MG MGB and MGB GT Tech Talk
Heres what I know. Have voltage to coil. (white wire). Have voltage from coil to distributor(b/w wire) when points open and key on. When checking voltage with key on and points closed(no voltage). When cranking engine and checking B/W wire from coil to distributor the test light flickers. But I get no spark to spark plugs. Tested spark plugs and they are good. I checked and replaced high voltage wire from coil to distributor, still no luck. Please help.
Maybe secondary winding in the coil is open? Do you have another coil to sub into the circuit?
Test the coil. Get someone to hold the end of the coil high tension lead about 1/4" from a good ground (e.g., the head). Make sure the engine is positioned such that the points are open. Use a screwdriver to bridge (short) the points. There should be a spark from the high tension lead.
Hello Pete,
I had the same problem on my -68 B GT couple of weeks ago.
Nice weather and I thought I should get the GT out of the garage for the first time this year. Did not start. I suspected that it could be lack of fuel but the fuel pump worked and it smelled fuel out of the exhaust pipe so that was not the problem.
Removed one plug and held it against the block while a friend cranked the engine. No spark.
Took off the distributor cap and checked the points. Looked ok. Tested that the white wire on the coil had power. It was ok, checked the wire from the coil to the distributor. It was ok.
Basically did all that you have done. Still no spark.
Held the high tension lead from the coil to the engine block as Terry suggested, no spark.
Then I gave up and had a beer to think things over.
I drove the car into the garage last october so what could have happened while it was sitting there?
Checked the wiring diagram, read the manuals and trouble-shooting tips I have access to and finally started to suspect the coil. Although unlikely, I have never had a problem with coils in my 30 years dealing with british cars, but that looked like the only option to me.
I did not have a spare coil, but I had new points, a new distributor cap, new distributor rotor and a new condenser.
So the next day I replaced all this parts, checked if there was a spark on the plugs and it was not. So I thought, it must be the coil afterall. I have replaced every thing else. But I will do one last try, hooked up everything and after about 10-15 seconds it started.
Since I replaced everything I can not pinpoint the cause, but I suspect the condenser. That I did not get a spark may be caused by not good enough ground. I am a bit cautious when I hold the plug against the engine block. Don't like electric shocks.
But, long story short, try to replace the condenser, and the points if you got, if there is a short in the condenser it may give you trouble and they do detoriate with age. If you have access to a spare coil, try replacing that also.
Regards
Gunnar