FQ2013

More on the Cummins M11... Performed starting charging test and got 10.43 cranking volts. Seems okay but I'll be back there in not too long. Back probe at ECM power harness reveals a blown fuse and a broken wire in the loom where it crosses between the frame rails. No change in the problem though... Do some more research through Cummins and come up with ECM needs to see 10.5 volts to power up. Okay I have in the neighborhood of 11v at the ECM harness as it has a dedicated power and ground. However, the switched power is supplied from the starter connections. Now I'm suspicious, to test my theory I set up my meter to test voltage at the power distribution block inside the cab (Supplies key switch/acc. power from the starter). During cold cranking voltage pulls down to 10.3-.4 range and slowly climes back. As soon as it hit 10.5v the truck would start almost immediately. With the engine warm the cranking voltage was 10.7 and the truck started fine. Performed voltage drop test on the battery cables and found 1.3v drop across the 2/0 positive cables. Replaced cables and truck starts consistently within 3 seconds. Previous crank times nearing 30 seconds.

Hours: 50