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MG Midget and Sprite Technical - '76 midget stalling when braking

'76 midget stalling when braking. starts, idles, & runs fine. car has electronic ignition. restarts immediately after stalling.
john vavasour

A similar problem on wife's Fiesta some years back. It was the brake servo. Do you have one fitted?
Alan
Alan Anstead

no servo (which i believe is the power assist) engine will also occasionally stall when depressing the clutch. as soon as you come off the pedal you get the engine back. effect is almost like switching off the ignition.
john vavasour

I had a problem with stalling after braking but it was as I put my foot on the gas it would stall. I eventually traced it to a leak into the inlet manifold due to old manifold gasket. This was on a 1275 Midget but it's worth a check.
Rob
MG Moneypit

That's an interesting conundrum.
I wonder if the carb butterflies are being sucked completely closed when you take your foot off the gas to brake and effectively strangling the engine? If so it's adjustable with the butterfly stops.
Or, a bit more left-field, is something electrical moving a tiddy bit under braking? Coil supply or ground, for example.
Greybeard


Does the common link seem to be something about the pedal box? Is it that pressing brake or clutch is moving or shorting something in that area?

May not be related to the current problem, but if depressing the clutch is slowing the engine at all I would do a visual check on crank end float. Especially if this is a 1500. Use a pry bar to lever between front cross member and pulley. Then, as your Attractive Assistant presses the clutch down look / feel for any forward movement of the pulley which might indicate worn crank thrust washers. You do this with the engine switched off, of course!
GuyW

Are the emission controls still in place? If I recall, this car came with a anti-run on valve that is electrically actuated when the ignition is off but there is still oil pressure. Could it have been connected to the brake light circuit?

A crunchy release bearing would lower engine speed when the clutch pedal is depressed.
Glenn Mallory

I’m going with Guy on this one. Excessive crankshaft end float will put a fore/aft load on the rods which they aren’t designed to handle, causing binding on the crankpins and wrist pins, excessive wear, and the occasional rod through the block. Thrust washers are actually pretty easy to replace; you can do it with the engine in situ.

-:G:-
Gryf Ketcherside

This thread was discussed between 29/08/2020 and 09/09/2020

MG Midget and Sprite Technical index

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