CM570 Low Fuel pressure woes

[Johnny LongRifle]

Hello gents,

Pardon me if this question has been discussed here before. I searched around and really haven't found the answer to my questions or another thread with the same symptoms.

A little background... I am an auto mechanic for 30+ years, but I am green when it comes to heavy duty stuff and especially the fuel system on this truck. I am trying to help my brother with his Kenworth that contains this CM570. ESN 14006005. Non EGR engine. A couple weeks ago he was driving and said the engine cut off like you had turned the ignition off. No spitting and sputtering, just pulling one second and dead the next.

I have quickserve and a scan tool that I am using.

We have power to the fuel shutoff solenoid, the lift pump (is not intstalled on the IFSM like all the exploded views shows) is running and making lots of flow, but scan data shows 3psi KOEO. I pulled the return line off and fuel flow was wide open. With my thumb in the hole I was able to get it up to 50ish psi. Tells me the lift pump is ok. I have removed and inspected the 250 and 400 psi regulators and didn't see anything obvious. I am having him install a mechanical guage tomorrow to verify fuel pressure.

Currently it is setting code 482.

The engine will start and show around 250psi fuel pressure on the scan data. As soon as you try to foot feed some fuel or set the PTO, fuel pressure drops and the engine stalls. Quickserve tells me to check the overflow valve in the IFSM, but I don't know where to look for that. Any ideas?

I dont have a good idea of how the fuel flow works inside this IFSM. It seems that there were multiple iterations, and I get real confused trying to sort through the information trying to figure out something I know nothing about.

The engine stalls because it can't maintain fuel pressure above idle, Im sure. Is there something in the IFSM that is dumping pressure back to the tank? I did clamp off the return line (good or bad) and the symptoms persist.

What am I missing here? I dont think its a bad HP pump, but instead something is dumping all the fuel back to the tank, I just don't know where to look.

Help a newbie please?