MG Car Repair: MGB loses power / no response to gas pedal, fuel pressure gauge, vacuum test

Question
Howard, my new 1980 MGB, which I've had a little over a week, has driven beautifully until a few days ago, when it began to lose power randomly. It started with little blips in 3rd or 4th gear where it would lose power for a second or so, but is getting worse. It idles fine, has good oil pressure, the temp gauge reads normal, and it starts fine. However, while driving, it loses power and pulls back, then picks up again. This will get worse and worse, until pressing the gas pedal does not result in a response. If I coast for a minute or so, it will "revive" and become responsive for a few minutes. The car does not actually shut off when this happens, it simply does not respond to the gas pedal (as if I were giving it gas while in neutral). What should I check? I am in Houston, Texas.

Answer
Hi Lieta,

If it were brought to me in a dealership I would first connect a "T" in the fuel line close to the carburetor and run a long hose out from under the hood and place a fuel pressure gauge under a wiper arm so I could monitor fuel pressure at the time of failing. Checking the fuel pressure while it is running good is useless info. You must see it when it is in the failed mode. Be sure to put clamps on all the hose connections.

A fuel pressure gauge is not expensive nor the additional equipment (The "T" connector and extra hose) Some vacuum gauges have a section for testing fuel pressure on carburetor systems. You want to see from 1.5 to 3 PSI at the time of failure. The next test is a vacuum test. Put the gauge on the intake manifold vacuum port (not the carburetor port) At not time should the vacuum go below 5 in. hg. no matter what the load is or throttle setting.

If all this is ok remove the vent hose from the carburetor float chamber and let it vent to outside air and test drive the car.

If all this is ok and it still has a problem you need to remove the carburetor and go completely through it as in a carburetor overhaul.

Your symptoms do not point toward an electrical nor mechanical problem and does point toward a fuel problem.

Howard