Was setting the timing on the '84 12A yesterday; got a signal from the lead plug but absolutely nothing from the trailing. Am using one of those timing lights that calls itself an 'induction pick-up'; just clips over the spark plug lead without having to disconnect anything. Are these lights just a bucket of junk or is there something else I'm missing?

Thanks in advance!

 

Those timing lights are fine. If there's no trailing spark then it most probably means you have either a faulty trailing ignitor or ignition coil.

Does your tach work BTW? Most 1st gen. tachs (though mine doesn't for some reason) run off the trailing ignitor so a non-working tach is a telltale sign.

If that doesn't help then I'd probably start by swapping the ignitors around and seeing what happens. Failing that the next step would be to try the same procedure with the coils. My money's definately on the ignitor though.

 

Tach works fine. I'll check the ignitors and the coil anyway. Wouldn't there be some really obvious probs though if either the ignitors or the coils were failed?
Car is getting poor consumption at moment, doesn't idle unless fully warmed up, choke function doesn't work unless held out manually; all of these led me to start fixing by checking and adjusting the timing, the idle speed and mix...

 

Well, if you had no signal from the trailing ignition then it means it's not working. This means the ignitor and coil are the two most obvious culprits. Poor fuel consumption and idle are signs of this as well BTW.

 

Thanks for the tips...I'll check both and see how it goes...

 

It could be a bad distributor cap or rotor too...I had that happen on one car, kinda. All my other stuff was fine (tach working) but had an intermittent spark on the trailing. Replaced the cap and rotor and all was fine. I think you could check the voltage coming straight outta the coil but just putting the induction lead on each coil wire and pulling the trigger. If it blinks your getting spark outta the coil. Try both of them. If your not getting spark out of one, you know its not the cap or rotor, if you are getting spark, you know the problem lays downstream a little ways like the cap and rotor .

~T.J.

 

I always thought the trailing plugs were meant to operate like that, they don't fire at low load/rpm ??

Can't remember where I read that though so its probably wrong as I can't see how that can be done without an ECU of some sort

 

I believe thats true only for the older cars, like the SA's.

~T.J.

 

I'll check the dist. cap as well; it burnt a cap out about 6 months ago and I replaced it, so maybe it's all related; though I don't remember any better performance directly after changing the cap, so who knows? BTW, what would be a common cause of a fried distributor cap? I can forsee a lot of checking going on this coming weekend...

 

i think it happens from excess resistance in the circuit. how old are your plug wires?