engine missing when warm

[Basilbrush14]

Hi all, I have just bought a mk 1 stag with auto box, triumph engine and have a couple of problems.

Problem 1, From cold start up and the drive is brilliant but after stopping for half an hour or so when warm/hot engine starts fine and revs ok but try to drive and it lacks power and is missing. This lasts for about a minute when it clears and from then on drives and responds perfectly. (Makes it awkward when pulling away into traffic). I thought it was a fuel supply problem but the pump is functioning fine.

Problem 2. After switching off the ignition light comes on and stays on. I have resorted to disconnecting the battery to turn it off, when the engine has cooled and battery reconnected the light is off. This does not happen every time but more often than not.

I do not know the car history so have just done an engine flush, I have refilled with new anti freeze and added water wetter. Oil and all filters, and a set of plugs. There are no knocks or rattles and the engine pulls like a train, there are no oil leaks or water leaks at all. What I have noticed is that the top hose appears to have been sucked in/contracted while cooling.

Has anybody experienced similar issues? I would love to hear the remedies if you have but all advice will be gratefully recieved. I am a diy mechanic but will have a go at anything.

[flying farmer]

Misfire after a hot start is a very common problem, usually down to heat soak boiling the fuel in the carbs and this forces fuel into the inlet manifold resulting in a rich mixture until it has burned the surplus. Fuel pressure regulators on the supply line help, or fit a switch to the fuel pump electrical feed and turn the pump off before switching off the engine to lower the level of the fuel in the float chambers.

When I had the Holley carb on my engine it would idle for a minute or so on the fuel contained in the float chambers, or get me about half a mile if I forgot to switch the pump on again, but flicking the switch instantly restored power and saved red faces!

Don't know much about alternators, but if it still has the original mk1 system with separate regulator you may need to convert to the mk2 alternator

Regarding the top hose sucking flat, check the cap on the expansion bottle has the little spring loaded cap in the centre of the rubber that lets air in as the system cools down, and is not a plain one that will create a vacuum.

Neil

[Basilbrush14]

Thanks Neil,
Like I said, new to the Stag but a car I've always wanted, aware of all the overheating talk but unaware of heat soak, - it makes sense, the engine does get extremely hot. The tip re the switch is something that sounds like a good idea and one I will pursue. - I am used to the half mile bit, I have an imobiliser and have forgotten about it on a couple of occassions which results in 'death' after a very short time.

I have looked at the alternator and can see a control box on the inner arch adjacent to it marked 4TR alternator control (Lucas). The light does not come on after every switch off but the thought with me is that this is a drain and obviously something live when all should be dead.

Re the rad. cap it looks like a normal one, it is spring loaded and the centre brass plate is spring loaded and appears to work but what you say sounds useful and a change of cap is not a bank breaker. I do know I need deep pockets to own and run a stag, thats why I've left it till now to join in.

Thanks again
Alan

[Stagsongas]

Alan,

An overheated (due to 'heat soak') Ignition Coil can display exactly the same symptoms.

I had a similar problem last year. I carried a cold coil in the boot and swapped it instantly (wiring only) for the hot one when the misfiring occurred to prove the theory, and did just that. The engine ran perfectly straight afterward.

My coil is now mounted on the bulkhead, not on the engine. I've had no further problems of that kind, even after 100 relatively slow miles in very hot weather last Sunday.

This is not to say that problems with fuel vaporising in the pipes and carb.s does not occur, it certainly does. I was ahead of the game in the diagnostics dept. on this one as my car does not run on petrol (unless I want it to!) so the misfiring could not have been due to any heat soak effect on petrol.

As for the Ignition light issue, I agree with Neil that the Alternator Regulator is probably at fault, and the best cure is to fit an ACR or later type replacement Alternator as they have the regulator built-in. Wiring out the 4 TR unit is quite straightforward to complete the upgrade.


Good Luck

Steve

[73stagman]

Lots of people are having this issue at the moment. Overheating coils....make sure your coil is not sitting too low in its mount and touching any part of the manifold. If you replace the coil dont by cheap buy quality economically!
Replacing coils is another minefield though so good luck and hope you get this sorted.

[KOY 23]

Lots of people are having this issue at the moment. Overheating coils....make sure your coil is not sitting too low in its mount and touching any part of the manifold. If you replace the coil dont by cheap buy quality economically!
Replacing coils is another minefield though so good luck and hope you get this sorted.

I like it.

[73stagman]

I like it.

I know its a bit of a conundrum but I guess the point is to try to buy known quality items (in this case Lucas or Bosch parts..because they are known to be pretty good quality) but to buy them at the best price you can find? Its not always easy and you may have to do some searching. Probably for some its easier to just pay the higher price because they can afford to but a good number of the rest of us are looking to save pounds and pennies!
I know if you go to high street motor parts outlets you will pay a high price for the better parts and there will be nice shiny bits of unknown manufacture and therefore unknown quality at a lower prices. The same thing can happen on line with a nice looking shiny picture and the words "High quality 100% positive feedback" to catch your attention. But you can buy proper high quality parts online or from one of our known Stag parts suppliers for better prices if you look hard enough. (Some of these things are not unique to Stags though....so you dont have to pay the "Stag" premium)
I saved a load of pounds on my Edelbrock 4 barrell carb by going "off piste" as it were and buying from a little known race car parts supplier found by chance with an online search. Its exactly the same carb, new, setup as best as possible, with all the Edelbrock gubbins that comes with it stickers cds manuals etc.... I paid a good bit less than 300 pounds including the purchase taxes and delivery fees. (Not off ebay either!) proper bargain I thought!

[Basilbrush14]

Thanks all,
lots to look at and try, I appreciate the advice - my coil does sit a bit low so thats an easy fix.

Cheers

[Guest]

Hello, did you solve your carb problem?

First check the very correct setting of both air vent lever! I have had problems setting up my MK1 carbs correctly (hot start problem, fuel is seeping through the injetion tube/needle into the intake manifold caused by overload pressure into the float chamber).

After changing the carbs to MKII type and did the correct carb setting the problem has gone!! Setting up MK1 air vent lever is difficult, because adjusting the idle screw affects the air vent position directly. Again and again I had to correct the carb settings!

Setting up MKII carbs does not permanently affect the air vent position. Once set up the air vent valves correctly, they were not affected by adjusting the idle screw any more...,.
Requirement: Intact needle valves, exact Carb balancing, correct setting of float chamber level, check poor/rich setting, and check the opening of the temperature compensators too.

Regards Claus

[Guest]

(I thought it was a fuel supply problem but the pump is functioning fine)

Have you done the petrol cap release, listening carefully for a sucking sound? I have had this problem on two different cars. If not sure just run without securing cap properly.

John.