I'm greatly enjoying my MJLJ (V3), especially the smooth acceleration and the fantastically improved starting (2 litre BMW M10 engine with twin Weber 40 sidedraughts). My car is a bit of a garage queen and is not driven as much as she should be, but when I do take her out I have, intermittently, this problem: when you turn off the ignition, sometimes the engine just keeps running! This isn't a question of a coked-up engine running on, either - it just keeps running until, curiously you pull on the handbrake! This was discovered to my embarrassment by the Mot tester last year - it had not done it to me at all in early testing. It will also usually cut out if you turn on the lights, so I am guessing this is some kind of stray voltage problem and the link to the handbrake is that it illuminates a dash bulb.
The MJLJ and coil pack are wired up to the same circuit, which is a 12V switched ignition circuit. Initially I wired them straight into the main ignition circuit but I later introduced a relay as I was concerned about drawing too much current from that circuit, so now the relay gives them a link straight to the battery. I don't think this is what introduced the fault, but I must admit I can't now remember the sequence of events. They are both earthed at the same point, too, as recommended in the installation guide.
I have this year's Mot test coming up next month and would like to fix this before then, as the tester might not find it so funny second time round! Can anyone offer any clues?
TIA
Engine keeps running on shut off!
Moderators: JeffC, rdoherty, stieg, brentp
Engine keeps running on shut off!
Tim
1973 BMW 2002
1973 BMW 2002
hi. i presume you mean the engine keeps running as if the key had not been turned off at all?
so we know that - sometimes - the MJ continues to see battery voltage on its supply line, which runs from the battery via a relay. so i would be focussing on four possibilities:
1. the relay is faulty, and sticking on. you might try giving it a whack when the key is switched off but the car still running.
2. wires incorrectly attached to the relay. if, for instance, you have the batt and the MJ connected to the terminals which are for the solenoid in the relay, the MJ would be permanently on, but without turning on the relay (which would then short out the ignition circuit wire).
3. faulty key switch not switching off the power. you would probably expect to see the oil idiot light or ignition light in such a case, and it doesnt sound like that is happening. you could check that by checking it the wire running from the switch to the relay still has voltage when the switch is off, but motor running.
4. the power wire from the key switch to the relay is either not connected to the right terminal on/near the key switch, or is somehow connected to the alternator output. maybe you MJ is on all the time via an incorrect path for its power?
regards
alexander.
so we know that - sometimes - the MJ continues to see battery voltage on its supply line, which runs from the battery via a relay. so i would be focussing on four possibilities:
1. the relay is faulty, and sticking on. you might try giving it a whack when the key is switched off but the car still running.
2. wires incorrectly attached to the relay. if, for instance, you have the batt and the MJ connected to the terminals which are for the solenoid in the relay, the MJ would be permanently on, but without turning on the relay (which would then short out the ignition circuit wire).
3. faulty key switch not switching off the power. you would probably expect to see the oil idiot light or ignition light in such a case, and it doesnt sound like that is happening. you could check that by checking it the wire running from the switch to the relay still has voltage when the switch is off, but motor running.
4. the power wire from the key switch to the relay is either not connected to the right terminal on/near the key switch, or is somehow connected to the alternator output. maybe you MJ is on all the time via an incorrect path for its power?
regards
alexander.
Last edited by alexander on Sat Jan 17, 2009 11:43 pm, edited 1 time in total.
Thanks Alexander.
Yes, I do mean that.
I will check those points and see what I find. At present I would say
1 Yes, I had wondered that too
2 Quite possible knowing me, but the relay does give a nice click when you turn on the ignition so at least part of it is connected properly
3 Possible - will check.
4 Could well be. I haven't made any connections at the switch itself. In theory the relay solenoid is powered from a splice from the igition circuit within the engine bay, earthed at the same point as the MJ and coil pack. Power to the MJ and coil pack is straight from the battery via the relay switched contacts.
The odd thing is that it seems to stop once there is some other current draw, such as the handbrake light coming on, and also the fact that the whole problem is intermittent. But I guess that's why we do these projects; it would be no fun if it was predictable and consistent!
Cheers
Tim
Yes, I do mean that.
