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monkie

Voltage at Stop Solenoid - Engine won't switch off

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As per the title. My Land Rover is a standard 1988 110 fitted with 2.5TD 19J.

This has just started to happen: When I switch off the ignition switch and remove the key the engine sometimes still runs (not every single time). I've done some investigation today with my multimeter. I started it up, switched off all electrical items such as heater blower, lights, wipers etc and let the engine continue to run with the key removed.

No problems detected with the ignition switch itself (it does have a cheapo after market switch fitted so this was my first port of call).

With key removed and the engine running I get 2.5v measured at the stop solenoid, obviously enough to keep it from closing and stopping the engine.

My question is, what could be causing this voltage at to the stop solenoid feed?.... The alternator feeding it?.... Maybe something else earthing through the solenoid circuit? Any pointers on where to start looking will be very much appreciated.

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Just had a little play with some solenoids and some batteries. 

3v DC was just enough to keep the solenoid open (proved working on a12v supply). It would hold it open from closed but not close it  

My 200 had a thing for keeping running, changing the solenoid would work for a few months. It’s never needed one since the pump was changed so it must’ve been related to the pump port/sticking etc. 

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Thanks for your input, I agree that just over 2v hardly seems substantial enough to open a solenoid, maybe it is just enough to keep it open once the key is removed? I will try another solenoid and see what happens as it is an old one fitted at the moment. Its frustrating that it is not a constant fault - this is why I often find electrical faults to be so frustrating!

I could well be showing my novice at understanding wiring diagrams here, but it seems to me that the feed for the stop solenoid comes from the ignition switch and also the alternator with a resistor in the path for the instrument light. I don't know where this resistor is to see if it could be at fault.

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the resistor is buried inside the loom about 8 to 10 inches from the instrument pack looks like a translucent inline fuse holder, usually covered with a insulated sleeve & tape, doubt it'll have any affect on the fuel solenoid operation. 

remove the sloeniod & make sure there is no unwanted dirt or metal swarf stopping it closing or jamming it open.

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Ah, yes I think I have seen that and wondered what it was. I will take the solenoid out and see what condition it is in. I have another solenoid from a spare FIP I have. Maybe the 2 volts I'm measuring is a red herring.

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What meter are you using to measure the voltage? Modern Digital Multimeters are spectacularly-sensitive and will show a voltage even when the circuit being tested is fed only by leakage across damp-paths.

For car stuff I generally prefer an old-style analog meter - something like an "AVO 8" - that is a lot less sensitive to false readings caused by leakage.

I vaguely remember that on old clockwork-Diesel Defenders there was a diode fitted somewhere in the loom which was designed to stop the alternator continuing to back-feed a voltage to the stop-solenoid via the ignition-warning-light bulb when you turned the ignition-switch off [and so keeping the engine running even though you'd told it to stop]. Could your problem be due to this diode or the dashboard-warning-light circuit having problems??

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I am using an inexpesive digital multimeter (£10 from screwfix) set on the 20v DC setting. 

I haven't noticed any problems with the dashboard wiring, but the intermittant nature of this problem is making me think about earths. I think the dashboard stuff is earthed to the point on the bulkhead. I have cleaned this up incase it was a fault here causing something to earth via the stop solnoid but it hasn't solved the problem. The diode point is interesting, but according to the diagram there is a resistor between the feed from the alternator and the dashboard lamp. I can't see a diode.

I am thinking that I might make it a 2019 project to make my own wiring loom starting with the engine loom as the insulation is getting quite brittle now in the engine bay after 30 years.

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Bought a new engine loom from Autosparks a while ago, fitted after the engine rebuild, replaced the dash/main loom some years ago after a switch meltdown, that loom came from autosparks as well. 

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It is best NOT to use a multi-meter as they lie!  For this sort of problem, use a test light that puts some current into the circuit.

Cheers

Peter

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I've looked at Autosparks and I can't afford a new loom off the shelf. I have in the past got bits and pieces from them and I have read a few threads on this forum about making your own loom. I managed to melt the glow plug feed a few years back so I got the appropiate coloured wiring and renewed that circuit. No matter what I do I absolutely want to stick to the correct wiring scheme for future fault finding. When I first got my 110 it took me many blown fuses to realise someone had been before me and used a black wire to feed one of the rear lights, which I kept earthing!

