Bad starter? Or solenoid? 2007 peterbilt 379

My "94" does the same thing here and there. Been told its the solenoid on top of the starter. If you can remove it and replace the contact point or clean it, it might resolve your problem. But these days, some parts are sealed and they make you replace the whole part, starter and all.

 

If the big solenoid is getting power on the small signal wire during a failed attempt, it is starter time.

 

Check your starter relay. I've had them go on the fritz and work when they want to.

 

Shouldn't be more than 3 bolts to the bell housing and 2 nuts for your electrical. You will need 1/2 in extensions longer than the starter for easier access to those bolts.
I'm thinking it's 5/8 12 point socket you will need and the nuts are 3/4

 

Get a multimeter and start poking around. See where the power stops.

My '89 does the same thing. I have to hold the start button for a bit before it kicks in. Different motor but same concept.

 

Starter is held in with basically 3 big bolts. They can be really hard to get out sometimes and you would need good quality 1/2" drive extensions and long breaker bar. First step, disconnect your battery cables at the batteries for safety, then disconnect your starter cables and make sure you label or mark them as to where they go.

 

1 hour, tops.