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MG MGA - Cause of loss of power today

I had the ignominy of being picked up today from the busy City Bypass on the back of a low loader. I'd done around 30 miles with the car struggling a bit with power on any sort of incline and was about 4 miles from home on the dual carriageway bypass when the car refused to exceed 20mph. Pulled over to the hard shoulder and was thankfully picked up within an hour. The cause of my problem was this slimy piece of blue silicone/gel that was trapped in the inline filter. Hopefully now sorted but no idea where the silicone has come from.

Ironically the car passed its MOT yesterday with no issues and having done 120 miles the other week with no problems I was reasonably confident that I'd complete my journey today without problem - these cars are full of little surprises!

On the subject of the MOT my garage were reluctant this year to put it through the test on the basis that if it failed they didn't want the responsibility of having to do any remedial works. I said I would be happy with a mechanic giving the car a general check rather than an MOT and that is what I was expecting but when I went to pick it up they had given it an MOT. I know these cars don't need an MOT but it is a bit concerning when a garage are minded to refuse to carry out a test. I think they only did what they did as I have been a customer of theirs for many years. They refused recently to do anything for a friend who has a 69 midget.





Tim Prime

Did someone coat the inside of your fuel tank?

Jud
J K Chapin

Tim
Cant really make out what the blue slime is. But good you have a filter that prevented it moving further along the system
As you probably know, the MOT looks mainly at safety factors, not how well the engine runs, etc.
My friend, who used to work for the ministry of transport, or whatever they are called these days, suspects the main reasons classics are MOT exempt, is because many garages and mechanics arent clued up in how to MOT our older cars, combined with the low mileage they do, so accidents are pro rata less than daily drivers. That makes sense to me as I have never understood the official line that classics are looked after very carefully by their owners, and fits in with your own experience with your garage
Graham V

I'd drop the tank and see if there's anything else floating around inside. Large floaters can get sucked up through the fuel pickup line into the pump, or jam and then free up from the pickup pipe, causing intermittent running issues. In my case I started to notice brown residue coating my fuel filter. I replaced the filter, but the residue continued to show up. I then dropped the tank, removed the sending unit and washed out the tank. Out came a few cigarette filters, floating tobacco and several of those silver plastic tabs that typically seal the openings of plastic bottles. The presence of seals was my fault as they probably came from fuel treatments I was using during winter storage; now I never pour treatment directly into the fuel tank. The cigarette butts, well they either came from a few mischievous kids at the car show, or they were original accessories from the vendor who sold me the fuel tank.


Nick Kopernik

I'll hazard a guess that the sealant had been put on the mating surface of the fuel level sender unit.

Steve
Steve Gyles

Some years ago I filled up at a garage only to have the car (a Ford Cortina ... apologies!) conk out a few miles later. I found a sludgy type of growth in the float chamber and traced it all back to a fuel tank full of the same sludgy mess!
A weekend was spent draining, flushing out everything, and the garage sent a sample to the Oil company (Shell, I think). I received a a new tank of fuel and a small amount of compensation for what was admitted to be a fungus!
I suggest you drain the fuel tank and see if there's anything else floating around in there.
Regards
Eddy
E Maher

Thanks for all the comments. I did in fact drop the tank a year or so ago and gave it a good clean out as best I could. I retrieved a number of things including parts of old fuel cap components! Also more of the silicon like gel substance. I agree with Steve that is probably relates to a PO sender unit installation. I had thought that fuel tank floaters were going to be a thing of the distant past but clearly not. I now know well enough the symptoms for these fuel blockages and its easy enough to check out/sort but not great when it strands you on a busy dual carriageway!
Tim Prime

Hi Tim

I had that as a recurring issue many years ago due to over enthusiastic sealant application. In the end I only solved my hacking a hole into to top of tank so I could get my hand in. I have had a new tank since then. The stuff seems to breed.

It is good to see this thread active again!

I am heading down to Lancaster this weekend to join another 70 MGAs at the Registers spring weekend.

Paul
Paul Dean

Hi Tim,
I had exactly the same problem with my car after I collected it 16 years ago. My engine would run for 5 to 10 miles and then begin to misfire going onto 3 cylinders, if I tried to keep driving the car, the engine would then drop onto 2 cylinders, then on to one and then finally stop altogether.

After about 10 or 15 minutes of checking all the usual suspects, plugs, leads, points, condenser, coil, distributor cap etc, the car would then start up again and run perfectly again for another 10 miles or so before it began to misfire again.

I must have changed the entire ignition system about 3 times over about 3 months to try sort out the problem.

We did check the fuel flow by pulling a pipe off in the engine compartment and checking how much fuel was being delivered to the carbs and it was fine (about a pint per minute).
We also looked at the aftermarket fuel filter which has a clear glass body and it looked to be completely clean.

The last straw was when we were Southbound on the A1, driving back from Scotland to South Yorkshire.
The misfire problem had returned on the journey back and I had stopped the car numerous times to check the ignition.
I couldn't fix the problem but I found that as long as I didn't go beyond 35 mph, I could keep the engine running.

This resulted in a couple of embarrassing moments, including one when convoy of about a dozen Austin Sevens flew past us at around 50 mph. I can still hear the jeers and shouted (fortunately good natured) insults!

Also, I was wearing a set of ear pieces with my mobile phone and I had it tuned to a local FM radio station to catch any road traffic reports so that I could hopefully avoid any traffic delays.

Imagine how embarrassing it was when I suddenly realised that the slow moving vehicle that was causing a 2 mile tailback on the Southbound A1 was me in my MGA!

I instantly decided to get off the A1 asap and crawl home on the B-roads where I could get away from being a mobile roadblock and let those Austin Sevens speed away.

I almost put the car up for sale when I got home because the misfire problem made the car so difficult to drive anywhere.

I took the car to Bob Wests and he and James Horner had a look at it.
Naturally, the car ran perfectly all the way to Bobs and so he decided to take it on a run to see if the misfire returned.
Bob was gone for about an hour and he obviously had broken down somewhere.

When he did finally limp the car back, he decided to check the fuel flow again.
The fuel pump was working but we found that the front carbs float chamber was almost empty.
Even though the aftermarket glass fuel filter looked clear, we decided to remove it and open it up.

That's when we found a flat section of clear silicone sealant floating about inside it.
The sealant was totally invisible in the fuel and the fuel flow would make it slowly float across the outlet hole inside the filter and restrict the flow, causing the misfire.
Then, when the fuel pump was switched off with the ignition, the silicone sealant would fall down to the bottom of the filter and unblock the fuel outlet.

Once we found the problem, I would regularly remove the filter to clean out any more silicone sealant.

I was plagued by this problem until about 8 years later when I fitted a brand new Moss fuel tank, which obviously contained no silicone sealant.

Cheers
Colyn




Colyn Firth

It’s interesting that Tim and my incident involved exactly the same colour sealant. I guess the message for Colyn is never use clear solvent unlike you previous owner. By the way my problem was always in the pipes by the pump never got as far as the carbs. What is different about my incident is I applied rather than inherited the sealant but the amount that blocked pipes and was found in the tank was vastly more than I applied, it seems to breed! Hylomar AF I believe. Like Colyn I now have the superb Moss tank, which has never seen any sealant.

Paul
Paul Dean

This thread was discussed between 13/05/2023 and 18/05/2023

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