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MG Midget and Sprite Technical - Its not quite right....

Various tinkerings such as performance leads, sports coil, new plugs, tuning carbs resulted in improving my mk 3 engine very well...for about a week. It then started to protest. Initially it started chugging up hills and almost cutting out. After some searching, I noticed a leak at the fuel pump union at the flexipipe to the hard piping in transmission tunnel. I thus simply tightened the clamp/jubilee and yes, clear improvement, but still lacking the crisp power surge as before. It must be added I let the thing run almost dry of fuel before noting the leak - so crud in the lines was also a possibility. I thus blew air throught with compressor at the carb end and pump seems to deliver fuel OK when turning on and emptying into jam jar - with the line break upstream of the filter

I am still thinking it seems some sort of fuel problem. Pump ticks rapdily on start, but does seem to take a while - say 10s or so - to prime the carbs from cold, but the amount it delivers when detached and into jam jar seems OK.

Next port of call is the in line (plastic) fuel filter - which I will just replace with the chrome thing from MGOC, and then try again. Also fiddled with the mixture settings on the carbs before I identified the fuel leak - but that would not really affect mid range performance would it???

Any further clues as to how to recapture the inital spiffing speeds much appreciated.

Mark O

Do you have points or electronic ignition?

If the former, what's the condition?

Have you checked ignition timing?

Compression check?

Valve clearances?
Dave O'Neill2

Dave

Electronic 123 and all checked out beforehand. Ran fine no more than a week hence - until fuel supply issues. Still think it is in that area somewhere.Prime suspect is fuel filter at present.
Mark O

Yeah...if it ran great untill a week ago and you traced issues to the fuel system... I wouldnt get to wild about with anytging beyound that

Id certuanly stay with the fuel system and nothing else until you have exhausted ever fuel option

I think the 2 key phrase are ....

1. you ran it almost dry , yeah thats never good esp in a steel tank that likes to rust

2. You fiddled with the carb settings...all those screws are irristable arnt they....hahaha

If it were me... Id do the pin test on the carbs 1st thing, to check for the correct A/F ratio

Then id replace the fuel filter and have a go at the inside of the pump, and blow some compressed air thur the hose that goes into the tank, make sure the tank is at least 1/2 full...take the cap off also while blowing air thur the line from the pump side to the tank...i cant remember if there is a filter inside the tank


Id also consider you may have damaged the fuel line when you blew thur the pipe as if the line had deterioated from rust and devoloped a small split or pin holes...and the compressed air made the damage more noticable

Anyway those are my thoughts
Prop and the Blackhole Midget

Valve clearance OK? Is your head converted to lead free? If not, it could be seat recession on the exhaust valves. Had the same on my '72 Volvo.
Alex G Matla

This thread was discussed on 10/09/2012

MG Midget and Sprite Technical index

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