TR6 starting problem

[Ziggy]

My 73 TR6 with fuel injection (lucas pump)  has trouble starting, and when does seems to misfire for about 30 seconds, then all is ok, runs nice after that. Always the same when starting cold or hot. Replaced leads, cap, rotor arm, points, just put injection cleaner in the tank, so no results from that yet. Could it be a faulty injector?  Is this a common problem?

[thescrapman]

Have you tested the fuel pressure?

Do you have a relayed power feed to pump from the battery? 

Coukd be pressure dropping whilst it cranks.

the 30 seconds misfire, does it sound like it is on 4 or 5? That could be a faulty one way valve on metering unit. Or a lazy injector.

[Nigel Clark]

Rough 4 or 5 cylinder start up isn't unusual for Lucas PI TR6s.

The two most likely causes are:

- Faulty injectors that dribble and don't hold line pressure when the engine isn't running. Sometimes a good blow through with compressed air will clear traces of dirt and cure the problem, sometimes a refurbished injector is needed.

- Non-return valves on the metering unit outputs to the injector lines failing and allowing pressure drop. This most often happens on cylinders 2 or 5, where the lines are connected by banjo bolts rather than straight unions.

Slivers of rubber seal or dirt in the fuel are the most common culprits. When replacing any rubber seals on the injection system, only purchase from a recognised Lucas PI specialist. Some of the others may be the wrong type of rubber, or a metric 'close equivalent' to the original imperial size.

Nigel

[rlubikey]

Ziggy, has it just started doing this or been getting worse over time? Or have you just bought your TR6?

As Nigel says, I believe this isn't unusual. In addition to those suggestions, another possibility is an inward leak in the fuel system. Petrol doesn't leak out when running but air leaks in when stopped - especially when cooling down after a run. (Mine has no problem started if I've previously run it for just a few minutes!) Has yours been reconditioned since ethanol fuel came in? If not then the various rubber seals and diaphragms will not be resistant and will deteriorate over time. I think mine just pre-dates ethanol and does this. Either live with it or send the metering unit & injectors off to one of the experts (KMI, Prestige, K Raven Smith, and ... someone in Kent I've forgotten) to have it recon'ed.

Do you know about feeling the fuel lines to the injectors for the "pulsing" as it ticks over?

Cheers, Richard