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Ignition concern

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Ed Porter

Freshman Member
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Hello all,
I have a 74 MGB GT. I took it out for the maiden voyage yesterday. When I got back to my garage, I turned the key in the ignition to shut her down, and the engine just kept right on running. I removed the key from the ignition, and she kept on running. I ended up using the clutch to kill the engine. Any thoughts???
confused.gif
 
Sounds Like Sneak Current, The Prince of Darkness strikes again! Sneak Current Tech Article

[ 05-10-2004: Message edited by: UltimateQuestion ]</p>
 
Was it actully running normally or "deiseling" and running on...if the later, perhaps a new anti-run-on valve will cure it if it become a habitual problem?

Just an easy thought...I have an extra if you want to try it...and don't mind if it is partially painted blaze


Bruce
cheers.gif
 
Ed, Another thought. I have had this same problem and found the fix to be in the alternator circuitry. Most alternators have a blocking diode that prevents the 12 volt alternator voltage from overriding the ignition voltage. If this diode has become shorted or rewired somehow, the engine will not shut down with the ignition key. Disconnect the alternator entirely and start up the car. If then you can shut it off with the ignition, you have found the problem. You can install a diode in line to the excitation voltage to stop this bothersome occurence. Good luck, Jack
 
if it is just running on try going on a long trip about 4 hours or so on the freeway at fast speeds and it should burn a whole lot of carbon out of the heads and should cut off normally. mine hadnt turned off under its own power since i got it two years ago and the night before last was the first time that it didnt run on
 
<blockquote><font size="1" face="Verdana, Arial">quote:</font><hr>Originally posted by Ed Porter:
Hello all,
I have a 74 MGB GT. I took it out for the maiden voyage yesterday. When I got back to my garage, I turned the key in the ignition to shut her down, and the engine just kept right on running. I removed the key from the ignition, and she kept on running. I ended up using the clutch to kill the engine. Any thoughts???
confused.gif
<hr></blockquote>

Sounds like the ignition switch isn't working. If you can remove it with wires attached, start car, remove correct wire to kill it. I would bet that stops it. If not some wire somewhere has shorted but I would still bet the switch itself or it is wired incorrcetly. I had a similar problem where I put a fuse in one notch higher that it was supposed to and kept a circuit open. It was sort of jammed bewteen two locations shorting the lot.

Or take out the ignition switch ( disconnect battery first) and remove all wires. Check continuity with a meter as you turn it on and off. Otherwise it might be as posted above, sneak current.

[ 05-10-2004: Message edited by: Bruce Bowker ]

[ 05-10-2004: Message edited by: Bruce Bowker ]</p>
 
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