1984 90 engine runs without key

Hello,

My 1984 landy was converted to a 300tdi some time ago and its now developed a really random problem. The engine will stay running with the key removed and ignition lights out! Only light that would stay on was the battery warning light so I though bugger the fuel.solenoids playing up, nope not that then though ooo I bet its the ignition barrel, nope not that either. Checked and replaced 3 of the 6 soldered together white cables that do the control circuit as they looked worse for wear and still no luck, if I put my window wiper on then the engine cuts out. Since I have done the basics solenoid and barrel would it be a safe assumption the problem is with the warning light box? If I disconnect that while the key is off and engine running the engine will.switch off. I have 14v going to the battery warning light with engine running and then 1.5v on the copper tracking on the bulb next to it (assuming the 1.5v is enough to.hold solenoid open) or should I not be getting 14v to the instrument warning lights and that what's causing the issue?

Your ignition is being back fed, you could try pulling fuses one by one to help locate the fault. The main harness in an 84 vehicle is a fairly simple thing, 1.5 volts isn't right though.

Check the state of your earths to the engine and bulkhead too.

I thought that as well, i had disconnected all cabling and tested to see what was going on to find the 1.5v back fed seemed to only happen when i had the alternator battery warning light connected, disconnect it from the voltage regulator and no problems it stops when needed. Just i couldn't determine how the voltage regulator was meant to work, does it regulate the 14v from the alternator to 12v for the warning lights or does it just maintain the 14v rather than fluctuations etc. I have ordered a second hand dash warning panel to see if thats the cause. Have also removed and cleaned the earths on the bulkhead. i that doesn't fix it then

Knackered diode in the alternator ?
Mo

do what Land Rover do stick a diode in the ignition warning lamp circuit if you have turned the ignition off you in affect have broken the circuit to the ignition warning light lamp

I go with Mo on this one, knackered diode in alternator.

Before you go replacing the alternator, remember the engine will not run without fuel. Check again what is happening with the fuel cut off solenoid. With the ignition off, there should not be any voltage on the wire leading to it - if there is (which it seems is happening) you have a wiring fault. Follow the wire back into the loom to see where the battery contact is. You have already found a few faults, there are likely more.