Weak spark probs

[COVDUBS]

Hi all,
My little project GT is coming to an end but has developed an ignition problem. I have a reasonable spark from the coil lead but a really weak spark from the plugs. So far I have changed the dizzy, dizzy cap, leads, rotor arm, plg leads and have even tried a spare coil. Its driving me mad now as this is only a recent problem which has developed on its own without any assistance from me!
Has anyone got any ideas?

[bengould]

Have you set the spark plug gaps? If they are too wide the spark will use more energy to cross the gap and be weaker.

Not sure of correct gap but will be in Haynes somewhere.

[ianaudia4]

What about changing the plugs as you haven't mentioned you have done it? Also was the spare coil in good nick?

[COVDUBS]

I've set the plug gaps to haynes spec but not replaced them, will try and get to halfrauds tommorrow.
As for the coil, got two knocking about from other projects and both in good nick, tested with a multimeter etc.
The spark from the coil isnt too bad but its not the hefty blue spark I'd expect. As for the plug spark its really weak. blasted easy start down the carb and wont even fire with that.
I originally thought it was the hall sender but the change of dizzy killed that idea.
Been trying it for days now and I've run out ideas.

[bensspares]

if all the above suggestions havent worked, it sounds like the engine isnt sufficiently earthed,check the strap from head to coil and strap from gearbox to body/battery.try a jump lead from the head to the battery negative...this will illiminate any earthing issues.
ben.

[ianaudia4]

Try GSF or ECp for the plugs, much cheaper than Halfords.

[COVDUBS]

Thanks for the replies. I'm off to get some plugs this morning before work and I'll check the earth straps when I get in tonight.

[sciroccodave]

Sounds like your having exactly the same problem i've just had for weeks! My car was running and then died. I had a good spark from the coil but not so good on the plugs, it would not fire at all, even though there was spark and fuel. I replaced the coil, checked the earth straps etc. It turned out to be the rotor arm had a small burnt out gap in it that I missed somehow. Other than that I can't see what else it might be, sounds like you've checked everything I did on mine. Good luck though!

Dave