Replacing a Starter on a Peterbilt 387

IMO, you should have a meter,learn the basics and carry the meter in your truck with you. It is a very valuable tool that can save you many dollars. The meters can be bought for anywhere from 10 bucks at harbor freight, to many hundreds of dollars. Buy the harbor freight if you have a store locally, or any tool store with have an economy model.

Make sure it can test continuity. This takes a battery in the meter. Usually a 9 volt or a AA. How you use it to test continuity is the meter will send a small trickle thru the wire. If you put a meter lead on one end of the wire, and the other lead on the opposite end of the wire, the meter will have a different reading than before you attached the leads.

This same method works to test which wire is grounding. You put one lead on the frame, and one lead on the wire. If you get no change in readings at the meter, that wire is not grounding. If you get a meter reading, then that is the ground wire.

You can use this meter for many things on the road to test for voltage in lights, light bulbs, alternators, trailer plugs. All kinds of stuff. And,......you can use it at home for many things that can save you money. It is a very easy meter to understand once you use it a time or two.

And yes, you can put hot wires on ground posts and vice versa at the starter. They usually use a 1/2" stud for both at the starter. It does not work to do so, but you can physically do so.

 

The positives go on the solinoid the negatives go onto the starter body stud. If you are sure of all wires except the one take it back off and continuity check it to ground to see what it is. Or with it off try connecting batteries and see if it still arcs.

 

Terry all posts are hot. If you notice both solenoid heads are made of a ceramic plastic which acts as an insulator. Notice the bolt protruding from the starter head has an insulator under it. That is because it's a hot going to the brushes. The only thing grounded on starters are the housings.

Now for the wiring. Seven wires one is ground. It's a big wire straight to battery ground. The smallest wire goes to the smallest post on the starter solenoid. That leads to five hots left. The biggest one is straight from the battery. It's only 4ft long you should be able to follow it to the batteries. You do have a jump post hot on the firewall near the coolant reservoir. It might junction there or it goes straight to the battery.

The 4 remaining wires are hot feeds to other circuits. They just junction at the starter since that's the best hot in the area. They all mount on the top post of the master solenoid along with the battery hot.

Isn't one of your mount bolts a stud? That's where your ground is suppose to go. It contacts directly with the starter housing base.

If you lost track which wire is ground you have two choices. Ohm the wires to ground until you find the right one. You can't test volts like I said 4 wires are hot feeds and have neither volts or ground. Your other option is to physically follow the ground off the batteries. It shouldn't be 3-4 ft long.

As far as that hard bolt you'll probably need a combination of extentions longer than the starter and a swivel at the socket.

In the future take a picture and mark your wires with tape.