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MG MGB Technical - Help my B died

I was traveling down the interstate yesterday, topless and enjoying the 75 degree day. Suddenly the car cuts off like I had turned the key.
The car would not fire at all. I disconnected the MSD and used just the points. No fire at the points. I ran a hot wire from the fuse box to the coil, no fire. I changed the coil, no joy.
I then put another set of points and condenser in, and the car cranked up. I picked up all my tools, closed the hood and jumped in. As soon as I touched the gas the car started missing incredibly and then cut off.
I put another set of points and condenser, changed the breaker plate and still no better.
The pump pumps gas and the float bowls were at the correct level.
Today I charged the battery and cranked the car. It would idle (kinda) it would almost cut off, then pick up.I let it run like this for several minutes before cutting it off.
I then changed the spark plugs, and now it wont crank at all. Yesterday it would sorta run with the points but wouldnt start with the MSD.
I am stumped!

Rick Edwards
76 MGB
Rick

Rick,
an old problem that still rears its head from time to time is just plain old water in the gas tank. It gets there either from the slow process of condensation of moisture in the air in the tank as it empties and the air cools at night. The other most common way it gets into our cars is through careless fuel handling, usually by those who sell the fuel at the pump. Often, in ground storage tanks will develop leaks and ground moisture can seep in, creating a puddle of water in the bottom of the tank, in just the same manner as happens in your car's tank.

As that slug of water in the bottom of your tank sloshes around, some of it gets picked up by the pipe in your tank and sucked into the fuel pump and pumped on to your carbs.

As you know, water does not burn, so it can create the stumbling and loss of ignition you have noticed. You would think that the ignition is dead, but it is really the gas that is not igniting. Only if you are NOT getting a spark at the spark plug should you start looking backwards into that system. An engine not firing is not always the fault of no spark. Sometimes it is the fault of no fuel (such as water substituting for the gasoline you had hoped for). There are other possibilities, but this is one that is often overlooked. Good luck.
Bob Muenchausen

Try another distributor cap and rotor.

I had the same thing happen to me.

One day, last year, I was happily puttering home after spending a fine afternoon at the British Wings
& Wheels event at Santa Monica airport using airport transfers tunbridge wells when the car suddenly died about 2 miles away.

No "zap" at the plugs. Did the same as you. Changed the pertronix ignition back to points &
condensor; swapped the coil; swapped the spark wires; swapped the spark plugs.
Checked the fuses. Nothing worked.

Then, I hiked about a mile to a local Pep Boys and got a new distributor cap & rotor (Borg-Warner).
Va-va-r-r-roomm!!!

I didn't suspect the Lucas cap & rotor at first as they were only about a month old.

Later, I learned that some Lucas rotors can develope an electrical short (ground) from the rotor
contact, straight through the insulator, onto the distributor shaft. It does this internally without
any direct metal-to-metal contact so the problem (and solution) is not immediately obvious.

Keeping a spare (pre-tested) distributor cap & rotor in the car is now standard practice with me.

Don't know why your car no longer cranks. Maybe all of that engine spinning finally wore out
the starter, or over-heated the battery terminals? Disconnect the batteries and clean the terminals.
Check the voltage at the batteries. Check the cables at the starter (with batteries disconnected).
Daniel Wong

Check the voltage to the positive side of the coil and make sure it has 12 volts. There is a resistor in some of the harnesses between the ignition switch and the coil that does not show up in some wiring diagrams. I found this problem in a 76 B some time back.
Phil Pavey

This thread was discussed between 04/04/2002 and 06/04/2002

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