TorontoTim Posted June 22, 2012 Report Share Posted June 22, 2012 Hi Guys, My normally smooth, reasonably fast and reliable tr4 (currently being given time off from rallying duty) has very recently developed and odd symptom and I was hoping that someone recognises it and can lead me direct to the source before I go round the usual "logical" route ;-) When I acelerate reasonably hard above 3,000 revs, I get a fairly serious loss of power and what appears to be almost total lack of firing. This seems to happen at any speed (and in any gear). However, if I back off on the throttle, the engine will climb more slowly to, say, 4,000. Hard down on the accelerator pedal, and the mis-fire/power loss returns - it comes in and out instantly with a greater throttle opening. As it seems to be hard-linked to the accelerator, I'm thinking fuel. Also, it ONLY happens under load and ONLY at these higher revs - and speed is entirely irrelevant (in that this can happen in first gear pulling away from the lights or at 80+ on the highway). In the (very) brief diagnostics I've done so far, I've checked points gap and damper oil in the carbs (H6). Next I'll go to condenser, new points etc. than back to carbs (springs, needles, mixture, pistons, etc.). Anyone got the magic bullet for this immediately? Thanks! Quote Link to post Share on other sites
Alec Pringle Posted June 23, 2012 Report Share Posted June 23, 2012 Hi Tim, makes me thing of fuel supply to the carbs rather than the carbs themselves . . . . **** in the tank, or the filter, or the pump, or even a collapsing flexible pipe ? That's where I'd start. Cheers, Alec Quote Link to post Share on other sites
TorontoTim Posted June 23, 2012 Author Report Share Posted June 23, 2012 Thanks Alec - makes sense as it's like it doesn't want to dump in fuel to accelerate hard but will gently accalerate fine on a half-throttle. I'll have a look at this over the weekend. Quote Link to post Share on other sites
Menno van Rij Posted June 23, 2012 Report Share Posted June 23, 2012 Hi Tim, makes me thing of fuel supply to the carbs rather than the carbs themselves . . . . **** in the tank, or the filter, or the pump, or even a collapsing flexible pipe ? That's where I'd start. Cheers, Alec Yes, my first thought as well. A guy in my hometown has recently bought an Alvis TF21 that has been used regularly, but gently. The new owner makes more use of the Alvis' power and this car showed the same symptoms. No power under loadd. It turned out that the fuel filters got clogged. Menno Quote Link to post Share on other sites
BrianC Posted June 23, 2012 Report Share Posted June 23, 2012 Those are exactly the symptoms I had earlier this year. Discovered on rolling road session that the fuel filter on the (mechanical AC) pump inlet tubes were softened and collapsing under load due to age. We removed the filter and fitted a new one with considrable improvement (already had new flexible fuel pipe), but was advised to not fit a filter on the inlet side, so removed it and hey presto - another huge performance improvement. So my money is on fuel starvation to or via the pump, due to collapsing fuel line or blockage somewhere between tank and pump. Other possibility is filler cap vent blokage. Plenty of similar experiences recounted on the Forum. [Of course, if you have an electric pump, there may be other issues]. Quote Link to post Share on other sites
TR 2100 Posted June 23, 2012 Report Share Posted June 23, 2012 I would have thought that there would be enough fuel in the float chambers to NOT give your symptons so quickly, but only after a few more seconds of faster running. Clogged up air filters, perhaps? Then look to the electrics (and yes, check out the other good suggestions above). AlanR Quote Link to post Share on other sites
Mark1965TR4aBRG Posted June 23, 2012 Report Share Posted June 23, 2012 I had the same problem a couple of weeks ago and having pulled over I went straight to my two in line fuel filters that catch the crud that detatches itself randomly from the inside of my tank. The primary filter was indeed full of crud, the secondary nice and clean so I gave the fuel pump a prime and trickled home on an almost closed throttle. New filters in and she's back to A1.. I change the filters regularly as they cost pence and carry spares.. Quote Link to post Share on other sites
Mark1965TR4aBRG Posted June 23, 2012 Report Share Posted June 23, 2012 but was advised to not fit a filter on the inlet side Not advice I would ever take and if the filter's in good order along with the pipework there is no issue. Could you imagine the trouble you'd have with sand in your carbs?? Quote Link to post Share on other sites
