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MG TD TF 1500 - Hard Starting

My TD used to be very easy to start. Since I developed generator problems it has become very difficult to start.

Now that the alternator issue is settled and it appears to be functioning properly I am still plagued with very difficult start from a cold engine. When I say cold I mean about 50F. That is about the lowest my garage gets.

I checked the timing and, at idle of about 1000 RPM I have about a 15 advance. At 3000 RPM I have about 32 advance.

The fuel pump and choke appear to be functioning normally and no changes have been made.

Attached is a picture of the plugs. Number two has a little carbon buildup but not at the point of spark. I carefully checked the gap and it is 0.028 on all the plugs. For my set up is this too large a gap?

During all the testing of the faulty alternator there was one time that I left the key on without the engine running. It might have been for 20 minutes or an hour, I dont recall. The coil was hot.
Could I have damaged the coil to the point where I get a poor spark?

I have a pertronix ignition and a Pertronix coil.

I also have a supercharger with one 1-1/2" SU carburetor.

Also during all of the testing and attempts to start, the battery was often run down and required charging.

I just had the car running for about one hour and checked the battery. The acid level is very good and the voltage when the battery is completely disconnected is reading 13.26 volts.

The next time I go to start I will have the voltmeter connected to the battery terminals where I can read them inside the cab.


Mort Resnicoff

With the location of your carb, can you still pull out the enrichener? I abandoned the enrichener years ago due to the increased friction from the required bend. My wife would just about rip the instrument cluster out pulling on that knob.

When ours is reluctant to fire right up, I'll pop the bonnet and tickle the carb for a second to see if it wants a bit more fuel to start. Alway tickled my BSA so it would start first kick cold.

Like the snow blowers I got out today, for years, I never try to start them without priming with a squirt of gas or starting fluid. Half the time I resort to this with lawnmowers, too.

May also want to check the point gap at the distributor. If it has closed up it can make it hard to start.
W A Chasser

With any running or starting issue, change the plugs first. The third from left has a lot of carbon build up. Overall they look about like my plugs do with normal running. Does it crank over at normal speed but not just fire? Or crank over slowly? Battery voltage needs to be checked while cranking. I recall that most electronic ignitions require at least 9V to fire. A failing battery's voltage may plummet while under heavy amp load. If it is spinning over normally, I would suspect fuel, ie the choke/enrichening is not working, or working well enough. You can give Jim's method a try- squirt a bit of gas into the intake, or you could even try ether starting fluid to help diagnose. The few times it is below 60 here there is no way my car will start without major use of the functioning choke. George
George Butz III

I agree with George---put a new set of plugs in it----that set don't look very new
No3 looks like it's been misfiring
AND if the plugs in the pic are the ones that came out of it them plug gaps look wider than .028"---from here on the other side of the world anyway-!
Don't get resistor plugs, just normal std plugs
William Revit

I had a similar issue with a Y-Saloon, Y-Tourer and my 1969 midget. I went to one step hotter spark plug and cured the problem in all three cars.

Maybe it's the fuel we get today, maybe just a bit more oil above the pistons ?.



When I want to check for spark, I'll hook up my timing light on the coil wire or individual plug wires looking for a miss.

You can view the timing light and see if you're getting a spark while it is rolling over.

I hooked a ballast resistor inline with our coil to be kind to it. Does yours have a ballast resistor?

Do you have a vacuum/boost gauge? A vacuum gauge might give a glimpse as to a vacuum leak. With a blower hanging out on the four little studs, your manifold gasket may be due for replacement. Next time you get it running, try spraying starter fluid around the intake manifold and blower to see if it speeds up with a whiff of spray.

Did nothing change except for repairing the alternator? Is the choke operating properly? Does it run as it did before once it starts? How about at highway speeds?

Older Pertronix can be damaged by leaving the ignition on for a long time but the newer ones are supposed to have fixed this problem. You can test for a coil issue by swapping it for a good known spare. Or find someone with a coil testing rig who lives closer than me. ;)

This is one of those problems where the process of elimination might be faster and easier than diagnostic work.
Steve Simmons

Next thing to check.

I checked the two volt meters and they give the same readings.

In this photo I have just turned on the key(no starter).

The yellow SunPro is directly on the battery terminals.
12.69 Volts

The smaller on is on the coil.
11.13 Volts

I have a 1.56 volt drop between the battery and the coil.

I will check all the terminals between them and try to cure this problem first.


Mort Resnicoff

Mort, I had a similar cold start problem with my MGB. It turned out the nuts that hold the intake/exhaust manifolds to the head had just loosened up enough over time and created a vacuum leak.


79 MGB
gary hansen

I discovered many years ago that the Pertronix in my car would not fire if it wasn't getting 12 volts. It may be your case as well? The symptoms were that the engine would not fire until I released the starter at which point it would take off and run. The battery had enough juice to spin the engine but the voltage was dropping below 12 volts in the process. New battery.... problem solved. If that is the issue with your car if may not fire and take off if the air temp is cold. Just something you could check by jumping a known good battery to your car and see if it makes any difference.
L E D LaVerne

Sorry I didnít catch that you have electronic ignition. But for those who may have breaker ignition and suffer a similar issue consider my
post above as a possible cause

Bill Chasser
W A Chasser

My bet is on the coil.
Lew Palmer

I had a similar, actually worse, voltage drop to the coil. Tried numerous coils with no difference. Close examination and testing of wiring from battery to coil via ignition turned up a corroded terminal on the ammeter and that had been the cause of my poor starting and intermitting cutting out for over 6 months.

David Wardell

The good news:
The car is starting and running well.

The bad news:
I don't know why!

I checked, tested and maintained:
The spark plugs
The coil
The starter switch
The battery cut off switch
The ammeter
The battery

With the assistance from Pertronix tech support the ignition was tested both in the car and bench tested.

I checked the voltage drops from the battery right through the power line to the plugs.

There are a couple of things that happened that might be clues.
When I checked the voltage at the coil I got different readings when I would turn the key to the on position. The readings would vary from 11 volts to 12.8 volts.
The wire going from the ignition switch to the Pertronix has a bullet connector. I had an occasion to disconnect and reconnect this a few times. Although there is no evidence of any corrosion, perhaps this junction was not making a good connection.

There is one caveat to it starting quickly. I let it crank for just one or two seconds and as I release the starter it fires right up. This happens about half the time.

My thanks to all the sources for the input.


Mort Resnicoff

Like I said.... it doesn't like to fire when under 12 volts.... and just as I discovered...when you release the starter it will fire.
L E D LaVerne

I'd had the use of a dielectric grease recommended on electrical connections to prevent corrosion but before I posted the suggestion here, I checked the internet. What a minefield! Some say it's a conductor - others that it's an insulator. Wikipedia cautions readers to treat the content with caution suggesting that the entire section needs to be rewritten. There are plenty of U tube videos that contradict each other. The dictionary defines dielectric as an insulator that sustains electromagnetic fields.

There does seem to be some agreement that dielectric grease actually does prevent corrosion and so its use on the electrical connections in our cars would seem to be warranted. Would it have assisted Mort with his problem? Who knows? I did discover though that Vaseline is not recommended because of its propensity to enhance combustion. A cotton ball impregnated with Vaseline apparently makes a great fire starter. Cheers
Peter TD 5801
P Hehir

This thread was discussed between 17/01/2019 and 26/01/2019

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