Lord Flashart Posted May 7, 2012 Report Share Posted May 7, 2012 Seems whatever I try this engine now diesels at every shut down. Here is where I'm at. On the advise of a TR specialist I had the previously in skimmed head skimmed by 40 thou. This made the inlet valve overhang very thin, so following the advice of the specialist I ground the combustion chamber sides verticle on this area. I then fitted a solid copper gasket, adapted to the new combustion chamber first, to avoid any hot spots. Then I set the static timing and tblhe carbs as per the manual. On shut down the car diesels really badly. I can stop it by either dragging the clutch slightly or by opening the throttle completely. Niether of which is ideal. I've tried adjusting the timing and even with severely retared timing it still does it. Reset the static timing and tried adjusting the mixture. Rich or lean makes no difference. What else could it be? I didnt have this problem at all until I tried to fit that infernal electronic ignition unit. But now even with the refitted point it still diesels. I'm wondering if maybe the dizzy is just the wrong curve for the engine or maybe the heat off the tubular manifold is having some sort of effect. I've even tried switching to a different brand of high octane fuel. My last resort will be to try and source a new cylinder head that hasn't been skimmed but mine has only had 40 off and is hardy high compression!! Any suggestions? Paul Quote Link to post Share on other sites
manray1 Posted May 7, 2012 Report Share Posted May 7, 2012 Hi Paul, did you fit an electric fan ? If yes, try to disconnect it and try again. Quote Link to post Share on other sites
graeme Posted May 7, 2012 Report Share Posted May 7, 2012 Hi Paul, My TR has always suffered with dieselling except when it was fitted with 40DCOE Webers. Some people say it is the modern fuels but I experienced exactly the same problem in the 70's with my first TR when fuel had lead in it and five star was freely available!! I don't have a solution and have always used third gear to stop the engine. You could try reducing the tickover (700RPM or less) as this seems critical. Cheers Quote Link to post Share on other sites
peejay4A Posted May 7, 2012 Report Share Posted May 7, 2012 You might need to resort to using an anti run on valve, or even two. I think one of the Roger Williams books shows such an arrangement. (null) Quote Link to post Share on other sites
Graham Harris Posted May 7, 2012 Report Share Posted May 7, 2012 Paul, Manray is right , if you have an electric fan this will be generating power after you shut off the ignition if it is not wired right. Graeme i see in your last posting you have the narrow belt conversion so i'm guessing you have an electric fan as well Regards Graham . Quote Link to post Share on other sites
vivdownunder Posted May 7, 2012 Report Share Posted May 7, 2012 Sometimes even the most expert TR engine builders can't find this problem, especially if it's an internal hot spot, rather than tuning related. Letting the engine idle for a short while before turning off can help. Viv Quote Link to post Share on other sites
Icarus60 Posted May 7, 2012 Report Share Posted May 7, 2012 Paul I guess you are running out of straws to clutch at. I assume that the running on is the erratic, engine rocking type of random firing of cylinders, rather than it just being just very slow to respond to the ignition key off, ( due the fan providing a diminishing few volts as it winds down, assuming it is wired through the ignition circuit). It may be worth trying switching off the engine by pulling off the HT from the coil to confirm an internal ignition source or not. ( Is there a clue in that the symptoms started post the electronic ignition being binned). If it still runs on a set of new colder plugs could worth a go? I wish you all the best with this one. Regards Gerry Quote Link to post Share on other sites
manray1 Posted May 7, 2012 Report Share Posted May 7, 2012 If it still runs on a set of new colder plugs could worth a go? same story with colder plugs, Quote Link to post Share on other sites
Icarus60 Posted May 7, 2012 Report Share Posted May 7, 2012 Are you stating a fact or asking a question Manray1? Quote Link to post Share on other sites
Lord Flashart Posted May 7, 2012 Author Report Share Posted May 7, 2012 (edited) Cheers guys, There is an electric fan, but it runs on even with the fan disconnected. I've tried a set of colder plugs. All to no avail. I'm going to try timing again today and I'll try removing the lead from the coil to see what happens! Paul Edited May 7, 2012 by Lord Flashart Quote Link to post Share on other sites
manray1 Posted May 7, 2012 Report Share Posted May 7, 2012 Are you stating a fact or asking a question Manray1? It's a fact as i already try colder plugs with no effect. Quote Link to post Share on other sites
