Running on!

Engine Oily Bits, Ignition, Fuelling, Cooling, Exhaust, etc.
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bigstraight6
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Running on!

#1 Post by bigstraight6 » Sun Apr 16, 2017 6:57 pm

My Mk2 2000 on Stromberg carbs is driving so well but runs on when the ignition is turned off, an issue which is very frustrating. I'm running on NGK BP6ES plugs, is there a hotter running plug I could use? I can't stress enough how well the car is driving apart from this running on performance.

I've also been told that the Stromberg carbs (which I took apart and rebuilt with new diaphragms and needles) are not that good and replacing with SU carbs would be a good move? Or perhaps I'm missing something obvious!.....

Dazzer
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Re: Running on!

#2 Post by Dazzer » Sun Apr 16, 2017 8:58 pm

Strombergs are good and react faster than SUs. The running on can be minimised by slowing down the tickover. Cheers Dazzer

Clifford Pope
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Re: Running on!

#3 Post by Clifford Pope » Mon Apr 17, 2017 6:42 am

Plug heat range terminology is confusing. As I understand it, a hotter-running plug means one that gets hotter, not one that can stand hotter combustion. So if you want to lower the temperature of the plug tip so that it doesn't provide a hot-spot for triggering running-on, you need a cooler plug not a hotter.

Combustion temperatures increase as you advance the ignition timing nearer to the knocking point. It's always said to be good to run the ignition as far advanced as possible just short of knocking, but the penalty is any red-hot carbon or the plug tips will tend to trigger running-on.
I found the 2000 engine especially sensitive to pinking and running-on. I read that unleaded petrol runs hotter than the old 4-star, which some engines are more sensitive to.

I did sometimes convince myself that letting the engine idle for a short while before switching off reduced the tendency.

bigstraight6
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Re: Running on!

#4 Post by bigstraight6 » Mon Apr 17, 2017 8:03 am

Thanks for the replies, mentioning fuel I don't think old cars like the grade of petrol
we have today, I use Castrol valvemaster plus additive as it's an octane booster. I will certainly have a play with the idle speed settings to hopefully sort the problem.....

Mike Stevens
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Re: Running on!

#5 Post by Mike Stevens » Mon Apr 17, 2017 7:32 pm

I've found that running the mixture a little bit on the rich side can help with running on.

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pete lewis
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Re: Running on!

#6 Post by pete lewis » Wed Apr 19, 2017 8:16 am

my mk2 has SU of which i have a avid hate of them , take apart both makes and lay out the component parts and compare the engineering in both its easy to see which is designed and which is a load of meccano ,

both can do a good job but stroms are far better in trouble free and economical terms ,, there are less needle specs available for Stroms if you need to play around with aftermarket must have filters.

fuel addatives are made for guys to buy , its not needed just use a 97-99ron fuel and keep the ££s in your pocket, you will find the addative will add to your problems not solve them.

i ran a emission test dept for our trucks and in the 70-80 lots of things changed , we did some tests on addatives as a way or reducing and in most tests the HC and C0 had increased vs plain fuel . the later products may be better but they are not needed in our cars

if you get problem with correct timing correct idle speeds correct mixtures then you could add a anti run on valve in the manifold to open when you switch off , the additional air weakens and it wont run on

some GT6 had this added just an idea

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Clifford Pope
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Re: Running on!

#7 Post by Clifford Pope » Tue Apr 25, 2017 7:37 am

I wonder if pressing the brake pedal would have the same effect, causing the manifold to draw in air from the servo?

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