Engine cutting out

[Guppy916]

I'm not sure if this should be in 'elctrics', any way, I was out for a spin last weekend in my MK3 GT6 when i noticed a misfire, about 3k then after a stop at a road junction it missed again about 2k, then a mile up the road it just died. on trying to restart, it would only fire then die many times, once I got it home I started from the beginning clean plugs, check fuel and filter, check for sparks, though not very good, then a friend said ignition switch 'sod off say's I' the key works the starter works, any way I jump from the battery to the coil, jump in the car hit the starter and it runs blinking great at this point my friend has this stupid grin, how, what is wrong, I have a new switch in the post, any ideas guys.

 

[Colin Caygill]

2 minutes ago, Guppy916 said:

I'm not sure if this should be in 'elctrics', any way, I was out for a spin last weekend in my MK3 GT6 when i noticed a misfire, about 3k then after a stop at a road junction it missed again about 2k, then a mile up the road it just died. on trying to restart, it would only fire then die many times, once I got it home I started from the beginning clean plugs, check fuel and filter, check for sparks, though not very good, then a friend said ignition switch 'sod off say's I' the key works the starter works, any way I jump from the battery to the coil, jump in the car hit the starter and it runs blinking great at this point my friend has this stupid grin, how, what is wrong, I have a new switch in the post, any ideas guys.

 

I don't know if the GT6 has a revcounter that works off the coil or if it's a cable driven one, but if driven off the coil any LT ignition problem will be confirmed by the needle bouncing all over the clock.

[Guppy916]

the rev counter is cable driven from the dizzy

I for forgot to say above the coil was swopped also 

Edited March 29, 2022 by Guppy916

[WIMPUS]

Did you change the condenser ? 

Had one failing on a Dolomite, took a while until we found it.

Edited March 29, 2022 by WIMPUS

[Guppy916]

no points or condenser all electronic

[standardthread]

4 hours ago, Guppy916 said:

I'm not sure if this should be in 'elctrics', any way, I was out for a spin last weekend in my MK3 GT6 when i noticed a misfire, about 3k then after a stop at a road junction it missed again about 2k, then a mile up the road it just died. on trying to restart, it would only fire then die many times, once I got it home I started from the beginning clean plugs, check fuel and filter, check for sparks, though not very good, then a friend said ignition switch 'sod off say's I' the key works the starter works, any way I jump from the battery to the coil, jump in the car hit the starter and it runs blinking great at this point my friend has this stupid grin, how, what is wrong, I have a new switch in the post, any ideas guys.

 

Have you checked the carb float chamber?

My Dolomite died at the traffic lights last spring (single SU), I wasn't there my daughter was driving. I went out to try and sort things out, there was a spark   (Sparkright electronic ignition etc.) but the plugs were dry. I eventually got it started and got the car home.

When I stripped the float chamber I found a greasy sludge at the bottom next to the fuel delivery pipe to the needle. I think it had partially blocked the delivery pipe. Modern ethanol fuel, the ethanol scavenging water from the atmosphere and dragging it through to the carb making an emulsion?

The car, Y reg (!) has done 46K from new, the previous owner laid it up over the winter and looked after it (as I do). 

 

 

[Guppy916]

HI yes all three webers are clean and the jets blown through 

[glang]

That sounds like you have a ballasted coil system so the supply to the coil, when running, passes through a resistor and is dropped to 6v. However while the starter motor cranks the resistor is shorted out and the coil gets the full 12v system voltage. If you lose the normal supply through a failed resistor or connection the engine only runs while the starter motor is turning.

Of course it will run with a direct 12v supply but shouldnt be done for long as the coil is only rated for 6v continuous. However I dont think your problem is the ignition switch as, at the same time, you would have lost a load of other electrical bits that are fed by the same supply as the coil. You really need to look at the wiring diagrams shown in the free to download Triumph workshop manual.... 

[Guppy916]

Cheers "gland" I was sure mine is not ballasted,  although I am on my third coil pic below, I have always purchased 12v Lucas coils, this is the coil I was running when I broke down, the first thing I checked was to see if it was hot, I would say hand temp. the car had a new loom when it was restored back in 2015

 

 

[glang]

hmmm a non ballast coil wouldnt get hot running on a 6v supply but also wouldnt give a full spark. Its the other way round when the coils get hot and the extra high output fries ignition components. Also note that its possible a coil has a 12v label but is for a 12v system using a ballast resistor. Confirmation is by measuring its resistance as 1.5ohms = ballast, 3ohms = non ballast.