I will check those points and see what I find. At present I would say
1 Yes, I had wondered that too
2 Quite possible knowing me, but the relay does give a nice click when you turn on the ignition so at least part of it is connected properly
3 Possible - will check.
4 Could well be. I haven't made any connections at the switch itself. In theory the relay solenoid is powered from a splice from the igition circuit within the engine bay, earthed at the same point as the MJ and coil pack. Power to the MJ and coil pack is straight from the battery via the relay switched contacts.
The odd thing is that it seems to stop once there is some other current draw, such as the handbrake light coming on, and also the fact that the whole problem is intermittent. But I guess that's why we do these projects; it would be no fun if it was predictable and consistent!
Cheers
Tim
Tim
1973 BMW 2002
1973 BMW 2002
yes, that is curious, and i am still pondering the likely cause. my suspicion is that you are drawing power from some point which is on the earth side of one of these lights (or some other current drawing device which creates a voltage drop across itself). when the light switch is not on, that point is drawing current through the lamp/s. there would be a voltage drop through the lamp, but not enough to stop the MJ working, and not enough to make the lamp glow. when the light switch is on, the point from which you are drawing power is then at earth potential and the MJ stops working. well, it is a theory anyway.thedaean wrote: The odd thing is that it seems to stop once there is some other current draw, such as the handbrake light coming on, and also the fact that the whole problem is intermittent.
cheers.
alexander.
Hi Alexander
I have had some fun with the voltmeter this morning and this is what I have found:
With the engine off, the relay clicks on when the ignition is switched on (12-13V is seen at the relay), and clicks off when I turn the ignition off (0V seen at the relay). So far, so good...
With the engine running, there is 13V at the relay, and when I turn the ignition off there is 4.5-4.7V at the relay and the engine keeps running - I assume that this voltage is enough to keep the relay switched on
When I turn off the ignition with the engine running, the ignition light DOES come on and the engine keeps running
The problem is NOT intermittent - as long as there is no other source of current draw, the engine will keep running
Switching on certain things in these circumstances (headlights, hazard lights, fan) will cause the engine to die, but other things won't (cigarette lighter, side lights, rear window demister, brake lights, interior courtesy light)
Other circuits that are switched by the ignition switch go off when I turn it off (wipers, indicators, radio, aftermarket voltmeter)
In case there was some kind of 'back EMF' (is that what it's called) coming from the relay and keeping things alive, I tried a diode between the ignition circuit and the relay, but it made no difference. I checked that the diode worked by reversing it and this stopped the relay from switching on
I tried disconnecting the relay and reading the voltage on the ignition circuit as I did so - it went briefly up to 6V and then fell quickly away to 0V. The engine died as soon as I disconnected the relay
Pulling on the handbrake does make the engine die if the handbrake was off, but if the handbrake was already on (and the handbrake warning light on), the engine keeps running!
If an accessory such as the fan is left on, the engine dies when I switch the ignition off
And finally - if I forget the relay and just wire the MJLJ, EDIS and coil pack via the switched ignition circuit, it works just fine and switches off normally.
This seems to point to your scenario 3, but I haven't been able to work out how to investigate it further. But at least I know how to stop it happening so it will not annoy the MOT tester - either leave the fan switched on or just dispense with the relay! Or perhaps a double pole relay that grounds the ignition circuit when it it switched off?
Nevertheless, if you do have any thoughts as to how to track down the source of this 4.5V, I'd be interested to know.
Thanks!
Tim
I have had some fun with the voltmeter this morning and this is what I have found:
With the engine off, the relay clicks on when the ignition is switched on (12-13V is seen at the relay), and clicks off when I turn the ignition off (0V seen at the relay). So far, so good...
