QuestionI have a 79 MGB, 100K miles. After driving at 55mph for 15 minutes, the car dies, but pumping the gas and putting in the clutch will keep it going-most of the time. I have replaced the alternator and battery, cleaned the carb, and blew out the gas lines. Is it the fuel pump?
AnswerLate B's are not my expertise (all the late emissions stuff), but I'll try...
Could be the pump, but more likely dirt still in a line. (You don't specify the extent of your blowing out the lines.) Disconnect the fuel filter, take a jam jar or can in hand, put under the fuel line (from the pump) and have someone turn on the ignition. Fuel should pour out.
1) If not, it's either the pump, or (just as likely) dirt in the pump lines. I don't know how easy it is to get to B's pump, but if accessible, disconnect both the banjo fittings and check for crud, especially on the inlet side, from the tank.
2) I don't know whether you are in a place with alcohol in your fuel. If not, could be water in the tank (not too likely really). Use a can or two or fuel drier.
3) If fuel does pour out, you have localized the problem to the filter, a float valve, or a jet. It's possible you still have a speck of crud around a float valve needle. The way I sometimes fix that problem is to loosen the float chamber tops, so that fuel can pour out when the fuel pump is pumping. For jet problems, take off the air cleaners, get the engine revving past 3000, and (i) open the throttle wide and (ii) at the same instant put your hand over the inlet for each carb in turn. The engine will likely die, but that sucks fuel through the jet like you wouldn't believe--in case there crud in a jet.
4) Finally...if the pump is still ticking, it's probably still working, or trying to: it's almost always the contact breakers that give up in pumps.
Good luck!