ianc Posted June 23, 2012 Report Share Posted June 23, 2012 Sounds very much like the problem I had in 1997 when on the way to the International Weekend, and which I described in TR Action 144 (now in Section K3 of the Technicalities CD) - dirt clogging the gauze filter in the pump's bowl when the engine is working hard. Certainly the bottom of the bowl and the gauze filter are the things to check first of all. If you have placed a modern in-line filter between tank and engine, then move it to a position between pump and carburettors. Following that, if you are running with points, then check the gap and try swapping the condenser. Some 45 years ago I had the clip of the condenser come adrift from the body not obvious until I undid the securing screw, but easily soldered back. The result of this bad joint was a misfire, but the car would run. Make sure that the inside of the distributor cap is clean - a build-up of graphite dust (from the inevitable wearing of the contact rod on the centre electrode) can cause a short circuit. Make sure that graphite rod is still there - it is designed to wear away (it's called a service item) and needs to be replaced eventually (Martin Jay, Distributor Doctor, can supply). Replacement is a bit fiddly and one needs to be careful in removing the remains of the worn-out rod, extracting the little spring, attaching the spring to the replacement rod, and then putting the spring and rod into the burrow! Try swapping the coil - could be a partial breakdown. Ian Cornish Quote Link to post Share on other sites
TorontoTim Posted June 23, 2012 Author Report Share Posted June 23, 2012 Thanks everyone. Clearly there is a large consensus on fuel supply so I'll look there first. And Ian, as always, lots of experience and sensible advice from yor years of TR ownership. Reading this sitting on my deck in the morning sunshine with my first coffee, people giving support and advice as they start their own weekends....what a great community we have! Quote Link to post Share on other sites
BrianC Posted June 23, 2012 Report Share Posted June 23, 2012 Not advice I would ever take and if the filter's in good order along with the pipework there is no issue. Could you imagine the trouble you'd have with sand in your carbs?? The filter is superfluous on the inlet side of the pump, provided the tank and supply pipework are in good order, as the gauze does the job if cleaned regularly. Plastic filters become soft after a year or so and hence need changing even if clean. Mine was still clean, even after 15000 miles but was clearly soft and hence collapsing under vacuum. It was fitted on the inlet side when the car was rebuilt 'just in case' of residual dirt in the original tank. I just forgot about it and should have removed or changed it - one of those jobs that seemed to keep getting put back as part of the 'must fit a fuel tap one day' task. I intend fitting a filter on the outlet side, but would not contemplate fitting a plastic one near the carbs again as we had one fail on Lynda's TR4A with consequent engine bay fire. However, the next one I fit will be either a metal one and/or fitted low down at the pump end rather than anywhere near the exhaust or dynamo! Quote Link to post Share on other sites
Mark1965TR4aBRG Posted June 23, 2012 Report Share Posted June 23, 2012 I'd agree with you regarding the lifespan of the plastic jobbies and I change mine regularly or even sooner if they clog.. Quote Link to post Share on other sites
MikeF Posted June 27, 2012 Report Share Posted June 27, 2012 (edited) I would have thought that there would be enough fuel in the float chambers to NOT give your symptons so quickly, but only after a few more seconds of faster running. Clogged up air filters, perhaps? Then look to the electrics (and yes, check out the other good suggestions above). AlanR On reading the symptoms my immediate thoughts were also ignition - probably condensor, possibly points/other, then coil, but as others had already said this better than I could and the forum went off on fuel I thought I'll wait and see. So what did you find? Is it fixed yet? Mike Edited June 27, 2012 by MikeF Quote Link to post Share on other sites
RogerH Posted June 27, 2012 Report Share Posted June 27, 2012 (edited) Hi Tim, read my story about 'holiday chaos'. Very similar symptoms to yours. Yesterday I spent one and half hours by the kerb side sorting out my contact breakers. It took so long I experienced three season changes. Anyway the problem was the thin flexible wire from the 'tag' on the side of the dizzy coming from the coil that goes to the 'live' side of the contact breakers. At both ends of the wire it is gripped, by the end tags, around the insulation and the end of the wire is soldered onto the tag. Alas; one of the soldered ends had detached but was impossible to see until wire was ungripped - whereupon the tag fell off. If all else fails it is worth a look. Roger Edited June 27, 2012 by RogerH Quote Link to post Share on other sites
ianc Posted June 27, 2012 Report Share Posted June 27, 2012 Roger writing about loose connection reminded me that my old TR2 developed a misfire which turned out to be the LT wire from distributor to coil - when I pulled the wire, it fell out of the connector at one end (hidden by the connector's sheath, of course). Ian Cornish Quote Link to post Share on other sites
