john.r.davies Posted July 25, 2004 Report Share Posted July 25, 2004 All, I'd be grateful for ideas, please, from the Pi experts. I've installed Lucas Pi in a Triumph 6 cylinder engine from a saloon, that was originally on carbs. TR camshaft, flowed head, raised compression(10.5), 6-3-1 exhaust. The fuel pump is a Bosch, the Meter Unit is reconditioned and all the pipework and injectors are new. Failure to rev to the limit was traced to an ignition problem, after prolonged search for a fuelling fault, but now there is a distinct lack of response. Slow acceleration is fine, but it will bog down if the accelerator is snapped open. If it were still on carbs, I would look to the needles or the dashpots. Fuel pressure 110psi. Vacuum at M/u instantly falls to zero. The engine runs well with an open vacuum control, but ridiculously rich. The butterflies are synchronised. Ignition 11 BTDC, centrifugals work correctly (+13) Where else should I look? Is it still the ignition, Stupid? John Quote Link to post Share on other sites
Richard Crawley Posted July 25, 2004 Report Share Posted July 25, 2004 John, have you checked the metering unit distributor timing is correct? Also read through all the manuals & previous forum posts for ideas;failing this it could still be an ignition problem. Quote Link to post Share on other sites
jonlar Posted July 25, 2004 Report Share Posted July 25, 2004 John, what ignition system are you using - plugs and points or one of the electronics? If P & P, try changing condenser, the faster the engine runs the lower the power to produce the spark? Quote Link to post Share on other sites
Guest andythompson Posted July 25, 2004 Report Share Posted July 25, 2004 Sounds very lean, try pulling out the choke in very slight increments and see if it improves response Quote Link to post Share on other sites
john.r.davies Posted July 26, 2004 Author Report Share Posted July 26, 2004 Richard, Yes, M/u timing double checked Jonlar, It was changing friom Newtronic (ex-Pirhana?) to good old points that cured the high revs misfire. Thank you, I'll chang the condensor - any idea what the curent Halfords part number is? One of them looks about the right size, but no Microfarads quoted. Andy, Thank you, I'll try that. What should I do if it cures the problem? The plugs are already very sooty indeed. John Quote Link to post Share on other sites
Guest andythompson Posted July 27, 2004 Report Share Posted July 27, 2004 John, Maybe the plugs are just fouled? Try a new set (not cleaning). However, the amount of engine mods you mention would suggest the MU would need some adjustment over standard If it is too lean top end it is matter of incrementally adjusting the full load setting... but this is not a matter to be taken lightly as it effect the whole range and you already mention thet the plugs are sooty... from low speed running? Have you driven enough miles to have an idea of mpg?... always a reasonable indicator of overall mixture Quote Link to post Share on other sites
Martti Ojanen Posted July 27, 2004 Report Share Posted July 27, 2004 John, I have made similar mods to my TR6 plus free flow K&N air filter and high lift roller rockers (10% more lift). I have the same symptom: lack of response at 3000-5000 rev range. Yesterday I changed ignition advance springs to a stronger set of springs and checked advance at idle to about 12 degrees. At test drive I noticed that this made a great improvement. The engine gives much more response now at least at 3000-4000 rev range. I wonder if I should increase max advance (now 14 degrees). I have sheduled a rolling road session for August the 10th and the engine will be measured and I can try ignition advance adjustments and if the mixture is tooo lean I plan to adjust M/U max fuel setting. I will report briefly in this forum and make a full report to my homepage. Martti :blues: Quote Link to post Share on other sites
john.r.davies Posted July 29, 2004 Author Report Share Posted July 29, 2004 My thanks to all for your advice. Since my first post, I have replaced all the ignition components, and changed from electronic (Newtronic) to C/B. No better. Doing all this, I haven't tried the choke trick yet. New plugs? Okay, seems like a good idea - I'm desperate now. John Quote Link to post Share on other sites
lee Posted July 30, 2004 Report Share Posted July 30, 2004 John I'm not any help I know but I can sympathise with you. I am going through exactly the same frustration as you. I have replace all the ignition side and working my way through the injection system now having so far replaced pump,prv,injectors and just about to replace the throttle linkage (if I get any advice from my recent posting) Its not fun and mighty expensive. And the summer is going. lee Quote Link to post Share on other sites
john.r.davies Posted March 31, 2005 Author Report Share Posted March 31, 2005 All, My thanks to all who contributed to this thread, and others elsewhere. This bl**dy well better be good for my soul, because I have to confess to extreme stupidity. As you can see from previous dates in this thread, this saga has been going on for over a year. It still wasn't fixed, after importuning everyone I knew and dodn't know about it. In desperation, I booked it in to the Rolling Road (Dennis Vessey nr.Scunthorpe). That was the plan, but AFTER it was running properly. Delivered the car, parked it on the rollers, went back to close up the tow car. When I got back they had spotted the open choke on the metering unit. Doh! Double Doh! The choke cable had a kink in it, and was holding it open, by about 5mm. Disconnect the choke, and it ran sweet enough. That was worth the trip to Scunthorpe ("Wear the fox hat!"), but it would have been, even if I had not needed a brain transplant. Dennis and his assistants took hours to extract the final HPs out of my car. Now it runs sweeter than ever and I'm very happy with 125 at the wheels. Thanks Dennis! Thanks, everyone! Mallory, here I come! John Quote Link to post Share on other sites
Richard Crawley Posted March 31, 2005 Report Share Posted March 31, 2005 This bl**dy well better be good for my soul, because I have to confess to extreme stupidity. Everybody makes stupid mistakes & misses the ‘bleedin obvious’ from time to time. If you ain’t making mistakes you ain’t doing anything, the trick is to not make the same mistakes but learn by them & only make only new ones. The best one I ever did was at 16 when helping my dear old dad rebuild a 1950’s BSA motorcycle engine. He asked me to cut a felt crankcase seal in half & guess which way I cut it; all he did was smile, get new one out of the spares box & then explained it was too thick; a bit like me at the time! Quote Link to post Share on other sites
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.