Nigel’s injectors play dirty
This should hopefully interest those of us with classics fuelled by Lucas petrol injection, mainly Triumph owners of course, though perhaps we have owners of Sixties Maseratis among our readers. I’ve found the Lucas PI system rather better than its troublesome reputation, but if there’s a weakness, in my experience it’s injector blockages. Uncle Joe’s fuel squirting device is sensitive to tiny specs of dirt, which lodge in the injectors and prevent their valves opening and closing. The result is a substantial reduction of power, or a misfire.
I’ve seen two such problems in the past couple of months. The first incident was on a Drive-It Day run with my local Nene Valley TR Register group, when heading to the Shuttleworth Collection.
It’s an excellent day out at the Shuttleworth, near Bedford, with a remarkable collection of classic and vintage aircraft, plus a few cars and motorcycles.
Chris Johnston’s lovely TR6 dropped to five cylinders on the run. Arriving at Shuttleworth, Steve Denton – Triumph owner and YouTuber – jumped in to help, swapping the stricken injector for a spare he was carrying in his ’6. After bleeding the air from the replacement injector, Chris’s motor was immediately restored to perfect health.
The second incident involved my own TR6, while on my way to visit Alasdair Southall to collect a pair of his uprated Triumph rear hubs (more on these on p128 of this issue). Turning off the M6, the engine dropped to five or fiv-eand-a-half cylinders. With 70 miles to go, I tried a couple of quick fixes – but I must add that these don’t always work, and sometimes there’s no choice other than to clean the injector properly or even replace it. The first and easiest possible cure is to floor the accelerator and briefly pull out the choke. This makes the warm engine misfire even worse, but the increase in fuel flow can sometimes clear the injector. No such luck this time...
Time to raise the bonnet
With the engine idling, it should be possible to feel a pulse in the injector feed lines. Five were thumping rhythmically, but No.4 injector had no pulse, so I readied my fire extinguisher and removed the relevant injector keeper plate. Engine idling again, I pulled the injector from the throttle body, keeping it away from the hot exhaust. Sure enough, No.4 was dribbling,
