Engine cuts out when hot, putting it into Drive. Why?

[Guest]

We have owned a Mk2 Stag Auto for 31 years and completely refurbished it in 1994 including engine, gearbox, axle, steering, brakes and all accessories.
The carbs were overhauled and Piranah electronic ignition fitted, new plugs, leads, HT coil
It only gets driven less than 500 miles each year and it kept under cover in a garage.
We had an issue a few years ago whereby when the engine got hot and you put it into Drive, the engine cut-out. Starts easily and revs easily but will not run under load.
This was initially traced to the HT coil and that has now been changed several times.
Problem re-occurred sometime later and the Home Tune guy eventually tracked the issue to a hairline crack in the rotor arm and that was replaced and all was good for a couple of years.
The problem has re-occurred recently.
Replaced the HT coil, fitted a new rotor arm (The Red Rotor Arm from The Distributor Doctor), replaced the rubber diaphragms in the Strombergs just in case.
And yesterday fitted a new Piranah electronic ignition just in case the old one was failing.
Car started first pull and left it ticking over on the drive.
After 15 minutes all was well and it pulled away and drove properly.
After 35 minutes it cut out.
Leave it 30 minutes to cool down and it starts and drives properly but as I don't want to get stranded anywhere, I have not tried it on a long run.
Does anyone have any suggestions as to what the problem may be?
Thanks

[wilf]

If it has been an HT ignition fault in the past, worth swapping HT leads and Distributor cap? How old are those items?

And don't think the Coil might not still be the culprit - took me 3 before I got one that still worked properly when hot.

[dickr]

The inhibitor switch misbehaving as the gearbox warms up?

[Tdm]

Often accused as getting things wrong, but as a start you could try :-

1) Bypassing the fuel cut off switch
2) Checking the fuel filter in the engine bay (and that it is pumping fuel O.K.)
3) Trying a different coil

Others will I am sure suggest additional checks. Could be dirt in the carbs, a split diaphragm, or another ignition problem.

[Guest]

Thanks for the input and I will revisit the HT ignition coil.
Rimmer Bros show two types
High performance 6v ballasted, or
Luminition Optronic Mega spark 12v ballast
which is recommended?
Our Stag Mk2 was shown as date of build 31st December 1974

[Lingen]

BigH.
There is something a bit suspicious about the Mega Spark 12v ballast description, as ballast coils are always around 6v, as quoted for the High Performance one.
Any electronic system that I have bought has always advised that it is used in conjunction with the components fitted to the car by the manufacturers. I would advise therefore that you find someone who can supply you with a good quality standard ballast coil. Mega Spark, High Performance etc. are just marketing ploys, and I doubt if they will improve the performance of you stag at all. Keep it simple, with good quality components, and the engine will run as it should.
Mike.

[Guest]

Thanks for the suggestion

[Carboy0]

Had you thought about fuel vapourisation?

[Guest]

Had you thought about fuel vapourisation?

Thanks for the suggestion
How do you overcome fuel vapourisation?
Is it a case of using different fuel pipes from filter to carbs or what?

[Joseph]

Hi Guys, I’m having the exact same problem with my Mk2. Runs fine from cold but leave it running for 10-15min and it cuts out when engaging drive. Did we find a solution in this thread?

[Goldstar]

Morning Joseph and welcome. It’s a tricky fault find. Could be ignition related or (less likely) fuel.

How old and more importantly, what condition, are the ignition components coil/ht leads/rotor arm/distributor cap. Does the coil feel hot after a short while? Dissy cap and rotor arm may be damaged and heat is making the damage more significant (ie a crack opens up more) only to return to looking normal when cold. Electronic ignition or points? If Lumenition with a chopper in the dissy, is the chopper damaged? The Lumenition has a connector just outside the dissy body. Is that good?

conversely when I had a fault with poor running it was fuel - the earth to the fuel pump was bad so under load the engine didn’t get enough petrol. Worth trying the pump with the pipe to the carbs disconnected to check you are getting a good flow.

let us know the answers re ignition components bearing in mind new stuff (especially coils it seems) can fail after a short time.

[Joseph]

Hi Goldstar, thanks for the suggestions. The car goes into the garage this week. I’ll mention your thoughts to the mechanic. I’m using a local garage but they have a classic car specialist. Fingers crossed they identify the problem. If not then I’ll have to take it to Enginuity or Stagbay.

[jbuckl]

Once any ignition foibles are sorted, I’d be checking for air leaks post throttle, using a volatile liquid spray on or around all joints.
Use a can of brake and parts cleaner… if you notice revs rising…. You’ve located the air leak.

Wrt ignition, keep it ballasted & use a dry resin coil …. Viper or similar.

[Stag About Town]

Once any ignition foibles are sorted, I’d be checking for air leaks post throttle, using a volatile liquid spray on or around all joints.
Use a can of brake and parts cleaner… if you notice revs rising…. You’ve located the air leak.

Wrt ignition, keep it ballasted & use a dry resin coil …. Viper or similar.

Agree with the air leak theory. I had a similar problem early in my Stag ownership. Cured it by simply putting fuel line hose clips on all the carb connections instead of just push fits. If clips are already fitted I would just check tightness. John

[sujitroy]

For the air leak, remove the oil filler cap with the engine on, if the engine runs rough or the idle speed reduces, you can rule out a leak.