Madmal Posted June 10, 2017 Report Share Posted June 10, 2017 Morning all, Just been out for a blast in the PI, running really well, pulls like a train with no smoke on overrun but a bugger to start. Ticks over well when hot and restarts fine, however, the problem is the mixture is very rich. The plugs are sooted up, but dry, and you can smell the petrol in the fumes. Its had a new pump and PRV plus rebuilt metering unit (from Prestige), lines and injectors plus rebuilt distributor (Distributor Doctor) and uprated coil and leads. Compression on all cylinders is about 180 and vacuum is about 8 although the needle seems to swing quickly between 7 and 9. I also checked the cold start lever and that always returns to home position. Also checked the MU diaphragm with the tongue test and that's all good as well. So looking through previous posts, I'm a little confused (easy for me i'm afraid). Does the vacuum control the mixture? Could a low or fluctuating vacuum result in the MU allowing more fuel to the engine? When I disconnected the brake servo vacuum pipe, the revs rise so I'm guessing the vacuum is not too bad. Is there any thing else that controls the mixture that I'm missing? Other than that, the car running really well..... Cheers Mal Quote Link to post Share on other sites
HSM Posted June 10, 2017 Report Share Posted June 10, 2017 Fuel pressure & vacuum control the fueling ( fluctuating vac. reading normal), if possible check fuel pressure first, if o.k. A2 adjuster on vac unit can be adjusted ( the central one) ,turn anticlockwise in 90" increments ( keep note of all adjustments ) to lean off mixture. Gas analyser ideal but colour tune a good substitute. If neither available road test between adjustments to check plugs. Harvey S. Maitland Quote Link to post Share on other sites
astontr6 Posted June 10, 2017 Report Share Posted June 10, 2017 Morning all, Just been out for a blast in the PI, running really well, pulls like a train with no smoke on overrun but a bugger to start. Ticks over well when hot and restarts fine, however, the problem is the mixture is very rich. The plugs are sooted up, but dry, and you can smell the petrol in the fumes. Its had a new pump and PRV plus rebuilt metering unit (from Prestige), lines and injectors plus rebuilt distributor (Distributor Doctor) and uprated coil and leads. Compression on all cylinders is about 180 and vacuum is about 8 although the needle seems to swing quickly between 7 and 9. I also checked the cold start lever and that always returns to home position. Also checked the MU diaphragm with the tongue test and that's all good as well. So looking through previous posts, I'm a little confused (easy for me i'm afraid). Does the vacuum control the mixture? Could a low or fluctuating vacuum result in the MU allowing more fuel to the engine? When I disconnected the brake servo vacuum pipe, the revs rise so I'm guessing the vacuum is not too bad. Is there any thing else that controls the mixture that I'm missing? Other than that, the car running really well..... Cheers Mal What series TR 6 have you got CP or CR? Vacuum S/B 10 Hg for CP & 14 for CR. Subject to this, look for air leaks from anywhere on manifold to M/U, leaking servo unit, worn valve guides and butterfly spindles etc. Do the tongue test on the vacuum pipe to M/U Do not go adjusting M/U as it has been re-conned. Bruce. Quote Link to post Share on other sites
Madmal Posted June 11, 2017 Author Report Share Posted June 11, 2017 It's a CP so maybe vacuum is not to bad?? If I blank off the outlet to the mu and cover the tick over valve the engine stalls but when connected the engine continues to run. Does that point to leaking mu? Cheers Quote Link to post Share on other sites
Peter Cobbold Posted June 11, 2017 Report Share Posted June 11, 2017 In the absencee of an obvious PI fault I think I'd check for good sparks, spark timing, and plug heat range . Peter Quote Link to post Share on other sites
Madmal Posted June 11, 2017 Author Report Share Posted June 11, 2017 So currently running with BUR6ET plugs, which have covered around 40 miles....is there a better plug? Mal Quote Link to post Share on other sites
peejay4A Posted June 11, 2017 Report Share Posted June 11, 2017 (edited) Isn't the BP6ES the standard plug for a TR6. I could be wrong, it's been a while since my TR6 days. Edited June 11, 2017 by peejay4A 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.