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MG Midget and Sprite Technical - Will Not Run On No 3

Hi All
1275 a plus engine and it does not appear to run on No 3 cylinder.

New Ht Leads
New Plugs
New Cap
New Condensor
New points

Have tried swapping the plugs around with no sucess
and I have a good spark there.

Just done a compression test got between 160---170 on all four

The car starts and seems to run ok but if you pull each plug lead in turn there is a notable diffrence appart from No 3 which makes no noticable difference to the engine speed / running

Where should I look next??
Many thanks Ian
I Pickering

Find a mate with a gunson's ColourTune kit and see what the combustion looks like?

I assume that it did this before all the new parts and not just after? New does not necessarily mean good. Especially these days.

You might want to pull the valve cover and check all the gaps again and, if possible, borrow a dial indicator to see if you are getting proper lift on all eight cam lobes.
David "next time ask BEFORE you have eliminated all logical possibilities ;-)" Lieb
David Lieb

does #3 work at all, or is it just completely dead....

david is correct new parts from china, doesnt mean that they actually are supposed to work...you got to pay extra for working parts in most cases.

prop
Prop

A series engines are notorius for sounding like number 3 is not working when testing as you describe. Does the car run normally or are you experiencing a problem?
Bob (robert) Midget Turbo

Thanks All

Yes bavid it ran like before new parts were fitted

Bob thanks for that it seems to run normally but i cant get any series testing at the moment, just nearing the end of getting it back on the road after 15 years. I think I should wait as you described I may not even have a problem.
I Pickering

I'm not saying this is your problem but investigating similar symptoms (on my 1098) revealed a hairline crack in the head between no's 2 and 3( see photo )
Fortunately, it skimmed out, so all is now well( in that department anyway!)


M J Chapman

skimmed out a crack in cast iron head?????

reminds me of when I had a flat tire, luckly It was only flat on the bottom and not all the way around the tire...lol.

prop
Prop

Try raising the idle speed and repeat morse test by removing lead #3 (might just be the way the idle is set, i.e. #3 not getting much juice in any case...)

A
Anthony

Had a similar baffling case once, turned out to be one of the inlet rocker adjustments (no 3 of course) had unwound itself giving very little valve opening. Odd thing was, there was not much tappet noise. Presumably it had got so far open that the valve train was on the slow bit over the nose.
Paul Walbran

I've had a spate new dizzy caps & rotors having a very short life.
Try a different cap & rotor arm, it may be that easy.
Brad
B Richards

After a good warmup, I'd pull all the plugs. #3 should look different than the others if it's not firing at all.
Jeff Grant

Check the points gap on each segment of the distributor cam, you may be surprised....

Mark.
Mark T. Boldry

I'd pull the #3 plug, ground it, and check for spark.

You may have mentioned this already, but have you replaced the rotor? You may also consider swapping plugs between #3 and another cylinder, and see if the misfire moves to the new cylinder.

-:G:-
Gryf Ketcherside

This thread was discussed between 09/09/2008 and 11/09/2008

MG Midget and Sprite Technical index

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