No crank electrical mystery

[Scooter81]

I have a 2004 M1114. IronPlanet said it would not start and I have never had it started. It appears that new new engine was installed just before the unit went to auction. The wait light and brake light briefly flash when the switch is turned to run. Nothing happens when the switch is turned to start. What have I done to diagnose?

New batteries.
Checked brake and neutral switches. No problems.
New box and GPC - I also tried a box from a working vehicle. Same issue. I put that box back in its original vehicle and it still runs fine.
Check all grounds and wiring harness connections.
Checked voltage at power plug on Engine harness cannon plug.
Checked voltage at starter connection.
Disconnected light switch plug. no difference.
Disconnected turn signal plug. No difference.
Tested starter switch. No faults.
Tried direct start by jumping the S&T ports next to the shifter. No joy.
Checked continuity on the two circuit breakers near the stearing column. All good.
I had some slimy crap on the wires on the chassis harness wires and some insulation was chipping and leaving exposed wires. I dressed and check all the wires. I peeled the nylon cover around the harness back several inches so I could inspect the wires thoroughly.

So Im planning to just replace the body wiring harness next. However I would really like some insight into what kind of (which and the wire number) faulted circuit might cause this issue?

 

[Mogman]

I have a 2004 M1114. IronPlanet said it would not start and I have never had it started. It appears that new new engine was installed just before the unit went to auction. The wait light and brake light briefly flash when the switch is turned to run. Nothing happens when the switch is turned to start. What have I done to diagnose?

New batteries.
Checked brake and neutral switches. No problems.
New box and GPC - I also tried a box from a working vehicle. Same issue. I put that box back in its original vehicle and it still runs fine.
Check all grounds and wiring harness connections.
Checked voltage at power plug on Engine harness cannon plug.
Checked voltage at starter connection.
Disconnected light switch plug. no difference.
Disconnected turn signal plug. No difference.
Tested starter switch. No faults.
Tried direct start by jumping the S&T ports next to the shifter. No joy.
Checked continuity on the two circuit breakers near the stearing column. All good.
I had some slimy crap on the wires on the chassis harness wires and some insulation was chipping and leaving exposed wires. I dressed and check all the wires. I peeled the nylon cover around the harness back several inches so I could inspect the wires thoroughly.

So Im planning to just replace the body wiring harness next. However I would really like some insight into what kind of (which and the wire number) faulted circuit might cause this issue?

You need to carefully jump the solenoid wire (#74) to 24V, you may have a bad starter.
The wires that go to S and T on the diag port are in a harness that is completely separate from the engine harness so it is less likely you have a fault on both harnesses.
The start/run/glow plug circuits go through the engine harness rather than the body harness to begin with.
Do any lights work?
Does the heater blower/ WW wipers work when in run?

 

[Scooter81]

You need to carefully jump the solenoid wire (#74) to 24V, you may have a bad starter.
The wires that go to S and T on the diag port are in a harness that is completely separate from the engine harness so it is less likely you have a fault on both harnesses.
The start/run/glow plug circuits go through the engine harness rather than the body harness to begin with.
Do any lights work?
Does the heater blower/ WW wipers work when in run?

No lights or wipers. I have run every inch of that engine harness. But I guess you cant see what you cant see. You think a bad starter would screw up the wait light like that? So... jump 74 to ground, or jump it to 81A. In all the messing about at least the brake light stays on now even though the wait light immediately goes out when switched to run. Would an error/fault/short in the GPC wires or connector cause the starter to not engage?

 

[Mogman]

No lights or wipers. I have run every inch of that engine harness. But I guess you cant see what you cant see. You think a bad starter would screw up the wait light like that? So... jump 74 to ground, or jump it to 81A. In all the messing about at least the brake light stays on now even though the wait light immediately goes out when switched to run

Considering you have tried known working PCB boxes then the glow plugs could be bad, that would cause the wait light to only flash on a smart start box, ohm each one out, they should be around 2 ohms, if bad they will be way off of that.
Have you checked ALL the battery cables pos and neg? there are connections at the inside walls of the battery box including the shunt as well as connections on the outside walls (tunnel) side of the box, very hard to get to, make SURE you have the batteries disconnected when working on these connections.
Take a wire from the 24V pos terminal on the starter to the starter solenoid terminal where the #74 wires connect to test the starter.
Also take a voltmeter and connect the pos meter lead to the pos terminal on the starter and the neg lead to the starter body and monitor voltage when you test the starter.

 

[Scooter81]

I got new glow plugs with the new PCB so I think they are good. I completely cleaned leads inside the battery box and that one inside on the frame rail. I will look at all of those again.

 

[Mogman]

There are two on the outside of the battery box (between the battery box and the frame rail) one positive and one negative, not on the frame rail.
The bolt that carries the negative from the shunt to the neg cable through the wall of the battery box seems to give allot of folks trouble.