 

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Just now, Puffernutter said:

It is best NOT to use a multi-meter as they lie!  For this sort of problem, use a test light that puts some current into the circuit.

Cheers

Peter

I like the idea of using a test light - but I'm not sure I understand what you mean about multimeters lying? I can see how they can be misleading though, I'm starting to doubt the significance of the 2 volts I've been measuring.

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Just because there is 12V there, doesn't mean there is a low enough impedance to be able to power something.

A meter will show 12V, but a test lamp won't light, or will look very dim.

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Thank you for all of the prompt responses with some good ideas.

I'm going to focus on the stop solenoid tomorrow and swap it for the other one, making sure there is no debris or rubbish around the plunger. I will also raid my spares bin and make a 12v test lamp and put inbetween the solenoid and the feed to see if it lights up with the key removed and the engine running. I'll feed back my findings....👍

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I assume you've tried this simple test. 

Engine still running with ignition "off", pull spade connector off solenoid. If it stops then you can prove the solenoid is being held open through a supply of power.

If it continues to run, then it's not power related.

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I have indeed, it's how I'm managing the situation rather than dumping the clutch whilst in 5th gear.

If you see a 110 park up followed by the bonnet popping up and someone climb out to reach into the engine bay momentarily before walking away..... come and say hello!

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Have you tried pulling the fuses on the ignition fed circuits that could feed back to the switch? Hazard switches can give some weird and wonderful issues, may be worthwhile giving that a look at too.

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I'd suspect debris stopping closing fully. As mentioned above pull the spade connector off to rule it out.

Mo

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10 minutes ago, Scotts90 said:

Have you tried pulling the fuses on the ignition fed circuits that could feed back to the switch? Hazard switches can give some weird and wonderful issues, may be worthwhile giving that a look at too.

That's an interesting point, I have had issues with at the fuse box very recently highlighted to me by the heater blower not working but that was after this this solenoid issue hence I had just put it down to the 110 being a general pain in the arse when I wanted to use the heater blower.

I'm sure I have also had trouble with the hazard switch in the past. I will add this to my investigations and start pulling fuses along with swapping the solenoid incase of some dirt.

I'm starting to be more and more convinced to do a re-wire! £432 sounds like an awful lot money for main loom - has anyone here any experience of making their own? Would you stick with the original type of connectors to join the looms, are these superseal weather proof connectors a good idea?

http://www.vehicle-wiring-products.eu/product.php/619/superseal-weatherproof-connectors

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I had a 110 fitted with a 200Tdi that gave the same symptoms. It is surprising how little diesel is required to keep an engine ticking over. Like you I also had to stop it by stalling it.  I removed the 12v feed and it still carried on, I removed and serviced the solenoid valve (no debris) and it still carried on, I replaced the solenoid stop valve and it still carried on. 

To be honest (and it is no help!) I never solved the problem!

Cheers

Peter

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Is the problem on your 110 intermittent?

 

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I've this problem in my 109 with a TDI 200. 

I have found that pressing the brake pedal whilst switching off is enough extra drag on the engine to kill it off. 

I assume the vacuum pump load stops it.

G.

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Yes and no. It would do it consistently for a while, then behave a few times!

I sold it, so I have no idea now!

Cheers

Peter

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4 hours ago, Gazzar said:

I've this problem in my 109 with a TDI 200. 

I have found that pressing the brake pedal whilst switching off is enough extra drag on the engine to kill it off. 

I assume the vacuum pump load stops it.

G.

Interestingly enough, the brake light circuit is fed from the same ign feed as the stop solenoid. Is the load of the lights enough to kill any stray voltage?? Hmm

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Oh! Never thought of that. 

The fitting of the resistor is on the long list of thing to do .

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If you still have power at the stop solenoid, turn on the heater fan....  The problem can be that the early trucks do not have a diode in the alternator warning light circuit.  The alternator can back feed enough power through the light to keep the engine running if there are no switched loads turned on.  A proper solution is to fit a diode as per the later trucks.  A diode costs near to nothing.  at the same time fit a bypass resistor around the light so the alternator can keep working with a burned out bulb.

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