john.r.davies Posted May 9, 2012 Report Share Posted May 9, 2012 It runs backwards?? Really??? Then it has to be a a problem that does not involve fuel being ingested from the carburettors, and points to excess crankcase pressure and leaky piston rings providing oil mist as fuel. John Quote Link to post Share on other sites
badshead Posted May 9, 2012 Report Share Posted May 9, 2012 (edited) I sometimes had running on and got used to it as part of the 'fun'. However, recently cleaned the K&N filters and replaced rocker shaft/rockers as it getting a bit loud - unexpected bonus is it no longer runs on. Bill Edited May 9, 2012 by badshead Quote Link to post Share on other sites
Graham Harris Posted May 9, 2012 Report Share Posted May 9, 2012 Hi JFerg, I think you have diagnosed the problem when you say when the temp is in the lower third on the gauge it shuts down ok but when its hotter it runs on. Next time you run it check to see if the cooling fan is running before you shut it off. If it is and it runs on, start it up again and disconect the electric fan then shut it off, you could be in for a suprise. Regards Graham Quote Link to post Share on other sites
RogerH Posted May 9, 2012 Report Share Posted May 9, 2012 Hi Jferg, as Graham states the lecy fan could act like a dynamo when it is running and the ignition is shut off. Also flushing of the block and getting clean water out does not mean the block is clean. The grot that builds up around #4 pot can be solid. I've had the occassional running on on the 4A. I happened to notice that if I turn the ignition key very slowly to the 'off' position it didn't run on. However I think this may be more coincidence rather than a miracle cure. Roger Quote Link to post Share on other sites
Guest ntc Posted May 9, 2012 Report Share Posted May 9, 2012 If it is through a relay? the supply is cut off if not rewire it Quote Link to post Share on other sites
Lord Flashart Posted May 9, 2012 Author Report Share Posted May 9, 2012 Yes mine was occasionally running backwards. Not everytime thought. I'll give it a good drive today and see how it is. I'm fairly sure my rings are in good condition as a recent leak down test showed zero leakage. Hopefully it was just mixture. Paul Quote Link to post Share on other sites
Lord Flashart Posted May 9, 2012 Author Report Share Posted May 9, 2012 (edited) Well drove the **** out of the car today and no run on at all. Also seems to be running a little cooler. I'm now going to hopefully get some miles on the damn thing! Thanks for all the help. The pointers about lean mixture and hot intake were particulary helpful. Cheers John! Paul Edited May 9, 2012 by Lord Flashart Quote Link to post Share on other sites
Mark1965TR4aBRG Posted May 10, 2012 Report Share Posted May 10, 2012 I only get a very even and smooth run on when the Pacet fan is on. Quote Link to post Share on other sites
JFerg Posted May 16, 2012 Report Share Posted May 16, 2012 Mine runs on backwards and roughly. Sometimes more strongly than others. I stall it in fourth gear. Sometimes it will jolt the car backwards, just enough to know that it is running backwards, not enough to actually move the car. What is the approved method for de-crudding the water jacket? Is there a chemical method, or it is strip the block to bare, pop out the welsh plugs, and dig it out with a bent bike spoke? The latter does not appeal even a small amount. thanks, Quote Link to post Share on other sites
RogerH Posted May 16, 2012 Report Share Posted May 16, 2012 Hi Jferg, you could try the 'Radflush' type stuffs to remove any loose surface rust/sediment and then flush out. But this will not remove the solidified lump around #4 pot. To remove this lump you will need to strip it down - head off, pistons/liners out etc Your bent bike spoke will stand no chance - you will need a long tatty screwdriver or similar device assisted with a hammer. Roger Quote Link to post Share on other sites
JFerg Posted May 16, 2012 Report Share Posted May 16, 2012 Thanks, Roger. No surprise that this does not come as jolly news to me. Perhaps a touch of the inevitable. Denial has not worked as well as I had hoped. cheers, JFerg Quote Link to post Share on other sites
Lord Flashart Posted May 17, 2012 Author Report Share Posted May 17, 2012 My engine is as clean as a whistle internally as I only cleaned it all out a few months ago when I fitted the new liner. It's really not a difficult job. The cause of my run on is almost certainly fuel related. I dropped the jets until it stopped doing it and there were way lower than normal but the plugs are a nice brown colour so I think all is well. Paul Quote Link to post Share on other sites
Prambert Posted May 17, 2012 Report Share Posted May 17, 2012 I had my carbs overhauled recently and the guy who did it has been racing for years - he suggested using the more expensive unleaded fuels (my 4A has had a conversion) from the forecourt from then on - both of these interventions have eliminated the run on.... Quote Link to post Share on other sites
