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MG TD TF 1500 - Engine sputters to a stop

After driving and getting to 80-90C, at 3100-3400 rpm driving along the engine starts to sputter and loose power and backfire. In the course of about 30 seconds at the side of the road it will eventually stop completely no matter what I do with the gas peddle. If I give it 3 to 5 minutes rest it will start, accelerate and run fine for about 1 minute and will again sputter and eventually stop again.

Because this has happened before, last week I took it to a British car mechanic. He did some adjusting to the carbs and adjusted the choke mechanisms, set the points, set the timing, new plugs, cap and wires.

On Saturday I drove it 35 miles without a problem but it was a cooler day.

When the engine sputtered to a stop (5 mins at high idle in the driveway) I cut the ign and pulled the float chamber tops...fuel in the floats is at the correct level, not staved - the pump is giving 4 to 5 healthy spurts per second. It's not a fuel delivery problem.

The water temp never went above 90C.

What else can I assume is overheating, and after sitting for a few minutes to cool will work until too hot again?

Coil? Condenser?

Stumped.

........
MAndrus

How about a clogged fuel filter?
Eric Brown

Nope, new and clean.

A fellow on Facebook suggested high ethanol fuel is boiling. Worth draining the tank to try it.

....
MAndrus

Try to borrow another coil...they do run hot normally and can break down intermittently. Doubt seriously that your gas is boiling.
Gene Gillam

Winter gas will vaporlock easily... one of the reasons it can be pretty common on the first warm drives in spring. " 4 to 5 healthy spurts per second" sounds more like it ISN'T pumping fuel. At least you can hear it clicking which pretty much rules out fouled pump points. If it has plenty of gas in the bowls, though, you can find it hard to believe it is vaporlock, but drain your tank and fill up with summer gas and it probably won't reoccur. Cross your fingers.
JRN JIM

"New plugs, cap, and wires." You didn't mention the rotor. I've had a bad rotor cause problems like that.
David Littlefield

Could you possibly have condensation in your fuel as it seems you're coming out of your winter layup? As you've changed the plugs, cap & plug leads the likely cause would be either coil, gas lock or water in the fuel. Cheers
Peter TD 5801
P Hehir

I had similar trouble with my (dare I say it) MGB and it turned out to be the condenser.
Don TF 4887
D J Walker

Are you saying you still have a problem?

which plugs are you using?
rotor arms and condensors usualy fail permanantly eg, stop and wont restart.
mog

I had a similar problem last year and, after replacing the condenser, problem gone.
Cliff Harvey

Rotor or coil
George Butz

Not water in the fuel, emptied and run 200 miles this spring already. New rotor.

I'm going to replace the coil and condenser. This will result in a brand new ign system.

I've had coils fail in a Model A Ford, but they usually quit and don't come back from the dead. Could be this one has fried inside and quits when hot.

This failure has yet to happen when everything is cold.

......
MAndrus

MAndrus, you might want to get a infrared thermometer and check actual engine block temperatures. My water temperature never exceeded abnout 90C either but the heat in the block got so hot it melted my center cam bearing. With a block filled with crud, the water could not circulate through the engine.

I want to set up a temp gauge that is actually useful, i.e. recording block temperatures, not radiator temperatures.
Geoffrey M Baker

I seriously doubt it is fuel/ethanol issue. Coil, rotor or condenser breakdown is much more likely. Surprised your "mechanic" just started swapping out parts. What troubleshooting did he do to arrive at the conclusion those parts were ALL bad? What is the likely hood they ALL fail at the same time. As a 40 year mechanic it concerns me when someone starts throwing parts at a problem. That is not troubleshooting. That is NOT being a mechanic...was there any recent work performed just prior to this issue.
90% of all carburetor fuel problems are electrical is the old adage.
Not temp related, but it is spark related and something easy to check...make sure your tach reduction gear box.. Or something else, is not shorting out the distributor.
When it happens again, troubleshoot..starting with the ignition system. Do you have consistent strong blue spark at the appropriate time?
Regards, tom
tm peterson

tm, The car had been sitting for 20+ years and hadn't been properly tuned up in who knows how long before that. The plug wires were so old they were rock solid. A few short trips out told me it needed at least a tune-up. Yep, plugs, point, wires - very old if not on their way out cheap insurance to just replace them.

This problem only occurs after the engine gets up to high temp, so the test trips he took didn't produce the problem.

My first thought was fuel delivery, a tough thing to diagnose on the side of the road and the first thing to address in the natural course of basic maintenance/troubleshooting. The mechanic gave her a "good going over" and got her running great until at upper temps for a while. The sputtering problem has to be something deeper, not usually addressed during a basic tune-up. That pretty much leaves the choice of gasoline mixture, the coil or condenser. The coil is the original 62 year old unit. Easy thing to change but I can't blame the mechanic for not swapping the coil out because that WOULD be 'throwing parts at it'.

