MG Car Repair: 1977 mgb, starter solenoid, volt meter

Question
my 1977 mgb after running for a short while and then shut off, sometimes will not start. it acts like the battery is disconnected. all leads are tight and test positive. after about 20 minutes it will start and run fine. any thoughts?
thanks much  gary

Answer
Hi Gary,
Easy one, when it is in it's failed mode just take a test light or volt meter and check for power to the starter relay (white w/red tracer wire) and if the relay clicks, go to the starter solenoid and test the small white w/brown wire when the relay clicks. If there is power check to see that the large battery wire is tight and has power.
If the white w/red wire has power but the relay didn't click check the black wire for a good ground and it is has the relay is bad. If the relay clicks and puts power to the solenoid and the solenoid don't click then the solenoid is bad.
Howard