tjs Posted July 23, 2022 Report Share Posted July 23, 2022 (edited) 71 PI, regular cam, Bosch pump, 4,11 final drive. HI All. So after moving back to the UK after a 6 year hiatus away from my TR I have been doing some little jobs and getting it road fit again for much more use than it ever had before (waterproofing, replacing fuel lines, tidying up interior etc). Anyway, took it for a shakedown before a much larger trip to Italy - pencilled in for September. Crewe to Manchester to Kendal to Crewe in pissing rain. 1. Wiper rocker snapped 10 mins after departure in the dark. Great. Operated by poking it with a screwdriver. 2. Rain leaking in through windows/ inner doorcards. Some window curtain type hack will fix that, on the to do list. 3. Pulled the heater switch, nice hot rusty water all over my left leg - great! What worries me more is 4 & 5... 4. Fuel consumption avg 22mpg (fill to fill) on almost all M61/M6 at 55-60mph cruise (I have 4,11 diff circa 3000rpm engine speed). roof was up, windows up. 5. Car feels reeeeally slow. Struggles to pull above 3000, no misfire, but just really flat and slow to increase revs. Did a 0-60mph GPS check (with a cheeky rolling start as I hate dumping the clutch)...15.5 seconds! With a 4,11 final drive! Now I know the 8 sec figure probably a bit ambitious, but nearly double that...crikey. I know this is a really open ended question but where to start? I have checked the timing and its correct (my car has the vac advance not connected). Metering Unit needs a recal? Im struggling to think of anything else. Brakes are not dragging Edited to add - tank drained, cleaned, all filters and lines replaced. MU - untouched. Cheers Alex Edited July 23, 2022 by tjs Quote Link to post Share on other sites
Mike C Posted July 23, 2022 Report Share Posted July 23, 2022 The high fuel consumption might be due to the fuel enrichment lever sticking open but after 6 years of exposure to stale fuel my bet is that the MU elastomers have deteriorated - especially the diaphragms. Quote Link to post Share on other sites
tjs Posted July 23, 2022 Author Report Share Posted July 23, 2022 Cheers Mike, edited to add - tank, drained, cleaned, all filters and lines replaced. MU - untouched. Quote Link to post Share on other sites
Mike C Posted July 24, 2022 Report Share Posted July 24, 2022 I had my MU and injectors converted to Viton elastomers & recalibrated about 5 years ago. The old nitrile components couldn't cope with modern high octane fuels. Just before I had this done a fuelling diaphragm that I'd replaced using a ( presumably nitrile ) component from a major UK supplier failed in under 2 hours (actual hours, not running hours)- the mixture went so rich that the wet plugs wouldn't fire and petrol dripped from the vent hole under the MU. There might be a simpler and less costly solution, but I'd suggest you let an expert rebuild & recalibrate your MU and injectors. Re your item 3 My heater core started dripping water 3 or 4 years ago despite following the recommended coolant maintenance regime. I just bypassed the heater, I don't go on long winter trips often and if I do I just rug up a bit more. I should note that I avoid driving the TR on days when the top should be up due to rain. Quote Link to post Share on other sites
zelrik Posted July 24, 2022 Report Share Posted July 24, 2022 Alex You asked where to start! An easy first thing is to undo the MU vacuum hose at the manifold and suck on it to see if it will hold suction pressure. If it holds pressure - good (& move on to next possibility!) If it doesn't hold pressure it means there is a problem with the sliding fuel mixture adjuster, a split diaphragm in the MU would be a likely culprit. " Smooth operation of the vacuum-controlled injection system is largely dependent on the “Vacuum Diaphragm and linkage”. If there is any vacuum leakage this results in the malfunction of the Metering Unit’s supply of petrol to the injectors, causing extreme fuel consumption." See, at about 4 minutes (good example but spoken in Dutch): https://youtu.be/n-suYwqOWD8 It could possibly be fixed with the MU on the car, however all the other rubber bits may have degraded over time too. Good luck. Quote Link to post Share on other sites
Waldi Posted July 24, 2022 Report Share Posted July 24, 2022 If the ignition is ok and the car moves freely (brakes), it will likely be a MU issue. Test the membrane as stated above. Check the choke lever is fully back. Next step is to have the MU serviced by a specialist, and I would do the injectors, PRV and black nylon fuel lines at the same time. Ask for Viton grade B seals and membrane. Waldi Quote Link to post Share on other sites
tjs Posted July 24, 2022 Author Report Share Posted July 24, 2022 Cheers guys. The suck test i checked a few days ago. Holding a good vacuum and I replaced the diaphragm center knuckle not so long ago. I know Malcolm/prestige had a flow bench etc but surely the metering needs to be calibrated to each car's block, timing, manifold depression etc being slightly different? About 6 years ago i built a rig to calibrate injector opening pressure, and I often found the spring tension adjusters would often just come loose, causing injectors to dribble. Loctite etc on the threads would never work as it just gets dissolved by the fuel. I never found a way to set and forget really. Quote Link to post Share on other sites
