QuestionHi Howard,
I have a 71' MGB. Bought last August as a fixer/upper. It did run and drive, but ran very rich. Put in my shop last August, and have since replaced the entire brake system, new distrubutor(reman.).
Went to start car for first time in a yr., it started right up, but still ran very rich, shut car off, and could never get it to restart. I know I have to fix the rich problem, but I was checking my spark, and found it to be intermittent, and yellow, not blue. Checked point gap, condenser, coil, all good. With test meter, found that even with points open, there was still a ground through the distributor, any where you touched it. When I removed the coil to dist. wire, the ground went away, and then tested the dist. not connected to the coil, it it would only ground when the points were closed as it should. When I took the wire of the positive side of the coil, and tested it, it showed that it was grounded some where. Found all white wires under the dash, one to the coil, one to the alternator, one to the fuel pump. These were all connected together to one large white wire from the ign. switch. After seperating all the wires, I found a ground in the white wire feeding the fuel pump. I disc. the wire from the fuel pump, and no more ground. When I put the test meter on the spade on the fuel pump where the white wire connects, it went straight to showing it being grounded, and this was with out the ground wire being connected to the fuel pump. The fuel pump appears to have been replaced not long before we purchased the car. I can't imagine that it had run last year in this condition, and now won't, is this a problem with the fuel pump? or normal? I know I am missing something. If possible, I would like to try to correct this then tackle the carbs and the rich problem. Thank you in advance for any help.
AnswerHi Bryan,
You need to leave the pump disconnected and spin the engine to see if you now have good ignition. If so take the pump and test it with two test leads by connecting it to a battery. (I would connect the ground and just scratch the power test lead across the positive terminal just in case it is shorted out so you don't melt your test leads.)
It does not mean anything if the pump ran fine last year or last week or two minutes ago. Testing it is the ONLY way to know.
As far as running rich, the only way a pump can have anything to do with that is if the pressure is too high. Connect a low pressure gauge to test it. You must see from 1.5 PSI to a high of 3 PSI. Some aftermarket pumps that you can get from an auto parts store will pump 5 to 7 PSI and they will make a set of SU carburetors flood and thus run rich.
Howard
