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Happy New Year everyone.

Throughout the 4 years I have owned my 1964 TR4 it has suffered from "running on" when the ignition is switched off. The car has an electronic 123 distributor. I have replaced the plugs with cool running NGK BP8HS units but still the car runs on. I have resorted to stalling it to prevent this happening! The vacuum pipe rubber connectors were renewed in 2016. I slightly retarded the timing but this merely flattened performance without curing the problem, so timing is back where it was. I believe the engine has a standard cam.

 

Any pointers to curing the problem?

 

Best wishes Willie

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Happy New Year Willie

I guess that bad fuel and excessively high compression ratio have been ruled out.

Long shot, but do have you an electric fan fitted that acts as a dynamo and continues to supply a LT voltage, after the ignition is turned off until the fan eventually winds down and the engine stops some seconds later.

(I have switched to BP5HS for everyday running and they work fine with a standard engine albeit that they run a little hotter than the "standard" BP6HS)

In the old days with running on you increased the octane of the fuel and or decoked the engine.

Regards

Rog

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It's dieseling, pulling through the premix in the inlet manifold. If the colder plugs haven't worked there's something else in the chamber remainin g hot enough to ignite the mix. I agree with Rog about an electric fan sometimes providing enough power for LT use, easily checked by isolating it electrically and trying on runs, failing that Anti dieseling kits used to be popular comprising of a valve in the inlet manifold which opened when the ignition was turned off reducing the mix and allowing the engine to stop although stalling works ok too.

 

Mick Richards

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Thanks Rog & Mick. The car is indeed fitted with an electric fan, along with alternator conversion. I fitted the cool running plugs after a contact made the suggestion. The engine previously had Champion L87YC plugs installed. What is the "dieselling" kit you refer to? I much refer a gentler way of stopping the engine than stalling! I assume the fuel I use isn't that poor [usually Texaco unleaded].

 

Best wishes Willie

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Hi Willie,

there is a thread on here somewhere about Shell being super duper fuel and keeps the internals clean.

Thus this suggests that the other fuels may cause gunking up etc.

 

Running on can be caused by carbon hot spots (cheap fuel).

Have you got a camera you can stick into a spark plug hole and have a look to see the condition of the top of the pistons.

 

A squirt of Redex in the fuel.

 

Roger

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Thanks Roger. I don't have a camera thingy, but if you are suggesting Redex additive, I'll give it a whirl. What ratio of Redex to litres of fuel would you suggest.

I haven't had a response from Mick Richards to the anti-dieselling kit. If such a device can be installed without too much aggro, I'll also give that a try. A bit uncool to arrive at a classic car show and demonstrate that the TR4 engine really IS a tractor!!

 

Best wishes John

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You can find a Ford anti run on valve on eBay from time to time. They're easy to tee into a vacuum servo line if you have one. It takes a feed from the white ignition wire to close the valve whilst running then when you switch off the valve opens the inlet manifold to ambient air.

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Willie, If a tank of 99RON cures it then its definitely auto-ignition, somtimes called dieseling. NOT preginition from a glowing ember, that would have killed pistons long ago. Slide 84,121, 120:

https://supertrarged.files.wordpress.com/2016/07/combustion-talk-iwe-2016-v2-ppt.ppt

Autoigntion: The engine will seem to jump back to life when it has almost.....but not quite....... stopped. The mixture autoignites withut any spark just with heat , pressure and time. Its a chemical reaction and needs time to trigger a flame. A high octan fuel will raise the a/i temperature by about 20-30 degrees C compared with a 92-95 RON fuel, roughly. So if high RON fuel cures it you're looking for a quite small temperature decrease to stop it running on.

My first port of call would be plugs, becasue 20-30C is small beer compared with their normal operating tmeperature:

http://prntscr.com/dqcqk8

Its easy to be caught out by heat ranges going in opposite directions by different manufacturers:

https://www.boschsparkplugs.net/learning-center/article/225/heat-range-conversion-chart

I would try two or three gades colder, maybe 3. It wont harm the engine, the limit being fouling with oil or when cold-starting.

 

Just in case you're using waterlees coolant- that can itself can raise temperatures enough to trigger a/i It was a 4-pot and hope the owner who discovered this will be along as I've lost the thread

 

Peter

Edited by Peter Cobbold
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My TR3 has this issue. The PO recommended the stalling technique to me and reasoned that it was the high compression ratio of the modified engine. With a little practice I can stall it almost without people noticing - particularly if you apply the foot brake firmly so there is no lurching!!

 

Interestingly since doing the RBRR the running on has virtually ceased maybe the 2000-mile blast burnt off any carbon deposits! :huh:

 

Someone else told me about NTC's trick but then again I worry about flooding the chambers with fuel washing down the bores...............

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I like Neils' trick. I think it will work because the fuel droplets will evaporate in the combustion chamber, but not burn, so cooling the plug. And the extra number of spins from a blipped engine gives the plugs more time to cool off before the rpm fall so low that a/i can light the flame.

Peter

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I find that my car runs on after a spirited or a long drive but if I don't switch off immediately and let the engine idle for ten seconds the problem goes away

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Here's a link to another post regarding setting the car timing to stop the dieseling

 

http://www.tr-register.co.uk/forums/index.php?/topic/40002-first-drive-if-the-season/?hl=%2Banti+%2Bdieseling

 

and here's a link to Moss where you can have your choice of 3 different models

 

http://www.moss-europe.co.uk/catalogsearch/result/?f=Anti+diesel+valve&q=Anti+valve

 

Ka Boom Tush.. IIIii tttthhhaaaannnkk yyyyyoooouuuuuu.

 

Mick Richards

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Shell V-Power cured it for me!

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A big thank you to everyone! You have all supplied food for thought, things to test, and resolutions.

 

I'll need to wait for spring to test the options. Whilst I have a very solid car now, both a Spitty Mk3 and a TR4A back in late 70s early 80s showed me how salt likes to munch on British steel. The car gets good runs as Herefordshire is both very quiet for driving around and is next to South Wales where we frequently take the car. Decent roads for a blast and to Shows!!

 

Best wishes to all Willie

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The electric fan acting as a dynamo supplying power to the coil is a problem i encountered after fitting a Revotec fan and following the wiring diagram from Moss.

 

The attached wiring diagram given to me by an Auto electrician here in Perth solved the problem and it may solve yours as well.

 

Graham

post-10268-0-00404300-1483362248_thumb.jpg

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