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monkie

Voltage at Stop Solenoid - Engine won't switch off

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I've done a little more investigating following all of the great advice above from everyone :i-m_so_happy:. As it was already dark when I got the chance to investigate so I have not made myself a test lamp, I did not change the solenoid nor look for dirt around the solenoid plunger. These are jobs I will do in the daylight when I get a chance. I did do the following:

(1) To it for a quick drive to warm it up, park up and removed the key - the engine remained to run (It now seems to do this with increasing frequency now). To clarify, the battery lamp is illuminated on the dash display when the key removed (as I would expect it to).

(2) With the engine running and the key removed, I turned on the heater, lights and depressed the brake pedal (I could see a reflection to confirm the brake lights are indeed working)- engine still continued to run.

(3) Put the key back in and turned the ignition switch to the running position and repeated step 2 whilst I turned the switch off and removed the key - engine still continued to run.

(4) With the engine still running and the key in my hand I got out and put my multimeter across the solenoid terminal and the engine block - 2v measured.

(5) Pulled the connection off the solenoid - engine stopped immediately.

(6) Restarted the engine, removed the key and engine continued to run; I played around with the hazzard light switch and indicator stalk - no change (hazzards working fine).

(7) Blipped the throttle to see if the voltage changed across solenoid terminal - engine stopped immediately!

(8) Restarted the engine and repeated the throttle blipping a number of times - it stops the engine every time.

I don't understand why blipping the throttle seems to stop the engine (It doesn't stop if the key is in the run position). It is a development at least and it is better than stalling the engine in gear or having to pop the bonnet up and pull the wire from the solenoid. Any thoughts on the throttle blipping?

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When I applied the 3v across the solenoid it was enough to hold it in the "on" position but not strong enough to overcome the spring and pull the plunger home  from the "off", the blip may cause enough of a draw through the pump to pull the plunger down onto its seating (overcoming the small voltages' magnetic force)

Did you see any momentary change in voltage prior to shut down? Was it still there after the engine stopped?

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I was wondering if the 2v was just enough to hold it partially open to allow the supply of fuel for tickover, I'm sure it is no where near enough to open it from closed. Your theory of the blip causing enough draw on the pump to shut the plunger (or maybe take more fuel than the pump can supply via the partially closed plunger) sounds plausible to me. I wonder if it could also be a weak or broken spring inside the solenoid - I will check in the daylight.

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2v is probably enough to hold a relay open enough to allow tickover. I found that blipping the throttle stopped it because it was starved of fuel.

Cheers

Peter

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Most likely a bad ignition switch then.  To test, pull the White/Black wire off the switch when it is doing this.  If the engine stops, it would be the switch.

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6 minutes ago, Red90 said:

Most likely a bad ignition switch then.  To test, pull the White/Black wire off the switch when it is doing this.  If the engine stops, it would be the switch.

This was my first thought as it is a cheap ignition switch (genuine ones were about £80 when I last looked). I pulled the wires from the back of the switch and the engine kept running. This is why I think the alternator might be supplying enough feed to keep the solenoid open?

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27 minutes ago, monkie said:

This is why I think the alternator might be supplying enough feed to keep the solenoid open?

It can't do that and supply power to the switched circuits.  Once the ignition switch is off, the only place to get power is through the warning light lamp and that is only around 1 watt maximum.

If it is not the ignition switch something is wrong in the wiring.  You will need to find it on your own.

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30 minutes ago, Red90 said:

It can't do that and supply power to the switched circuits.  Once the ignition switch is off, the only place to get power is through the warning light lamp and that is only around 1 watt maximum.

If it is not the ignition switch something is wrong in the wiring.  You will need to find it on your own. 

I think so in terms of something wrong with the wiring - I have (like many LR owners) had earth faults that appear from no where, this might be similar. I will follow the voltage along the wires and hope I find the problem. For now, stopping the engine with a blip on the throttle is more satisfactory than the other methods.