Peter Cobbold Posted July 24, 2022 Report Share Posted July 24, 2022 The intact MU diaphragm points me away from mixture towards ignition timing. Too much retard will kill 0-60 and raise consumption. Check/set points gap then find optimum tick-over rpm by turning the disy a few mm to and fro. (beware HT shocks). The TDC mark on the crank pulley can displace as the rubber in the damper deteriorates. Quote Link to post Share on other sites
tjs Posted July 24, 2022 Author Report Share Posted July 24, 2022 Hi Peter, I've always read different figures for optimum advance at Idle. What do you recommend? Checked with the light but as you correctly sway it can be swayed by the state of the damper. Cheers. Quote Link to post Share on other sites
Peter Cobbold Posted July 24, 2022 Report Share Posted July 24, 2022 1 hour ago, tjs said: Hi Peter, I've always read different figures for optimum advance at Idle. What do you recommend? Checked with the light but as you correctly sway it can be swayed by the state of the damper. Cheers. Alex, If you dont want to set the best tickover rpm by turning the disy slightly with the engine running , then try adding say ten degrees (crank) to the present setting. Do a test drive and if it doesnt pink when flooring the throttle add a few more. Find a point when it just does not pink. Book static timing for the PI was I think 11-12 BTDC ( but I havent had PI fitted for 30 years so I might be wrong). However if you have a low compression head ( eg USA-spec fitted to replace the UK PI head) static can be around 16-18 BTDC. Peter Quote Link to post Share on other sites
wheeler Posted July 24, 2022 Report Share Posted July 24, 2022 Hi Alex, I had a similar problem with my TR6 earlier this year. I sent my MU off to Neil Ferguson for refurbishment and reinstalled. I checked cylinder compression, around 200 psi per cylinder - all OK thankfully as I had fitted new pistons last year and had the head skimmed and new valves etc fitted not so long ago. I bought new plug leads, spark plugs, distributor cap and coil. Checked fuel pressure 105 psi, bled injectors and set ignition advance. I have Luminition electronic ignition and that appeared to be working OK. Set tappets, balanced thottles, fitted new air filter and now I have a smooth responsive engine that is a joy to drive. Recently returned from round trip with mates to Classic Le Mans approx 800 miles and got nearly 30 miles to the gallon and we weren't hanging around. Hope this helps, good luck. Bill Quote Link to post Share on other sites
Waldi Posted July 24, 2022 Report Share Posted July 24, 2022 Total (maximum) advance is more important than static timing imho. If you have a std car I would set as indicated in the WSM. If that does not solve your issue, have the MU etc. serviced. Waldi Quote Link to post Share on other sites
tjs Posted July 24, 2022 Author Report Share Posted July 24, 2022 (edited) Thanks, well noted about the timing. Off the top of my head i think i set it to around 20deg btdc at 1000rpm, but I'll recheck. Did however find this, potential elephant in the room. I guess the off position is fully off on the spring! Edited July 24, 2022 by tjs Quote Link to post Share on other sites
Mike C Posted July 24, 2022 Report Share Posted July 24, 2022 The enrichment lever needs to be bolted to the MU with a clearance gap when the choke is fully in. Have a look at page 13 of this: https://app.box.com/s/zz3e6x4gr4u7t360makeqbm0adxr4cu9 Quote Link to post Share on other sites
Andy Moltu Posted July 25, 2022 Report Share Posted July 25, 2022 A reasonable rule of thumb is to set the max advance with a strobe - to say 32 degrees of advance at 4000 rpm. It won't be far off and you can make minor adjustments to this with the knurled nut. If it pinks retard it a little, if it doesn't you can advance a smidge. Quote Link to post Share on other sites
tjs Posted July 25, 2022 Author Report Share Posted July 25, 2022 13 hours ago, tjs said: Thanks, well noted about the timing. Off the top of my head i think i set it to around 20deg btdc at 1000rpm, but I'll recheck. Did however find this, potential elephant in the room. I guess the off position is fully off on the spring! Update: this was the problem. Its been like this since I've owned the car! The EFL was set basically a third of the way up it's travel by the cable. Sorted it out now with a smidge of clearance on the cam in the fully off position. Starts and runs like a dream! First time I've experienced the real power of the 6! I always did wonder the idle air screw was always wound fully in and the idle still too high! Cheers all. Quote Link to post Share on other sites
Bluestone Posted July 25, 2022 Report Share Posted July 25, 2022 Great result tjs Quote Link to post Share on other sites
Jonny TR6 Posted July 25, 2022 Report Share Posted July 25, 2022 Happy days ! Well diagnosed in the end Quote Link to post Share on other sites
Steves_TR6 Posted July 26, 2022 Report Share Posted July 26, 2022 Excellent! i love the PI system and its really reliable once set up correctly i refurbed mine in 2013 and haven’t needed to touch it since steve Quote Link to post Share on other sites
stephen cooper Posted July 27, 2022 Report Share Posted July 27, 2022 Might want a new set of plugs if its been running rich for so long! Quote Link to post Share on other sites
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