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1977 MGB engine wont stay running

Posted by mandrpainting

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1977 MGB engine wont stay running #1
mandrpainting Michael Rogers Colorado Springs, Colorado, USA	Posted: June 17, 2012 07:11PM Registered: 1 year ago Posts: 1

I have a problem with my MGB. The engine turns over starts running with starter. Will not stay running.
When the key is released I have used the coil to short across engine starts and runns. Thought it was a
ignition problem. Bought a new starter ingnition installed and same problem.
Will not stay running unless I short across.

I have disconeccted the run on valve also and shorting across
The engine will run but not with the key.
I read that the battery cables and battery could not be putting out enough
power? If corroded...

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Re: 1977 MGB engine wont stay running #2
flash75 Clifton Gordon Asheboro, North Carolina, USA	Posted: June 17, 2012 07:30PM Registered: 6 years ago Posts: 2,634

If if was your battery cables the car wouldn't start. You probably have an ignition
feedback problem. Try the attached link.

Clifton

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Attachments:

Ignition Feedback.pdf (1.31 MB) –

Re: 1977 MGB engine wont stay running #3
mk21965 Stuart Brainerd CT, USA 1948 Triumph 2000 Roadster	Posted: June 17, 2012 08:02PM Registered: 6 years ago Posts: 138

Possible faulty resistor? Would need to spend a little time with a wiring diagram but it sounds like the ignition is being fed from the starter circuit but not the run circuit. Or it could be a main relay feed problem... I'll check when I get to work tomorrow if others here don't solve it first.

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Re: 1977 MGB engine wont stay running #4
Vern Vern Smith Truckee, CA, USA	Posted: June 17, 2012 09:41PM Registered: 14 years ago Posts: 895

Probably a bad ballast resistor or connection in the resistor circuit. The battery voltage goes directly to the coil (thru the relay) during start to give a full 12V for starting, then when the key is released, the resistor drops the voltage to around 6V to help keep the points from arcing. If you have electronic ignition, the ballast resistor system is usually bypassed. If you have an after market electronic ignition, you should have had an instruction to eliminate the ballast resistor.

Make sure your ignition relay (passenger side fender well) stays energized when you release the key. Or if you don't have a meter or test light, just listen for a click at the relay when you turn the key to on. If you do, it's working, if not you have a bad switch, because the relay has to be picked up in "start" for it to start at all, even if only in the "start" position".

If this makes no sense, slap me! I'm a techno geek, so sometimes I talk in circles. (Makes me sound smarter). Remember..."If you can't baffle 'em with brilliance, befuddle 'em with BS"

Or the one I like even better...."It's not pushing the button that's hard, it's knowing which button to push!"

If you pretend it ain't broke, you don't have to fix it!

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