Gt6 mk3 misfire different now

[dave.vitesse]

One area worth checking is the valve clearance. If there is no clearance, closed up, then it will not rev much above 4,000 rpm. The gap should be 10 thou when cold.

As for arcing, well smell the roto arm and dizzy cap. If it's arcing then there is a burnt Bakelite smell.

Pete's right about the coils. I have a 1.5 ohm Bosh make marked 12 Volts. I bought it 40 years ago as a replacement from Unipart against a Triumph part number!

Dave

[Pete Lewis]

Im getting lost,  are we certain this is 6v  ballast feed or 12v feed  certainly running a 1.5 ballast coil on 12v will get overheated  and cook points and the high HT will wreck caps and rotors  etc.   The opposite  running a 3ohm on 6v gives only half the HT and you get performance  losses

May seem daft but coils are engine mounted to make use of engine cooling to keep the temperature stable, hence its mounted  on a  thick bracket  fairly common practice in the day.

Pete

 

 

 

[Dolomitejohn]

Hi pete. 

I am getting confused too.  The coil fitted currently is a lucas and came with the car. It measured 2 ohms across the low voltage windings. I am misfiring when hot around 4000 rpm with occasional miss around 3500.

The coil fitted last week was removed from my sprint and was supposidy a lucas sports ballast coil. It measured 3 ohms.  Misfire when hot at much lower rpm.. Worked OK on the sprint. 

As far as I can tell the gt6 has a ballast system. I. E. It measures 6 volt or thereabouts  across coil with points closed and ignition on.    The coil feed ( +ve) when disconnected from coil measures 12 volt with ignition on. I guess this is correct and only drops to 6 when connected to the coil and measured in the circuit.  

I guess the original coil could be faulty. It is clearly very old.  

Yesterday it was so hot I could not have held it in my hand had I wanted to. Is this normal.?  

The issue is clearly temperature related.  Car is OK for first few miles even with temp gauge on normal. When the car is really warmed through the trouble starts. So driving up edgehill (12% gradient and steepest longest hill in Warwickshire) set it off last night. In fact triumph used this hill for development back in the day....  After a engine off soak the misfire was worse and did not recover on the 5 mile drive home even driving carefully. 

Can you recommend a non lucas coil for ballast system? 

Will get there eventually.... Cheers

John 

 

[johny]

John, first lets confirm once and for all if yours is a ballasted system: measure the voltage to earth at the +ve side of the coil with the ignition on, engine off and points closed. 

[NonMember]

Johny - he's already done that test and confirmed it's ballasted, as stated in the immediately preceding post.

 

John - as Pete said, I don't like the position of those points. They look, to me, to be way too small a gap. This will result in excessively long dwell, which will cause the coil to run hot. It may also, when things get generally hot, lead to the points not opening enough to get a good spark. If the gap is too small (or opens too slowly) then the flyback voltage on the primary winding will jump the points gap and your spark energy gets wasted in burning the points instead. A weak condenser will accentuate that problem.

[Dolomitejohn]

Hi nonmember. 

I have  new points and condensor to fit so that is next job along with resetting the timing statically using the bulb method. I might invest in a new balast 1.5 ohm coil also. 

[Pete Lewis]

the coil you mention off the sprint at 3 ohms is unsuitable for a ballasted supply its a pure straight 12v coil   

ballasted must be around 1.5 ohms 

lucas types DLD101  or 105 is straight 12v 

 DLB 102  is 6v for ballasted feeds

pete

 

[poppyman]

10 hours ago, Dolomitejohn said:

Hi tony

No not yet. I purchased a new original type from td fitchet a few weeks ago. It's un branded and came in a plastic bag. 

Where do I get a bosch condensor from. What is part number? 

Yesterday when i was driving and playing with it I noticed the coil (original lucas) was so hot to touch. Even with nitrile gloves on I could not have held it in my hands. Do gt6 owners move the coil from engine to keep it cooler? 

I probably need to buy a new dizzy cap, ht leads and ballast coil plus rotor arm to eliminate them. Got new points to fit also. 

Getting a bit fed up with it now. Just want to drive... 

https://www.ebay.co.uk/itm/NEW-BOSCH-CONDENSOR-FITS-FORD-FIESTA-MK1-SPORT-VAN-1976-86/113700681620?hash=item1a7916b794:g:1FkAAMXQcVNQ6aZ9 

This is the one John.

[Dolomitejohn]

Hi all

Just measured the voltage across the coil. Coil resistance at cold is 1.9 _- 2.0 ohms. 

With ignition on the voltage across coil is 5.68 volts rising slowly as the coil warms.  The battery voltage is 12.25.

