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MG MGB Technical - 79'B won't start

I need lots of help. Wife wants her car back and I want my 'B back. Problem is the baby will not turn over. I turn the key and nothing, no click, nothing. There is power to the rest of the car, lights, radio, flashers, wipers, etc. I have had the starter tested and was told it is ok. Cleaned the starter connections, the battery, checked the starter relay next to the fuse block. All seams clean and tight but it will not click or turn over. Also it won't jump start but it will push(compresion) start. Can anyone help with a possible answer. I have just moved to Georgia (Peachtree City) and don't know of any shops that I can take it to. Any and all help needed.
Scot Macdonald


Here's the thread to your original question - I think it dropped off into the archives while you were moving. It gives you some information about Atlanta.

I'll be glad to try and help, but I'm no expert, just willing.

John English

Scot. Have we been over this problem before? I seem to remember something like it recently. Get yourself a good voltmeter, analog is fine, and some jumper leads. Measure battery voltage at the battery terminals (not the battery cable clamps). You should see about 12.5 volts (but, I have seen up to 13.0 on a good battery.) Have an assistant try to crank the engine while measuring battery voltage. If the voltage drops below 11.0 volts (some say 11.5V), look to a bad battery.

If you have 11.5-12.5V at the battery terminals when attempting to crank, do the same test on the battery clamps. You should see the same voltage. If there is a drop, it is corrosion or a bad connection. (Remove, clean, reconnect and re-check.)

If the voltage is good at the battery clamps, check for voltage at the main terminal of the starter solenoid. If you see a reduced voltage, it is a problem with either the cable from the battery (+) to the starter, or the cable to the frame (-). In this case, use a set of jumper cables to run, first, from the battery clamp to the starter terminal. If all goes well (the car starts and good voltage on the volt meter) bad cable on the positive terminal. Bugger to replace. Have seen this once.

If the car does not start and still shows low voltage at the starter, disconnect the jumper cable to the positive terminal (but leave connected at the starter) and connect the black clamps to the negative battery clamp and the frame. Do the test again. If the car starts and the volt meter shows good readings, it is a ground cable problem. Have seen this once with broken wires in the cable to clamp.)

If you are still getting low voltage indications at the starter, connect the positive terminal of the battery to the jumper wire going to starter solenoid. This would indicate that both the ground cable and the cable to the starter are bad and are combining to make your problem. At this point, the car should start. If it does not, you have a starter/solenoid problem or a problem with the starter relay not supplying current to the starter.

With the key in the run position, quickly jumper the brown and white/brown wires on the starter relay. (Located to the rear of the fuse box.) If the car starts then, replace the starter relay.

I believe that this covers all of the possible problem areas except a bad starter/solenoid.

If, at this point, you cannot figure out what is wrong, contact Paul Hunt, possibly through his website, "The Pages of Bee and Vee" and ask him to pop up and comment. Most of what I know about car electrical systems is a result of Paul's patient coaching over the years. If I am considered an "expert" on electrical systems, as some seem to think, it is a result of Paul's excellent instruction and clear guidance.

Les Bengtson

Les covered almost everything, the one other component that could be at fault is the column switch itself. The switch on our 79 is starting to fail and it occasionally demands a quick wiggle of, or thump on, the key to get everything working.

However, I couldn't tell you how to isolate that as the problem in the same way Les did for all other components above, I will let someone else do that.
The Wiz

Be sure you are working with the starter relay, it's the one all the way back on the RH side, NOT the one in front of the fusebox. There are two types of relays: old rectangular Lucas with W and C designations, and later round or square with plain numbers. They are interchangeable and the later type is a standard item in parts stores - used on many cars.
When starting, the key sends power through White/Red to relay W1 or 86, so check for power there with key in START position. If not, there is a problem with keyswitch or wiring.
Relay W2 or 85 is ground = Black. Relay C1 or 30/51 is browN = always hot power.
If all this is OK: Relay C2 or 87 is White/browN to solenoid, should be hot with key at START. If not, relay is bad.
On the solenoid there are two male spade terminals. Normally one is 1/4" and one is 3/16", but I have heard that some have two 1/4". The 1/4" one is where the W/N wire goes, which switches the solenoid ON. The W/LG to feed 12V to the coil for starting goes on the 3/16" blade. If these are switched, as could be if you have two 1/4" blades, it won't work. Connect a jumper from the big solenoid terminal with all the N wires to the 1/4" blade, and the starter should operate, if not the starter or solenoid is bad; this bypasses all the wiring, key, and relay. If you have two 1/4" blades, connect the jumper to either; the one that makes the starter work is where the W/N wire goes and the W/LG goes on the other.
FR Millmore

Mike. The way you check for that is lack of voltage/power at the white/red line going to the starter relay when the ignition switch is turned to the "start" position. Never had that problem myself, but did have a bad wire from the switch in the "run" position. This powers the white wire circuit and the car would start, but, when the key was moved to the run position, die immediately. You picked up on the one area that I forgot to mention because it had not happened to me. Good show!

Best to Stef and Teenlet. Les
Les Bengtson


Try the basics first. Check that the terminals on the battery are clean and tight put some grease on them as well to stop corrosion. Also chech that the ground cable has good contact remove and clean is a good idea. Good luck. John

If there isn't even a click from the starter relay, and the lights stay bright when you have turned the key, then the ignition switch is not operating the relay. This will either be because of a faulty ignition switch or a faulty relay, or connections between them like at the multi-plug at the steering column. As Les says monitor the white/red at the switch, both sides of the multi-plug and at the relay while you turn the key to 'start'. If you don't get 12v on any of them the switch is faulty. If on all of them the relay or the ground conenction to it is faulty. If on one side of the plug but not the other see if one of the pins has been partially pushed out of the block.

Two other possibilities are if there isn't 12v on any of the white/reds then check you still have 12v on the brown when turning the key to 'start', if not then there is a bad connection in the brown to the switch which could also be in the multi-plug.

The 2nd is that if you get 12v on the white/red at the relay before junking the relay make sure the white/red connector is making good connection to the relay spade. Also you don't say whether this suddenly started on its own or after some work. If the starter relay is a metal can Lucas 6RA type make sure the white/red and black are connected to W1 and W2 (either way round). If a modern relay they should be on 85 and 86. Also check that there is 0v on the black (ground) spade when there is 12v on the white/red spade, if so then the relay is faulty.
Paul Hunt 2

Thanks for your help everyone. I will be working on this for the next few days trying to sort it all out. Paul, you asked if it suddendly started or after some work. Suddendly started. Drove grandaughter to the park, started fine, went to leave nothing. I will post again when all is well. Again thanks all.
Scot 79B
Scot Macdonald

OK, shouldn't be a mis-connected relay then, but still check that the black relay spade and connector remain at 0v when the white/red is energised.
Paul Hunt 2

This thread was discussed between 18/10/2005 and 20/10/2005

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