.....
MAndrus

Given that it seems to run fine for 30-35 minutes, it sounds very much like the experience I had with the old coil. After I sat by the side of the road and enjoyed nature for 10 minutes or so, the coil would cool down sufficiently to start and run a few more miles. Inspection of old coil yielded some of the oil was leaking out. Replacement with Lucas Sport coil solved THAT problem. Now, if Spindeltop would quit leaking oil...
Charles Duffy

Spindletop???????
Steve Wincze

Make sure rotor red and not black.
George Butz

FWIW, there is a diagnostic process in the WSM for situations like this (Section C.2). The problem with an intermittent fault is that you have to have the car in failure mode before you can test. This is how I diagnosed my bad rotor.

There are some rotors out there that are bad out of the box or fail quickly. As George indicates, you should have one of the red ones, certainly not the pear shaped black ones with the rivet in the contact.
David Littlefield

Red rotor.
MAndrus

The screen in the tank may be partially clogged. Next time the tank is almost empty drain it out and remove the fitting and screen. Try not to disturb it as you take it out and take a look. I would bet that it has picked up some rust particles.... so clean and replace. You may want to flush out the bottom of the tank if you find rust.
... CR
C.R. Tyrell

Nope,, not fuel,, MAndrus indicated that the bowls are full to where they should be,,
Steve Wincze

I had the same problem when I first got my car.... Didn't have a complete blockage, fuel just couldn't keep up when running. Whenever I checked the level in the float bowls, it was always fine, always started well.. ran great for a bit... then starved. Took me forever to figure it out.
... CR
C.R. Tyrell

CR, it's not fuel delivery. Clogs wouldn't show up only after driving 15-20 miles and then clear up after sitting for 5 minutes.

The pattern is, run 15-20 miles til hot - sputter to a stop at ANY rpm range - cool down - run fine again til hot.

This isn't fuel, but that was my first thought.
MAndrus

Fault finding by replacement is not a bad way to go but to correctly identify the faulty component, just ONE item at a time needs to be changed. If you are able to borrow a functional coil & a rotor button to begin with & then test these one at a time, at least you can cross those items of your list of possible causes. If you've eliminated water in your fuel my bet would be one of the above. I'd start with the 62 year old coil. I plan to carry a spare coil, rotor button & dizzy cap so I don't see these purchases as money wasted. Cheers
Peter TD 5801
P Hehir

Years ago bad coils or condensers would fail intermittently when hot (on Chevy/Ford, etc. so nothing new). Pretty sure there are a bunch of lousy condensers out there now- I think Lonnie Cook did a write up on that, check the archives. I don't think fuel either. George
George Butz

What about ""vacum " in the fuel tank.
Thoralf Sorensen (TD4490)

Thoralf, given the poor quality of the fit of the tank's cap and the now 62 year old seal under it, I couldn't pull a vacuum on the tank if you offered me a winning lottery ticket.

Nope. The pump's delivering plenty of fuel. Good guess though and worth looking at.

......
MAndrus

Sounds like the condenser to me.
Rich (TD 3983) Taylor


Sounds like you've eliminated fuel related issues, so IGNITION problem appears apparent. Sounds like Something is opening up and causing the system to break down with heat. Since condenser, rotor, coil and other related items have been mentioned, I won't re-address those (all possible).
However, one possibility that I have personally witnessed cause a problem hasn't been mentioned. On the early distributer clamp, there is suppose to be a ground wire. Some get away without it, but on others, a combination of loose fitting parts and warm oily parts causes loss of grounding through the clamp. Is your ground wire there?
A picture of one from the internet.

Richard Cameron

Just made a 30 mile trip, not a hiccup.

New coil. Done.

......
MAndrus

Always nice when you solve a problem! :)
Geoffrey M Baker

Do y'all like the Lucas Sports Coil (Moss143-200)?

Thanks. Jud
J K Chapin

I did not notice any difference with my stock car with the sports coil so I went to the reproduction for aesthetics.

If anyone wants a very slightly used sports coil you can have it for shipping.
Christopher Couper

A new coil solved the same problem with my TF.
And then 6 weeks later, it came back. Another new coil, and 6 weeks later, back it came again. Something was causing the coil to fail. Only solved it by new condenser and new coil at same time. Better electricians than me can comment but don't the condenser and coil form a circuit?

David
David Wardell

1 over 2 Pi root LC
mog

David.... my bad, interweb shorthand. Coil and condenser set.

....
MAndrus

MAndrus

See my latest post, might be worth investigation as my fault was at its worst when the engine was hot.

Graeme
G Evans

Mog. That "rings" a bell. Jud
J K Chapin

This thread was discussed between 21/04/2015 and 25/04/2015

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