2018 Mack GU813 S/N: 1M2AX16C9JM039991 When you turn the key to start it, it wont engage the starter. But if you hold the key in the start position for a couple seconds, then it will begin to crank over. Or if you cycle the key a couple times it will work also. This morning, it wouldn't do anything. I ended up jumping the starter while the driver had to turn the key to the starting position, while I jumped it. I'm assuming the starter relay is the problem. I just want to hear other input before I replace anything.
It could be several things between the start signal on the key switch all the way to the starter solenoid. I'm not familiar with Mack trucks, but I'd bet that signal with run through a neutral start switch and possible start relay at the very least.
Can you rephrase that? I don’t fully understand what you mean.
Mack said it doesn't have an old style style large relay. They told me to check the ignition relays in the cab. I found 2 of them and they tested good. I don't know if there are supposed to be more than 2. There is an over-crank protection solenoid/ relay underneath the starter solenoid. I don't know if that would cause this issue. Or if the issue could all be in the ignition switch itself.
How many miles on this truck?
258k
With ignition key in start/exciter position how many volts at that terminal on the solenoid? Is this a 39MT starter with a small relay mounted to the starter which feeds the solenoid?
It was that relay mounted to the starter. One terminal was loose/ broken. It would start when I wiggled it. Got a new one, and it started up no problem. Thank you, appreciate the help.