Lights kill engine stone dead (any lights)

After some advice if possible.

I've got a 1987 Defender/90 with 200Tdi engine conversion.

Sometimes, only sometimes - maybe 50% of the time, and only in the first 30 minutes of being fired up, my Landy kills the engine whenever a light is switched on.

These lights could be activated via turning on the reversing light by putting the truck in reverse, or brake lights via applying the brake, or indicators or normal headlights.

Engine is running fine and no problems and then suddenly it just stops dead as if I've turned the key (except I haven't). Often teamed with this is a problem where at very low revs it dies (tickover) as well.

I have to do a restart and it normally fires up and drives along for a little while until more lights have been activated and the problem returns.

I'd diagnose a bad earth but have no idea where to start - plus the fact that sometimes it's absolutely fine and doesn't do it at all.

Lately I managed to get it to stop by fiddling around with the heater fan control but that might have been a coincidence.

Just passed it's MOT where I picked a good day for the test - i.e. a day without the problem - so the truck is in good shape apart from this infuriating problem.

Any idea where to start?

Sounds to me like something is stopping power getting to the Stop Solenoid on the Diesel Pump.

Check how thats wired.

multimeter out, turn on ignition and see if the fuel solenoid wire has power.

switch light on, has the power gone?

since it's a conversion, follow that wire back and see where the guy get the power from and and the state of the wiring.

basically make sure it isn't a total bodge job before you go earth/short hunting.

Is it just the lights that do it? What about wipers/radio?

Wipers seem ok, or at least haven't triggered it yet and the radio is very rarely on (i.e. front face removed 99% of the time) so I haven't checked that.

It's very weird as 50% of the time there simply isn't a problem or, as is more often the case, I drive 40 miles without missing a beat then park up and switch the engine off and when I return to the vehicle the problem occurs. This happened just recently when I was about 3 miles along a farmers' track up near Thruscross (north Yorkshire) and I was fretting I'd never get back to where I could legitimately call the RAC...

So nothing that anyone else has mentioned in the years gone by?

Have you tried doing what trax has said?

I will give it a go. Just at work at the minute but determined to get it fixed. Thanks very much for the input.

Can we have some more clues before we reach for the Stanley, volt meter and wire cutters?

Do the instrument lights stay on when the engine stops?
Does it start straight up again (dont have wait anytime) after its stops?
If it does start up again does it stop when the lights are turned on again?
Does it start up with the lights still on?


losing the power to the fuel solenoid will of course cause the the engine to stop but by switching on the lights you are introducing voltage into parts of the system not losing voltage on the solenoid wire. This to me would suggest that there is too much load on the system when you turn on the lights and not enough voltage to keep the solenoid open. Its hard to check transient voltage you could try with you multimeter testing across the fuel solenoid and ground and try and see if you get a voltage drop with the engine running then get someone to turn on the lights

To prove you have short on on the solenoid wire you could either put in a temporary cable, or fit a temporary fuse inline as near to the supply end as you can and see if it blows, if doesn't you just saved hours chasing a short that wasn't there.

I would also do a battery voltage check from cold and a charging check as a matter of course.

My pm box is always open, especially for fellow Yorkie

Regards
Lee

Do the instrument lights stay on when the engine stops?

Yes - the battery light comes on as you'd expect if the engine stops.

Does it start straight up again (dont have wait anytime) after its stops?

Yes - starts up straight away, often when the machine is still rolling with no bother.

If it does start up again does it stop when the lights are turned on again?

Sometimes yes it does start up and then stops again when the lights go on again. Other times that first couple of stoppages makes it work fine again - or it goes on for an hour stopping and then being restarted.

Does it start up with the lights still on?

Yes it does (I think). An example would be a flashing indicator - it will stop it dead but doesn't stop it starting (I don't think) if it's still on.

if its starts straight back up with lights on, the white wire to the solenoid cant be pulled to ground or it wouldnt start again. I think you may have a problem with power from the alternator, my thinking is that loading the sytem with lighting could be pulling down the voltage on the fuel solenoid this is also bourn out by the fact you say it happen at low revs. which is why i said do a charging check to rule this out

I would clean up all the contacts on the alternator, battery conections and spade conection to the fuel solenoid which will probaly be corroded or covered in oil, then see where that goes. try the cheap easy stuff first.
Lee

I hope you get it sorted, I'm gonna follow this thread to find out what it is in the end, best of luck.

Cheers - I'll be getting the spanners out this weekend to fit some rear bench seats so I'll see if I can get my hands on a volt meter at the same time.

I've asked my garage for a quote on replacing the alternator too just in case that's an easy (if expensive) fix.

Just a thought.

Measure the voltage between the diesel pump body and chassis earth, with the engine running, then turn a light on.

If you see anything other than a fraction of a volt - you have an earth problem.

Also check voltage between battery negative and chassis with engine running and lights on. And pump body to battery neg voltage too.

You can try and carry out a temporary cure by connecting the pump or battery to the chassis with a jump lead.

Also, be aware that the throttle cable can act as an engine earth ( which is a very bad idea, as the throttle cable can melt and stick open - as happened to me).

captainbeaky said:

Just a thought.

Measure the voltage between the diesel pump body and chassis earth, with the engine running, then turn a light on.

If you see anything other than a fraction of a volt - you have an earth problem.

Also check voltage between battery negative and chassis with engine running and lights on. And pump body to battery neg voltage too.

You can try and carry out a temporary cure by connecting the pump or battery to the chassis with a jump lead.

Also, be aware that the throttle cable can act as an engine earth ( which is a very bad idea, as the throttle cable can melt and stick open - as happened to me).

Click to expand...

Thats instresting, one to chalk up for reference, i not sure you have an alternator fault just yet but possible high resistance some where thats causing a voltage drop, the only real way to diagnose is get the volt meter out and do some checks. Maplin do a half decent volt meters for 20 quid and theres a big store on regent street.

If you sort this Dan for the cost of a volt meter just image the buzz and next time you will a lot wiser

Lee