BlueTR3A-5EKT Posted May 7, 2012 Report Share Posted May 7, 2012 Seems whatever I try this engine now diesels at every shut down. Here is where I'm at. On the advise of a TR specialist I had the previously in skimmed head skimmed by 40 thou. This made the inlet valve overhang very thin, so following the advice of the specialist I ground the combustion chamber sides verticle on this area. I then fitted a solid copper gasket, adapted to the new combustion chamber first, to avoid any hot spots. Then I set the static timing and tblhe carbs as per the manual. On shut down the car diesels really badly. I can stop it by either dragging the clutch slightly or by opening the throttle completely. Niether of which is ideal. I've tried adjusting the timing and even with severely retared timing it still does it. Reset the static timing and tried adjusting the mixture. Rich or lean makes no difference. What else could it be? I didnt have this problem at all until I tried to fit that infernal electronic ignition unit. But now even with the refitted point it still diesels. I'm wondering if maybe the dizzy is just the wrong curve for the engine or maybe the heat off the tubular manifold is having some sort of effect. I've even tried switching to a different brand of high octane fuel. My last resort will be to try and source a new cylinder head that hasn't been skimmed but mine has only had 40 off and is hardy high compression!! Any suggestions? Paul Having cut away the combustion chamber and the gasket to match did you taper the liner top edge to match the gasket/combustion chamber? Could be the top edge of the liner becoming the hot spot. Cheers Peter W Quote Link to post Share on other sites
john.r.davies Posted May 7, 2012 Report Share Posted May 7, 2012 (edited) M'Lord F., Running on seems to be a perrenial problem with Triumphs of all marks - possibly with all enhines of this age. So I collated a list of know causes, from the TR's own archives and elsewhere. It is, no doubt, incomplete, but there may be some ideas there: Some ideas on running-on, from TRaction 177, 179, 180 etc Running-on is “dieseling”, where mixture auto ignites, just like a diesel engine that runs without electric ignition. It is due to excessive temperature in the ccombustion chamber. This may be caused by: Weak mixture Excess advance Poor cooling Structural Sediment in block Unequal compressions Cooling system faulty, sedimented. Use water wetter? Adjustable Carbs Mixture too weak Worn jets/needles Worn/maladjusted butterflies Unbalanced carbs Idle speed too high Intake air hot Ignition Excess advance OR excess retard ( may be due to mismatch of UK with US retard parts) Plugs too hot Stnd- BP6ES. Next colder BP7ES. BP8ES should not be a problem Valves Cam timing Tappets tight Others Use max. octane fuel possible The one not listed is truely dieselling, an engine with worn piston rings that with a closed throttle sucks up so much engine oil vapour that it can run on that. But that only applies to worn out engines, and from the work you quote I suspect this isn't possible! But something is fuelling the engine, as well as igniting it (TRiad of fire?) so I'd favour attention to the carburation. John Edited May 7, 2012 by john.r.davies Quote Link to post Share on other sites
MikeF Posted May 7, 2012 Report Share Posted May 7, 2012 Fwiw, I had intermittant running on (also a backfire on quick throttle closure as a further diversion) whch seemed to have been caused by a sticky or slow float valve. I went through the usual ignition/mixture drills and arrived at the float chambers in frustration as the only things left unmolested in the carbs.. Float was low in Carb 1, so I drilled, drained and resoldered it and fitted Grose valves for good measure, no further problems. Mike Quote Link to post Share on other sites
Lord Flashart Posted May 7, 2012 Author Report Share Posted May 7, 2012 Cheers chaps. I'll work through the list and report back. Car at least put a smile on my face again today. Other than the run on its driving really well with great acceleration and power. Paul Quote Link to post Share on other sites
dingle Posted May 8, 2012 Report Share Posted May 8, 2012 Many years ago I had a TR4a with a "run on" problem". I finally cured it by removing the pcv and fitting the road draft tube+ oil cap from an earlier model. The pcv must have been causing a vac. leak. Keeping the idle speed as low as possible and removing all sharp edges in the combustion chambers may also help. Berry Oregon Quote Link to post Share on other sites
manray1 Posted May 8, 2012 Report Share Posted May 8, 2012 finally cured it by removing the pcv and fitting the road draft tube+ oil cap from an earlier model. The pcv must have been causing a vac. leak. I removed the pcv and added an oil catch tank, but sometimes i still have run on. Specially in the summer. Quote Link to post Share on other sites
JFerg Posted May 8, 2012 Report Share Posted May 8, 2012 Flashart, I am sooooooooo pleased to learn that I am not alone. I could stop my 4A running on with really, really cold plugs. Problem was that I couldn't start it or drive the mongrel with them in it. Starting, warming, the changing plugs is not an option. I have even been to the extent of making needles for my SU's, trotting up to Mr Dyno man and having a proof-positive printout that the mixture is now perfect stoiciometric right through the range. Six pairs of needles I made, and now I get invited to Mr Dyno man's kids birthday parties. I run premium unleaded, have flushed out the water jacket, and now run "water wetter" in my coolant. The distributer advance curve has been re-set by the gurus, I've checked that the timing marks are correct, using a dial indicator last time the head was off. By the temp gauge it is over-heating. I have an electric fan that kicks in early and keeps engine temperature mid-scale. Last straw-grasp was a new water pump, which made not one jot of difference. I won't fit air bleed valves to the inlets because that is just not right. BUt neither is stopping the mongrel by stalling it in fourth. It is a beautiful car, lovely to drive, lovely to be in, but I am starting to hate it. My next recourse is to pull the head off again and perhaps take to it with a dremel to remove anything that looks like a potential hotspot. Surely this has been dealt with before and there is and answer for Flashart and myself? JFerg Quote Link to post Share on other sites
