MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey 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 MGB Technical - Hot running problem

My 78 "B" has decided when its hot to stutter and virtually cut out when accelerating. It only does it for a second and then picks up. It runs ok otherwise. I've checked points, plugs etc. She has been standing for a few months and didn't do it before. Any suggestions for things to check would be appreciated. Thanks.
D Callaghan

Have you checked the level of light oil in the dashpots damper tubes? Could be the problem.
Martin '61 Frogeye & '59 A40 Farina

A marginal coil will act worse when hot. It could be that when you push the throttle, the extra gas is enough to overwhelm a weak spark. If you check the archives, someone has posted the correct resistances for the coil windings. You might also check Paul Hunt's web site. It seems like the kind of thing he'd have listed.
Matt Kulka

Try some fresh fuel? Good quality with lots of detergent. A new condensor often helps, but I recentley had a bad batch with poor quality connections.
Stan Best

Sounds exactly like the carb dampers not damping to me also, oil thinner than engine oil in hot weather could be the cause, try engine oil. But check the level first - if you unscrew the damper cap, lift it up, press it back down, and feel the resistance of the damper before the plastic cap reaches the alloy piston cover, you have enough. How much before tells you how much of a 'reserve' of damping oil you have.

Can also be ignition problems, when you open the throttle you get higher compression pressures and this makes it harder for the spark to jump the plug gap. Ordinarily of course this has no effect , the voltage just rises a bit higher until it *does* jump the gap. But if you have some marginal HT components that bit higher voltage could be causing them to break down. But OTOH if you leave the throttle open and it rapidly picks up again, then would point me back to carb dampers.

If you can reproduce this with your head under the bonnet it is relatively easy to remove the air cleaners and watch the pistons as you open the throttle smartly.
Paul Hunt 2

I had the same problem, turned out to be..... the ignition switch! As Paul says, spark problems can be related to throttle opening, not engine speed - could run flat out no problem but high-vacuum acceleration was a problem.
Neil
Neil

Do you have non standard air cleaners and have you taken them off prior to this problem occuring?

There was a recent post on the MGA board where the cause of the same symptoms you are describing was caused, by one or both of the air cleaners being re-fitted upside down, and this blocks the two balance holes on the outside flange of the carb, could also happen if the gaskets were fitted upside down.

If you have had the filters off it's worth checking, and you can also check that the pistons are rising and falling properly. If there sticking at all you can remove the alloy covers and give them a clean with carb cleaner.

Kevin.
Kevin Jackson

This thread was discussed between 17/07/2007 and 20/07/2007

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now