77 MGB Starter

[rj fisher]

When I started my MG yesterday, the starter continued to run even after the ignition key was removed, resulting in the battery disconnect to stop it. Has anyone experienced this before?
Thanks

RJ Fisher

[Flash75]

RJ, Did you have the handbrake on when you started the car and does it begin cranking when the ignition switch is turned to the run position?
If that is your situation try releasing your handbrake, that should turn the starter off.

To understand why go to this web site.
http://www.mgb-stuff.org.uk/wn_suspensionframe.htm
Click on "electrics"
Then click on "Won't Start"
Scroll down to, ""It starts cranking as soon as I turn the ignition on and won't stop until I release the handbrake or disconnect the battery!!

The instructions there will tell you what to do. If you have a Haynes repair manual the wiring diagram for your car is Fig 10.34.

For a color wiringdiagram go to,
http://www.advanceautowire.com/
On the left click on, "Stock Schematics"
Scroll down and click on "MGB" You will get a PDF file with several pages of schematics. Page 17 is the correct wiring diagram for your car. It's easy to print out page 17, you can have if blown up at Kinko's or other printers.

If this doesn't locate your problem post back and perhaps someone can help. I don't have a 77 but that problem happens pretty often, that's the reason Paul Hunt included it in his web site.

Good luck, Clifton Gordon

[rj fisher]

Originally Posted by rj fisher

When I started my MG yesterday, the starter continued to run even after the ignition key was removed, resulting in the battery disconnect to stop it. Has anyone experienced this before?
Thanks

RJ Fisher

I put the hand brake off and the first time it started right up. Then a few minutes later I restarted it and again the starter kept running until I disconnected the battery. Because of my novice mechanical ability this is really puzelling. Does anyone have any thoughts and remember I am a beginner. I have been told it is the solenoid, ignition switch or the relay, but how can I find out which? Thanks for any suggestions.
rj fisher

[rj fisher]

Originally Posted by rj fisher

I put the hand brake off and the first time it started right up. Then a few minutes later I restarted it and again the starter kept running until I disconnected the battery. Because of my novice mechanical ability this is really puzelling. Does anyone have any thoughts and remember I am a beginner. I have been told it is the solenoid, ignition switch or the relay, but how can I find out which? Thanks for any suggestions.
rj fisher

One more thing, this does not happen until the starter switch is full engaged to the start position. The starter does not turn until then.

[Flash75]

rj, I assume you didn't try disconnecting the diode as Paul Hunt suggested. It could be solenoid, relay or the ignition switch. Your car has one or perhaps twob diodes and they are usually the cause of the starter not shutting off. I will outline some steps you can take to narrow the problem down. I don't have a 77, my car is a 74 so I cannot tell you where certain components are in your car. I do understand wiring, relays and switches.

You need someone to help, first you need to find the start relay, it should be in a small metal can with four wires attached to it. Look under the hood back near the firewall. The start relay will have a brown wire, a brown/white wire, a black wire and a red/white wire. When you locate the relay look for the brown and the brown/white wires. Note the wires can be removed from the relay by removing a slip on terminal. pull on the terminal not the wire. There is 12 vols on the wires so don't let them contact bare metal, they will not shock you. Have your helper start the car, as soon as it starts remove either the brown or the brown/white wire. Either wire is ok, did the starter stop? If it did the solenoid is good. Turn the engine off and replace the wire.

Locate the black wire. Start the car and remove the black wire. Did the starter stop? If it did the relay is probably good. You can try it again and remove the red/white wire. If it stops the relay is good. Don't assume the switch is bad yet.

You need to find the diode in the hand brake and brake pressure failure switch circuits. It's a black tube like device probably on the firewall on the passenger side. It has a red/white wire ononeend and a green/orange wire on the other side. Start the engine and unplug either wire on the diode. Did the starter stop? if it did the switch is good and the problem is in the diode or it's associated circuits. It will not hurt to leave the wire off the diode, tape the ends. Since the brake failure switch is in that circuit, any recent brake problems like light on all the time?

These steps should help you narrow the problem down. Let us know what happens. Just be careful and don't short something out.

Clifton