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MG Midget and Sprite Technical - what's happened?

Ok, need some help here please. Went out for a drive 2 days ago, all going well when there was a distinct change in exhaust note; quite a bit deeper and growlier. Didn't see any smoke and oil pressure and temperature gauges remained constant. Perhaps a very slight reduction in revs and a tiny loss of power maybe. Anyway, continued home for several miles then just as I arrived, electric fan cut in and car coasted to a halt. Temp gauge and oil pressure gauge hardly changed.Fan ran for a bit longer than normal. Wondered if I'd blown a hole in the exhaust but can't see anything obvious.
Tried to start the car today but seemed slightly slow to turn over, fuel pump not clicking as enthusiastically as normal and car didn't fire. Battery checked and fully charged, less than 6 months old (good quality Bosch).
So, where to start looking?
Car is an IOW frogeye with 1275 engine, twin SU's, electronic ignition, K and N filters but normal camshaft I believe.
Any advice appreciated!
aj robinson

weird set of circumstances. .

I would pull the plugs out and see what you find. I hope nothing. . . .

Mine did something similar and it was dropped exhaust valve, which was then in two parts, stem in the collett, head on the piston !!

but other wiser souls than me will crack this one for you im sure.


P Bentley

I hope so. It was running soooooo sweetly! And the sun is shining.....
aj robinson

Can you do a compression test?

If not remove all the plugs, put the car in gear (try 2nd) and rock it fore and aft with your thumb over each plug hole in turn. You can feel if one cylinder is markedly lower compression than the others, and it may correspond with a different coloured or oily
plug.
Guy W

Hi Guy,

Should be able to borrow a compression tester otherwise I will follow your advice. Just found the coolant level very low;not sure exactly how low but will find out tomorrow. Will also check oil and plugs and report back. Cylinder head gasket maybe.....??
aj robinson

If the coolant level is low then it can have the effect that the temp gauge sender is left high and dry in the cylinder head. The gauge then doesn't register a rise in temperature. In fact if the gauge reading suddenly drops, this can be an early warning sign.
Guy W

Any mayo in the oil or oil cap... smell of burnt rad fluid


Low fluid.. that sucks

Any chance its just a loose hose ?

Prop
Prop and the Blackhole Midget

Thanks for your comments. I'm going to check all the hoses today Prop and see if there are any obvious leaks. No smell but will check for mayo in the oil.
Interesting point Guy, makes a lot of sense.
Will try and report back today but more likely tomorrow.
Many thanks
aj robinson

Unfortunately this does sound very much like what happened to my 1215 when it lost water, it resulted in partial seizure of 3 and 4 pistons in their bores and cracked the block between the bores. It did still run but not as well as it should and it smoked a bit.
David Billington

Latest update:
Topped up radiator about 300ml/ half a pint. I will leave this overnight and see if it goes down.
No mayo in the oil.
Did Guy's 'thumb test' over each spark plug hole and healthy pressure on all 4 cylinders when engine cranked.all 4 spark plugs tan coloured.
Gave the battery a trickle charge overnight and engine turns over very well but will not fire. Fuel pump not clicking very much so cleaned inline filter, removed fuel pipe at carbs and observed good fuel discharge.
Opened float bowls and both clean inside with good fuel level. Carb pistons move up and down freely, also dashpot dampers checked.
Starting to wonder if I have a fuelling issue somewhere, but how does that explain the coolant loss?
aj robinson

Now the fuel pump has packed in! I'm going to check the electrical supply then remove the fuel pump and check it out for blockages etc.
aj robinson

Could be the fuel pump was the root cause. In its death throws it would be feeding less fuel in, causing a weak mix, causing a bit of heat, fan cuts in, bit of coolant loss results.
Mark O

Mark's explanation sounds sound!

At least you have eliminated burnt valves and HGF which is good news.

I presume that you realise the fuel pump stops ticking, or only ticks very slowly once the carbs are full? Don't take that as necessarily a sign that the pump is on its way out.

I presume that your fuel tank had a reasonable amount in it ? (Don't rely on the gauge too much!)
Guy W

Hi guys, removed the electronic fuel pump and bench tested it: totally dead. Replaced it with a spare which chatters away nicely until the carbs are full. Fuel tank was filled just before my run out 2 days ago so plenty in. BUT, car still will not fire! Where next? and what about the distinct change of exhaust note?
aj robinson

Have you checked a spark at the plugs?
Bob Beaumont

Thats next on the list Bob! But why, when the car has been running so smooth for quite a while, would the spark plugs/ignition be affected? Rotor arm maybe?
aj robinson

What kind of electronic ignition? I had a similar experience with my '72 Volvo. Powerspark hall effect gave up. Car started, but no power and not revving at all. Do you still have a standard ignition to try?
Alex G Matla

I wouldnt cry over 1/2 pint of rad fluid lost

You got fire at plugs, you got compression, you have a working fuel pump.

