Replacing a Starter on a Peterbilt 387

How much, or how strong is the spark? If you have anything in the cab that has a clock or memory that requires constant power, it will cause a small spark when connecting the batteries. But if it is an ark that has a pop to it, you do have something crossed up somewhere. Always connect the positive first, then the ground.

 

Take em all off get test light an ck. them 1 by 1 till you find ones are hot and ground, alt. are not cheap.

 

If you have'nt had to time to fix it yet, take the cable back off and use a multi-meter to find which cable it ground.

Not all meters will emit a sound, mine does, but the sign for the continuity is like this...



Most trucks that ground the starter with a cable, do so with a pretty short cable to the frame somewhere reasonably close to the starter.

IMO, it seems that you must have the starter ground cable on the same terminal with one of the positive leads. It's easy enough to do when working in tight spaces with crud falling in your eyes.

 

There should be a wiring diagram that came with the starter. Sounds like you have the main positive and negatives mixed up, either at the starter or at the batteries. That doesn't look too different from a standard 39mt starter. Bottom large post on the body is negative, large post on top is positive. Don't use the middle post. There should also be the trigger wire to the magnetic switch, but that isn't the concern here.

There's also likely a big negative coming from the engine block or the frame.

 

Yes, I mostly understand. Before you take any cables off then, try the meter between the frame and each large terminal on the starter and solenoid. That may narrow it down to which terminal has the wrong cable to it.

The large solenoid terminal, I believe, should only have hot cables to it. If you only have one large starter motor terminal, on a gear reduced setup, it may be a ground terminal. ? If this is the case, you can go back to the batteries and use the meter between the frame and the positive battery cable. If you have continuity, you have a hot and ground cable on a starter terminal. Determine which cable is ground and remove it from the terminal.

One way or another, the meter will aid you in finding your short. It must be in a large cable to make such a large amp arc.

 

its wired up the same as your old starter just in a little diffrent way you need to trace every wire to find which ones are ground and which ones are positivethere should be a grouns from the frame to starter,block to starter,cab to starter and battery to starter, should be a power wire from circuit breaker to starter from alt,pos battery to starter.and one for main cab power feed, buy a power probe well worth the money i prefer it over my multi meter