Peterbilt 386 starts and dies immediately

[shawn21998]

(11-18-2023 )Rawze Wrote:  

(11-17-2023 )shawn21998 Wrote:  ...
Fuel pressure while cranking 6300psi, up to 7400psi when it runs then drops out to around 2000psi after it dies. Oil pressure is 2psi while cranking then 10.5psi when it fires. ECM voltage while cranking drops to 8.5 from battery voltage while key switch voltage stays at 11 at ECM. Jumps up to 11 when it starts then dies. Component #128 voltage drops to 8.5 as well. There is no active or inactive codes on Insite. Jpro is showing low voltage codes from EC-60 ABS and component #128. Using jpro while monitoring voltages it shows the component #128 being CECU3.

8.5 volts while cranking is a problem..

some guesses..
bad/corroded grounds, maybe battery terminals that are not making proper contact, or the wire from batteries to the ecm is shorting out.
this may also help... ref: http://rawze.com/forums/showthread.php?t...05#pid3505

or might could be a bad ecm?.

Thank you for your input, I have cleaned all the battery connections along with the chassis and engine grounds and replaced the ECM already. I load tested all power and grounds going to the ECM as well. Performed voltage drop tests on battery cables as well all tested good.