waltmcc

I have no ignition light when key turned to position II, no indicators, wipers etc. yet the engine turns over and there's a good spark at plugs, but wont start. Previously (last year) ignition light came on and I could usually hear the fuel pump clicking before proceeding to start - now there's no sound from pump. I suspect the ignition switch and am trying to prove this before changing it. Any ideas?

KimMG

You will need a wiring diagram and a meter or test light. Wiring diagrams are available at http://www.advanceautowire.com click on stock schematics. If your car is fitted with an ignition relay, use the wiring diagram for '78 and later from Bentley.

The ignition light goes to the charging circuit. If it is not part of the ignition circuit. If it is not working the alternator will not charge.

With the ignition switch in the on position, test for power to the fuel pump and green wires connected to the fuse box. If you don't have power to the third fuse or the fuel pump, check the power output of the ignition switch (white wire).

waltmcc

Thanks KimMG that helps. With ign switch in ON position I do have power output at the white wire but not at the 3rd fuse. There appear to be 2 relays either side of the fuse box and after removing and replacing one of these, the fault has changed - when I turn the key to start the car I now have the ignition light come on and fuel pump can be heard ticking away - however now the starter motor doesn't turn at all. I swapped the two relays with each other but no change to symptoms. Thinking of replacing one or both relays (are they relays?) Comments would be greatly appreciated. Walt

KimMG

They are common Bosch style relays available at most auto parts stores for less than five dollars. Just ask for a generic 30amp Bosch style relay.

If you look at the wiring diagram, the ignition lamp and fuel pump should have nothing to do with the relays.

Ignition relay

white wire - pin 86 - pin W1 - should have 12 volts when the ignition switch is in the run position.

black wire - pin 85 - pin W2 - should be connected to ground.

brown wire - pin 30 - pin C1 - should always have 12 volts.

white/brown wire - pin 87 - C2 - should only have 12 volts when the ignition switch is in the run position and the white wire has 12 volts.

Starter relay

white/red wire - should only have 12 volts when the ignition switch is in the start position.

black wire - pin 85 - pin W2 - should be connected to ground.

brown wire - pin 30 - pin C1 - should always have 12 volts.

white/brown wire - pin 87 - C2 - should only have 12 volts when the ignition switch is in the start position and the white/red wire has 12 volts.

The ignition relay provides power to the third fuse, radiator fans, coil, and the distributer.

The white wire circuit supplies power to the fuel pump, ignition lamp, overdrive (if fitted), and the ignition relay.

Sounds like you are having intermittant failure in the white wire circuit and/or with the ignition switch. Check to make sure all connections are clean and secure. Use dielectric grease to prevent future corrosion and aid in the ease plugging the wires into the sleeve connectors. If you need replacement sleeve and bullet connectors, they are available at http://www.britishwiring.com
You will find instructions for attaching bullet connectors in the instruction manuals for wiring harnesses at htttp://www.advanceautowire.com

waltmcc

This fault is changing and not for the better. When I turn the key to start I now have nothing except the Handbrake warning light. I am satisfied the ignition switch is functioning correctly having checked all outputs in all key positions. At Ignition relay, all is as you say except nothing at the white/brown wire in the run position. Starter relay - all OK except again, nothing at white/brown wire in the start position. I'm continuing to check all connections, focusing on the white wire circuit. (diagram 19 for 1977 model). Don't want to give up just yet and call in the professionals!

KimMG

Sounds like both of your relays are failing or have poor ground connections.

Use the diagram for '78 and later from Bentley. In '77 wiring was changed and an ignition relay was fitted and is only shown on the diagram for '78 and later from Bentley.

http://www.advanceautowire.com click on stock schematics.

Make yourself a couple of enlarged copies, one for reference and one to make notes on and keep track of your progress.

Sounds like you may have more than one problem. At this point, I can only suggest systematically checking and cleaning each connection. One important connection not shown on the diagram is the engine to chassis ground strap. Make sure its connections are clean and secure.

waltmcc

Fixed by replacing both relays. Original fault was combination of ignition switch and relay. (I had stripped and cleaned the switch contacts a few days back). The starter relay was self-inflicted and went bad when I tinkered with it a few days ago, although both relays were originals and 30 years old after all. Thanks a lot to KimMG (where are you?) who gave me valuable pointers and I 've learned a lot about the electrics. Car going well and ready for another season!