Hot misfire after standing

[JeffW]

Hi

I continue to have a misfire when hot after the car has stood parked and shut off. Once I start moving again, the misfire eventually stops and never misfires throughout the rev range as long I as I am moving. I have not been in standstill traffic for a while so I don't know what would happen in those circumstances.

I dread to bring up this confusing subject again, but am I running a suitable coil? I am running the Bosch Red coil that so many on here run and my car is 1976 Mk2 with no ballast resistor. Just to confirm I have an older Luminition optical ignition, new distributor cap, new plugs, new rotor arm, and brand new Magnecor leads. The coil is not touching the engine, but is still mounted in it's original position.

For the life of me I cannot figure out which coil is suitable for this setup, or if the Bosch is fine, what the hot misfire could be attributed to.

Thanks

Jeff

[Hettiherald]

Jeff. I had a similar problem in my herald. Turned out to be vapour lock in the fuel lines. Heat from the engine caused the fuel to boil and only when cool fuel flowed through the lines the misfire disappeared Hope this helps. Dave.

[JeffW]

Jeff. I had a similar problem in my herald. Turned out to be vapour lock in the fuel lines. Heat from the engine caused the fuel to boil and only when cool fuel flowed through the lines the misfire disappeared Hope this helps. Dave.

Thanks Dave. How did you cure it? Better insulated fuel lines?

Jeff

[DJT]

Make sure the fuel lines in the engine bay are run as per original design with the filter mounted on the wiper motor side of the suspension turret. Mine is just so and never get fuel vaporisation even on the hottest days. I’ve seen some unusual setups with owners complaining of vaporisation.
FWIW I run the Bosch Red coil on my Mk2 mounted on the inlet manifold, with the original ballast wire, but now have a Distributor Doctor rebuilt dizzy c/w his Petronix ignition.

[JeffW]

Make sure the fuel lines in the engine bay are run as per original design with the filter mounted on the wiper motor side of the suspension turret. Mine is just so and never get fuel vaporisation even on the hottest days. I’ve seen some unusual setups with owners complaining of vaporisation.
FWIW I run the Bosch Red coil on my Mk2 mounted on the inlet manifold, with the original ballast wire, but now have a Distributor Doctor rebuilt dizzy c/w his Petronix ignition.

Thanks DJT. The fuel lines are new-ish and run in the normal way from the filter mounted in it's original spot by the wiper motor.

I am wondering if my Luminition is faulty too - I have read both that they can act strangely and conversely will either work fine or not at all.

[MandM]

I got this info from the forum
TB17-Optronic-Ignition-Check-V1 (1)[11312].pdf

I also have Bosch red coil, mounted on the bulk head, as is said in the notes above check the 3 pin plug

[taroz]

Just adding to JDT’s comment- check that the fuel line clip on the cam cover is being used. I’ve read of someone not realising that the clip was for that and the line was resting on the cover itself. Guessing that could cause the vapour lock issue. Tariq

[StagJonno]

Jeff - to clarify - you say you don't have a ballast resistor. Pretty sure you will have one (unless a PO has seriously buggad about with the wiring) - as yours is a 1976 car, it is not in the form of a discrete wound ceramic device mounted on the coil. It is in fact in the form of a resistive wire to the +ve coil terminal. Colour is pink/ white (though age may have faded the pink). As far as I can find, Bosch only produce red coils suited for an external ballast. For verification, the most usual Bosch Red has P/N 0221119030 as per this from Amazon https://www.amazon.co.uk/Bosch-0221119030-Ignition-Coil/dp/B000BZIYE8/ref=asc_df_B000BZIYE8/?tag=googshopuk-21&linkCode=df0&hvadid=310715971624&hvpos=1o2&hvne tw=g&hvrand=13743460187891187447&hvpone=&hvptwo=&h vqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006794 &hvtargid=pla-571575276435&psc=1&th=1&psc=1 .

Connecting a coil designed to run with a ballast resistor direct to the 12V supply for more than a few seconds is likely to overheat and damage the windings.

Worth checking that the power supply to the Lumenition is taken from a full 12V supply - a favourite is piggy backing onto the white wire connection to the inertia switch. It must not be taken from the coil +ve as this will cause erratic performance and possible damage to the Lumenition. Make sure that any exposed connector is well wrapped with insulating tape or heatshrink to avoid incidental contact with the body or other earthy bits as the white circuit isn't fused.

Jonno

[tvrgeek]

Kind of doubt it is vapor lock as we have pusher pumps. More likely heat soak messing up the thermal compensators. Any vapor in the line will be quickly purged as soon as the pump comes on and the floats drop. Shoud not last more than a few seconds. The traditional vapor lock was with front mounted pumps that could not self prime when vapor between the pump and the tank. TR6 etc.

One way to avoid heat soak is to put a controller on an electric radiator fan that runs for a couple of minutes after turn off. Just like modern cars.

Lumenition amplifier module should be mounted front of the core support so it stays cool. Yes, heat can effect anything electronic.

