Wiring My PMGR Starter

[det0326 192]

Bob does your starter spin the engine as it should with out anything heating up abnormally? If it does I'm not so sure this has anything to do with your breaking starter issues. While I would like to see a sufficient cable from battery to engine block on the grn side, I not sure if it is needed because the trans does have a pretty solid connection to the engine. I may be completly wrong but I think you have other problems

[RPM 1,246]

The starter does spin the motor as it should, but I've not felt the starter to check the heat. I will though on future tests.

[Mach1 Driver 597]

6 hours ago, RPM said:

Judge away Terry, most of my friends do :)

An example would be the #4 of my first test where before cranking the volts at the battery connection (forward big lug) on solenoid measured 12.6v and 11.1v when cranking, I came up with a 1.5v drop, instead of giving an 11.1 value.

The cable from the + battery post in the trunk to the solenoid is pretty close to 15 feet.

In your Word post questions, to which starter terminals is #3 measuring, B to C? And which terminals is #4 referring to?

OK, now the measurements are making more sense. The reason it's called a voltage drop test is because the wires have resistance, so they use some of the power flowing through them and turn it into heat. If we measure the voltage from one end of the wire to the other end when power is going through it, we can measure the wasted voltage (the drop voltage) that never makes it to the motor. The greater the drop voltage, the worse it is.

Since I don't have your starter in my hot little hands, I can't answer your question directly. Does the wire on B go to the front terminal of the fender mounted solenoid (B+)? Where does the wire on A go- I'm guessing the rear terminal of the solenoid? 

Your wire diagram may not exactly match your starter. The diagram seems to show a cable between the PMGRs solenoid to the motor. Does C just connect the PMGRs solenoid directly to the motor with a lug? If so, then just disregard #4. If ALL of what I just guessed is correct, then in test 3 you would measure from B to C, and there wouldn't be a test 4. 

However, it would be instructive to measure from C to the front terminal of fender mounted solenoid. This is only true if I guessed correctly above, and it would give you the voltage drop for the entire path for B+ for the starter. 

I calculate that a 15' #2 stranded copper wire will drop 0.716v at 300A. It is 0.159 Ohms/1000 ft.

I'm not saying that any of this is causing your problem, and Dave may be right. I'm just saying that it is contributing by slowing the motor down and heating it up. It would be good to know what the voltage drop is. In Woodchuck's test, the drop on the supply side should be less than 0.3v, and your longest cable pencils in at 0.716v drop. Then there is the second cable to add to it. 

[Nos681 2]

Verifying connection points Bob.

A = front terminal of fender solenoid/battery (+) from trunk/auxiliary fuse panel

B = rear terminal of fender solenoid 

C = PMGR starter terminal and jumper to PMGR solenoid (negative side).

I looked at my Motorcraft PMGR starter from my 92 Mustang.

This solenoid on this starter has “ground side” connected to terminal “C” not to chassis ground.

 

 

[RPM 1,246]

Dan (NOS681) is correct on my wiring. Thanks for jumping in Dan.

[RPM 1,246]

Corresponding connections on my solenoid and starter.

 

 

[Mach1 Driver 597]

OK, based on Dan's correction to Bob's original diagram, see the file: "Bob's voltage drop test2.docx"  on my Google Drive: https://drive.google.com/drive/folders/10FqYlsGT1XXr8B5TCF9WAASkU4vdPtuJ?usp=sharing

[Mach1 Driver 597]

Bob, you had the nose casting break off on the last one? Maybe this will give you some ideas: https://www.vintage-mustang.com/threads/starter-ears-broke-off.1225975/?post_id=10987910#post-10987910

[RPM 1,246]

Hey Terry,

Ya, I saw and read that post the other day but didn't learn anything. 

Yesterday I made a #2 wire from the rear big lug on the fender mounted solenoid to the small post on the starter. I also remove all of the wires from the solenoid and cleaned up the area behind it. while tightening the front big lug nut I heard a click from the starter. At that point I decided to change out the solenoid to another Motorcraft. In the 12-hours since, the car started just fine over ten times, including twice today. Hopefully it continues.

I do thank all of you guys who have offered your time and knowledge here helping me. And a special thanks to Terry for encouraging me to start a thread on my problem.

I was going to post this last night, but didn't want to jinx Roseanne.

Thanks again guys.