Blogs Car Info Our Show Deals Mechanics Files Vehicle Donation

MGB won't start without ether

I have purchased a '68 MGB that had a major engine rebuild about 10 years ago but then the car was put in unprotected storage until 2 years ago.

When cold, the engine will start only with spraying ether into the dual SU carbs. Once warm, the car will start fine.

This occurs in any type weather-wet or dry, hot or cold.

The fuel pump is fine and delivers adequate fuel to the carbs. I’ve all but ruled out vapor lock. Timing maybe?

Any help comments would be appreciated.

Are the chokes working?

Have you checked the venturi plungers in the carbs to make sure they’re not sticky? The carbs probably need to be cleaned out.

Make sure you float chamber are not leaking through the hoses that go to the jets, this of course will leave your float chambers dry and will not have any gas to get started.

When you pull on the choke handle, look to see if the same hoses mentioned above were pulled down,both of them, this is your choke on those carburators.

The plungers must also be free and have oil in them. Transision oil or 3in1 will do the trick.

That whole system is very simple.

chokes work.


Thanks. I’ll check it out.

Thanks. I’ll check it out.

SU carbs don’t really have chokes as I remember. When you pull the “choke” knob out, the metering tubes are pulled down out of the carbs (which quickly wears out the cork seals and makes them leak) and this action allows gasoline to flood the carbs which hopefully causes the engine to start. A poor system right from the get-go. Some SU’s have a “tickler” pin sticking up from the float chamber which, when depressed, will also flood the carbs and help start the engine when cold.

Many British car owners rigged up a “primer button” that pumped a little fuel right into the manifold to aid cold starting. Older snowmobiles and lawnmowers use this starting system too…

You might want to buy this book ($18). I hear SUs work fine, once they’re rebuilt and properly adjusted.

Here’s another, includes other types:

This sounds like the jet body isn’t dropping when you pull the choke. To check this remove the carb dashpots and pull the choke fully out - then measure the amount of jet body drop vs the height with the choke fully in. The difference should be between 1/8 - 1/4". If the jet body isn’t moving, check the actuation assembly. Without this working you will never get an SU equipped car started since you have no choke at all.

You’ll note that it’s usually hard to pull the choke out, always floor the throttle when pulling the choke on an SU, flooring the throttle helps overcome the throttle spring resistance and extends cable life.

Acquaintance who’s owned numerous British cars said "You know, 9 times out of then, if they’d just a) run the jet adjustment upward until it homes, then back off 12 faces of the nut and b) balance the two carbs and c) static time the car, it will probably run like a dream. "

Couldn’t hurt!

Try squirting gas instead of starting fluid if gas works its the carbs if it does not start check compression when cold.
I have had 2cars,1 jeep and 1 motorcycle with low compression that would only start with starting fluid. Do NOT use wal-mart brand fluid it is real weak

Just one question to qualify my earlier reply -

This car hasn’t been equipped with an SU AED (Auxiliary Enrichment Device) has it ? It’s not standard on MG cars (usually Jaguar) but I have seen them fitted on some cars. If you have a cast unit measuring 1"x2"x1" with a black bakelite top mounted between the carbs then you have an AED fitted.

AEDs are actually a miniature variable jet carb and are dreadful to set up. If you have one of these let us know and I can post the setup instruction manual.