MG Car Repair: 79 b starting issue, voltage drop test, tracer wire

Question
i found a question that you answered a while back from a guy with a 75 mg that would not start. i could not believe that he was experiencing not but two identical problems. First if i read correctly after i have done a voltage check(which seems ok) i should replace the ground strap? I think that my problems began when i tried "bump starting" my b many times to a point where it would not statrt anymore. I have replaced the starter relay and solenoid any i am hoping you can confirm that i am on the right track. thanks again.

Answer
Hi Harry,
If you have read some of my past answers you will see that I advise not to replace any part until you have been able to ID the failed part.

You first have to clarify what you mean by "Won't Start". Will not spin over? or spins over fast but does not start running? By you saying you have been replacing relays and the solenoid I guess it does not spin over.

Start testing with a volt meter, by testing the battery (post to post NOT cable ends) Should be 12+ volts. Now with the volt meter on the battery (POSTS) turn the starter on. Read the volt meter. What is the reading? If it is still 12+ v. put the positive (red lead) of the volt meter on the (+) post of the battery and the negative test lead on the (+) post of the solenoid and turn to "Start" again. What is the reading? and did the starter try to turn? That is called a voltage drop test of the (+) cable (if the starter operated)

Put the (+) test lead on the small wire White w/red tracer wire on the solenoid and turn to start and see if you see voltage and how much? If none you need a wiring diagram to start testing wiring and the new relay.

Think of current as going down a road from the battery and on to the solenoid and the solenoid opens a gate for an expressway from the battery to the starter motor. This expressway is useless unless the other end of the expressway is also clear from the case of the starter motor to the engine and from the engine block to the frame of the car and from the frame of the car to the (-) POST of the battery. If there are ANY bottle necks in that express way on the (+) or (-) side, the traffic will not flow. And the starter will not spin.

Howard