TorontoTim Posted June 27, 2012 Author Report Share Posted June 27, 2012 Have ordered all usual ignition bits based on my gut instinct (similar to yours, Mike) - yet to arrive and, therefore, fit. Points, Rotor arm (red), Condensor and Coil - I'll have a look at the LT lead too and replace it if it looks in ANY way dodgy. Just replaced all the flexible hoses (and I now smell of petrol - it's SO much fun replacing fuel lines that are lower than the fuel level in the tank...) but haven't test-driven yet. Will report findings in due course. Quote Link to post Share on other sites
RogerH Posted June 28, 2012 Report Share Posted June 28, 2012 Hi Tim, when you 'look' at the LT wire be sure to ungrip the wire from its tag otherwise you will not know if the solder is still doing its job. It maywell be worth resoldering the wire to the tag. Roger Quote Link to post Share on other sites
Rob Salisbury Posted June 28, 2012 Report Share Posted June 28, 2012 Hi Tim, just a thought, ..... while you're looking at the carbs have a careful look at the two flexible throttle spindle couplers, they can partially fracture but appear to be complete and only fail when you give the throttle pedal some welly, meaning that the driven carb suddenly shuts down leaving the carb directly coupled to the throttle linkage to do the work of two. Ask me how I know this? It's happened to me on a couple of occasions on both my TR and on a Triumph 2000 saloon I used to have long ago. First time round with the T2000 it took ages to find out what was wrong and only discovered as I was putting the carbs back having taken the head off to have a look!! .... when TR went in for the same lead foot misfire I knew in an instant what was wrong. Cheers Rob Quote Link to post Share on other sites
littlejim Posted June 29, 2012 Report Share Posted June 29, 2012 (edited) Just throw this in, but probably not relevant for you, as you don't mention electronic ignition. I fitted a Mobelec electronic system to my Merc in '76, which was great. Several years later it developed symptoms of cutting out when I took my foot off the throttle, then firing OK on acceleration. First time was the most exciting, lost ignition going down Macquarie Pass (miles of hairpin bends). After the first two bends the power steering and power assisted brakes had used up all the reserve and it changed from driving like a luxury car to driving like a clapped out truck. Both feet on the brakes to get a result and Schwarzeneger efforts to turn the wheel. (Very exciting) It turned out the lead from the rotor sensor inside the distributor had fatigued, and when the vacuum retard operated, a gap in the lead opened up and no current flowed, when the advance/retard came back to rest the current could jump the tiny gap. (Mobelec sent me a free replacement from the UK, which eventually did the same a long time later, so the points went back in.) Edited June 29, 2012 by littlejim Quote Link to post Share on other sites
North London Mike Posted June 29, 2012 Report Share Posted June 29, 2012 Ref plastic in line filters, had the same problem on LNK last year, died under load, traced back to a collapsing fillter internals (bad batch) replaced, back to 100% so now change annually regardless of mileage and carry a spare Filter location, in the engine bay, high up in the fuel line so easy to see, check and replace if required Run without filters? I don't think so, with tanks getting older and lines breaking down due to Ethanol, a filter is easier to change than a carb is to clean Quote Link to post Share on other sites
MadMarx Posted June 30, 2012 Report Share Posted June 30, 2012 (edited) I didn't read all contributions so it might have been mentioned. I had a similar power loss once. At my engine it was fatigued valve springs. At 3500 rpm with a stock cam the valves start to hop on the seats which make them backfire to the carbs and lowers the compression quite a lot. The engine won't in my case rev higher than 4300 rpm. After changing the set of springs, power was there all the way up. Cheers Chris Edited June 30, 2012 by MadMarx Quote Link to post Share on other sites
TR 2100 Posted June 30, 2012 Report Share Posted June 30, 2012 MadMarx - An interesting one. How did you find out? Trial and error? AlanR Quote Link to post Share on other sites
MadMarx Posted June 30, 2012 Report Share Posted June 30, 2012 I've checked everything and found nothing wrong. Then I pressed down the valves by hand and found it easy to do. I had a new set of springs on the shelf and swapped them. It was a racing set from Cargraphic but the engine was great after the swap. Cheers Chris Quote Link to post Share on other sites
Guest ntc Posted June 30, 2012 Report Share Posted June 30, 2012 Stuart can back you up on that one Chris Quote Link to post Share on other sites
stuart Posted July 1, 2012 Report Share Posted July 1, 2012 Oh yes! Killed a set of springs stone dead last year, mind they`ve had a hard life New set from Racetorations sorted that problem out. Stuart. Quote Link to post Share on other sites
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