Id try squirting some starter spary into the carbs and see if you get any pops...if you do then its probably the float needles playing up/sticking... welcome to ethonal fuel

If still nothing then id be looking at a slipped timing chain


Try pulling the dissy cap and giving the engine a spin while looking inside the dissy, it could have a sticky dogleg or a broken spring

or even a broken dissy drive gear...aka (sheared pin)

Still another option thats dangerous is the ignition wiring is chaffing on a sharp metal edge or you pinched it or you put a screw in it attaching something to the firewall

Prop
Prop and the Blackhole Midget

Ignition can play up in all sorts of ways. It may be the electronics have decided to go AWOL or perhaps the coil is dying.For example I dug my Frog out a month or so back and it was running sweetly then a couple of weeks ago it died at the side of the road. The condenser had failed! it was a genuine old stock Lucas one a year or so old. I got another from the Distributor Doctor who said condensers have a shelf life of as little as 5 years! New one fitted and normal service resumed.

Bob Beaumont

Morning all!
The good news: No further coolant loss, fuel pump working fine and good spark at all 4 plugs.
The bad news: It still refuses to fire!
What am I missing? It's got to be fuel surely?
This is driving me mad..
aj robinson

Do the easy stuff first....check ot the carbs fully, clean jets and needles thoroughly. Heat the spark plugs in the oven, and before replacing, squirt some petrol into the cylinders. If it fires, it should draw the fuel through.... and any crud causing blockage..
Mark O

Thanks Mark, will do that. When you say 'heat the spark plugs in the oven', is that to a sort of hand-hot temperature?
Just a thought, could it be the fuel itself? I filled up at a small country garage which I've never used before and the problems occurred half an hour later.....or am I clutching at straws?
aj robinson

It sounds like it could be a timing issue as Prop suggested. Is the dizzie loose? If not it's still possible for the timing chain to slip as Prop said, but I imagine you'd have heard the sound of protest from the timing case before that happened. If it did slip the valve timing and ignition timing would both suffer of course as the dizzie is driven from the camshaft.

One other thought. You'd just filled the tank - somebody locally did that to a fairly new BMW bike recently which soon declined all attempts to start it. Turned out he'd accidentally put diesel in it.
Not saying you've done that but it does happen now and then. As your car ran for half an hour after the fill up it's improbable but may be possible.
RS Hughes

Aj

I guess it "could" be anything, but as nothing has really changed apart from failure of the pump itself, then likely to be pump as root cause, with anything in the fuel system being most likely after that - so carb blockage, crap in filter tank pick up etc.

Consider carefully what has changed since last it was running well and work from there...though of course, that does not rule out sudden failure of (particulaly) electrical equipment.

Highly unlikely to be fuel when filling up - but I guess you cannot rule it out completely.

My bet - crud in the jets......

Mark O

Good point about the fuel. It does happen that water gets mixed up with petrol if the forecourt tank is getting low. Any evidence in the carb float chambers?

Also check the ignition timing is correct. You said you had a spark at the plugs so the rotor arm must be moving. This would confirm if anything had moved, slipped etc.

Bob Beaumont

Thanks guys.
I like Mark's analysis; nothing has really changed apart from the fuel pump packing in and me filling the tank from a garage. My tank was fairly low so could be crap in the system. Carb float chambers are clean of crud and appear to have clean fuel, no sign of water but then again, how could I tell?. Definitely NOT diesel but worth a punt because it can happen. Fuel filter (inline) was cleaned a couple of weeks ago pre mot and still looks clean.
Dizzy good and tight, no adverse noise from timing chain; only the exhaust note changed markedly but car ran for a good few miles after, I thought it might be a hole in the exhaust until the car stopped working.
aj robinson

Sorted! (I think)....
Gave carbs a careful clean and now got car started. Engine running smoothly but exhaust note still a bit more growly than it used to be. Not quite 'fluttering' and I can't see anything blowing underneath, so could it be the effects of the fuel? I'm thinking of siphoning most of it off and replacing it with some new fuel from a different source. Might even have it tested.
Many thanks for everyone's input; any thoughts on the exhaust noise appreciated
Regards.
Andrew
aj robinson

I would check the point clearance first and then re-time it. It could have been a slightly loose distributor.
SANDY

Bob makes a good point about water in the fuel. It's not unusual, especially from smaller petrol stations with relatively low sales volumes.
Also water can and does condense in fuel tanks over a winter layoff. I always had to drain and flush my boat's tank every spring.
A petrol engine can usually tolerate a little water, but it will run a bit rough. A lot of water will stop it. Maybe you had water in your fuel as Bob suggests, but you've now got rid of most of it?
RS Hughes

I would fully support a good clean out and fresh fuel from a known source. I think the later tanks do not have a drain facility which makes cleaning them more tricky.

You can check the exhaust for leaking by getting an assistant to hold a rag against the tailpipe with the engine ticking over and then listening for leaks.
Bob Beaumont

It might be too late now but is it possible you filled with diesel?
I.M. CHRISTIE

Hahaha IM Christie - so I'm not the only one who dares to think the unthinkable!

(Read earlier posts - Andrew has eliminated that).

