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JMBT · 12-23-2017, **(Subject: Fuel pump actuator )**

For anyone wondering the fuel pump actuator for the 2cyl and 3cyl pumps on the CM2250 & CM2350 is the same per Cummins. The new part number is 4307411 and it replaced 2872888.
I just replaced mine and it helped the problem I was having with measured fuel pressure deviation from commanded pressure and surging at idle. The truck was runnng fine even with a fluctuating 3000psi deviation between measured and commanded pressure. Even pulled great at 92,500 lbs gross. The only clue of the deviation was a surging sound at idle and while in cruise control. Was the repair necessary? I don’t know. But the new actuator seems to have fixed it for the time being. I now have about a 300psi deviation between minimum measured and maxium measured when the commanded is constant. Leakdown test looses 500psi in 60sec, on a CM2250 with 642K.

Also a side note, the actuator I replaced was brand new, NOT reman, and less then a year old.

Rawze · 12-23-2017, **(Subject: Fuel pump actuator )**

It is good that you found it. Thanks for sharing your story as I am sure others can learn from it.

snailexpress · 12-24-2017, **(Subject: Fuel pump actuator )**

Hey JMBT I have some news. Due to 50/50 my own stupidity to trust people and smart ass broker got stuck in Dalls for 5 days. So nothing better to do as playing with Insite. Now I have different numbers for fuel pressure:huh:
It's only 8005 psi commanded, 7963 psi measured.
I have no idea what is playing key role to make those significant changes. Temperature, barometric pressure, fuel quality????????????

JMBT · 12-25-2017, **(Subject: Fuel pump actuator )**

I did a lot of monitoring on mine through this ordeal. When I start it up cold at 650Rpm it hovers around 6K. As it starts to warm up, usually around 80 degree oil temp I bump it to a high idle of 850rpm, the pressure comes up to the 8K range. At about 150 degree oil temp and coolant temp to match the commanded fuel pressure locks in at exactly 11936 psi. From this point at any idle speed 650, 850, even 1100, the commanded remains locked on 11936 psi. It must be set that way in the tune I guess. It never drops below that threshold again until I shut the truck off and it cools down again. It does of course increase with throttle application.