With the engine running, there is 13V at the relay, and when I turn the ignition off there is 4.5-4.7V at the relay and the engine keeps running - I assume that this voltage is enough to keep the relay switched on
When I turn off the ignition with the engine running, the ignition light DOES come on and the engine keeps running
The problem is NOT intermittent - as long as there is no other source of current draw, the engine will keep running
Switching on certain things in these circumstances (headlights, hazard lights, fan) will cause the engine to die, but other things won't (cigarette lighter, side lights, rear window demister, brake lights, interior courtesy light)
Other circuits that are switched by the ignition switch go off when I turn it off (wipers, indicators, radio, aftermarket voltmeter)
In case there was some kind of 'back EMF' (is that what it's called) coming from the relay and keeping things alive, I tried a diode between the ignition circuit and the relay, but it made no difference. I checked that the diode worked by reversing it and this stopped the relay from switching on
I tried disconnecting the relay and reading the voltage on the ignition circuit as I did so - it went briefly up to 6V and then fell quickly away to 0V. The engine died as soon as I disconnected the relay
Pulling on the handbrake does make the engine die if the handbrake was off, but if the handbrake was already on (and the handbrake warning light on), the engine keeps running!
If an accessory such as the fan is left on, the engine dies when I switch the ignition off
And finally - if I forget the relay and just wire the MJLJ, EDIS and coil pack via the switched ignition circuit, it works just fine and switches off normally.
This seems to point to your scenario 3, but I haven't been able to work out how to investigate it further. But at least I know how to stop it happening so it will not annoy the MOT tester - either leave the fan switched on or just dispense with the relay! Or perhaps a double pole relay that grounds the ignition circuit when it it switched off?
Nevertheless, if you do have any thoughts as to how to track down the source of this 4.5V, I'd be interested to know.
Thanks!
Tim
Tim
1973 BMW 2002
1973 BMW 2002
wow! this is like one of those logic puzzle books...
thoughts at the moment...
i am thinking about this wire you have spliced into. what is that wire, and where else does it go? i would think it should be the wire that previously went to the coil, but if that is so, you would so much need to splice into it, as simply reconnect it to the relay. if it IS that wire, where does the original end of it go now?? if it is NOT the ignition coil wire, what is it and what else is connected to it?
what model car is this? perhaps i can find a circuit diagram online, which would make it easier to consider the problem.
regards
alexander.
thoughts at the moment...
i am thinking about this wire you have spliced into. what is that wire, and where else does it go? i would think it should be the wire that previously went to the coil, but if that is so, you would so much need to splice into it, as simply reconnect it to the relay. if it IS that wire, where does the original end of it go now?? if it is NOT the ignition coil wire, what is it and what else is connected to it?
what model car is this? perhaps i can find a circuit diagram online, which would make it easier to consider the problem.
regards
alexander.
Hi
Thanks for staying with this!
Right, I have had another look today and made a few discoveries but didn't manage to find the source of the rogue volts before it got too cold and I decided to come in.
The car is a BMW 2002, so not naturally equipped with many other electronic gizmos, although as a tinkerer I have added one or two over the years.
The only one I can think of that might affect the ignition circuit is a Lumenition electronic ignition module, which replaces the points in the distributor with an optical switch. I left this, the coil and distributor in situ as I wanted to be able to revert to that if the MJLJ didn't work. I wired it to take its power supply from the same point as the MJLJ and coil pack (i.e switched by the relay) and yesterday it came under my radar as a possible culprit so I disconnected its 12V supply, but it made no difference. Today I made sure it was fully disconnected from everything and again, no change.
Re the wiring for the relay power, I realise now that because I left the original ignition wiring in place so I could reinstate it quickly, I took a switched 12V supply that might not be part of the ignition circuit at all. Apologies; I may thus have seriously misled you in trying to sort this out. I can't remember exactly where I took that switched supply from and for once I seem to have been reasonably neat in running the wire so it wan't obvious today; I have traced it back to near the fuse box so it's possible that I piggy-backed onto another switched circuit at the fuse box, but it's also possible (as the fuse box is near where the wiring loom goes through the bulkhead into the car) that I ran that wire inside and took a feed from under the dash somewhere. That obviously needs to be checked and will be my next step.
I had previously only disconnected the coil -ve to disable the conventional ignition when running the MJLJ. Today I made sure the coil was also fully disconnected - again, no difference. Then, inspired by your last post, I had the idea of using the coil 12V supply to power the relay - which would be really simple, as they are next to each other. But before doing that, I checked the voltage to that point. It turned out to have exactly the same voltage readings as the wire supplying the relay, including the continuing low voltage when the ignition is switched off! So whether deliberately or otherwise, I do seem to have tapped the relay supply into the ignition circuit. Because the voltages were the same, I didn't bother trying to power the relay from this supply today, but I realise that I should have done, for empirical consistency.
