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MG MGA - loss of power and stalling

Morning All,

I am looking for some pointers as to the source of my issue.

I am having a problem with my 1600 MGA. I can start the car no problem and its idles beautifully. I can even set off on a drive and will have no problems for a random amount of time.

But after a while the car, whilst going along a road, will start to splutter and lose power and effectively stall. Pumping the accelerator seems to have no affect, but one it stalls, I can pull the starter button again and get a re-start, but then in less than a minute the problem occurs again.

If I pull over and let the car cool, I can start up and drive off again, but will get the same problem again. The car generally runs at 190dF with the odd spike to about 210dF

My current thinking is that its due to vapour lock. I am in the process of fitting the air pipe on the right hand side of the engine bay to just inside the grill to focus more air on the carbs and also installing a bilge fan to the pipe as well. To help with general cooling I am also putting back in the felt radiator/bonnet pad, which was also missing and adding a fan shroud.

Am I on the right track or should I be looking elsewhere?

Thanks

Rob
R Rundle

Condensor
dominic clancy

Sorry should have mentioned that, changed the condenser, coil and distributor cap/HT leads and spark plugs.
R Rundle

Doesn't sound like a vapour lock if you are drving along at speed and it happens (when you have plenty of airflow thru the engine bay). I would check fuel supply as is a simple job. Check pump flow into a bowl. Check fuel filter if you have one in the line. Clean carb inlet strainers, check float valves for sticking, check float bowls for debris, check passage between float bowl and main jet (blow thru with compressed air). Have you ever drained the fuel tank and flushed out - any evidence of rust ?
Mike
Mike Ellsmore

Thanks Mike, I haven't drained the tank, but the fuel pump filter was absolutely clean not a sign of any debris or rust, but I havent checked the carb strainers. I'll do a pump test and see what happens. Having done the cooling bits, my next step was to service the carbs.
R Rundle

Condensor

Just because it is new doesn't mean it isn't cr*p.

Most "fuel problems" are caused Lucas

Try putting an old old one back in
dominic clancy

It may be a vacuum in the fuel tank, due to blocked vent. Try it with the fuel cap off.

Colin
C Martin

@Dominic, I'll give it another condenser, will have to be a new one as the old one was a cause of misfires previously.

@Colin, Thanks, gave that a shot, didn't make any difference.
R Rundle

Certainly sounds like classic coil failure and if not, almost certainly ignition related. You didn't mention the rotor arm, but I am guessing you changed that too (for a red one).

Unfortunately, as Dominic says, just because it's new doesn't mean it's ok. Ideally you need to swap with known good parts from another car.

It doesn't sound at all like vapour lock. Fuel starvation perhaps, if the pump has an intermittent failure when it gets hot. Easy to rule out or confirm if it is fuel. Just drive the car until the symptoms occur and then immediately switch off the ignition. A quick check of whether or not there is fuel in the float bowls will give the answer. A very quick way to check those is to switch the ignition back on and see if the pump needs to work much!

Another thing to check is the low tension wire, particularly the cables inside the distributor. An intermittent break or short somewhere; not uncommon.
Neil MG

Been there with my TD. Look for the sputtering to a stop threads in the TD section.

Same... after 5-10 mins to cool down, starts right up and runs again for about 3 minutes.

Went though the gamut... new fuel pump, new coil, points, wires, plugs, non-ethanol gas, timing, jets, I even put a heat shield behind the carbs. Switching to a pertronix igniter eliminated the condenser but didn't stop the sputter to a stop thing.

Finally, I changed the exhaust to a factory spec unit from British Stainless Exhaust in Michigan (PO installed a Midas Muffler shop "good 'nuff' POS). I also flushed the cooling system. I immediately dropped 5*C on the temp gauge and could put my hand on the float bowls after a long run for the first time ever. The exhaust manifold was notably cooler.

