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MG MGB Technical - fuel to carbs but not to cylinders

Greetings All-

I've been away from the list for a while but am now back with a new engine (1K miles ago) so maybe I can contribute something in the near future.
This morning my '69 BGT would crank but not turnover. I'm getting good spark and fuel to my bowls. The fuel pump is pumping in a contant stream at the carbs but not exactly with a lot of pressure (I don't have a gauge to measure although I understand flow should be around 2psi). There is fuel present on the carb bridges at the jets and pistons are moving freely. I squirted some fuel in a couple cylinders and she fired right up for 5 seconds or so and died. Although the pump is ticking and supplying some pressurem is it possible its just not enough pressure? Its pretty obvious the fuel is just not making it into the cylinders. Could it be anything other than low pressure from the pump? I doubt if both floats would develop problems simultaneuosly...

Mike King
'69 BGT
'72 E-Type
Michael King

How long since it last ran Mike? My bro in law let his sit for a few months and when he started it the engine ran REAL rough. He cleaned up the carb needles and jets and all was fine.
william fox

I forgot to mention, this is my daily driver and she runs like a top (until now)
Michael King

Michael - If you have an SU fuel pump, the pressure to the carburetor float bowls will be between 1.5 and 3 PSI. I doubt that the problem is fuel pressure, but it might be volumn of fuel being delivered. It does sound like you are having a fuel problem if you can get the engine to run a bit by squirting gas into the carburetor throats. I will send you a fuel delivery troubleshooting guide that may help you out in isolating the problem.
Good luck - Dave
David DuBois

Maybe a massive vacuum leak. Check all hoses to fittings on the intake manifold for tightness and any cuts. Also check the end plugs on the manifold itself.

Mike
'79B
Mike Janacek

Mike,
if you are having trouble with it not starting from dead cold, please check your choke controls. You would obviously note if the choke cable were broken, but you may have overlooked some other facet of the choke linkage mechanism. If your choke mechanism is not working correctly it may be your problem.

If I try to start my GT from cold without the choke, it is very unwilling to fire or start, but just halfway out on the choke cable makes all the difference - it then will start on the first swing of the flywheel!
Bob Muenchausen

If the float chamber are full you should be able to blow into the overflow pipe and see fuel coming up the jet.
Paul Hunt

Boy, this is a strange one. I'm getting plenty of fuel through the jets and car will start with a puddle of fuel there, then it dies. Keep in mind I drive this car everyday with fine performance until yesterday am when she wouldn't start. Some bizarre all-of-a-sudden gross manifold leak is the only thing I can think of so far. I'm stumped.
Michael King

Hi Mike,

Just a thought, I saw a thread recently about someone pulling away from a gas station, just after filling the tank and the car stumbled and stopped. He was getting fuel etc. but nothing. The long and short of it, there was a plug at the end of the intake manifold that fell off or something to that effect and it caused a huge vacuum leak. It appeared to be their problem. Worth a check.

Regards,
Ed
Edward Bullard

Bingo Ed and Mike! This is in fact exactly what happened. When I first looked over the manifold I missed the front plug so when I looked again, there it was-a gaping 1" hole!
I found the plug buried on the bottom of the engine. Now, I'll pull the manifold, epoxy, and bang into place. Indeed it was a"bizarre all-of-a-sudden gross manifold leak". I guess logic won out-this time!
Thanks to all that responded.
Michael King

This thread was discussed between 09/08/2002 and 10/08/2002

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