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Rawze · 11-18-2023, **(Subject: Peterbilt 386 starts and dies immediately )**

(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?.

JimT · 11-19-2023, **(Subject: Peterbilt 386 starts and dies immediately )**

You said earlier that the batteries were just replaced due to old ones only having 8v... now I'm not an expert here but maybe you have a short somewhere else (not the ecm) that is draining the batteries? I would start by checking all the cables in the aluminum battery box as I've had shorts in there myself. Next I'd check all the grounds again starting at the battery and starter. While you're at it how is that starter? Is it drawing too much current to turn over? how about the solenoid, connections clean, no problems inside or out? Also, have you checked the alternator output?

I'm no expert, but all those voltages you mentioned seem too low. 11 instead of 12, dropping down to 8.5 while cranking instead of 10.5-11

Also, I've mentioned this before and seen others mention it as well. But on my truck, a 2012 Pete 587, when the key is off and all lights off I still get a slight glow from my brake lights (they are LED's so a resistor might 'solve' my problem). I've heard from others that this is common and it's something to do with the CECU or body controller, I forget exactly. I bring this up as that might be another place to check for a short or parasitic drain.

Rawze · 11-19-2023, **(Subject: Peterbilt 386 starts and dies immediately )**

Another easy check is to see how badly the headlights dim while on out during cranking. They should not dim by very much at all on a healthy system. If they do, something is quite wrong.

shawn21998 · 11-21-2023, **(Subject: Peterbilt 386 starts and dies immediately )**

(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.

tree98 · 11-21-2023, **(Subject: Peterbilt 386 starts and dies immediately )**

So then why are you only getting 8.5 volts to the ECM? Something isn't right somewhere.

Hyliard15 · 04-03-2024, **(Subject: Peterbilt 386 starts and dies immediately )**

Did you get this fixed? I’m having the exact same issue with my 587. Thanks

Rawze · 04-03-2024, **(Subject: Peterbilt 386 starts and dies immediately )**

(04-03-2024 )Hyliard15 Wrote: Did you get this fixed? I’m having the exact same issue with my 587. Thanks

what make.model/year truck?... engine?.

maybe some history as well.

Hyliard15 · 04-04-2024, **(Subject: Peterbilt 386 starts and dies immediately )**

13 Pete 387. Getting the same code and same symptoms. Have done everything he has done as far as testing inputs but randomly the truck pos that code about power 1 low or short and the truck shuts off until I get out and pull the power relay fir a couple seconds and put it back in. Im going to pull steer off this weekend and get down around starter looking for a bad wire or plug and also going to power wash the area and see if I can reproduce the issue. Everything that has been said in this feed my issues almost mirror them. Thanks