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MG Midget and Sprite Technical - Engine stalls in traffic

My midget runs fine until it's left ticking over in traffic then it seems to choke up and won't run until it cools down . I've replaced plugs points condenser the coil and cleaned the carbs but it still has the fault. It starts but won't Rev it back fires pops and bangs.
David Hughes

If the ignition system is up to scratch and the carburation is sorted then you're left with valve problems. If your car is a 1500 then expect to have oil-supply problems to the valve gear if the engine has not been rebuilt and/or the oil pump is not providing adequate pressure or flow. Broken valve springs and sticking valves are common if the oil flow to the top of the engine is not as it should be. Are your valve clearances consistent? Does the valve gear look 'cooked' or is it nice and smooth and oily?
Nick Nakorn

(if you've not already done so, then) if you've replaced the CB points then you'll also need to check/adjust (plugs,) timing and mixture in that order

(if you've not already done so, then) best to start at the beginning and check adjust the following in the following order - tappets/CB points/plugs/timing/carbs mixture – if you have to adjust any item in this chain then you’ll need to check/adjust all the items that follow it in the chain

have you rechecked the CB points gap, dashpot oil, manifold leaks, etc.

what reading did you get on your water temperature gauge just before stall

as Nick has put a bit more info about your car would be useful (you could add your vehicle profile, see next to my name here)

a photo might be useful too, in case you have something like the heatsheild missing

also note that many modern made CB points and condensers (and rotor arms and dissy caps and HT lead sets) can be poorly made and cause problems immediately or soon or a bit later
Nigel Atkins

well done nigel, all that writing and not once did you mention the handbook. hahaha,

bob.
bob taylor

Bob
Ha ha ha.

You can sum up Nigel with four topics he loves.

His wife

His continuous deniel of tool usage or knowledge.

His workshop book worship.

His beer snobbery.

Now you know everything about Nigel.....Nothing to see here folks, lets move along.





Steven Devine

Wait, what ? ... Theres a handbook/manual for these cars?

Prop
Prop and the Blackhole Midget

Im not sure Prop, Ive never seen one myself.

I wish Nigel came with a hand book so I could activate his "Off" Switch
Steven Devine

Hi
If all else is well, could this perhaps be fuel vapourisation? Modern fuels are contributing to this.
g Victors

Carb heat shield in place?

What colour were the plugs when you replaced them?

Cheers
Mike
M Wood

If this where hot weather... id say the heatshild

But im thinking this is a classic lean fuel condition...

choke needs fiddling , vacume leak, carb out of adjustment, carb jet hieth to high compared to the float, timeing set to advanced, clogged fuel filter, packed up fuel jets ...

What happens if you pull the choke out while idleing ???

And agian as mentioned above modernday unused ethanol fuel may have sat to long in the tank and is going off

Prop
Prop and the Blackhole Midget

David

Weak mix leads to hot engine and yes, it can cut out and splutter as a result.

One reason ....Thoroughly dismantle and clean the carb, not just spary carb cleaner in there.... especially consider the jet/needle/pilot jet - there may be some crud in there causing the weak mix at low revs.

Have a look at the air filter while you are there.....

Clearly, check out any other reason why it should be running hot - coolant, thenrmostat problem, oil feed, valve clearances etc. Working methodically should find it....
Mark O

What colour is the rotor arm on my MGB I chased a problem of the car cutting out when hot when left to cool started and ran perfectly. Changed everything including rotor arm same result, this was before red rotor arms one day it wouldn't restart and found it was the rotor arm had to find nos lucas item problem solved.
G.J. Puxty

You say you have replaced lots of items and now :-

'It starts but won't Rev it back fires pops and bangs'

Is this only since the replacement items ? are there now two issues ?

Have you taken off the aircleaners - if so check you havn't put them on upside down or the gasket(thereby blocking the carb air holes.

As Nigel - check dash pot oil and carb pistons are free to fall etc.

R.
richard boobier

Richard

Oh yes indeed!...those carb air holes are certainly a factor - especially if you don't know about them!

Agreed that after tinkering about and failing miserably, one should always remember to revert to exactly to what it was!

Don't ask me how I know this.........

Mark
Mark O

Maybe a wild hare, but if your float valve isn't sealing well it can allow the chamber to overfill and gradually flood the engine at idle. Once you're up to speed, demand keeps the level in check. I think I had this happen myself a few years ago.

-:G:-
Gryf Ketcherside

This thread was discussed between 01/03/2015 and 09/03/2015

MG Midget and Sprite Technical index

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