accleration problem

Recently purchased a 1977 mgb in good physical and mechanical shape. Have put approx. 700 miles on it. After driving it for about 10 days or so I had a problem with it. After shifting through to 4th gear and driving at a constant speed (say 45 -50mph) all at once I could no longer accelerate. The engine continued to run and because I could not accelerate the car slowed to a stop even as I pushed the gas pedel. I also noticed during this adventure the tach imediately went to 0 rpm's but the engine was still running. After stopping I turned the ingition off and back on and the car ran fine. This has happend four (4) times in the last three weeks or so. I have (since it happend the first time) replaced the coil and coil wire and thought the problem was solved but after about 8 or 10 days of troublefree driving the problem has come back. I have gone through about 2 tanks of fuel during this time and used different brands of fuel each time and check my spark plugs - they look fine. I need some advice on what to check next. This could be a very deadly problem and I am concerned about someone behind me not noticing me slowing down suddenly. I can also hear the electric fuel pump working as I start the car but I have not been listening when the problem occurs (too busy trying to get off the road and restart). If more info is need please let me know.

It sounds like your engine stops running when the tach drops to 0 and you may be leaving the car in gear while it rolls to a stop? I suggest you move the shifter to neutral when you have the problem and brake the car to a stop. I think you will find the engine has stopped running when the tach drops to 0.

I don't have an answer to your problem, you said it will start again after you stop and turn the key off and on. We need some more information about your car to try help you solve the problem. Is it a USA or UK specification car? If USA has the distributor or carburetor been replaced? If USA does the car still have the emission equipment on it? After you start the car again how long before the engine stops again? What kind of cooling fan/s do you have? If electric do they stop when you have the problem? Do you have an SU fuel pump or is it an after market pump? Let us know this information and we will try to help, the fact it immediately restarts is puzzling.

Clifton

If the tach suddenly goes to 0 it sounds like the old mgb original electronic distributer.Replace the electronics with an aftermarket allison electronic ignition.I had the same problem but my car would die suddenly and I'd sit on the side of the road for ten minutes or so then drive for about another week till it happened again.If your car is still running could be a sticky float jet.mgbss63

Also check fuel filter and fuse box.mgbss63

If I had to guess I'm thinking you have a fuel delivery problem, Did the car sit for an extended period before you bought it? Does it have any type of fuel filter installed? Has any fuel additive been added to the tank recently? I'm thinking the pick-up in the tank may be getting clogged when you reach the point where you are flowing a certain rate, when the engine stalls for lack of fuel, the clogging material falls off the pickup. This may also be occuring in the filter if there is one.