Guest Cherrywood Posted April 6, 2004 Report Share Posted April 6, 2004 I recently bought myself a 1969 TR6 , it is in excellent condition but have discovered a misfiring issue. It only happens sometimes, it seems to happen when I put a bit more revs into the engine and then it happens the whole time after that. It has also stopped driving once while I was cruising at 30 mph. The engine just kept misfiring until it cut out. Then I left it alone for 10 mins and when I restarted it drove perfect. I wonder could it be a fuel issue?. I am running on unleaded fuel with a shot of lead replacement in it. It has triple Webbers. You ideas would be greatly appreciated since I am very worried about taking it out with this problem. Quote Link to post Share on other sites
marvmul Posted April 6, 2004 Report Share Posted April 6, 2004 Of course there are a lot of possibilities. Recently there seems to be really bad rotors that only last a hundred miles or so : the isolating material degrades when warm and the spark is earthed via the distibutor shaft. I had one that completely failed and one that made the engine misfire. The name Lucas(no A/AB181 part no DRB106C for a TR6) is on the box, but there is no brand name on the rotor itself. I heard from rotor failures of other TR owners and also in the magazine Practical Classics this issue was mentioned. Quote Link to post Share on other sites
Guest Cherrywood Posted April 6, 2004 Report Share Posted April 6, 2004 Thanks for your reply. I thought I'd try this and I replaced the rotor arm since the issue started and but it is still occuring. Quote Link to post Share on other sites
JRCWeedon Posted April 6, 2004 Report Share Posted April 6, 2004 You could try checking the float chamber levels and also that you are getting the right pressure from the pump. A visit to a rolling road might be a good idea they could replicate the problem and hopefully sort it. I have always found a visit to a RR money well spent. Regards John Quote Link to post Share on other sites
JohnC Posted April 6, 2004 Report Share Posted April 6, 2004 Sounds like a problem I once had with e TR7. Dodgy points in that case. Worth fitting new points just in case? John Quote Link to post Share on other sites
Guest Neil Russell Posted April 6, 2004 Report Share Posted April 6, 2004 you seemed to indicate that the car was missing under load? if so then the Condensor could be the source of the problem. The coil could be at fault. if the fault is intermittant then I would err toward an ignition problem rather than fuel. Neil. Quote Link to post Share on other sites
JohnC Posted April 6, 2004 Report Share Posted April 6, 2004 Good point Neil. I don't remember ever fitting new points without a new condenser. My '7 may have had a dodgy condenser, not points. Whatever, I replaced both and the problem went away... John Quote Link to post Share on other sites
Red Leader Posted April 6, 2004 Report Share Posted April 6, 2004 Check the quality of the crimp joints on all the 12 volt spade terminals to and from the coil and distributor. I chased a similar problem around for ages, then when a friend suggested this it cured it in an instant Quote Link to post Share on other sites
Richard Crawley Posted April 6, 2004 Report Share Posted April 6, 2004 If you were running a PI system I would start with that but as you are on carbs, faults like this usually turn out to be electrical rather than fuel related. Quote Link to post Share on other sites
Tom Fremont Posted April 6, 2004 Report Share Posted April 6, 2004 Like Richard and others say, probably an electrical issue. I have run triple Webers on my '250 for about 60,000 miles and so far they've been very consistent. In addition to the foregoing posts, I would add that the lovely repro battery cables (+) are not soldered to the clamps, and can cause sudden death as you describe, only to promptly revive when re-started. I've soldered two of them on my cars... Glad to know someone else is running Webers ( was beginning to wonder! ) and will gladly impart tips from my experiences. :: Quote Link to post Share on other sites
Guest ron Posted April 6, 2004 Report Share Posted April 6, 2004 Don't know if this is of any relevance to a TR6 but years ago when I had an Elan it was quite important that the Webbers were not bolted tight to the manifold, they mounted on a double O ring plate and the nuts that held the carbs were only nipped against a double spring washer called a 'thackery washer' thus allowing the carbs a bit of protection from engine vibration. If you tightened them up hard you got similar symptoms as you describe caused by the fuel frothing. Ron Quote Link to post Share on other sites
marvmul Posted April 6, 2004 Report Share Posted April 6, 2004 Sometimes you can year sparks jumping, for instance in the distributor. Misfiring is more likely a matter of the high tension circuit of the ingnition. No ignition at all is more likely to be a fault in the low tension circuit, but not always. I sometimes found the cause of a misfire by running the engine in a dark garage(not too long!) and looking for short circuits : sparks jumping between cables and engine, over the spark plugs and so on. Old ignition cables can also be the culprit : when the are getting old, the resistance can be higher, especilly with the silicone types, and the ignition spark finds a shorter way then : short circuit in the rotor, distributor cap, coil... Quote Link to post Share on other sites
Tom Fremont Posted April 6, 2004 Report Share Posted April 6, 2004 An afterthought concerning the fuel system: often Webers are set up with electric fuel pumps which then have to be regulated so as not to produce excess pressure. Too much pressure and the carbs will flood, etc. My only experience has been with the stock mechanical fuel pump used on U.S. cars, and its pressure is quite OK for Webers, as is the output. You may want to rule out fuel pump/pressure issues in your case... ??? As for the soft mounts, I have run without them on a '250 and had no problems whatever. I use softmounts now though space barely affords the option on TR5/TR250 and I think '69-'70 TR6 due to the right side wheel arch. 6-cyl engines are sufficiently smooth to bypass the frothing issue, apparently. Quote Link to post Share on other sites
Guest Cherrywood Posted April 7, 2004 Report Share Posted April 7, 2004 After all that, I first checked the fuel pump and low and behold , it was filthy.I will test the car out now but am pretty sure that this could have been the problem. Fingers crossed. I will need to bleed the fuel tank completly by the looks of it. Quote Link to post Share on other sites
Tom Fremont Posted April 7, 2004 Report Share Posted April 7, 2004 Congratulations on your discovery! Note the carbs have fine wire mesh filters at the fuel inlets; you may need to clean these too. These should effectively stop anything large enough to cause problems downstream. I employ an inline fuel filter, too. Cheap and easy to replace periodically. Quote Link to post Share on other sites
Guest ron Posted April 7, 2004 Report Share Posted April 7, 2004 Glad to know someone else is running Webers ( was beginning to wonder! ) and will gladly impart tips from my experiences. :: Tom I would gladly join you and fit Webbers, unfortunately they're a bit out of my price range Ron Quote Link to post Share on other sites
Tom Fremont Posted April 7, 2004 Report Share Posted April 7, 2004 TomI would gladly join you and fit Webbers, unfortunately they're a bit out of my price range Ron Hang in there, Ron - I recently found a complete setup on ebay ( comprising 3 40DCOE2s + manifold + linkage ) for the equivalent of 300 quid - and I hardly ever find bargains! :: Quote Link to post Share on other sites
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