I'm fairly convinced I was boiling gas in the carbs. I've had a few 30-80 mile trips without a cough.
MAndrus

A picture of my old exhaust below. It had two pipes stretched between two small mufflers. You can see the 1" pipes are choked down to 3/4" or less by really bad manufacturing. The engine has got to be breathing a bit easier, yes?

....


MAndrus

Thanks everybody for your input, looks like it is going to have to be a diagnostic approach, removing one possible cause at a time.

I put the radiator back in at the weekend with new Carb cooling pipe and directed fan, so will get that all connected back up and go for a spin.

Rob
R Rundle

Rob

Just browsed through the posts. One thing you have not mentioned is how did it all start? Had you been doing any engine work immediately prior to the symptoms occurring?

My old favourite is the rear carb filter box fitted upside down - very common. Done it myself. This causes the carb piston to seriously lag behind throttle demands, causing weak/rich fuel at all the wrong times. Once you stop (idle) for a short while the piston catches up and all is ok for the next time you accelerate away - for a short time, then it all repeats.

See here on my website: http://www.mgaroadster.co.uk/odds_and_sods.htm

Steve
Steve Gyles

Rob, when checking the fuel tank, see if the pickup tube is blocked. You can also have an intermittent blockage if something is floating around in the tank. This can get picked up by the vacuum in the tube and it may block gas from entering; engine then stalls and the flotsam then falls off once there is no vacuum. Engine will run again, until the next time the tube picks up the same flotsam.
Nick Kopernik

@Steve,

I only purchased the car recently, it has been garaged prior to that for approx 5 years. I have had it serviced at my local mg specialist and their general opinion was the car was in good shape. But this problem has been evident since the first turn of the key for me.

Rob
R Rundle

Rob

Still worth a check that the writing (Vokes Ltd) on that rear canister is the correct way up. Bob West was telling me that about 50% of similar poor running issues brought to him by customers have that box on upside down.

If the manufacturers had drilled out the other 2 holes to match the gasket there would not have been this issue.

Steve
Steve Gyles

Rob

I have just been thinking about my last post. The outside filter box lid having the name the correct way up does not necessarily mean that the main box is round the correct way. Both items can be rotated 180 degrees independently of each other. Definitely worth a check if only to rule out as a cause - one less item to think about.

Purely out of interest, do you know what air filter elements you have installed? Some of the modern 'original' looking filters are absolutely rubbish and can play havoc with the mixture, often causing the engine to run very rich as if the choke was partly open.

Steve
Steve Gyles

Steve,

I still haven't got as far as the air filters, still working on getting the radiator back in and connected. I'll see if I can find time to look tonight and see whats what.

Thanks for the ideas though. Something must be causing the problem, just a frustration.

Rob
R Rundle

Coil, as it heats up it quits and after it cools it works until it heats again. Being tightened too tight or rubbing against something can cause a small hole and the oil will run out over time causing the symptoms you have described.
Bill Haglan

Thanks Bill, It is a new coil that my local MG specialist put in, but as the others have pointed out, with these things, that just because they are new, doesn't guarantee they work.
R Rundle

My car had not been run for 15 yrs. On start up did same as yours. Run good for 8 miles then sputter and not idle. Cool down and then go another 8 miles . After many dollars on ignition work , it turned out be a plugged carb. vent pipe Vapor pressure builds up when the carb heats . Mud dobber (small bee) made nest in the end of pipe.
Dave
DL Rezin

Update from the weekend, finally got the radiator back in and the carb vent fan connected, everything works however didnt get opportunity for a run.

Reason for this decided to check the air filters as suggested by Steve. First discovery is that they were they were reversed, front filter was on rear carb and rear filter was on front carb. Not sure if that would make a difference.

But they are poor chrome after market things and in trying to get one off, discovered i couldn't get the top cover off it. its off now, but decided to order replacement original replacements from Moss along with K&N inserts.

However, I thought as the air filters are off, I might as well go the whole nine-yards and service the carbs at the same time. So now time to remove them and wait for the service packs to arrive.

Rob
R Rundle

This thread was discussed between 04/06/2015 and 15/06/2015

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