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MG TD TF 1500 - Need your thoughts loss of power

Hi All. I am still having loss of power issues with my TD since finishing the restoration and wanted input from the group.

It starts great and will run on the road for a few miles, but will suddenly lose power. Like it is only running on two or three cylinders. I live on a hill, and the car will not make it up the hill in first gear.

If I stop and rev it a few times, power comes back.

Here is what has been done.

Distributor is running points and was set up by Advance Distributors for this restoration. I replaced the condenser with one of the ones recommended by the group as very good.

New wires, cap, rotor, plugs.

I took off the air cleaner and checked the carbs to see if a piston is sticking. Ran the car for over an hour, at various RPM and frequently accelerating it. No sticking pistons, and the motor ran fine.

Coil is an original 1949 Lucas Sports coil, but it checked out fine on a coil analyzer.

When I got it back in the garage after todays run (with loss of power), I pulled each spark plug wire off the plugs one at a time. I got a good spark jump between the plug and the wire on each cylinder.

I was thinking the coil may be not working correctly when it gets warm, but that would not explain why the power comes back.

I have checked to assure I don't have any grounding between the coil and the tach cable. I even insulated the tach cable as a precaution.

Just not sure what else to look at.
Bruce Cunha

Hi Bruce,
See my post 24 April "Burnt valves pt2"
It was a sticking valve, I re=reamed the offending guide
I found it by switching off the ignition, leaving it in gear engine turning. I could hear the tappet click due to the excess clearance. When I stopped all had returned to normal.
I have a spring compressor that allows me to take valve springs in place. I then pushed each valve while twisting and found the offending valve.
So head off and another £50 down the drain for parts.
If you know it is not electric then a sudden change is valves
Ray TF 2884
Ray Lee

I'm reminded that "90% of electrical problems are fuel related (and vice versa)." Could there be an intermittent fuel pump issue or some kind of partial blockage in the fuel system?

Jud
J K Chapin

I always suspect condensers as the first item of something you describe.

If it were me I would take the car out and try and find a road where I can pull off to the side and work on it without getting run over and drive it until it fails and shut the key off immediatly and then pull off to the side of the road. I would then remove each float bowl cap and be looking to see if the bowls are filled or either one might be dry. If I found both bowls full of fuel I think that would eliminate fuel delivery as the issue and I would turn my attention back to the electrical side of things.

If not a fuel delivery issue I would see if you could borrow a condenser from another T car that is running well without issue for a test. While you may get a nice spark at idle, you still might get a problem when the car is under load. Finding a good known unit would help you to eliminate that possibility for sure and you could move your attention else where.

Another possible source of failure....and keep in mind I'm just throwing out ideas...is a faulty ignition switch. You can check that by using a jumper wire with alligator clips on each end. Place one end on the fused side of the horn feed on the fuse box and connect the other to the hot feed side of the coil to bypass the ignition switch.

These are just a few things I might be looking at.
L E D LaVerne

Well from the owner's manual:

ENGINE LACKS POWER AND IS SLUGGISH

*This in a new car may be caused by general tightness of the engine and will wear off after the car has been used for approximately 1,000 miles (1600 km.).

*It may also be due to faulty setting of ignition or to a seized automatic control due to lack of lubrication.

*Faulty setting of the carburetter mixture control is also a source of trouble of this nature.

*In an engine which has seen some use, sluggishness is an indication of excessive carbon deposit, particularly if accompanied by "pinking" when the engine is pulling hard.

*It may also be occasioned by faulty valves or faulty valve rocker clearances.
Christopher Couper

Some good things to work on. I bought 5 of the blue wire condensers, so I can try a few of them.

Interesting thought on valves. The motor only has about 3000 miles on it since rebuild, but it had not run in a few years when I did the restoration. So it is probably 6 years since it ran.

What I find odd is that I can't reproduce this running it in the garage at various speeds over time.

I will try the new condenser, then try a different coil. If it occurs again on the road, I will check the fuel bowls.

Hopefully I can clarify if it is Fuel, Electrical, or mechanical.
Bruce Cunha

At one point I ran with all new parts including the distributor from an independent battery. This pinpointed it was not ignition.
Ray TF 2884
Ray Lee

All these engines need to run is correct fuel mixture, a compression stroke and spark delivered at the proper time.

Are you working through a methodical troubleshooting scheme?

Do you have fuel of the proper mix ( corroded points on the fuel pump would give intermittent to no fuel pressure as would a plugged fuel filter or no fuel / bad fuel)
Do you have compression? (Good rings, valves properly timed and set)
Do you have a good spark with correct ignition timing ?

Regards, Tom
tm peterson

Just a thought, many years ago I had a new fuel hose made for a car, they used the old fittings with new hose. I suspect they used a metric hose as the rubber curled up in front of the barb, almost blocking the ID. The car ran fine until I got up to a certain speed, or climbing a hill when the engine would run rough and loose power. As soon as I slowed down or stopped the car would run fine. Took me a while to find but once I cleaned the ID out, ( both ends) car ran fine again. I cannot remember if it was the hose to the carbs or the one between them, but I think it is worth checking. This was a straight fitting hose which was easier to clean out than on with a round fitting on the end.
B W Wood

Try draining some fuel from the tank - see if there is water in it.

