MG Car Repair: 1977 MGB electrical ignition problem, inertia switch, volt meter

Question
I'm having a great time with my 77 MGB that I recently purchased, however, I have an inconsistent starting problem once the car gets warm by driving it or just by leaving it in the sun. I have to wait until the car is cool before I can restart it (this may take up to a day or longer). Recent example: when I left it in the hot sun for several hours, I turned the ignition switch and could not hear the fuel pump or the two front fan motors turn on (I have the fans wired so that they always run). The car will immediately start but will stop after about 45 seconds because it’s not getting fuel (you can see that there is no fuel in the glass fuel filter). When I turn the ignition switch ¾ of the way, there is no sound at all however, I can turn on the radio.  Please note that when the car is cooler or cold, I can hear the fuel pump and fan motors turn on when I turn the key ¾ of the way. Since the fuel pump is new, I know it’s not the pump. I checked for loose wiring from the coil to the distributor and everything looks OK.  This problem would occasionally happen prior to when I rewired the fan motors (so that they run all the time) so I don’t think that this is causing the problem.  Where else could I check?  Could it be the coil? Could it be the ignition switch? The fuse connections also appear to be OK.  Thank you for your help with this challenge.

Answer
Hi Frank,
You need to do some testing and it must be done in the failed mode. Take a 12v test light or volt meter and check for power on the fuel pump wire with the key in the ignition position. If you have no power test for power on the white wire off of the ignition switch. If you don't have power there then the switch is either bad or you have lost power to the switch. If you do have power to the white wire then you need to check the inertia switch.

When you have any electrical problem always test only one circuit at a time and forget what it might be. A wiring diagram is a MUST any time you try to work on electrics. If you don't have a diagram you can go to my web site and copy one.
http://mg-tri-jag.net/76MGB1x1.jpg  and
http://mg-tri-jag.net/76MGB21x1.jpg
(the 76 and 77 were the same except for the fans and the OD)
Howard