Soni have a balast system but is coil resistance too high? 

John 

[NonMember]

Your resistance measurement may not be terribly accurate if you're using a "normal" multimeter. The 6V reading is a much better indication and shows it to be the right coil.

[Pete Lewis]

I would prefer to see the coil ohms at 1.5   when you checked  across the coil was it disconnected ????

I  agree about the voltage shows  its about right  

Normal hot ( eng temp,) is one thing  ........but serious hot ( fry eggs)  has a solution waiting to  be solved

pete

 

[Dolomitejohn]

Hi pete. 

Normal hot. Not fry egg hot. 

Yes 1.9 / 2 ohms was disconnected. 

I will replace the coil, fit new points, new condensor, check valve clearances and purchase a new strobe (old one packed up) to confirm ignition advance is working.  I might stretch to new rotor arm, csp and leads.  Where do you get this red rotor arm from? 

Going to have a week away as of Sunday so I will go quiet for a while. Will update when I get back and have had time to investigate further. 

Cheers. 

John 

[NonMember]

Check your points gap and/or dwell angle!

You're on a Delco distributor, are you not? The red rotor arm is a Lucas thing, IIRC.

[Dolomitejohn]

I don't know the dizzy manufacturer. 

How can I tell or can you tell me from the photo I posted? 

Also I don't have a dwell meter. So an only go by points gap. 

John 

[NonMember]

The photos you posted are a Delco. You can also tell because it's stamped on the distributor somewhere.

When you get your new strobe, get one with a dwell meter built in.

[Pete Lewis]

if the dizzy is made with the correct cam the dwell should match  with the specified points gap

yours is a delco doenst need a red rotor thats lucas only 

dont change too many at the same time ,

Pete

and dont keep thinking its heat of electric  ,,,, its probably the fit of the boot lid ,  sometimes these odd occurrences  are masked by 

the classic ghost.  of when you find a fault is wont cure the problem 

Pete

[poppyman]

I will second above...... no point in replacing the car as you wont no what the fault was.  I had a mate who relaced every bit or the ignition system (fortune spent) only to find broken distributor baseplate  wire!!!

Tony.

[Pete Lewis]

way back on the old forum we once had a guy  changed the engine because of overheating ...was the wrong  era /type of sender 

always the simple and cheap  jobs first  one at a time 

pete

[Dolomitejohn]

Hi all

Would the carb temp compensator be a possible cause? It let's air into the bridge when hot? 

Is there a repair kit for these or can they blocked off? 

Cheers. 

John 

[Pete Lewis]

Easy fix , if these are open or opening at normal temps  you cant set the idle speed or mixtures correctly

Remove the comp hsg  just two screws,

These have two 0 ring seals one down the bore one on the boss .

The plastic plunger must be shut , give it a jiggle most are partly open , screw the small nut to close it onto its  seating  in fact screw the blasted thing fully shut,  its an emmission  device to speed up and lean a hot idle .to reduce emmissions

Between carb and manifold the gasket has a hole in it to feed the temp comp  bypass into  the manifold 

Turn  this upside down  and you  seal off  the bypass

Its more important these are closed at normal running so you set the idle and mixture without any throttle  bypass

Set the biased needles with the small delrin washer just flush  with the base of the air piston as a basic setting

Pete

 

[Dolomitejohn]

Hi pete. 

Managed to remove the temp compensators today. Both just off closed at cold temp.  Are you saying I should tighten the nut until the valve is closed hard and continue tightening until the nut bottoms out?  If I do this will I be running rich at idle when hot?   

It does make sense. Change from 3 ohm coil which misfire at low rpm to 2 ohm coil which misfire at higher rpm (weaker spark with 3 ohm coil). If these compensators are weakening off too much......... Although the fueling could be generally too weak I guess....? 

 John 

[Pete Lewis]

there is a long drawn out test we wont go there,

in the main screw the nut till the plunger is nicely seated at a high temp. may need popping back in a hot carb a few times to twiddle it closed 

at normal running temperatures , no you dont have to gorilla it shut .

they should onlt bypass an air bleed when very hot like traffic jams etc. all other operating they should be closed 

if open at normal then youre not getting the base needle adjustment right at idle

its only a small hole it wont affect open throttle running very much

as said the biased needles (sprung mounts) have a small delrin washer at the top of the needle this should be adjusted to be level with the base of the air piston use an alen key down the dashpot tube to adjust the needle positions  (mixture) 

loads of good clues on https://www.buckeyetriumphs.org/carburetors

not always the same spec as youres but the basics and pictures are excellent so it all relates to simpulze  !!

Pete