LGFromage Posted May 17, 2012 Report Share Posted May 17, 2012 For my money it is the PCV causing the problem. As well as a flame trap this unit has a diaphragm activated valve. At low intake vacuum (ie when the engine is pulling) the engine breathes into the inlet manifold; whilst at high vacuum (ie idling with no load) the valve closes and the breathing stops. The problem comes when the engine is about to shut down the vacuum disappears and breathing recommences. After a nice sporty run the oil is hot giving off plenty of oily fumes and it is these that are being sucked into the inlet manifold on shut down causing the engine to diesel. Obviously if the engine is cold and there are not many fumes dieseling is less likely to ocur. On the TR4A the problem is made worse by the location of the breather pipe to the manifold. It is located at the rear of the inlet manifold giving a direct route to no3 and 4 pistons. On the six cylinder carburetter engines the PCV is located at a mid point on the inlet manifold thereby making the route more difficult. It should also be remembered that a piston in a 4 cylinder engine will have more suck than one in a six cylinder of the same capacity giving yet more reason to diesel on shut down. So if you do not like dieseling get rid of the PCV and associated oil filler cap and fit a crank case breather - but do not tell the MOT man. My car diesels on shut down but I have got used to it - at least it shows it is running nice and hot. I hope this helps, Tim Quote Link to post Share on other sites
JFerg Posted May 17, 2012 Report Share Posted May 17, 2012 Thanks, Tim, this is an interesting, reasoned, sensible, logical and to me, new, possibility. My car obviously has an overheating issue. The thermo fan and aluminium radiator manage that, but it would be fair to expect more hot oily fumes in a hotter engine. I will try this at the weekend. Luckily, we here in Oz do not have to have an annual MoT. thanks. JFerg Quote Link to post Share on other sites
manray1 Posted May 18, 2012 Report Share Posted May 18, 2012 So if you do not like dieseling get rid of the PCV and associated oil filler cap and fit a crank case breather - but do not tell the MOT man. My car diesels on shut down but I have got used to it - at least it shows it is running nice and hot. On my 4a i removed the pcv and the problem remains. Quote Link to post Share on other sites
LGFromage Posted May 18, 2012 Report Share Posted May 18, 2012 On my 4a i removed the pcv and the problem remains. Did you fit a crankcase breather aka early TRs? If not the oil fumes could be finding another way to the cylinders viz the valve guides. I have to say that if my theory is invalid I won't bother to try it!! Tim Quote Link to post Share on other sites
graeme Posted May 19, 2012 Report Share Posted May 19, 2012 (edited) Tim, I removed the PCV and fitted a crankcase breather but I still get dieselling (running backwards). My engine was recently stripped down to replace a damaged camshaft, and the waterways were given a thorough cleaning all to no avail, the engine does not run hot! I am convinced it has to do with fuelling, maybe the jet height? of the SUs, as when I have Webers fitted, it does not happen at all. Cheers Graeme Edited May 19, 2012 by graeme Quote Link to post Share on other sites
manray1 Posted May 19, 2012 Report Share Posted May 19, 2012 I am convinced it has to do with fuelling, maybe the jet height? of the SUs, as when I have Webers fitted, it does not happen at all. I have strombergs and did a lot of things to cure this problem. I think some engines are not well born. Quote Link to post Share on other sites
Rien Posted May 19, 2012 Report Share Posted May 19, 2012 Flashard, Just some ideas and thoughts, Normally there is no spark when you shut off the engine, so iginition timing are not relevance ( except for temprature). If the electric fan produse enouch energy to power the coil ( I don't think so), The solution is simple, mount a diode of sufficient power in parallel with the motor, (sper direction from + to -). All the Triumph I had for this problem had a bad or worn carburettor system (leaking butterfly's, worn out spidles or SU's with butterfly's with a POP-UP valve!! and no shut off valve! To rich mixture (worn jet and/or needles) and/of to high fload level. External rocker oil feed and no seals give a extra carbon on intake valves and plug's. To high compression ratio give to high temperature, bad cooling system and faulty ignition tyming to. We no there are three parts needed for dieseling, temperature, fuel and air, take away one of them and you have resolved the problem. Cheers, Rien Quote Link to post Share on other sites
Lord Flashart Posted May 19, 2012 Author Report Share Posted May 19, 2012 (edited) Mine turned out to be overly weak mixture. I was following the tuning instuctions for a standard engine, which mine is anything but. Once I stopped following the norm and tuned the engine by listening to it all seems well. Paul Edited May 28, 2012 by Lord Flashart Quote Link to post Share on other sites
JFerg Posted May 27, 2012 Report Share Posted May 27, 2012 This afternoon I disconnected the PCV, plugged it, and ran a breather out to atmosphere off the rocker cover. Then I went for a flogette. No discernable difference to the running on. rats!! JFerg Quote Link to post Share on other sites
RogerH Posted May 27, 2012 Report Share Posted May 27, 2012 Perhaps they just want to keep going - Roger (only here to help) Quote Link to post Share on other sites
manray1 Posted May 27, 2012 Report Share Posted May 27, 2012 Perhaps they just want to keep going - Roger (only here to help) I never imagine that, but i think your are right. Quote Link to post Share on other sites
Lord Flashart Posted May 28, 2012 Author Report Share Posted May 28, 2012 Ran mine for a few miles today and I'm convinced my problem is fuel supply related. It's fine with a full tank, but when the level gets below quarter of a tank It starts to run on. Should be an easy enough fix. Fuel pump is coming off today! Paul Quote Link to post Share on other sites
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