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MG Midget and Sprite Technical - Midget 1500 - runnings problems

Hello all

I have a 1500 midget which I've just done a fair bit of work on but it's just not running right and I'm losing the will to go on with it. Can someone point me in the right direction -

It was running OK. That is to say it started and drove and, for an old car at least, sounded and ran pretty well. However it had no oil pressure. I took the engine out, dismantled it and rebuild with ground crank, new shells. Also put new oil pump on and while I was about it I replaced the fuel pump because I had a brand new one lying around and replaced all the valves.

When I first started it up it ran OK, similar to before but now the oil pressure all good, sits around 40. Then it passed its MOT and all was well.

However then it sat in the garage all winter.

Now I've got it out it runs like an old tank. Really lumpy, sounds like its firing on 2 cylinders. It wont tick over under its own steam and its back firing at a rate I've never experienced before in any car.

I dont really want to strip the whole thing again, I hate doing a job twice!

Any ideas anyone what might have gone wrong?

Many thanks in advance for any replies.
Cheers
matthew stubbings

Hmmm.... correct me if i'm wrong but I was pretty sure that a decent oil pressure in a 1500 is between 40lbs minimum and 60-80lbs standard, I seem to remember that I had an uprated 1500 engine which the cam had not been correctly run in and initially showed an oil pressure between 60-40lbs at start up and could hold that pressure on a short 20 mile run but after this would drop off rapidly. It ended with a full rebuild and a new 1300 spitfire cam with cam bearings machined into the block (1500 cam doesn't have cam bearings as standard and the poorly fitted cam had ruined the block!)

40lb seems too low to me, unless it is on a warmed engine at tickover, a blip of the throttle should immediately send the oil pressure gauge up to 70-80lbs unless there is a major issue, and usually a large drop in oil pressure (if not based on leakage)is down to heat. As I say in my experience the heat was generated by the friction of a poorly run in cam on a new performance engine build.

Does the oil pressure start at 40 and remain there? or is it higher at start and have a slow but continual drop?

Dave
D Prince

Hi,thanks for the reply

Re the oil pressure - 40 is the tickover reading (ish)when warm. Goes up when under load.

I'm pretty convinced the oil pressure issue is fixed, what is frustrating me is the fact it barely runs now, when it did before.
matthew stubbings

sounds weird. to start and then not run well, be systematic and you will find something obvious i should guess, after all its starting, have you looked at timing, could it be a loose dizzy, coil breaking down . . . be strong and dont let the beast beat you !
p bentley

Hi Matt sounds like you have done a great job and now just need to get everything back to right.

Like everything else if the basics are not right you will be wasting your time trying to find problems so:

1 Set the timing correctly, this includes ensuring leads are correct to cylinders and you get a spark at each plug. You need to be 100% positive it is done correctly if you can not do then ask or seek help

2 Set the carbs up correctly, again they need to be 100% and again if you can not do it ask or seek help.

3 Check fuel is flowing via the new pump, easy to do disconnect carb pipe and place in a handy container and turn the engine over and watch loads of fuel flow.

4 It is often worth doing a simple compression test on each cylinder if you have any doubts about any mechanical issues with the engine
With all this done the engine WILL run fine or it will then be easy to say why not.

Best of luck.
Bob Turbo Midget England

I doubt there is much wrong with the rebuild. It just needs a methodical approach to finding the fault. I would:
Check the plug lead firing order.1342
Then, with it running, pull each lead of in turn with insulated pliers to determine which cylinders are lazy.
Once this is identified, check those plugs are sparking ok
lf they are, move on to checking the air and fuel supply, and also check the ignition timing.

It will be something simple!
Guy

sorry Bob, synchronised typing again !

My comments are because it was running ok, it is likely to be something that has deteriorated over the winter. Or inadvertantly been changed like the plug leads.
Guy

Matt, I take it from you story that it was running okay before winter. Ist just afterwards this spring that it now doesn't.

So logically timing and valve clearances etc should be okay ...

I wouldn't disagree with advice above checking plugs -are they oiled/black/ligt grey - to indicate oil in cyl/too rich /lean on one cylinder.. Then might indicate manifold air leak or stuck needle. Doing the plug disconnect tets is a next step for me - both of these are quick and don't need any strip down.
If you find nothing here then on to more significant investigations as above.

Good luck - if it worked before there can't be much wrong !
John Barber

Yeah, I agree with most of above. Logically to me it sounds like you could have a problem with your carbs - possibly with a fuel pipe that has perished somewhere so you could be leaking fuel - if its running on 2 - is it the front 2 or back 2 - that would inidcate one carb not working properly... perhaps the jet it one has stuck? perhaps the float bowl isn't filling up...

I know this doesn't help now, but my other advice would be not to leave the car for 6 months. Take it out for 5 miles once a month.

C L Carter

I agree with the previous diagnosis of carburation/fuel problems. Specifically, I would say that one of the float chambers has dried out and stuck closed. It sounds like the engine is running on the two cylinders served by the one working float chamber/carburetor.

Dismantle the float chambers and check the the needle valves and plastic floats.

I had exactly this problem when my 1500 was laid up for 6 months.
Andy Hock

The first thing is to pull the plug leads in turn to narrow down which cylinders are not firing. It will then direct you more specifically to where the fault lies and save unnecessary work.

Nigel must have been out checking on his local real ale breweries last night, and still be asleep or he would by now have recommended a full service as per the handbook.
Guy

This thread was discussed on 06/05/2012

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