

 

[Birken Vogt]

I don't know if this is right

https://www.amazon.com/GlowShift-Pr...=2025&creative=165953&creativeASIN=B01BW1RJVS

 

[thepumpguysc]

That's ALMOST it.. but the back side is pretty large & you'd spend 1/2 a day tying to figure out fittings to adapt down to a gauge..lol..
I have 1 I can send ya.. send me a "prvt conversation" w/ your address & just pay for the shipping. You'll have it in a couple a days..
BUT.. if u found the electric pump wasn't working.. u found the problem..??
Are u using that as a helper pump to PUSH fuel to the actual supply pump on the inj. pump??

 

[Tenwheeler]

Some of the Ford 8.3 I recall had a screen in a housing toward the back of the engine. Follow the fuel line. It looks like it could have been a spin on fuel filter housing that was blocked off on the bottom. Take it apart because there is a screen in it.

 

[thepumpguysc]

I never knew what that dam "filter head" was called.?? BUT it was a MAJOR source of trouble.!!
Between the screen that was ALWAYS rusted, theres a "plastic" ball in it.. & u have to take it ALL A PART.
Good luck..

 

[Pipevine]

I don't know if this is right

https://www.amazon.com/GlowShift-Pr...=2025&creative=165953&creativeASIN=B01BW1RJVS

That's an m12 and they are plentiful. I ended up just (very carefully ) tapping the stick bolt.

 

[Pipevine]

That's ALMOST it.. but the back side is pretty large & you'd spend 1/2 a day tying to figure out fittings to adapt down to a gauge..lol..
I have 1 I can send ya.. send me a "prvt conversation" w/ your address & just pay for the shipping. You'll have it in a couple a days..
BUT.. if u found the electric pump wasn't working.. u found the problem..??
Are u using that as a helper pump to PUSH fuel to the actual supply pump on the inj. pump??

Thank you, my bolt is working for now I'll let you know if that changes. As far as the electric pump yes that's what I was trying to do

 

[Pipevine]

I never knew what that dam "filter head" was called.?? BUT it was a MAJOR source of trouble.!!
Between the screen that was ALWAYS rusted, theres a "plastic" ball in it.. & u have to take it ALL A PART.
Good luck..

Yes I've cleaned the screen a few times now and replaced the dry rotted o-ring. There was no "ball" in it though