Matt1 Posted May 13, 2021 Report Share Posted May 13, 2021 Hi, I’m a newbie and I apologise in advance for my lacking engineering knowledge. I have owned my ‘73 CR model for one week. It is a steep learning curve but I’m really excited to understand how things work and to do as much maintenance as my limited knowledge, the manuals and the Internet forums allow. All in all it seems to run well, have been reasonably well looked after, and have had attention on and off over the years. After the journey back from TRGB, thanks Gary, and a few local trips it seemed to be stuttering a little. Following advice I took it out for a blast and that appears to have cleared that problem. I have yet to check the spark plugs. But it does smell like it’s running rich and I have just taken the air intake connection off between the air filter and the “triumph” airbox that takes the air to the inlet manifold and there seems to be petrol and a bit of grime inside it, also down the connector leading to the air filter. A. Is this normal? B. If not what can I do about it? C. Perhaps I haven’t got the hang of the forum search yet and the answers to these questions are elsewhere, if so, please point me in the right direction. Many thanks Matt Quote Link to post Share on other sites
Steves_TR6 Posted May 13, 2021 Report Share Posted May 13, 2021 Welcome to the forum and to TR6 ownership Matt! the Lucas PI system does tend to run a little rich, it lacks any acceleration enrichment so is better set a little rich to compensate also the system has a ‘fuel enrichment lever’ on the metering unit which is operated by the ‘choke’ knob, this sometimes does not fully return causing richer running whereabouts are you located, am sure a local member will be more than happy to lend a guiding hand ! steve Quote Link to post Share on other sites
Peter Cobbold Posted May 13, 2021 Report Share Posted May 13, 2021 Hi Matt, welcome to the forum. It's a great place to get help, especially for owners looking to learn about fettling thier TR themselves. A PI TR6 will have a rather smelly exhaust when in decent tune. But if at warmed-up tickover you can detect particles of soot on a hand cupped over the tailpipe it might be running too rich. So start with the tongue test, engine off. Suck on the hose from manifold to MU and close it with tip of tongue, if it holds suction for a second or so the MU diaphragm is OK, if nto its punctured and needs replacing. a common fault. It is always a good idea to checl sparks and timing before blaming other faults on the PI. Tweaking the MU can be done, with hlep from here. The plenum chamber often will trap smelly brown fluid, its blowby that has not been sucked back into cylinders. Dont clean off the carbon around the butterflies it helps them seal. Dont worry about forum searches, threads wander anyway. Just ask. Peter Quote Link to post Share on other sites
Matt1 Posted May 13, 2021 Author Report Share Posted May 13, 2021 15 minutes ago, Steves_TR6 said: Welcome to the forum and to TR6 ownership Matt! the Lucas PI system does tend to run a little rich, it lacks any acceleration enrichment so is better set a little rich to compensate also the system has a ‘fuel enrichment lever’ on the metering unit which is operated by the ‘choke’ knob, this sometimes does not fully return causing richer running whereabouts are you located, am sure a local member will be more than happy to lend a guiding hand ! steve Thanks Steve. I’m in south Nottinghamshire if anyone is local. i was shown the choke in my once over as I left TRGB. It appears to be in the right place (I.e off). Peter, I’ll check the plugs once the engine cools a little. My timing gun arrives tomorrow. What a lot of new toys! Quote Link to post Share on other sites
Peter Cobbold Posted May 13, 2021 Report Share Posted May 13, 2021 Matt, re timing. The mark on the pulley can slip due to distortion of the rubber in the damper with age. A work-around is to set the tickover to tis fastest by slightly rotating the dsiy to and fro , engine running. Caution with HT ! Peter Quote Link to post Share on other sites
barkerwilliams Posted May 13, 2021 Report Share Posted May 13, 2021 (edited) Grime & petrol in air intake. There is usually some condensate in the Triumph intake air box from the engine breather tube in the centre of the plenum. This box slopes rearwards and there is often some corrosion where it collects. There is not really a source for petrol into the airbox, if an injector leaked then the petrol would flow down the manifold and collect near the cylinder head. In use there is so much heat coming off the exhaust manifold / block & cylinder head I would expect any petrol to evaporate in a few minutes after a car is parked. But perhaps a clean out of the airbox would be good start. If you are cleaning then do not clean any residue from the air intake (throttle body) to the butterfly, there are many comments that this "dirt" effectively seals the butterfly - intake manifold and assists at tickover. When the car is ticking over no air should enter the engine past the butterflies, the engine being fed via the large screw on the RH side of the throttle bodies, this has the effect of starving cylinders 5 & 6 (bulkhead end) of a little air which then run rich and many of us run with a hotter rated spark plug in 5&6 than 1-4. This aids those cylinders not carboning up at tickover. This often shows as a few seconds of lumpiness as the car pulls away from stationary and the spark plugs clear. If you have been driving with the hood down and have a centre (wheelbarrow handle style) exhausts on the centreline of the car then fumes can enter the cockpit. Similarly the boot seal rubber can allow fumes to work their way back into the cockpit. These often have a petrol/rich smell as the injection is designed to run a little rich. The PI is really very simple but completely different to carburettors and takes a little understanding. Most things safe to play with but don't touch the metering unit settings. Where the fuel lines attach to the metering unit, particularly those two between the unit and the block (2&5) can have leaky "O" rings and it might be possible to see tell-tale runs down the block in that area, this can also make the cabin smell of fuel. A very solid and reliable engine that I hope you have lots of fun with. Alan Edited May 13, 2021 by barkerwilliams Quote Link to post Share on other sites
Matt1 Posted May 13, 2021 Author Report Share Posted May 13, 2021 Thank you all so much for all the advice. I will give the suggestions a go over the next week and come back if I have any more questions. many thanks Matt Quote Link to post Share on other sites
Conradski Posted May 15, 2021 Report Share Posted May 15, 2021 Great thread - as a new owner with a very healthy fuel smell in the cockpit, this has given me a few more jobs to do. Thanks for kicking off the discussion Matt, and when I'm in your neck of the woods visiting some very old and dear friends it would be cool to have a run out. Good luck from another new & happy owner. Quote Link to post Share on other sites
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