MG-Cars.net

Welcome to our resource for MG Car Information.

Recommendations

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGA - New and Bigger Problem

While driving the car has started hesitating dramatically, typically while increasing load (up a hill, accelerating, etc)

The problem has been getting worse over the past 3 weeks.

What is the diagnostic tree for this?

For background the car has a pertronix Electric ignition and a flame thrower coil. Replaced plug wires, distributor cap.

They were replaced variously 7 to 10 years ago, but only have 10,000 miles on them.

The only thing that hasn't been replaced in the 15 years I've owned it is the fuel pump.

Thanks,
Tysen McCarthy

Sounds like fuel starvation Tysen
Art Pearse

Whip the plugs out and have a look and report back what you see
Dominic Clancy

One of my traveling companions to GT-44 had similar sounding problems on the way to the GT and it ended up being a bad fuel pump.

Jim
JL Cheatham

Sounds an awful lot like clogged fuel filter(s). Jud


J. K. Chapin

Like Jud said, probably fuel flow problems, either failing pump, partially blocked fuel filter or some restriction in the fuel line somewhere.

Pull off the fuel supply pipe to the carbs, put the end into a measuring jug and switch on the ignition.
You should get at least 1 pint a minute if the fuel system is working correctly.

This is how this problem usually manifests itself, the reduced fuel flow will let the engine run fine at low throttle openings but as soon as you open up to a higher speed or need to climb a hill etc, the engine doesn't get enough fuel and begins to misfire.

Let us know what you find.

Cheers
Colyn
Colyn Firth

Tysen
Depends on what you mean by " hesitating dramatically"
Does it feel like it's running out of fuel and cutting out/loosing power-going flat
Or
is it missfiring on what feels like one cylinder when under load

If you keep your foot into it uphill does it continue getting worse and worse or does it just intermittently missfire

willy
William Revit

If the fuel flow turns out fine, it could be weak spark.

I once had a similar problem that ended up being a weak capacitor grounding.

Car ran fine at idle and once up to a constant speed, but severe hesitation during acceleration

Fuel flow was good, so I replaced the points but not the capacitor under the old assumption that they are either good or bad.

When that didn't work, I cleaned up all the connections in the distributor and found a bit of corrosion between the capacitor and its grounding strap. After that the problem vanished.

- Ken
KR Doris

Have you cleaned the Carb's Dash Pots lately. My "A" suddenly wouldn't go over 40mph. A pal mentioned the Dash pots where I found the pistons and bore rather oily instead of dry. The problem here can be dirt particles drawn into the carbs can adhere to the oily surfaces which can cause the piston to hang-up giving a horribly lean mixture. I simply cleaned mine out and have not had the problem since. Then I learnt about the correct max level for the damper oil. Many folk do overfill these - as I was.
Pete
PeteT

This thread was discussed between 30/07/2019 and 28/08/2019

MG MGA index

This thread is from the archive. The Live MG MGA BBS is active now.