Okay - I'll come clean. I once did the same in reverse. I put a gallon can of petrol in a diesel pickup and just realised it in time before I did any damage. Still it was a bl++dy silly thing to do.

Hope it's okay now Andrew.
RS Hughes

Aj

Glad you have it started. This is invariably a major hurdle that needs to be overcome! ....On exhaust note, it may be that having now given the carbs - and I trust the jets - a through clean, you have adjusted the mix ratio slightly thus causing a slightly different exhaust note.

More than likely you have actually improved matters, so perhaps nothing too much to worry about. Give it a run and observe low down pick up and temperature.

If it runs a little less hot and pick up is improved that may indicate a slightly richer mix than previous - brought about by you cleaning the carbs and removing them of obstruction and so proving the theory...
Mark O

Thanks everyone.
I will definitely replace the petrol (I've double-checked and it is NOT diesel!)Fortunately my tank has a drain plug but it hasnt been disturbed for ages so might use a siphon.
Mark, cleaned the jets/needles/carbs thoroughly and will go for a drive today. I guess I would be unlucky for the fuel pump to die AND the exhaust to blow at the same time, but this is classic car driving of course!!! Nevertheless, I will check for leaks as Bob advises.
That being said, the exhaust note is much deeper and growlier, although sounds pretty good actually. I will take Mark's advice and check out the temp and pick up when driving.
aj robinson

Aaaaarrrgh! Bloody thing won't start! DEFINITELY fuel!! Now where's that rubber tube...?
aj robinson

aj, have you driven it when it started last time?
I would still try another ignition first....
Easy to do and if it doesn't solve anyhing you can always mutter about with fuel and hoses and buckets.
Alex G Matla

Alex, started it yesterday, eventually, and ran it for good 15 minutes but didnt drive because it was pouring down. Ran up to temp, good oil pressure, smooth running but exhaust note still growly. Weather dry today so wanted to drive but couldnt start. Will have to clean the jets/needles again anyway so draining the tank and system is just another chore....
aj robinson

Easy clean your jets; Start while covering carb, full throttle, engine will suck jets empty.
Alex G Matla

Aj


Disconnect fuel pipe as close as you can to carb, turn on ignition and see if it is pumping. Have a jam jar ready and don't smoke. If it is pumping OK - and if your float bowl is already full, then it is likely to be your carb. Drain the float bowl to actuate the float and to remove any crud - it may be sticking. Give the carb a belt with a soft mallet. Reconnect the fuel and try again.

Failing that, take a closer look at the float needle and seat, any pilot jets and the main jet. All jets must be scrupulously clean, float must be set correctly... RTFM....and must seat. You may have picked up a load of crud from your empty tank preventing this. Often it ends up in the float bowl.

It may be flooding though. Float needle may be passing - due to crud in there preventing it closing.

Good luck....
Mark O

Yepp... sticking closed is as bad as being stuck open

Prop
Prop and the Blackhole Midget

Thanks everyone; great advice as usual
aj robinson

It's a bit of a long shot, but could fuel problems lead to a leaner mixture and hotter combustion (though the cooling system was able to maintain the correct engine temperature), but hotter exhaust gasses burnt some of the stuffing out of the silencer? That would make it sound deeper and growlier. I used to run cheap exhausts and it was not long before the stuffing started to burn and blow out (quite spectacular if it was at night and you caught sight of it in the mirror!).

Jonathan
Jonathan Severn

Drained fuel tank today then flushed with clean fuel, including all lines. Cleaned carbs thoroughly. Added fresh fuel and a tiny bit into each cylinder and......IT FIRED FIRST TIME!
Looks like crap fuel so going back to retailer tomorrow.
Couldn't drive as raining today but ran for 15 mins, got up to temp and revved cleanly, although a tiny bit of blue smoke at high revs. Exhaust note has largely changed back to normal also, but still a slight odd noise so Jonathan may be correct about the exhaust.
aj robinson

have you put a simple fuel filter before the carbs - fits onto the hose. Always looks half full but it could be crud in the line still at this would stop it. Either way a cheap fit and forget for a while. Good luck.
Dave
Dave Price

Hi Dave,

Yes, fuel filter fitted just before carbs.
aj robinson

I would venture it was crud somewhere rather than crap fuel.
Mark O

Think you are probably correct Mark.
aj robinson

Im voting for crap fuel... ive been a victim of this

My understanding is you guys are now starting to get the full enjoyment of ethanol based fuel... granted its only 5% but you have to rememeber ethanol has to be reformulated for winter and summer

So if he got fuel that was more then 3 weeks old and it was a winter blend on a warm day...then yeah, it wont run to well

I have alot of problems with fuel just setting for 4-6 weeks unused.

Todays gasoline is definatly not my fathers gas he grew up with.

I think its modern day fuel is the reason we dont see to many vintage cars on the roads these past 2-3 years

Prop
Prop and the Blackhole Midget

This thread was discussed between 28/04/2015 and 04/05/2015

MG Midget and Sprite Technical index

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