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MG MGA - Engine sputters

fuel pumpking on my $5000
david kirkpatrick

Pull your float chamber covers.Check and adjust float levels...One or both of your float needles may be sticking open, or there is fuel in the float, causing too much fuel....
Other possibility is a vacuum leak....Disconnect the vacuum line at the carb, and suck on the line....If you get no pressure, your advance diaphram is shot , and you have a vacuum leak...If there is pressure, then you are probably o.k. , there.
Edward Wesson 52TD

It could be that the SU pistons are sticking or they have no damper oil.
If the carburetors are fitted with piston lifting pins lift each piston in turn and let them drop.
Listen for a "clunk" sound.
If no lifting pins you may have to remove the air cleaners to lift the pistons.
This is done with the engine stopped.
Do you have oil in the dampers?

M F Anderson

Have you disturbed the choke cable and is this preventing the choke from retracting - in other words have you effectively got the choke permanently on?

If that is OK then often forgotten are the thimble filters in the fuel inlets to each float chamber. If the car has stood for a long time, then maybe the crud has now partially blocked the filters.

If these are ok, then I would suggest a methodical check through the carbs, making sure that the rear air filter backplate is on the right way up ( that is if you have done any work here). If all checks out, start a methodical check of the ignition electrics that all connections are clean and tight. I say this because my low tension cable to the coil developed a loose connection a few weeks ago and it took me a few head scratching hours to trace it, but when it died at the side of the road it was obvious, and the fix was instantaneous!

dominic clancy

Sometimes the jets get sticky after sitting for so long...reach under the carbs with the choke off and make sure the jets are going all the way home by pushing up on them. If not, you will have to disassemble and clean them...I have had success polishing them with 1000 grit paper if they are not smooth and shiny.

AJ Mail

Be fore pulling anything apart get a can of SeaFoam and put about a 1/4 of the can in the fuel.
David Werblow

Everybody immediately zeroes in on opening statements. Let's not forget that 90% of all apparent fuel problems are in fact electrical. Let's not forget the basic set-up, including ignition advance etc.

Steve Gyles


That's why I suggested an orderly check of the electrics!

dominic clancy


So you did. Missed that sentence! Didn't have my glasses on.

Notwithstanding what I/we said, if it turns out to be petrol related, I recall a year ago when I could not get my carbs properly adjusted (weakened sufficiently). It turned out that my Facet pump was pushing out too much pressure and I did not have my Fuel King regulator turned down enough. It was set to a bit over 3 psi. I adjusted it to 1.5psi and all my problems went away. Our carbs do not like too much pressure.

Steve Gyles

As it turns out it was the front float chamber. No fuel was getting to it. I cleaned the screen and the float needle. It now runs. Thanks for the help and advice.

david kirkpatrick

Yea! Sometimes I do get it right! (but not often, according to my wife).
Edward Wesson 52TD

1955 MGA 1500 has no heat shield between carbs and engine, is this something I should fit.

The car runs well but really does not like crawling when its sunny, it will stop when the fuel boils, which at the moment seems to happen on a regular basis as the weather is so fine.

Once there is a bit of air flow she runs really well.

So I think it is related to temp under the bonnet.

Seen lots of others and loads of pics, but not seen another one without the heat shield, was it a factory standard fit?

thanks for all input.


laurence dunnett

There's some interesting info about cooling the carbs on the Guru's site.

david kirkpatrick

1st get (or fabricate)the shield and install it. Then if you still have problems, think about the bilge blower. Oh, I'd also replace those pancake air filters with original style. Mine did not breath enough.
Chuck Schaefer

david Kirkpatrick

Rubbish in the float chambers can be a regular pain.
Normal symptom is sudden rough running when the float chamber needle has grit caught in it, keeping it open and flooding the carb.

Additional symptom is fuel pouring out of the float chamber overflow on to the exhaust pipe.

Further symptom is an engine compartment full of flames and black smoke.

There's another strainer in the fuel pump

D Brown

This thread was discussed between 29/07/2013 and 09/08/2013

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