MGB & GT Forum

Hi everyone. I recently picked up a 1964ish (long story) MGB as my first vintage car and am loving the experience so far but the car developed a misfire recently and I need some help.

The car is currently parked at a friend's and I want to get it out of their garage soon because I feel like It's going to be an inconvenience soon. But I have limited days to go over and work on the car and every time I try out a new theory and it doesn't work, then I have to order parts from Moss and wait for the next opportunity.

So this Sunday, I bought a bunch of parts hoping to get the thing back on the road.

Anyways... On to the problem.

The car has developed a misfire. I checked the plugs, they all looked good. Checked the distributor, the cap looked new but the points looked tagged. So I bought points and condenser and installed them. Only to drive the car and find the problem worse. When I pulled the plugs after, they were black.

The point and condenser seemed like it was installed fine. What should I do? Coil? Plug wires?

If your plugs are black I would lean out the carbs. If you are uncertain how to do that go to the tech library. I would have a very difficult time trying to tell you how to do it. It is not hard and would not take long. Good luck

If you go under the tech library, scroll pretty far down and you will see adjusting the SU carburetors. Under there you will come to adjusting the fuel mixture. That should help you find what you need. Good luck with it.

First you need to adjust the points, then adjust the timing.

Only after you adjust those 2 issues you should chase something else.

Look for John Twist at University Motors youtube of what to do when you replace points.



Each time you change the points there is a difference of timing and the amount the points overture varies a lot.
Then adjust the valves 0.015 cold
Then adjust the sparkplugs to proper gap (old points around 0.025).

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1977 MGB Red 'Victoria' and 2018 Jaguar XE 'Meghan'
All Classics:
Married, 2 children, MG MGB May to December, Jaguar the rest of the year.

Checked point gap? .015 inch
Proper plug gap? .025 inch
Adjust valve lash .015 cold
Check timing?

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LNDRVR4X4.COM
Home of Project "INCARN8'


1957 Series 1 Land Rover electric VEHICLE CONVERSION

FIXITUPCHAP.COM
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VIETNAM 1969-1972

If the misfire happened rather suddenly, then definitely don't touch the carbs (unless you see something obvious like fuel leaking from carb overflow tubes, which would indicate a stuck float or something).

Proper adjustment of the points or funky condenser seem most likely. Also check the distributor rotor carefully - the cheap riveted ones can cause all kinds of weird issues.

Good luck
Bob

Check for the presence and integrity of the small wire inside the distributor that grounds the breaker plate to the distributor body. Also, take a glass jar with you, remove one of the fuel input lines from one of the carbs, and pump several inches of fuel into the jar. Fuel delivery should be at the rate of a pint in 30 seconds, which is unlikely to be your problem, but more to the point, inspect the fuel for presence of water, especially if the misfire developed shortly after refueling. Fuel and water don't mix, so if water is present the two liquids will stratify and the difference will be obvious...

Dick

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Errabundi Saepe, Semper Certi
(Often wrong, but always certain)

The carbs are very set and forget. Do not adjust at present. Black plugs are often dizzy related.

Several choices.

Fuel flow. Look for overflows. Stuck floats.

Possibly dizzy. Verify timing at idle, 3000 rpm, and vacuum advance.

Vacuum leaks.

A couple of hours of effort will fix you up.

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L.W.(Larry)Baygents
63B
77 Spit

Hey everyone!

Just wanted to follow up. The MG rides again!

It was frustrating for me doing research on problems to find a person with similar issues who never said what got the car running right again.

I tried a whole bunch of things before swapping my Made in China spec ignition coil out from a shiny new unit from Moss (love that place).

That did it and the car was running great after.

Thanks again everyone who helped out.