alaric Posted July 6, 2019 Report Share Posted July 6, 2019 TR4 Misfire I have owned wetliner TRs since 1962 , my present TR4 since 1984 and thought I knew the engine fairly well. But I have a problem and have run out of ideas for fixing it. The car has always run well on SUs and a Facet fuel pump, and for the last 10 years or so with an electronic 123 distributor, but recently it has started to misfire badly. Starts promptly hot or cold, idles well and revs freely. Seems to run normally on very light throttle and will maintain 50mph on the level, but as soon as the throttle is opened to increase speed or climb a hill the misfire cuts in. General Mechanical Overall good condition. No induction leaks. At idle 21"Hg vacuum. Cold/dry compression test, all cylinders read 160psi. Valve clearances checked and adjusted to 0.012” Fresh petrol 95 octane good fuel flow with/without filters. Fuel flow not measured but flow and pressure seem OK Fuel tank removed and flushed, but fairly clean. A small piece of plastic was found in the tank outlet union which I thought was the cause of the problem, but this has proved not to be the case. Fuel pipes blown through with compressed air. Float levels checked. Jets and needles inspected and seem OK SU carbs set slightly rich. Run with/without air filter Ignition New plugs New ignition leads New coil New rotor arm New distributor cap Alternator disconnected. Short Vee belt running water pump only. Hot wired with +12v direct to coil New earth wire, distributor body to engine. Extra earth wire engine to battery negative. 123 Distributor returned to Dutch factory, some electronic parts replaced. All these changes and checks have had no effect on the misfire. What have I missed, what else can I try? Dick Goodey Quote Link to post Share on other sites
TR 2100 Posted July 6, 2019 Report Share Posted July 6, 2019 Symptoms are consistent with a weak spark. Did you replace the condenser? Even new ignition components can be faulty, especially coils. I assume rotor arm is a top quality item, e.g. from the Distributor Doctor. AlanR Quote Link to post Share on other sites
ctc77965o Posted July 7, 2019 Report Share Posted July 7, 2019 Worn cam? Clearance is correct but valve not opening?? Quote Link to post Share on other sites
alaric Posted July 7, 2019 Author Report Share Posted July 7, 2019 To AlanR Yes, at first I thought it was an ignition problem, but the car has been fitted with a 123 electronic distributor for many years. No condenser. The 123 is built in a Bosch body and uses Bosch cap and rotor arm, original and recent replacement. Have never heard of Bosch producing duff stuff. To Dave No loss of power before misfire problem so I doubt worn cam (I had that with a fast road cam about 10 years ago, now running a standard TR4A profile). I will measure valve lift next time I take the cover off. Thanks to both Quote Link to post Share on other sites
RobH Posted July 7, 2019 Report Share Posted July 7, 2019 The Bosch rotor arm has a suppression resistor built into it and its not uncommon for that to cause a problem. https://www.tr-register.co.uk/forums/index.php?/topic/54044-123-distributor-catastrophic-rotor-failure/ http://www.da7c.co.uk/technical_torque_articles/bosch_distributors-ROTOR ARMS.htm Quote Link to post Share on other sites
RogerH Posted July 7, 2019 Report Share Posted July 7, 2019 Have you checked the oil level in the SU dash pots Roger Quote Link to post Share on other sites
alaric Posted July 7, 2019 Author Report Share Posted July 7, 2019 RobH Reading those links has shattered my faith in German engineering! Externally, both my Bosch rotors look OK. RogerH Yes. Wilko's best 20-50. Quote Link to post Share on other sites
RogerH Posted July 7, 2019 Report Share Posted July 7, 2019 Did you replace all the ignition components one at a time (giving each a test run). If not, have you still got all the old parts. If yes then refit them one at a time plus the test drive. Usually it is only one components that goes iffy. Roger Quote Link to post Share on other sites
stillp Posted July 7, 2019 Report Share Posted July 7, 2019 17 hours ago, alaric said: Starts promptly hot or cold, idles well and revs freely. Seems to run normally on very light throttle and will maintain 50mph on the level, but as soon as the throttle is opened to increase speed or climb a hill the misfire cuts in. Sounds to me like something limiting the fuel flow. I had a similar problem, only cured by removing the float chambers and float valves, then turning the engine over on the starter (mine is a mechanical fuel pump). I'd already blown through the fuel pipes but I think there was something stuck in the fuel duct inside one of the carbs, that air wouldn't shift. When you rev the engine with air cleaners removed, are both pistons lifting? Pete Quote Link to post Share on other sites
Rob Salisbury Posted July 7, 2019 Report Share Posted July 7, 2019 Check the two coupling links that join the throttle spindles, they sometimes partially break but look to be complete until you open the throttle wide, at this point one of the carbs shuts down and you get the misfire, ... this happened to me on both my TR and a Triumph 2000 (Stromberg carbs but the same link system). Cheers Rob Quote Link to post Share on other sites
Hamish Posted July 7, 2019 Report Share Posted July 7, 2019 This is what you call a misfire !!!! It was fuelling. !! Quote Link to post Share on other sites
stillp Posted July 7, 2019 Report Share Posted July 7, 2019 Ouch, that hurt my ears! Quote Link to post Share on other sites
tim hunt Posted July 7, 2019 Report Share Posted July 7, 2019 I have had a 123 on my 4A for 12 years and not a single problem so far. However, I always carry the original Lucas distributor and leads as belt and braces. Just a thought Dick - if you still have the original distributor why not try it, if it has no effect on the misfire at least you will have eliminated the 123 as a potential culprit. Tim Quote Link to post Share on other sites
alaric Posted August 5, 2019 Author Report Share Posted August 5, 2019 Finally cured the misfire. It was a white gunge, consistency and appearance similar to silicon sealant. Not really sure what it was, but presume it was introduced in a bad batch of fuel? The bulk of the gunge was in the pipe between tank and carbs and because it was semi fluid it allowed only small quantities of fuel and compressed air to flow. After several attempts I believe I have finally got rid of it. Thanks for all the helpful suggestions. Quote Link to post Share on other sites
stillp Posted August 5, 2019 Report Share Posted August 5, 2019 Had the tank been slosh sealed? Pete Quote Link to post Share on other sites
RogerH Posted August 5, 2019 Report Share Posted August 5, 2019 The original Mark 1 Slosh is affected by Ethanol in fuel. Roger Quote Link to post Share on other sites
alaric Posted August 5, 2019 Author Report Share Posted August 5, 2019 No Slosh Seal. Never heard of it until now. Just Googled to find out what you were referring to. What is the link between Slosh and white gunge? Quote Link to post Share on other sites
RogerH Posted August 6, 2019 Report Share Posted August 6, 2019 The original Slosh could be affect by the Ethanol - go soft and start to peel off (so I have heard) The latest version is safe against Ethanol. (so I have heard) Roger Quote Link to post Share on other sites
stillp Posted August 6, 2019 Report Share Posted August 6, 2019 16 hours ago, alaric said: No Slosh Seal. Never heard of it until now. Just Googled to find out what you were referring to. What is the link between Slosh and white gunge? Someone posted a while ago that they'd had a fuel blockage due to slosh sealant peeling off and clogging the fuel feed. Pete Quote Link to post Share on other sites
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