Peterbilt starter problems

K19 behind inst. pnl. (not certain about 2009)

 

Remove the S or crank signal wire from the small terminal on the starter solenoid. Hook up the battery's and check for 12 VDC at the wire while disconnected. If there is power to the wire either the starter relay is stuck or you have a short to power on the ignition circuit.

The other possiblity is you have a main power cable shorting to the signal for crank or possibly cables on the incorrect solenoid terminal or possibly accidentally touching the motor or solenoid out post?

What was the issue before the starter was replaced?

 

Used to be a starter circuit was pretty straight forward to isolate and check, but now days it gets a little more complicated with a few more components to sort through such as starter interrupt circuits and a lot more wiring. That single "start" wire at the starter itself runs a gauntlet through the main engine harness which has to end up at a main plug (1 of 2) at the firewall/bulkhead, and I believe in this case P103/J50. A simple continuity check would eliminate this "leg" of the start circuit (nothing's simple anymore) especially if you knew the pin number at the plug end (pin 10 also and ONLY), (mapping of a round Deutch? connector helps). Eliminate this "leg" of possible stray voltage and your halfway there. As you enter the cab side (J50)(the "pack a lunch" side if its wiring) the circuit runs through the cab controller CECU to K19 (which is a micro ISO relay; a little smaller). Now the "power" side of that relay IS the starter wire that goes to the key switch (another conversation in depth), the "control" side of that relay comes from the CECU derived ground that enables or disables the Starter Interrupt Relay. Even if all the wiring is good (hopefully), there are a few things that have to be "right" before the CECU will allow this circuit to energize which is again a whole other conversation to be considered... anyway I'm just hoping that that friggin relay is just stuck, Ha, or maybe the key switch isn't the correct one, hope this helps.

 

Well let’s clear some things up first. When the starter went out did it burn itself out because it would always engage or it was just it’s time to die? If it wasn’t doing this before chances are you’re just connecting a hot wire to your solenoid, I’m not questioning your knowledge or anything. If not that, then the starter relay, or IGN switch where you have your battery power,run power,starter usually labeled as BAT,RUN,IGN depending on the switch and if any of those get crossed up or the BAT decides to make contact with the starter wire then that could cause the problem but again highly unlikely