What I did instead was to think about how I can reduce that 'quiescent' voltage, so that it's not enough to keep the relay held on. Interestingly, today the voltage at the relay with the ignition switched off but the engine still running was 2.9V as against the 4.5V I was getting yesterday. This was, frustratingly, enough to keep the relay on, although a slight flick on the relay body would cause it to go off. That got me thinking about what I could put into the circuit that would drop the voltage enough that the relay would still come on when it was supposed to, but would go off properly when switched off. I thought at first of a resistor but my electronics knowledge is too rusty to be able to work out what value and what power rating to use. Then my eye caught an old LED and I wondered if that would do the trick. Sure enough - with the LED in series with the relay solenoid circuit I got a nice red light when the relay was armed, and when I turned off the key, light, relay and engine all switched off. Hooray!
This gives me the bare bones of a solution to this problem (and possibly an excuse for another warning light inside the car!), but as I don't know very much about LEDs I don't know if they are supposed to be used this way or if there is a danger of the LED overheating or burning out over a long period of time with the ignition on. It also of course means that I haven't actually tracked down the cause of the problem. But that is where I've got to and I will now have a week of pondering on this before I can get another chance to investigate next weekend.
Anyway, thanks for reading this far. I am sorry about the misreporting of where I got the power for my relay from, although it does ultimately sound as though I have spliced into the ingition circuit. This I will check at the next opportunity.
Cheers
Tim
Thanks for staying with this!
Right, I have had another look today and made a few discoveries but didn't manage to find the source of the rogue volts before it got too cold and I decided to come in.
The car is a BMW 2002, so not naturally equipped with many other electronic gizmos, although as a tinkerer I have added one or two over the years.
The only one I can think of that might affect the ignition circuit is a Lumenition electronic ignition module, which replaces the points in the distributor with an optical switch. I left this, the coil and distributor in situ as I wanted to be able to revert to that if the MJLJ didn't work. I wired it to take its power supply from the same point as the MJLJ and coil pack (i.e switched by the relay) and yesterday it came under my radar as a possible culprit so I disconnected its 12V supply, but it made no difference. Today I made sure it was fully disconnected from everything and again, no change.
Re the wiring for the relay power, I realise now that because I left the original ignition wiring in place so I could reinstate it quickly, I took a switched 12V supply that might not be part of the ignition circuit at all. Apologies; I may thus have seriously misled you in trying to sort this out. I can't remember exactly where I took that switched supply from and for once I seem to have been reasonably neat in running the wire so it wan't obvious today; I have traced it back to near the fuse box so it's possible that I piggy-backed onto another switched circuit at the fuse box, but it's also possible (as the fuse box is near where the wiring loom goes through the bulkhead into the car) that I ran that wire inside and took a feed from under the dash somewhere. That obviously needs to be checked and will be my next step.
I had previously only disconnected the coil -ve to disable the conventional ignition when running the MJLJ. Today I made sure the coil was also fully disconnected - again, no difference. Then, inspired by your last post, I had the idea of using the coil 12V supply to power the relay - which would be really simple, as they are next to each other. But before doing that, I checked the voltage to that point. It turned out to have exactly the same voltage readings as the wire supplying the relay, including the continuing low voltage when the ignition is switched off! So whether deliberately or otherwise, I do seem to have tapped the relay supply into the ignition circuit. Because the voltages were the same, I didn't bother trying to power the relay from this supply today, but I realise that I should have done, for empirical consistency.
What I did instead was to think about how I can reduce that 'quiescent' voltage, so that it's not enough to keep the relay held on. Interestingly, today the voltage at the relay with the ignition switched off but the engine still running was 2.9V as against the 4.5V I was getting yesterday. This was, frustratingly, enough to keep the relay on, although a slight flick on the relay body would cause it to go off. That got me thinking about what I could put into the circuit that would drop the voltage enough that the relay would still come on when it was supposed to, but would go off properly when switched off. I thought at first of a resistor but my electronics knowledge is too rusty to be able to work out what value and what power rating to use. Then my eye caught an old LED and I wondered if that would do the trick. Sure enough - with the LED in series with the relay solenoid circuit I got a nice red light when the relay was armed, and when I turned off the key, light, relay and engine all switched off. Hooray!
