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Discussion Starter #1
I have a puzzling electrical issue that I hope someone has seen and fixed before :)


'88 110 with 19J:


Starts and runs fine, but when I turn the key off, and remove the key, the battery indicator light comes on and the engine still runs...
if I remove the wire to the solenoid (or just loosen the nut) the engine turns off.


This is intermittent. Sometimes, the engine shuts off while I'm getting ready to stall it, sometimes if I wiggle the key back and forth in the ignition, the engine shuts off. A few times, I could push the rear washer button and the engine would shut off (all of these could be coincidence, since nothing is consistent). Sometimes the engine shuts off normally.


Does this sound like the ignition and if so, can I just replace the switch in the back of the ignition? Or is this the problem that I've read about where there is backfeed from the alternator to the cutoff solenoid, in which case I need a diode? Does the lit battery indicator give me a clue? (I'm not very good at electrical issues... but I find myself staring at the wiring diagram late into the night ) Would checking the voltage at the solenoid help deciding between ignition/backfeed? (ie. 2volts is backfeed, 12 volts is ignition?)
Or is this a ground issue (seems to be a common culprit in most electrical issues), in which case I have to find out where the grounds are:))


Also, am I doing any damage by stalling every time I stop?


Any help would be appreciated!
 

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Your ignition switch is flaky.
You can replace it or install a "one way" diode on your charge indicator light from the alternator which may compensate for the faulty switch position.
The best solution is to replace the IG SW because if it still supplies juice to the solenoid with the key switched off, then it will also run your battery flat.
Off is off and on is on, but in your case, when off is still on, then off is not off, it's on when it should be off.
 

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Hey Ed - It would seem to me that since the ignition barrel is a switch that opens and closes, if it was functioning correctly it would cut the power when you turn it off and remove the key. I would replace it since they are relatively inexpensive. I'd also test for the ground and back feed issues while you're at it.

Let me know if you would like another set of eyes (and tools) to help sort it out. I'm in Wexford.
 

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Probably the switch but you should test it first with a meter. The start relay could be sticking (if your truck has one).
 

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Discussion Starter #7
Thanks for the help!

While I'm tracking down a new switch, I decided to poke around with a volt-meter.

Would this change anyone's mind, or is it still the switch?

Volts measured at the cut off solenoid.
1. key in off position (truck not running): 0 volts
2. key in on position (truck not running): 12 volts
3. key in on position (truck running): 14 volts
4. key in off position (truck running): 1 volt

and interestingly, if I put a pair of pliers on the solenoid nut, the truck shuts off.

Can the switch be supplying 1 volt when the truck is running, but not when not running?

Thank you!
(electricity is not my friend)

Ed
 

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Sorry! I have to say it.
Check your ground connections. You NEED a ground from battery to motor heavy enough to start the engine. You ALSO need a ground connection from the battery to the chassis.

I once tore a ground wire off and when I stopped and turned off ignition the diesel engine kept running until I shut off the headlights. Stop solenoid was acting as a earthing route for the headlights, in other words, the headlights were powering the solenoid.
 

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Discussion Starter #9
To put this problem to bed...

The problem turned out to be backfeed through the dash battery warning light to the shut off solenoid. A diode solved the problem. (LR added a diode to the post-91 harness)

On to the next problem:)
 

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I have a puzzling electrical issue that I hope someone has seen and fixed before :)


'88 110 with 19J:


Starts and runs fine, but when I turn the key off, and remove the key, the battery indicator light comes on and the engine still runs...
if I remove the wire to the solenoid (or just loosen the nut) the engine turns off.


This is intermittent. Sometimes, the engine shuts off while I'm getting ready to stall it, sometimes if I wiggle the key back and forth in the ignition, the engine shuts off. A few times, I could push the rear washer button and the engine would shut off (all of these could be coincidence, since nothing is consistent). Sometimes the engine shuts off normally.


Does this sound like the ignition and if so, can I just replace the switch in the back of the ignition? Or is this the problem that I've read about where there is backfeed from the alternator to the cutoff solenoid, in which case I need a diode? Does the lit battery indicator give me a clue? (I'm not very good at electrical issues... but I find myself staring at the wiring diagram late into the night ) Would checking the voltage at the solenoid help deciding between ignition/backfeed? (ie. 2volts is backfeed, 12 volts is ignition?)
Or is this a ground issue (seems to be a common culprit in most electrical issues), in which case I have to find out where the grounds are:))


Also, am I doing any damage by stalling every time I stop?


Any help would be appreciated!
Just started happening with my 200TDI. We followed a few weak grounds but ultimately found that the fuel shutoff solenoid(the component that strangles the fuel flow to the engine causing it to shut down) was somehow stuck in place and it just required being plugged in and u plugged a few times. That allowed it to wiggle back to operation. It was very strange that it happened at the same time I was working on my wiring which led me to believe I shorted a circuit or blew a relay. Side note, even when the solenoid is “off” it will have about an amp power
 

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Probably the IG SW, but could be the shutoff solenoid or the alternator.
Do you have the original type alternator?
Some after-market alternators will allow the field coils to feed (+) current back through the IG warning light bulb filament and keep the IG circuit powered.
The solution to this scenario is to install a diode on the brown with yellow field wire.
Common issue with some of the Delco 10Si units.
 

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What year truck? Pre-TDI trucks do not have a diode in the ignition charge light circuit. If there are no power draws on the switched power side, the charge light circuit can back feed and provide enough power to keep the fuel solenoid engaged. Most people do not notice because the heater fan is always on and that is enough to prevent the issue.

And, the other advice above is possible as well. Ignition switch, starter relay, crap in the solenoid valve.
 
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