engine wont switch off

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steve4179
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engine wont switch off

Post by steve4179 »

hi im having a little trouble with my ms3x its been switching on and off fine until recently when now it starts fine but I can switch the ignition off and take the key out and it keeps running!! I can pop the earth off the battery and it keeps running, the only way I can turn it off is thru a switch ive got wired to the coil for use as an immobiliser, ive changed all of the relays and checked all the connections and they all seem fine, any ideas anyone???

cheers in advance
steve
DaveEFI
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Re: engine wont switch off

Post by DaveEFI »

Don't disconnect the battery ground with the engine running - there's the possibility of the alternator producing far more then 12 volts and turning your MS into toast.

It sounds like a relay is holding on by getting volts from somewhere other than its switch. Impossible to guess at without a circuit diagram of the entire car, and MS installation.
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steve4179
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Re: engine wont switch off

Post by steve4179 »

Its an old car (78 capri) that had alot of electrical gremlins chances are the ignition barrel or the place on the original fuse box that i took a live for the relay from has gone south
Barton
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Re: engine wont switch off

Post by Barton »

use ONLY switched 12v to power all the relays, inyectors, coils, idle valve, etc etc tec connected to the ms, I'm sure your problem is there.
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kjones6039
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Re: engine wont switch off

Post by kjones6039 »

Barton wrote:use ONLY switched 12v to power all the relays, inyectors, coils, idle valve, etc etc tec connected to the ms, I'm sure your problem is there.
Very good advice! Voice of experience here........ I once had a 'run on' condition in which the cooling fan acted as a generator and wouldn't let the engine shut down. All caused because I, in my infinite wisdom, decided to vary from the manual just a little bit. BAD idea! Stick with the recommended wiring in the manual religiously!

Just the old guys 2 cents.......

Ken
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slow_hemi6
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Re: engine wont switch off

Post by slow_hemi6 »

You sometimes get an issue in old cars when you change them to internally regulated alternators where the alternator keeps the car alive. Generally a diode rather than a bridge across the old ext regulator plug fixes the problem.
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Cheers Luke
Nightstalker1993
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Re: engine wont switch off

Post by Nightstalker1993 »

I actually encountered something similar last year when I was running an MS2.

Was burning a tune file my friend sent to me via MsDroid over Bluetooth to the MS2 and the firmware got corrupted, showing me 16k RPM and other wacky readings with the engine off. The ECU refused to turn off and my ign was clearly turned on even with my key out, suspected my turbo timer was faulty and even after removing the turbo timer the ECU was still switched on. After reflashing the MS2 and disconnecting/reconnecting the ECU, the problem was solved. Honestly no idea what caused it though until today....
steve4179
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Re: engine wont switch off

Post by steve4179 »

The wiring diagram has been followed and the relay is powered up by an ignition live taken from the original fuse box that powers a new fuse box that powers ms3, injectors, fuel pump, lambda, coil, and something else that i can't remember right now, its been working fine for ages then i had an issue with the fuel pump relay not switching the pump on so i changed that and then it started doing this so i assumed that the power relay had died to and changed it and double checked all wiring and it still runs on!
DeadStiff
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Re: engine wont switch off

Post by DeadStiff »

Turn the ignition on then off, then start pulling relays until the MS turns off. Then inspect how the offends relay is wired.
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steve4179
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Re: engine wont switch off

Post by steve4179 »

so done a few electrical tests and it turns out the place on the original fuse box that I took the ignition live from is now somehow still getting about 8 volts once the ignition is switched off and the engine is running which seems to be just enough to keep everything going, im gonna pull the bay loom and check for any damaged wires that could be feeding the ignition some power, short of that ill put the power relay on a switched live instead of ignition

cheers for everyones help
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