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MG Midget and Sprite Technical - Intermittent stalling at stops

1974 MG midget 1275cc. Yes, I have searched through the archives and read many threads (often responded to, or resolved by Prop, thank you) regarding stalling and have some ideas but am still not convinced that my problem was covered there. The car stalls at lights/stops intermittently, which is what makes it so maddening (and scary)! It is not an idle setting problem as at one light it’s fine, then fifteen stops later, it stalls out of nowhere. It will re-start usually fairly quickly, within 1-2 minutes. I would look at the condenser (shhh) but I have a pertronix ignition installed so that’s out. I can see fuel in my in-line filter when the stalling occurs but I have not checked for a hot coil yet because I thought they were only good or bad (or about to be bad) so didn’t think to touch it. I will also check for cracked insulation on the wires entering the Pertronix chip as suggested by Prop tomorrow, but was wondering if anyone had any other suggestions at this time. What’s happening is now, I am afraid the car is going to quit altogether while on my way to work which is most of my mileage so I leave it home instead (being late or out altogether in this economy because your 35 year-old British sports car failed is not good). Thus, I have less data to work with.
Thanks, Matthew
M Moment

I'm not good at troubleshooting, but I had the same problem with my 1500 and it turned out to be vapor lock. Once I got a heald shield it quit.
Rik
Rik Hogan

wow, I must be good, Im creating an international mystic about myself...LOl

Id add maybe look at the fuel pump....maybe install a temporary fuel pressure gauge and watch when it stalls .

the fuel pump is located in the rear passanger side wheel well it has a set of points like the ignition and a diaphram and after 30 plus years they will die evntually

also look at the fuel cap to make sure its clean with no blockage around the vent hole...next time it stalls quickly pull the cap and see if it makes a swish sound as air rushes in...that would be a sign that you got blockage on the vent hole cap

Anyway you got a good starting point to look thur...just take it methodically and common scence wise...let us know what you find

Btw...when it dies, what does the tach do, does it just go straight to zero with no bounces or flutters (electrical issue) if it does flutter and dance around as its about to die means its most likely a fuel or compression issue.

Prop
Prop

Matthew,

I am not saying that it is your problem, but coils are not just good or bad. When failing, they often produce symptoms that feel like fuel starvation, and they can work when cool, but not when hot.

Charley
C R Huff

Could be a vacuum leak, too.
David "the vacuum in my head keeps leaking in" Lieb
David Lieb

to test davids thinking...spray some carb cleaner, wd 40 adound the joints of the intake and carbs with the engine running and warmed up....if the engine picks up in speed .... theres the problem.

Prop the Internationalist Problem Solver
Prop

IMO and I am certainly not as skilled as Prop in these matters, but it is obviously a mixture related issue.
That is because when an engine is running under load it is capable of overcoming a rich mixture, it simply burns the fuel away. Equally it will cope happily with a weak mixture just as easily.

However when the engine is asked to idle then mixture is super important as a rich mixture will simply overcome the plugs and will cause the engine to die after a few seconds or a couple of minutes depending on plug grade or how far out the mixture is, similarly a weak mixture will eventually cause the engine to faulter in a short period of time.

So what causes a bad mixture set up.

incorrectly adjusted carbs, by far and away the most common fault.
Vacuum leak, vapourization, fuel pump all as described etc etc etc...

So adjust the carbs correctly, get help if you are not confident (ensuring that the choke switches off correctly very common problem) and finally what plugs are you using, if not NGK BP6ES or NGK BPR6ES then put some in sharpish!
Robert (Bob) Midget Turbo

This thread was discussed on 08/11/2009

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