Big electrical problem

[Boomer]

Hi guys, i've had this problem come and go of its own accord before but it is not fixing its self this time.

I went to start the car (1987 SE) and all the vehicle's electrics went dead. Engine did not crank it just died. i've tried disconnecting the battery but to no avail. Any help would be much appreciated as the MOT re-test is looming

Cheers

[fitz]

first thoughts

- flat battery
- does your car have an immobiliser fitted?
- main power relay failed?

[Boomer]

Battery is new, it does have an immobiliser but its new ish and never given any trouble. Would the main power relay give these symptoms of absolutely nothing electrical working?

many thanks

[ttedj]

For there to be no power to anything is a little strange and unlikely to be an immobiliser unless it has been wired through all harnesses or the main earth or positive binding post - can't see why or how due to the gauge of cable.
Therefore it is probably a problem with the main earth or positive.
Having been doing a bit of reading in the service notes, it would suggest that the battery is connected to the chassis as the main earth in the rear drivers wheel arch. ALL of the negative from all harnesses earth through a stud at the right handside of the pedal box. This is then connected to the engine block which is in turn connected to the chassis via a main earthing strap.
This is where I would look first. If it all failed as you started to crank the engine, it may well be the main earth strap from chassis to engine block has a bad connection or needs replacing. Or it could be the connection of the lead from stud to block or this lead needs replacing. You should be able to find this as it runs out from under the area of the brake servo.

If it isn't this it is probably the main positive binding post which connects somewhere by the front left leg of the chassis and then runs to the starter relay. Not sure where from the manual but should be easy to trace from the starter solenoid.

Worth getting a multimeter onto the chassis and the positive supply on the starter solenoid to see if there is 12 volts. If there is it is probably the engine to chassis earth.

Hope this helps and is just my interpretation of the manual after a few beers.....

Ted