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MG MGA - another electrical problem

Iím having an electrical problem in an MGA that I am restoring. It has a new wiring harness, and Iíve put in a fuse block with half a dozen fuses instead of the usual two. I've removed the voltage regulator, as there is an alternator with one built in.
All is hooked up as per the wiring diagram, and each individual circuit works when tested: the lights come on, the plugs spark, the fuel pump pumps, the starter turns vigorously, etc.
The problem is that when the ignition key is turned on and the ignition-hot circuits are activated, the engine cranks very slowly. When the ignition is turned off, the engine cranks rapidly.
I expect that I have something set up wrong, but I canít figure out what it is. Thanks in advance for your help!
Mike
M.E. Whalen

Why not pull a fuse, one at a time, while cranking the starter over with the switch on? That should allow you to eliminate the problem to a particular circuit.
Gene Gillam

I have the same problem with mine.I have changed everything and it still cranks slow. NOT a problem in the summer,but I drive it every day it does not snow.My battery and alternator show 13.5 volts. JOHN
John Gordon

You may find that the ignition timing is very advanced. It may be trying to fire on the upstroke. I had a similar symptom when converting to a pertronix.
Pull the high tension line from the coil and see what happens.
Dave Ahrendt

X2 what Dave said, to much spark advance. For a test, disconnect one of primary wires from the ignition coil and crank it with key on. It will likely spin over quickly without starting. Reconnect the wire, and it will "kick back" and crank hard with switch on.
Barney Gaylord

MIKE, I just solved my slow cranking. The long skinny screws that hold the starter together were loose. A pain to get to, but a big difference in starter speed. Hope this helps! JOHN
John Gordon

This thread was discussed between 08/11/2013 and 12/11/2013

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