No coil likes to be left with full current for very long. With a Lumenition, I believe you should be running a 3 Ohm coil and no ballast. The PO put a Pertronix in mine so I ordered the Pertronix 60130 e-core coil and will see how it works. He put in some unknown unmarked coil.

A give-away if it is ignition or fuel, is when it is stumbling, an ignition problem will usually make your tach erratic.

None of this is unique to our Stags. All CD175's compensators can stick. I fixed that in my TVR with a Ford Motorsports GT-40 5.0 and Edlebrock. Fixed it on the Spit with an HS6. Bought new on the Morgan.

[JeffW]

Jeff - to clarify - you say you don't have a ballast resistor. Pretty sure you will have one (unless a PO has seriously buggad about with the wiring) - as yours is a 1976 car, it is not in the form of a discrete wound ceramic device mounted on the coil. It is in fact in the form of a resistive wire to the +ve coil terminal. Colour is pink/ white (though age may have faded the pink). As far as I can find, Bosch only produce red coils suited for an external ballast. For verification, the most usual Bosch Red has P/N 0221119030 as per this from Amazon https://www.amazon.co.uk/Bosch-0221119030-Ignition-Coil/dp/B000BZIYE8/ref=asc_df_B000BZIYE8/?tag=googshopuk-21&linkCode=df0&hvadid=310715971624&hvpos=1o2&hvne tw=g&hvrand=13743460187891187447&hvpone=&hvptwo=&h vqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006794 &hvtargid=pla-571575276435&psc=1&th=1&psc=1 .

Connecting a coil designed to run with a ballast resistor direct to the 12V supply for more than a few seconds is likely to overheat and damage the windings.

Worth checking that the power supply to the Lumenition is taken from a full 12V supply - a favourite is piggy backing onto the white wire connection to the inertia switch. It must not be taken from the coil +ve as this will cause erratic performance and possible damage to the Lumenition. Make sure that any exposed connector is well wrapped with insulating tape or heatshrink to avoid incidental contact with the body or other earthy bits as the white circuit isn't fused.

Jonno

Thanks Jonno, a very clear explanation. I do have a somewhat pink wire to the positive side of the coil.

The question then comes full circle back to my first post - which coil should I use to replace the Bosch 9030 I have installed?

Thanks again

Jeff

[StagJonno]

The Bosch Red I referenced has a P/N ending 9030, so is probably the one many have recommended. I bought one myself and will be fitting after engine rebuild, though I have no issue with the one fitted (other make) which will become a spare. You could get a spare and swap it to see if that cures your issues - relatively cheap.

Worth getting a tester like https://www.amazon.co.uk/s?k=spark+p...nb_sb_ss_i_3_4 which you insert in line between the plug and the HT lead. This gives visible indication of spark which you can observe when you're having a problem.

Jonno
..

[JeffW]

Hi Jonno

Now I am more confused unfortunately.

The Bosch Red coil ending 9030 is the one that I have installed and the one you referenced as incompatible with Mk2 cars as I don’t have an external ballast resistor. But your post last night appears to suggest this one is ok.

I’ll have to try the spare test and see if that cures the misfire. I am not convinced it is fuel related but will start eliminating other causes first.

Jeff

[DJT]

Surely it doesn’t matter which type of ballast is fitted. They both work the same way i.e supply 12v to the coil during starting and 6v when running. As far as the coil is concerned they are both External. The above mentioned Bosch coil works fine with my Mk2.

[Hettiherald]

Hi jeff I cured my problem by insulating and re routing of the lines away from any heat source. Also converted the pump to electric so that any heatsoak from the mechanical pump was removed. Not an issue with the stag i know, but volitivity of the fuel nowadays is much more than the old 5 star fuel. Underbonnet temps can be very high with the stag, so i would insulate as much as possible.
If you do this first, it would a least rule out this as a problem, and then move on to more expensive cures. I am a firm believer in doing one thing at a time starting with the cheap and easy before moving on. Most problems are cured with easy stuff in my experiance!
dave.

[marshman]

Hi Jonno

Now I am more confused unfortunately.

The Bosch Red coil ending 9030 is the one that I have installed and the one you referenced as incompatible with Mk2 cars as I don’t have an external ballast resistor. But your post last night appears to suggest this one is ok.

I’ll have to try the spare test and see if that cures the misfire. I am not convinced it is fuel related but will start eliminating other causes first.

Jeff

Jonno didn't say it was not suitable. He said the Bosch Red needs an external ballast resistor. What he did say, and what may have caused some confusion/lack of clarity, is that later Stags did not have a discrete ballast resistor but one that was "built into the loom" in the form of a piece of resistance wire. All Stags did have a ballast resistor of one form or another (either external bolted to the coil or hidden in the loom) from new. I would think yours is the later (resistance wire in the loom) and these have known to fail, so don't worry about your coil being the correct type.

I would look at the Lumenition and follow the helpful guide linked to by MandM or consider the fuel vapourisation route. Persoanally not sure vaporisation would take that several miles to clear and would give starting issues. The optic sensor and connectors etc. on the Lumenition however are known trouble spots. Any chance you can temporarily revert to points to rule out the electronic ignition?

Roger