TR 2100 Posted May 8, 2012 Report Share Posted May 8, 2012 I was going to suggest trying colder plugs to check a possible problem, but I see the suggestion has already been made. There must be a hot spot somewhere. Even if a background problem is the engine running too hot, making it more liable to running on, there must be a hot spot somewhere. AlanR Quote Link to post Share on other sites
TR 2100 Posted May 8, 2012 Report Share Posted May 8, 2012 Further thought - does it run on on all cylinders? Or does it run on roughly, which would imply a hot spot in some chambers, but not all? AlanR Quote Link to post Share on other sites
Lord Flashart Posted May 8, 2012 Author Report Share Posted May 8, 2012 Mine runs rough so its probably just one or two cylinders. I'm going to try a couple of things, as suggested my liners my be causing a hotspot where the head is relieved, but I'm reluctant to remove the head again as I've only just put it back on. The above list mentions hot intakes. My car has no heat shield over the (wrapped) tubular manifold and the carbs and intake manifold do get quite warm. I'm going to make a heat shield today. Also I noticed that the rear carb had to be set with the jet considerably lower that the front to get the mixture correct. So I'm going to pull that to bits and see what is gong on. I'll report back. Paul Quote Link to post Share on other sites
JFerg Posted May 8, 2012 Report Share Posted May 8, 2012 I don't know how many cylinders mine runs-on on. It's rough for sure, but for fear of crankshaft breakage I don't listen to it for a second longer than is necessary. I fitted a heat shield between carbs and exhaust. It made an improvement, so I wrapped the exhaust headers. Now the heat shield makes no difference. My car has an aluminium radiator, too. This was fitted when I bought the car, and suggests that it has always had a tendency to overheat. In my ownership I've had the head reconditioned and fitted with hard valve seats, so I expect that water flow through the head is as good as it can be. I have also tried various thermostats. I've also run the engine with zero fixed advance, and with 2 degrees of fixed retard, and neither made any difference to the running on. Premium unleaded reduces the running on a fair bit. However, when I tried premium in my previous 4A (which did not ever run on) it merely dislodged 40+ years of crud and dissolved the fuel lines, so be sure that your fuel system is clean and new before trying that. The running on correlates directly with engine temperature. With the gauge in the bottom third it will shut down properly. With it in the upper third it will run on, and around the half way point could do either. I realise that the gauge is only a rough indicator, but there is a pattern there. Desperate times are upon me. I see the only options now as being hot spots in the combustion chambers, or a coolant blockage in the block. I think hotspots unlikely. When I bought the car it had had the "race rebuild", with a daft camshaft etc, and I assume some head work, which would have dealt with that. Or maybe created some... To clear the block would mean a complete strip, which I am not going to do. The coolant is always clean, and the system flushes both freely and clean. So I think that I have dealt with all of the obvious as well as the less obvious and even the obscure, but it still runs on. It is truly exasperating. JFerg Quote Link to post Share on other sites
Lord Flashart Posted May 9, 2012 Author Report Share Posted May 9, 2012 Update. Made a heat shield, better but still a little run on. Dropped the jets four flats. Success!!! Re advanced the timing from previous TDC setting and the car runs really well. I think it's a little bit to rich so tomorrow I'll raise the jets by a flat. Conclusions, My colour tune lies. Reading the plugs is inaccurate. I think it's been running lean despite the colour tune and the nice brown plugs giving a contrary indication. This is all preliminary though as I've not driven it far yet, but previously it dieseled every shut down. Now it's not so at least I'm on the right track. Almost certantly carbs! Cheers for the help lads. Hopefully I can put some miles on the jalopy now. Paul Quote Link to post Share on other sites
graeme Posted May 9, 2012 Report Share Posted May 9, 2012 As I said earlier the problem on my car went completely when I fitted 40DCOE Webers without changing anything else. I think you are on the right lines Paul, blaming the carbs, but I doubt you will cure it completely. Cheers Quote Link to post Share on other sites
Lord Flashart Posted May 9, 2012 Author Report Share Posted May 9, 2012 If I can get to a compromise where it's not every shut down I'll be happy. Occasional wobble is fine but a minute of running backwards makes me want to pull the insurance and make it a garage ornament! Came very close this week to advertising the car and concentrating in my Healy sprite instead. Then a good blast and a possible fix and I'm feeling better about the car. I much prefer the TR to the healey but economically the TR is on the borderline. If I don't get some driving out of it before something else goes wrong it'll be gone before the end of the summer. Hopefully a bit more fiddling and it'll be right. Paul Quote Link to post Share on other sites
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