1972 mgb gt non-Starting Problems
Discussion
I hope someone can help me out here, I have a 12V system in a 72 mgb gt, recently while we were out the heater valve failed and dumped coolant all over the dizzy and starter motor. However, once it was topped up, it started and drove, and got us back.
I came to move it a week later and there is nothing. No ignition light, no fuel pump noise, and definately no spark.
I went away to look at the circuit diagram, went back out and the lights all worked in the first position, but when I tried to start her, everything went dark again. I can now intermittantly get an ignition light but that is it.
I have 12V at the ignition, 6V(?) at the starter on the big brown cable terminal, and 12V at the fuse box. Earths are clean and the battery terminals have been cleaned and checked.
Is it the starter motor that is the problem?
Thanks for readng, and any help you can offer.
I came to move it a week later and there is nothing. No ignition light, no fuel pump noise, and definately no spark.
I went away to look at the circuit diagram, went back out and the lights all worked in the first position, but when I tried to start her, everything went dark again. I can now intermittantly get an ignition light but that is it.
I have 12V at the ignition, 6V(?) at the starter on the big brown cable terminal, and 12V at the fuse box. Earths are clean and the battery terminals have been cleaned and checked.
Is it the starter motor that is the problem?
Thanks for readng, and any help you can offer.
6V at the starter doesn't sound right - you put a ? so are you sure there's only 6V? Some cars have a 6V coil and a resistor to take up the other 6, no idea if Bs have that, I've not heard of any 12v cars having 6v starter.
The starter isn't going to cause intermittent ignition light, did the Voltage regulator get wet as well, sound more like there might be a problem there.
The starter isn't going to cause intermittent ignition light, did the Voltage regulator get wet as well, sound more like there might be a problem there.
I'm guessing you are testing for the presence of voltage with a test meter. That's OK, but won't reveal a circuit with high resistance in it, which won't flow sufficient current when needed.
I suggest testing the critical points in the circuits with a tester with a 12V bulb in (easy to make a simple one yourself with a tail or brake light bulb) to see whether the circuit can actually deliver a reasonable current when required to do so.
Years ago I had a problem with the horn circuit on an Austin 1800 and it had exactly this problem. 12V present and correct, but the connection to the battery was so poor that no worthwhile current could flow, which was onlt revealed with a test light. Cleaned up the connections and all was well.
Good luck with the fix.
I suggest testing the critical points in the circuits with a tester with a 12V bulb in (easy to make a simple one yourself with a tail or brake light bulb) to see whether the circuit can actually deliver a reasonable current when required to do so.
Years ago I had a problem with the horn circuit on an Austin 1800 and it had exactly this problem. 12V present and correct, but the connection to the battery was so poor that no worthwhile current could flow, which was onlt revealed with a test light. Cleaned up the connections and all was well.
Good luck with the fix.
Hi
Thanks for the suggestions, but I think its something else. The battery has 12.4V so could do with a charge, but its the fact that there is nothing on the ignition circuit thats the issue.
I dont think its the alternator because thats uphill from the vale, and it was a fast trickle not a spurt.
Thanks for the suggestions, but I think its something else. The battery has 12.4V so could do with a charge, but its the fact that there is nothing on the ignition circuit thats the issue.
I dont think its the alternator because thats uphill from the vale, and it was a fast trickle not a spurt.
Eliminate the simple things first.
Fully charge the battery with a battery charger of fit a fully charged battery (don't assume a brand new one is fully charged BTW!) & see what happens.
If the same then connect a good quality jump lead directly from the battery earth terminal to a good clean point on the engine block & see what happens.
Fully charge the battery with a battery charger of fit a fully charged battery (don't assume a brand new one is fully charged BTW!) & see what happens.
If the same then connect a good quality jump lead directly from the battery earth terminal to a good clean point on the engine block & see what happens.
paintman said:
Eliminate the simple things first.
Fully charge the battery with a battery charger of fit a fully charged battery (don't assume a brand new one is fully charged BTW!) & see what happens.
If the same then connect a good quality jump lead directly from the battery earth terminal to a good clean point on the engine block & see what happens.
This !Fully charge the battery with a battery charger of fit a fully charged battery (don't assume a brand new one is fully charged BTW!) & see what happens.
If the same then connect a good quality jump lead directly from the battery earth terminal to a good clean point on the engine block & see what happens.
It certainly sounds like the probably braided earth from the engine block to the chassis is failing or has failed . It's probably just a coincidence that the problem has appeared after the leak .
Is this also an MGB with twin 6v batteries? Could be one of the batteries has a failed plate causing an erratic short .
As suggested above, battery/earth problem. Being a 72 B this presumably still has the two 6 volt batteries? Has it got those awful battery terminals BL used at the time? Like a big lead cap with A screw down the middle, they were useless and a B had 4 of them. cut them off and fit some decent terminal clamps if its not been done already.
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