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MG MGB Technical - So I turned the key, and...

So I finished the wiring, hooked up the battery (after checking checking for shorts), checked the lights, signals, washer, wipers...all good...then I turned the key to crank the engine and...nothing. Not even a relay click. I've rechecked the wiring; everything looks good. I've checked the brown wire into the relay; it has power. The relay and the starter are new. I'm assuming that the relay is bad. How do I test it? Is there anything else that could be wrong? Any help is appreciated!

Also, my hazard switch is bad and it seems that the '72 switch is no longer made. It's been replaced by one with 5 prongs (the original had 6); anyone have any experience hooking the new one to the old harness?
Brian LaVoie

Hi Brian,

Sounds like you've made good progress. I would suspect the ignition switch. It's been a long time since I've done any wiring on a "B", but I recall the ignition switch on my '72 being "troublesome", (to be generous). I think there is a red (?) wire that energizes the solenoid when the ignition key is turned to "start". First check that it is getting power to the solenoid. Second, you can carefully, jump the solenoid directly from the battery cable and it should turn the motor over if the solenoid is okay. Wait a minute, that's not right, red wiring is the parking light circuit. Maybe it's yellow. A little help here, anyone?
Steve Mc

Doesnt Pauls web site have the circuits on it, If you put a volt meter, or buld on the solenoid wire what does it do? Did you put the earth back on the engine ( very long shot )
Tatty

http://www.mgb-stuff.org.uk/

Paul even has a section in the spanners/electrics called wont start.
Tatty

White/red from the ignition switch to the relay, white/brown from the relay to the solenoid.

Someone else recently wrote to me about using a six-spade hazard switch on a five-wire system - easy-peasy:

"The extra terminal is for a tell-tale lamp on later cars. With the switch off two of the terminals should be connected together (should be 7 & 8 if they are numbered) and none of the others should be connected to anything else. These two are for the two greens that feed the turn signal flasher. With the switch on, the other four (1 to 4) should all be connected together and you can connect the light-green/brown, green/white and green/red to any of them, although the book shows green/white going to 1, green/red to 2 and
light-green/brown to 3."
Paul Hunt

I appreciate the comments!

I was checking the connections to the starter relay this morning; brown had power always, both white (w/trace) wires got power when the key was turned. I was about to test the ground when I smelled smoke and yanked the battery cable.

Yesterday, everything attached to the rear harness worked perfectly, and I pulled the ground off the fuel pump so it wouldn't keep going (the carbs aren't attached yet). Then this morning, I put in a new fuel line from the tank to the pump. I suspect I grounded out one of the fuel pump lines without noticing while I was working. The (new) rear harness melted almost to the main harness, starting at the pump.

This is the first problem I've had, so I'm able to be philisophical about it rather than mad as hell. I closed up shop for the day, grabbed a good book, and set up the hammock. Tormorrow I'll figure out if I can re-use the old rear harness, and confirm (I hope) that the damage didn't reach the main harness. If it did, I'm looking at the Painless Wiring option.
Brian LaVoie

Since the same current flows throughout the circuit - brown, ignition switch, white all in the main harness and the white in the rear/body harness you are just as likely to have damage in the main as in the rear.
Paul Hunt

This thread was discussed between 17/05/2002 and 20/05/2002

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