QuestionMy question is related to the thread below.
I have a 1967 MGB with negative earth ground and an inertial stater motor.
When I turn the ignition, I hear a awful sound, which I assume to be the start motor trying to turn.
I replaced the starter motor and hear the same sound.
I can push the car foward in 4th gear, so the engine is not seized.
When I check the voltage on the battery when turn the ignition key, the voltage drops from 12v to 5v.
What does this mean?
If I short across the starter solenoid with a jump cable, the starter motor does NOT make a sound.
What does this mean?
Question
QUESTION: I have a 1967 MGB which now clicks (solenoid?) when the key is turned but the starter motor does not engage. Battery seems fine - jumping did not help. Any tests I can run before ordering and installing a new starter motor? Thanks much.
ANSWER: Hi Mike,
You need to do voltage drop tests of the cables. If it is a clicking noise with a charged battery then you either have a bad cable connection, solenoid bad, starter bad or locked up engine. You need to do some testing before ordering all these items.
You need a volt meter to do the tests. Put the volt meter across the battery posts (not the cable ends)and hit the starter and read the volt meter. If you show more than 12v while the clicking is going on then set the voltmeter to a low volt scale and put the negative lead (black) on the negative post of the battery and the positive lead (red) on Battery connection on the starter solenoid and have someone hit the starter. You should read less than half a volt. Next connect the negative lead of the voltmeter to the starter cable on the solenoid and the positive lead on the starter post and hit the starter again, again you should see very little to no voltage. Next connect the negative lead to a metal part of the engine and the positive lead on the positive post of the battery and hit the starter again. You should as on all of these voltage drop tests read little to no voltage on a very low volt scale. Any voltage reading of over a half volt indicates a bad connection.
If on the first test of the battery voltage 12v+ reading, you seen the voltage drop when the starter was engaged, you need to put the car is 4th gear and see if you can roll the car a little (which turns the engine) This makes sure the engine is not locked up.
Next test take a jumper cable and attach one end of one cable to the solenoid and with the car in neutral and key off, scratch the other end of the jumper cable on the negative post of the battery. You should see sparks. Then touch the jumper cable hard on to the negative post just for a second (no longer) The starter should spin the engine a little. This tests the starter and the solenoid. If the starter does spin the engine then the solenoid is at fault, if it does not then the starter is at fault. (This is only true if you did ALL of the first drop tests correctly)
Be sure you have the battery cables connected correctly. Positive post to ground and Negative post is the hot cable that goes to the solenoid.
Let me know,
Howard
ANSWER: Dan, you will not find out what is wrong unless you do the tests I gave you. When the voltage drops to 5v with the starter activated you either have a locked up engine (which you confirmed you don't) or you have a locked up starter (you shouldn't because you replaced it once) or you have cable problems which can be tested by doing voltage drop tests as I told you to do. DO THE VOLTAGE DROP TESTS!
Howard
---------- FOLLOW-UP ----------
QUESTION: Hi Howard,
Here are the voltages between test points when I turn the ignition:
Battery + to Battery - = 5V
Battery – to Solenoid battery connection = +3V to +5V
Solenoid starter post to Solenoid battery connection = -5V
Battery + to Metal part on engine = -5V
There is a 0 ohm drop between a metal part on the engine and the other side of the strap that connects the engine to the chassis.
There is <10 ohm drop between the Battery – and a metal part on the engine.
To ensure I had a good ground (again car is - earth) I ran a jumper cable from the Battery – to a metal part on the engine got the same results when I repeated the tests.
During these test, I did not hear the starter motor whirring up, just a clicking.
When I connect a jumper cable to the Battery + and touch the other end to the post on the starter motor, nothing happens. This is a new starter motor.
Before I swapped it, I took the old starter motor out, whirred it up on the bench top, put it back in. The first few times I tried to start the car, I heard metal on metal. After the third time, I heard what I am hearing now. I reseated the old start motor and again heard metal on metal the first few times.
Could this problem be due to bad teeth on the flyweel?
Best, Dan
AnswerDan, your test results don't sound right. First the 67 B was a positive ground car and had two 6v batteries connected in series to make 12v.
Do you now have it set up as a negative ground system and one 12v battery?
(Battery + to Battery - = 5v)
1. If you have a voltmeter on the two posts of a 12v battery and turn on the ignition and the voltmeter drops from 12+ volts down to 5 volts, you either have a internal broken battery post or you have a very large heavy dead short in a positive cable or solenoid. At this time that cable would have to be getting very hot and smoking.
(Battery - to Battery solenoid connection = +3v to +5v)
2. If you have a negative ground system you should have gotten a 12v reading.
Either your voltmeter is no good at all or you are not connecting where you say you are connecting. All of your readings are impossible.
Howard