This has given me the inspiration to make my own wiring loom. I will start with the engine loom. I've seen the correct wires are available from autosparks and vehicle wiring products. I have sourced a new Lucas alternator 3-pin plug, anyone know where I can find a new connector like the one on the right hand side of the picture below (from autosparks' website)

 

LR427-1.jpg

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You won't find the rubber plug they are moulded onto the pins, my '89 loom has those rubber conections all over it. they are not detachable without cutting/destroying the rubber.

the ring terminal is fairly common as is the spade terminal in plastic cover.

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That's a shame. Never mind, I'll just have to use a different type of connector.

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Perfect - thank you. I clearly need to improve my searching skills. I did look, honest!

It even mentions 2 volts holding the solenoid open (exactly what I am measuring) and a diode as mentioned by Red90.

 

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Remarkable really - the user seems to have posted that helpful post, got no replies, and not visited the site since 😮

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4 hours ago, monkie said:

Perfect - thank you. I clearly need to improve my searching skills. I did look, honest!

It even mentions 2 volts holding the solenoid open (exactly what I am measuring) and a diode as mentioned by Red90.

 

You do not have the diode.  They started adding them with the 200TDI.  That is not your problem.

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2 hours ago, Puffernutter said:

Do you have a diode - I have a plentiful supply of 1N4001 (silicon 1A), happy to send you one.

Cheers

Peter

Thank you for the kind offer. I do not have a diode so I would gratefully recieve one.👍 PM sent.

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3 hours ago, Red90 said:

You do not have the diode.  They started adding them with the 200TDI.  That is not your problem.

I agree. If I were to just fit one and do nothing else I would consider it a sticking plaster. That interesting thread from the past does however give me something to go on and describes my problem exactly. Could it be a sign the alternator has seen better days or maybe the resistor I mentioned in the wiring diagram failed? However when I do find the problem I think fiting the diode is a sensible modification given Land Rover must have recognised this in the 200Tdi era.

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No, this issue has nothing to do with the condition of the alternator.  If the ignition switch is working, the alternator is separated from the engine solenoid circuit except for the wire through the dash light.

You do not have the resistor either and this has nothing to do with the problem.

Attached is from the 300TDI wiring, but is the same as the 200TDI showing the diode and resistor.  Earlier trucks don't have these.  I doubt this is your issue.

Capture.JPG

Edited by Red90

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I see what you mean regarding the alternator as my understanding is that the diodes on that are there to rectify AC from the alternator to DC for the circuits. However I will test the theory of current straying via the dash lamp by removing this connection to see if that has any effect. I'm quite sure I do have the resistor though as I have seen it. I will of course double check to be sure. It is shown on the wiring diagram.

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This is the early wiring.  72 is the alternator, 39 is the warning light.  You are right.  63 is the resistor.

Capture.JPG

Edited by Red90
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I’ve been reading this thread with interest as I am experiencing exactly the same issue. Mine started 12 months ago and to stop the engine required pressing the brake pedal. On Sunday this now no longer works. Mine is 200tdi in a series vehicle with no resistor or diode.  

Having trawled other threads some would suggest it could be the solenoid at fault and replacing it (and ensuring it’s not bits of gunk) blocking the seal. It was recommended that a genuine part or well established make is better than “blue box” and at about £15 it seems a cheap way to rule in or out.

Agreed a diode might solve the issue now but doesn’t explain why it worked for 6 years without issues, and why it suddenly started?

If you do solve it, let us know as I too am equally keen to resolve as stalling it every time is getting a tad frustrating and somewhat embarrassing.

Ed

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2 hours ago, Puffernutter said:

That was where I first got involved!  I solved the problem - sold the car!

This is why every Defender I buy, I get to spend 40 hours fixing the wiring from the previous owners. 

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Wiring was the first issue I had when I first got my 110. It took all of 48 hours of getting it home to show it self

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