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I picked up an M1078A1 that's been uncooperative to start. The POC at pickup said they couldn't get the truck to start but I noticed the battery disconnect switch was in the off position and was hoping that was the issue..but it's deeper than that.
Attempting to slave start the LMTV off my wrecker gives it plenty of power to crank but it's not firing off. No warning lights or dash codes, it all acts normal. I pulled the fuse cover off and inspected the fuses which look good. All LED lights show green when power is on and ready to crank. This is the newer "green board" and not the blocky older style board.
I've bled both fuel filters and pressurized the tank to ensure it's getting fuel. There is a fuel pressure governor/restrictor on the rear of the engine for the return fuel. I've read those can be a problem by not allowing fuel pressure to build up when starting the engine. I took the return line off the fuel tank and pressurized it again getting nothing from the line. When cranking a steady stream comes out so it tells me pressure is being built and retained.
I wanted to eliminate the possibility of the dead batteries causing a problem when cranking so I pulled all 4 batteries and managed to save 2 to be put back in. The 12v and 24v systems were hooked back up correctly (verified by fellow members) and she cranks like a champ.
A quick squirt of either/starting fluid for an internal completion test was done. She does run..or wants to.
I bought a truck code reader to plug in the j1939 socket and see if the computer would talk to be but it ends up with a communication error when scanning. I can talk to individual parts of the truck for any current or stored codes but nothing is logged. (I thought this stuff was supposed to make this easier?)
I pulled the P1 connector (right side) on the ECU/ECM (engine computer module) to check for power to the unit. Pins 52 and 53 are always hot reading 24v. Pin 70 reads hot when power is on as well as cranking, reads at 24v.
It's clear to me the injectors aren't getting the signal to fire but I wanted to verify it anyway. I pulled the valve cover and used a non-contact voltage meter to sense the current to fire. None was seen.
At this point I'm suspecting a faulty ECU/ECM unit. Thoughts? Anyone have a good one on the shelf I can use to test my theory?
Attempting to slave start the LMTV off my wrecker gives it plenty of power to crank but it's not firing off. No warning lights or dash codes, it all acts normal. I pulled the fuse cover off and inspected the fuses which look good. All LED lights show green when power is on and ready to crank. This is the newer "green board" and not the blocky older style board.
I've bled both fuel filters and pressurized the tank to ensure it's getting fuel. There is a fuel pressure governor/restrictor on the rear of the engine for the return fuel. I've read those can be a problem by not allowing fuel pressure to build up when starting the engine. I took the return line off the fuel tank and pressurized it again getting nothing from the line. When cranking a steady stream comes out so it tells me pressure is being built and retained.
I wanted to eliminate the possibility of the dead batteries causing a problem when cranking so I pulled all 4 batteries and managed to save 2 to be put back in. The 12v and 24v systems were hooked back up correctly (verified by fellow members) and she cranks like a champ.
A quick squirt of either/starting fluid for an internal completion test was done. She does run..or wants to.
I bought a truck code reader to plug in the j1939 socket and see if the computer would talk to be but it ends up with a communication error when scanning. I can talk to individual parts of the truck for any current or stored codes but nothing is logged. (I thought this stuff was supposed to make this easier?)
I pulled the P1 connector (right side) on the ECU/ECM (engine computer module) to check for power to the unit. Pins 52 and 53 are always hot reading 24v. Pin 70 reads hot when power is on as well as cranking, reads at 24v.
It's clear to me the injectors aren't getting the signal to fire but I wanted to verify it anyway. I pulled the valve cover and used a non-contact voltage meter to sense the current to fire. None was seen.
At this point I'm suspecting a faulty ECU/ECM unit. Thoughts? Anyone have a good one on the shelf I can use to test my theory?
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