Anyway if its a problem with the ignition switch you will have lost lots of other things as well such as wipers, indicators, brake and reverse lights. Once you get it running again I would use a meter to measure the coil supply voltage because sometimes the ballast resistor isnt obvious as its actually installed in the wiring...

[Guppy916]

Yes that's what is beginning to worry me could the supplier have sent the wrong loom,  3.0ohms is that across the + and - terms 

my coils measure 3.9 and 3.5ohms

Edited March 30, 2022 by Guppy916

[glang]

Yes thats across low voltage side and those readings show non ballast coils. Now you need to check if youve got voltage (to earth) at the +ve side of the installed coil with the ignition on but not running. There shouldnt be unless youve got an intermittent fault and you need to work backwards using the wiring diagram to find where the break is (this supply should come from the ignition switch or fuse depending on your model)...

[RobPearce]

25 minutes ago, glang said:

There shouldnt be

Did you mean to type "there should be"?

With ignition on, the +ve terminal of the coil should be at 12V (or whatever the battery reads) or, if a ballasted system, half that, depending on whether the points are closed. As you have non-ballasted, expect always battery volts. Re-check with the -ve side grounded to confirm there's no resistor in the loom.

[glang]

well I was going on the basis that the original fault is still present and the 'ballasted' supply has been lost (it needed a temporary supply connected to the coil to continue running). However if there is now a correct voltage the fault must be intermittent and so much harder to find.... 

[Guppy916]

Rob, gland, tomorrow is a new day, and hopefully a bit warmer,  I shall start checking your idea's out, many thanks for your help

[Guppy916]

Update, new ignition switch fitted "gland" you were right it still wont run,

So Iv'e checked volts to coil , +ve ignition on,  NO volts and NO volts at -ve also,

Turn key to crank motor 12v +ve , and 12volts -ve,

fit a temp feed from battery to  +ve and car runs great  

checked the wire from coil +ve to starter relay no breaks or shorts this is the white/yellow wire

[RobPearce]

2 hours ago, Guppy916 said:

checked the wire from coil +ve to starter relay

That's the one that bypasses the ballast resistor during cranking. Your symptoms are classic for a failed ballast resistor. If you have a non-ballast coil you should not even have that white/yellow wire, just a white wire from coil +ve to the ignition switch.

[glang]

Yes depending on which version of Mk3 GT6 you have the white continuous feed wire comes from the ignition switch or fuse panel. You need to find this and it could be confusing as theres quite a few white wires. I would look on the fuses where there may be one or two white wires coming into one fuse. If two, one of these is the running supply to the coil that has failed and if only one then that supply comes instead from the ignition switch. Once located you need to disconnect it at both ends, check both for resistance to earth (infinity) then connect one end to earth and measure resistance to earth at the other end (almost zero or 1.5ohms if resistance fitted or, most likely, infinity as broken).

I guess youre going to have to run a new wire from the fuse to the coil. I would get the correct size white wire and thread it through to the coil where the supply from the starter relay can be permanently disconnected at both ends. Your system will then be non ballast same as the earlier models of GT6. 

Remember all this should be done with battery disconnected.... 

[Guppy916]

gland is that why my hair has suddenly gone curly

I am checking this morning many thanks guys

[Guppy916]

Iv'e unwrapped 6" of loom and found this little rascal i shall start tracing wires both the wires are White and Yellow, Pink ?

[Guppy916]

both w/yellow wires check out ok ‚ 1.1 ohms & 1.3 ohms, now to find the other end of the pink, it's not on the fuse box or ing switch 

[glang]

I think the pink is the resistance wire and will run a certainly distance to achieve the 1.5 ohms and then join to a white wire in the loom somewhere which will then carry on to the ign switch or fuse....

[RobPearce]

The pink is probably the late model resistive ballast wire. It should go to a white wire that then goes to the fuse box. I'm not sure where the pink-to-white join lives as my GT6 is the slightly earlier model with the ceramic resistor next to the coil.

[glang]

hey, great minds! Its got to be right if two people say it, hasnt it🤪

[Guppy916]

So am I reading you correct, can I solder the w/yellow wires back together, that will be the connection   between the coil +ve and the starter relay, make the pink safe, (not use)

then pick up a ignition "on" continuous feed (new wire ) to the coil +ve as well  

my head is beginning to hurt