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Discussion Starter #1
I am having a problem with my Falcon, it wont stop the engine running when the ignition is turned off with the key. It has an electronic distributor and the timing has been checked and is set ok. If I ground the positive connection on the coil it stops, but won't start again until the igntion switch id back in the on position? I'm not sure what else to check, can anyone help? :confused:
 

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heyboy said:
I am having a problem with my Falcon, it wont stop the engine running when the ignition is turned off with the key. It has an electronic distributor and the timing has been checked and is set ok. If I ground the positive connection on the coil it stops, but won't start again until the igntion switch id back in the on position? I'm not sure what else to check, can anyone help? :confused:

Doc here, :pimp:

You have the alternator back-feeding the Ignition system, either wired past the switch, or on the Ignition line OR you have a 12 volt source hot all the time on the Ignition wire..

Some Ignition systems require a diode on the power line to the coil for Charging system Isolation.

If you keep grounding that line you will burn out the Ignition AND maybe the alternator..

Doc :pimp:
 

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Is it a 6 cyl with a DSII distributor? if so, check it for power when the vehicle is off compleatly. pretty common to wire them so they do that.
 

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Discussion Starter #4
It is a 351 V8 with an aftermarket distributor and coil. It was fitted to the manufacturors specifications and ran fine to start with, then it started to run on a little and now it just keeps on running!!
 

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Doc here, :pimp:

Howdy and welcome..

Have you recently changed the Alternator or Regulator or added an amp gauge?

Done any recent wire changes?

Doc :pimp:
 

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Discussion Starter #10
There was a kill switch fitted in the glove box for security. When this problem started I removed the switch and wiring though.

Stu
 

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Doc here, :pimp:

OK, that answers volumes!

Most likely, what that switch was doing, was cutting of a residual voltage after the ignition was turned off..Most likely from the alternator...

A Quick test for that is ..

Remove the output wire, and the plug, from the alternator, start and run the vehicle..then shut it off..If it stops, you have a backfeed from the charging system, You need to move the output wire from where it is at to the Starter solenoid big terminal.

If that fails the test, put a DVOM on the Ignition +Coil wire (or Ballast resistor) and look at the voltage static, It should be zero. Then start and run the vehicle , shut it down and watch the meter..If it stays at 12 volts..and remains running, pull the fuses and relays ONE at a time until it dies and goes to zero..

When that happens, trouble shoot that branch circuit, Find out what is hanging up after shut down, then repair or disable as needed.

If you can't find the problem at all, you may order a Diode Kit from MSD to install on the Ignition line to prevent a backfeed.. (And some kits require them) That will set it right.

Doc :pimp:
 

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Discussion Starter #14
Hi there, sorry it's taken a while. We just moved house and been very busy at work, anyway the advice was spot on and the car is running a treat now with a diode fitted.
Cheers
:thumbup: Heyboy
 

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Doc here, :pimp:

Kewl! Glad to hear it is working now!

Thanks for posting back the curative! :thumbup:

Doc :pimp:
 
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