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MG Midget and Sprite Technical - Back firing

Hi My car has developed a habit of backfiring a couple of times not long after starting. Today when its been cold it was much worse and took a while to run smoothly. Any ideas what I should look for? In simple terms for a technical idiot please.
L Drew

Not enough choke. Me Thinks
Bob (Robert) Midget Turbo

points need adjustment [0.015" 54º dwell]


Bill

Too lean.

R
Richard 1979 1500

Hi
Had full choke at the time, but think it may run a little lean. I presume that would effect the choke as well?
Will check the points.

ta
L Drew

It's just cold.
Brad (Sprite IV 1380)

Maybe a service is due?
Alex Sturgeon

Lisa

What do you mean by 'backfiring'?

- spitting out gas from the carb inlet?
- petrol being ignited in the exhaust?

A
Anthony Cutler

Hi Anthony

Ermmmm the car basically sounded like it had ate far too many beans....
Not sure where thats from but sounds quite amusing.
Lisa Drew

So you got that real fast series of back fire as its de-cellerating....(the back side of accelleration)???

yeah it would still fall under ...too lean, not enough choke, could be a loose carb or intake manifold as well

if its a carb or manifold loose, warm up the engine and spray around those areas with a can of wd40...if the engine speeds up when spraying a certian area, then you found the loose area that needs tightening or some RTV sealer if its a gasket wear area

prop
Prop

If hesitation and backfire in the exhuast, could be moisture on HT system (maybe evaporating of parts of engine that warm quickly and condensing on those that don't liek the cap) causing plug to miss for a short while, fuel to escape into exhaust, and then later ignited.

It's hard to have a weak mixture when choke is on... fuel really pours into manifold. The amount the jets are lowered is huge compared with the normal running adjustment on the threaded nut...

HTH

A
Anthony Cutler

I had a wierd backfire problem this last summer...the choke kept sticking and did the drible backfire farts...I did get it fixed....but never understood why a sticky choke would cause backfire farts...In hind sight,,, maybe the carb gasket became to compressed, I did notice the exhaust maniflod had a bit of play when I pulled the engine many weeks back...I dont know...mute point now.

Prop
Prop

I had a severe backfiring problem, actually blew out a 2 inch diameter hole in the rear muffler.
(This was in my MGB)
The problem ended up being a bit of "something" on the surface of the points. After removing them and filing them my problem went away.
I discovered this with my multi meter, seeing if I got a truly closed circuit when the points looked closed.
The answer - not always. After filing, all good.

I am not saying this is your problem, I am saying take the time to closely examine every system to see what's doing this to your car.
Rick Bastedo

Lisa.

All of the above are relevant points. I would start by checking the points gap / dwell and contact security, then the ignition timing. I would then check carb and manifold security and finally, mixture and balance of the carbs. If you still have problems after that, we need to think deeper....

Mark.
Mark T. Boldry

Mark

Agree with that... but really would be helpful to know if a backfire means:

- spit out of carb
- explosion in the exhaust
- just a misfire

.. then correction is more obvious...

A
Anthony Cutler

Hi Thanks for the advice, fiddled a bit in my normal hesitant manner, wasn't much better. So I took it in for a service. Apparantly the points were out, the choke sticking and had muck in my fuel pipes... and my indicators work much better not!
When in doubt get the profesionals in.
L Drew

>>>>>>>>>>>When in doubt get the profesionals in.<<<<<<<<

NOT!!!!

Lisa, please only use classic british car mechanics, these are often hole in the wall shops, with old guys that are known mainly as piddlers, Please dont use modern day mechanics, the tech is to diffrant and suprisingly vary few even know how to set points and condensers, or properly balance a 3 piece welded wheel.

prop

BTW, I glad you got it fixed, just in time for a polar bear run.
Prop

Change your points for an Ignitor, saves a heap of bother.
Brad (Sprite IV 1380)

Learn to love your car and fit the reliability triumvirate;

1 - Electric ignition, Luminition etc...
2 - Electric pump points, or Facet style solid state fuel pump.
3 - Electric fan and thermostatic switch.

J!

J E G Eastwood 1

Yes, but at what point do you stop and buy a Toyota instead ?
I mean, a spare set of points and a condenser take up hardly any room in the boot; how can you amaze your passenger when the car dies on the motorway, by opening the door, slamming it to re-start the pump and then when the car overheats, what better excuse is there for you to ask your companion to remove her tights?
Surely, the ability to effect a roadside repair is one of the major benefits of classic car ownership ??
M J Chapman

Agreed. Nothing better than sputtering off to the side and saying to one's self (or one's pantyless passenger): " Right.I should be able to fix that".

Having replaced many of the problematic original parts with more reliable aftermarket stuff, I must say the anticipation of such an event looms more fondly in my mind as the frequency lessens.

Lonely spares in boot
Corolla collecting dust
midget keeps running

R.
Richard 1979 1500

In my opinion, If you find a romantic spot you can blip the gas pedal, in rapid succession, then turn the key off and on vary quickly then on a downward section of road, turn the key to the assory position with the engine dead ( letting cly fill with fuel) put car in nutral to let it roll, then turn the car back on for a huge back fire, then you can pull to the side fiddle a bit, say the car is toast and cant get a cell signal, so you will just have to spend the night under in the farmers old barn just over the holler.

never tried it myself, but seem good, and you can use modern day parts

prop
Pro P

This thread was discussed between 02/12/2008 and 27/12/2008

MG Midget and Sprite Technical index

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