Onemoparnut

Hey guys I am posting this here because the truck has a vp44 pump like a second gen dodge. I am working on a 2000 ford 650 with a 24 valve cummins in it. The truck won't start unless you give it a shot of starting fluid then it will run fine all day. I noticed it looks to have a new electric lift pump on it. I was testing for power and when I unplugged the pump the truck started right up. I plugged the pump back in and the truck just cranks. I loosened the fuel line on the pressure side and cranked it for a second and it has plenty of fuel. Is it possi le that who ever replaced the lift pump put the wrong one on it and this one has too much pressure and the vp44 won't let it start with too much inlet pressure?

patdaly

Yep, I can't remember where the line is, but something like 25 PSI is where I remember it. Put a gauge on it and see what she has.

drewk88

In the Dodge Cummins, the simplified version of the start-up sequence is as follows:
When the ignition is switched on, the lift pump gets power for about one or two seconds, then the power is switched off.
This pressurizes the input side of the VP-44 to only 3 - 5 PSI.
When the engine starts, the power to the lift pump is switched back on and remains on until the ignition is turned off.
Sounds like the lift pump is getting power from an ignition circuit, rather than from the ECU.

dennismorgan

The vp44 is pressure sensitive,i just increased my lift pump pressure to 23psi and experienced hard starting,also it seemed like the injector pump was getting hot to the point of over heating ,heating up the fuel.Consulted an expert and was told 18 psi is optimal and could even do damage to the vp44 with to much fuel pressure.When i returned the pressure to what my fuel pressure had been all the problems went away.