This gives me the bare bones of a solution to this problem (and possibly an excuse for another warning light inside the car!), but as I don't know very much about LEDs I don't know if they are supposed to be used this way or if there is a danger of the LED overheating or burning out over a long period of time with the ignition on. It also of course means that I haven't actually tracked down the cause of the problem. But that is where I've got to and I will now have a week of pondering on this before I can get another chance to investigate next weekend.
Anyway, thanks for reading this far. I am sorry about the misreporting of where I got the power for my relay from, although it does ultimately sound as though I have spliced into the ingition circuit. This I will check at the next opportunity.
Cheers
Tim
Tim
1973 BMW 2002
1973 BMW 2002
hi tim. no need to apologise for anything. this is a discussion forum, and i continue to read it because i like discussing things! so youre doing me a favour 
i think the logical step is definitely to determine exactly where the power is coming from ie which circuit. if it is indeed the correct wire ie old coil supply, then there is also the possibility that something else has been incorrected joined into that circuit. that could be tricky to identify, but you could start like this: make a list (well, i guess you have) of all devices which kill the ignition when they are swithed on. then start the car and shut the switch off; presumably car will still be running. then progressively pull out fuses till (if) you find one which stops the car, and note which circuit that is. it could narrow it down, but there could be other issues that process doesnt cover.
regards
alexander.
i think the logical step is definitely to determine exactly where the power is coming from ie which circuit. if it is indeed the correct wire ie old coil supply, then there is also the possibility that something else has been incorrected joined into that circuit. that could be tricky to identify, but you could start like this: make a list (well, i guess you have) of all devices which kill the ignition when they are swithed on. then start the car and shut the switch off; presumably car will still be running. then progressively pull out fuses till (if) you find one which stops the car, and note which circuit that is. it could narrow it down, but there could be other issues that process doesnt cover.
regards
alexander.
...or just find a feed from somewhere else that is only on when the ignition switch is in "Run" and "Start" positions and wire the MJLJ power to that (with an inline fuse)
Otherwise you might be looking at this strange wiring for some time....
Sounds like an earthing problem to me - you sure that the MJLJ 0v pin on the Molex is connected to a sound earth??
Martin
Otherwise you might be looking at this strange wiring for some time....
Sounds like an earthing problem to me - you sure that the MJLJ 0v pin on the Molex is connected to a sound earth??
Martin
Thanks Martin. Yes, of that at least I am sure - Brent's wiring instructions are so clear on that point that even I had to follow them!
I think I have more or less tried to wire it up as you suggest - what is giving me problems is my decision to introduce a relay into it all, in what is turning out to be a misguided attempt to avoid overloading existing circuits. I could ditch the relay and it would be fine (which is what I'll probably do to get it through the annual inspection), but now that I know about this stray voltage I'm quite enjoying trying to find it!
Thanks both
I think I have more or less tried to wire it up as you suggest - what is giving me problems is my decision to introduce a relay into it all, in what is turning out to be a misguided attempt to avoid overloading existing circuits. I could ditch the relay and it would be fine (which is what I'll probably do to get it through the annual inspection), but now that I know about this stray voltage I'm quite enjoying trying to find it!
Thanks both
Tim
1973 BMW 2002
1973 BMW 2002
-
Hamiltonguitars
- Posts: 8
- Joined: Fri Jan 27, 2006 10:22 pm
Hi Tim:
I had a 73 Tii (I don't think I would have ever tried to megajolt it though). Those cars are notorious for wiring shorts, especially at the fuse box. I pull the power form under the steering column from one of the wires that comes out from the switch when power is on.
rod h.
You should stick with the British cars
Mine is a 1959 austin healey sprite with a ford zetec engine (megajolted)
I had a 73 Tii (I don't think I would have ever tried to megajolt it though). Those cars are notorious for wiring shorts, especially at the fuse box. I pull the power form under the steering column from one of the wires that comes out from the switch when power is on.
rod h.
You should stick with the British cars
Mine is a 1959 austin healey sprite with a ford zetec engine (megajolted)
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