M923A2 - Loss of Power While Driving

This is fun!

I gravity fed directly to the lift pump, from a fuel can, still no change in pressure. I would think this should eliminate trash in the tank, collapsing fuel lines, or sucking air.

I hooked the trucks fuel line back up to the lift pump, and checked the flow at the inlet to the injection pump. Cranking the engine at a little over 200rpm for 15 seconds the lift pump pushed 125ml through the secondary fuel filter. So, I think volume checks ok.

I installed a new adjustable tork tek over flow valve, may have gained 1psi. Adjusted the valve in a half turn to max pressure, with no pressure change. Backed the screw back out a full turn, still no change.

Next, I decided to clamp the return line completely closed. Started the truck, pressure went from 17psi up to 21 psi at idle. Increasing the throttle would actually drop the pressure a bit, and would never go above 21 psi with throttle held at any rpm.

So, I guess at this point I’ll throw a new lift pump at it and see what that does. Any other ideas???

That's your wife's measuring cup from the kitchen! Sweet bro. Glad to see you paying taxes on your fuel. Can't say mine looks like that, but I do drive my truck off-road. Ha! Does that count?

I read somewhere that the 8.3L mechanical lift pump has the ability to generate up to 100psi if fully dead-headed. So, sounds like yours could be going out to lunch. They are very low cost and simple to replace. Same as a Ford 302 or Chevy 350, 2 bolts and you are off to the races. No magic.

Let's see some more pics of your garage inside. I want to pick out something you could send to me.

Shhhh... I’ve been playing in the diesel fuel so much lately, she cant smell it anymore either. I’ll get some pics of the garage later, but heres some goodies my wife made that I can send you.The kids say you can barely taste the diesel.

Back to the lift pump, any recommendations? I don’t want to cheap out but, hate to spend a bunch throwing parts at a problem I’m unsure of.

Cummins OEM 4988749 $90

Delphi HFP701 NAPA $202 or ebay uk $80

Cummins 3936316 Chines knockoff from ebay $22, and if it don’t fix my problem I can box it up with 74M35A2s cookies and send it to him.

Or any othe options?

Bosch cook top and a new lift pump. What else does one need?

I thought you would like that. Unfortunately no Bosch or Mitsubishi lift pumps found... any idea where the Delphi pumps are made? From what I’m reading it sounds like the Cummins OE replacement pumps are made in Jhina?