Jim Barry
J Barry

My thoughts: As suggested, when it acts up, kill engine, pull over and remove float bowl top to check fuel level (I would do this first). Pull plugs and look- are any wet- not firing, or white-running too lean? That will tell a lot. Remove the floats and look in bottom of the bowl for trash and water. Ditch the ancient coil. Make sure the carb throttle shaft clamp isn't slipping. Try driving with air cleaner manifold off. I had a sticking valve due to new too tight bronze guides and a lean carb (due to dirt in the jet or something?). It would suddenly drop a cylinder, and start tapping. Very obvious. Make sure the tach drive isn't flopping over shorting the dizzy. I can't believe a plugged up exhaust would be intermittent, but I guess possible? Water in fuel very possible with ethanol gas if not stored in a very tight climate controlled garage. Good luck! George
George Butz III

I love the shorted tach drive on the distributor. Once you experience that you can instantly tell if it happens again. :-)
Christopher Couper

I had this same problem a couple of years ago and did almost all the suggested checks but couldn't solve it. Finally, I considered the influence of the air intake and removed the original filter—problem solved! Since then, I've been using individual filters and have abandoned the original. I'm suggesting this in case it helps. By the way, if anyone knows why this might be, I'd appreciate an explanation because I'd like to go back to the original filter.
Gabriel Martínez

I'm a bit late to the conversation but a friend of mine had a problem with his TC that sounds almost like yours...turned out it was his gas cap wasn't venting and letting air into the tank. Next time it happens (if you haven't sorted it out yet) open your gas cap and see if it starts running smoothly again.
Gene Gillam

Just yesterday three of us (my MGA, Rick's MGB and Chuck's TR-4) were headed up to Sapphire Valley for lunch. Right at the git-go Chuck's car started to sputter and exhibit no power. After sitting for a few moments it would restart and seem to run fine. Chuck (a seasoned racer and decent mechanic) determined that the coil was failing when it got hot. I bought Chuck a generic coil from a nearby NAPA and, on its installation, the car seemed to run fine. problem solved for almost 1/2 a mile. Sputter, sputter, no power, pull over again. I suggested that the "electric problem" was lack of fuel. 50 years ago my TR-4 had the same symptoms and the cause was a sticking carburetor piston fixed by a sharp rap on the dome. Chuck applied that fix and away we went for another 1/2 mile. Sputter etc. Took the domes off, pistons were sticking, cleaned the dome and away we went - for another 1/2 mile.

After doing this 3 more time Chuck allowed as how he'd installed a fuel filter just downstream of the tank under the car. I said that's a no-no so on the side of the road Chuck slides under and with a handy spare piece of rubber fuel line, bypasses the filter. Car ran great for the next 160+ miles and is still running great as I type.

Bruce, you wouldn't happen to have a fuel filter between the tank and your fuel pump, would you. Just asking.

Jud
J K Chapin

Well, yes there is somewhat of a filter, and it is another possibility although it has not affected the car since it was built.

This is in my fuel tank. Some years back, I put a scope in the tank and this was found.

It is in the section where the fuel outlet is. No way of getting to it without cutting the tank apart.

I figure it is a shop rag, as there is no other way this could have gotten in to the tank.

I will run the pump disconnected from the carbs and see if it fluctuates.

PS in 73, I used sealer on the tank, so this is pretty much a solid piece now.


Bruce Cunha

Wow! That looks like a good candidate for a fuel partial blocker. Fuel can flow enough for low demand but not enough for high demand = intermittent sputter and power loss. I'd sure try to get it out with maybe a long skinny grabber. I know it would involve taking the tank off and emptying it but could you go in where the sending unit is? I don't know if that hole is any bigger but it might be.

Good luck.

Jud
J K Chapin

The fuel sensor unit hole is around 2" which would hopefully be enough to get hold of the rag (if it is still near the sensor and outgoing fuel line. The idea of going through the filler neck is a possibility but you would have to get around the baffles in the tank.
You need to make sure that the tank is pretty well drained. The screws that hold the fuel sensor go directly through the tank itself with no inside backing, i.e. if there is fuel in the tank and you remove any of the screws holding the sensor you will have fuel coming out. I found this years ago and it is not fun!

Larry

As an afterthought, I used gasket sealer on the screws when I installed a new sensor years ago and have never had any leaks.
LD Kanaster

Actual driving would be the best test. Rig up a temporary fuel system like on Roadkill. A lot of the sealers dissolve into a gloppy mess with ethanol containing fuel, that could be a problem too. George
George Butz III

Does your new engine have stainless valves by any chance or bronze guides or both---
William Revit

William. Engine has about 3000 miles on it since being rebuilt. For this restoration, I just replaced the steel welch plugs with brass ones. I had the distributor rebuilt by Advance Distributors (one of the best in the US.)

I will not be getting back working on the TD until october. I will update this post then.
Bruce Cunha

This thread was discussed between 19/05/2025 and 08/06/2025

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