westcoaster

So,
2000 cummins 8.3L ISC with the CAPS injection pump.

Does a guy need to crack the injector lines to bleed air? or will the pump take care of it similar to a common rail system?

Symptoms:
Would run smooth for 30 seconds at startup then start stumbling like it was starving for fuel. Previous owner said it would run fine so long as it was pointed down hill.
I pulled the fuel filter and housing off the block to find the outlet of the filter housing finger tight. Also found the banjo connector on the fuel return line leaking fuel.
Lift pump runs for 20 seconds or so then you hear it dig in to the fuel, fuel filter 1/2 full.

Back to me yanking the filter and housing off the block... set up a gravity feed from a jerry can sitting on top of the motor. primed the system and cranked.
Engine will now only pop before shutting down. Could be air elsewhere or, It could be in for a new injection pump...

edit:
Lift pump only runs for 30 seconds or so at startup to prime the system and when running the injection pump is supposed to suck the fuel from the tank.

2006BLKMegacab

what is the engine in? I have an 8.3 with the CAPS pump in a case ih tractor and have had a few hiccups with it but not what you have described, I will ask a buddy or 2 on the inside at case if they need to be bled the old fashion ed way or not tomorrow

westcoaster

It's in a 2000 freightliner FL80

When I turn the key on and the lift pump runs, it can go for 15-20 seconds before you hear it change tone and start digging in to fuel. Does yours do the same?

Trying to figure out what is "normal" and what's not. Truck was purchased this way (not running)

sewman

Yes,that is normal for the lift pump.It runs only on startup thens shuts off as the pump takes over.I'd say you might have a cracked fuel hose somewhere & your losing prime.
I have a 2001 FL70 with the same engine.

westcoaster

Thanks for the reply,
Kind of what I thought. Waiting for the lift pump to catch fuel is not normal...

Dieselbuilder

I would check all the fuel lines for rub marks for any holes for air leaks. I had something like this happen on my old Freightliner and the hole was the size of a pencil with no fuel leaking out as the hose had a twist in it !

westcoaster

I think I can rule out fuel supply.
Set the can on top of the engine. Used an outboard boat motor hose with the priming ball, bled out all air.
Engine still only fires once then dies.

Would having the lift pump unplugged set something in the ECM preventing the engine from running?

One thing I didn't check was a blocked fuel return line...

sewman

When my lift pump went out it only caused hard starting,had to crank it a lot,once the injector pump is primed it pumps that's why the lift pump shuts off.You might want to check the ECM for codes.

beanguy

I would assume that by now a solution was found? I'm Having the exact same trouble with my caps pump on a CaseIH tractor. Would like to know where to start looking. Somewhere there's air getting in, but no fuel leaking out.

westcoaster

When it got to the point of looking like it was the injection pump I passed off the troubleshooting of this to my buddy (who owned the truck)

At the end of the day he replaced the lift pump and the injection pump and the "resistor" (name escapes me now) that is attached to the side of the block.

The truck ran for a bit then died again with the same symptoms...

We believe it now to have been an electrical connector on or around the injection pump with an intermittent short/open. He had a couple instances after pump replacement where wiggling wiring would get the truck running again.

He had bought the truck not running with paperwork from a cummins shop indicating the lift pump needed replacing.


As far as the air in the system, I'm not sure if replacing the lift pump corrected that issue or not.... Either way the truck is running reliably now.