One secondary plug not firing
 

I have a strange problem in that just one of my secondary plugs in my 964 engine is not showing any signs of spark as it is untarnished after running hard around the racetrack (all other 11 plugs show the right amount of "soot")

I have tried three different tested plugs, grounded this cylinder #2 lead a couple of times and it has a nice strong spark, belt is good on the distributor, and I am running a good quality Clewett wires that are making a nice audible click onto the plug.

However this cylinder leak down is at 83% cold while all the others are between 89-94% if that makes a difference?

Any ideas?

Thanks
S.Chapman

how about fuel into that cylinder? you could have a faulty injector.
oh.....just reread regarding the other plug in that cylinder being ok...hmmm
regards,
al

I know ...weird, eh?

...and if the head wasn't grounded properly wouldn't the other plug suffer too?

Thanks
S.Chapman

What happens if you run that cylinder without the other plug connected ?

Plug wire ?

Try cleaning contact in distributor cap where rotor makes contact as well as wghere plug wire goes in , I used acteone on a q tip..seems bosch had some sort of varnish on them

Aha!

I just pulled the wire to the injector on that cylinder and the engine note doesn't change hardly at all as when compared to the other injectors. Pulled the upper plug and one beside it to compare fuel smell and it is none existent in this cylinder too... Additionally pulled the primary plug wire per DanielDudley's suggestion and same result but a little bit of smoke out the tail.

Would a partially working injector maybe allow just enough fuel to be burnt off by the primary plug and leave nothing for the secondary one? This would certainly explain why that Datsun 510 was pulling away from me in the straights during last race and my lap times were off by almost 2sec?

Yours in Motorsports
S.Chapman