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Join Date: Jul 1999
Location: Atlanta, GA
Posts: 107
ignition woes, little help?

Hey y'all,

Here's my situation. I've completed the second rebuild in three months. Never forget loctite on a web cam, that's all I've to say about that.

Well in trying to breathe life into my little honey we get nothing. Check compression, cool, fuel cool, ignition. . .

Now the timing light shows nothing on any one wire or the high tension lead. So I pull the high tension lead and arc it to the case, good spark timing light flashes.

So I have 12v at coil + (15)
I have replaced cap and rotor
I have swapped coils (both test good)
I have checked all ground straps, including an improvised one made of booster cables.
I have checked wires, all ~15K Ohms
I am running Allison Crane optical ignition and it's working fine.
Everything tests fine
EXCEPT

When I jumper a plug wire with the high tension lead(eliminating the cap and rotor) the timing light flashes when the wire is grounded but not when firing through a plug. I've tried several plugs grounded in differing areas of the car.

What's up? Like I've said ground straps are good. Coils are good, throw 2.5" long sparks from high tension leads. Optical ignition unit tests fine and throws good sparks. Wires seem fine, have even tested the above with a new wire left over material. Tested a half dozen plugs. Good voltage to coil positive lead.

any thoughs? I've also set up the old points and condensor and gotton the same results.

Thanks
Ian
Old 12-20-1999, 04:23 PM
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John Rogers's Avatar
 
Join Date: Dec 1969
Location: chula vista ca usa
Posts: 5,207
Check the resistance of the rotor, center to the tip, sounds like it may be open? Also check the distributor cap to make sure there are no opens between the outer plug wire holes and the inside. Make sure the cap and rotor are not shorting to ground. Finally, did you lube the spark plug threads? If you did, might be a pretty good insulator so always use a conductor as a plug lube? Good luck.

[This message has been edited by john rogers (edited 12-21-1999).]
Old 12-21-1999, 06:56 AM
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Thanks for the ideas. I've replaced the cap and rotor, and they look flawless. The plugs, no anit-seize. So there should be great conductivity.

After thinking about it I'm just going to replace the wires and plugs today. That will take all the major replaceables out of the loop.

I'm still puzzled. Weak spark when firing theough the wire and plug. Good spark when arcing through the plug, wire and some (~1 cm) air. . .

sigh,
Ian
Old 12-21-1999, 07:19 AM
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Join Date: Dec 1969
Location: chula vista ca usa
Posts: 5,207
I had a rotor that looked flawless a couple of years ago on our 1987 Turbo and it was running really poor, turns out the resistance had gone way too high? I'd measure them. Also measure the wires since they could have opens and could be arching inside? I like to run our 914s at night (no light) now and then to look for voltage leaks and it is amazing what I see. Finally, the plugs might be open inside the center electrode, this is a common trick used in auto shop trouble shooting classes. Good luck.

[This message has been edited by john rogers (edited 12-21-1999).]
Old 12-21-1999, 10:38 AM
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Well believe it or not it was the wires! I replaced them quickly last night and asked my brother to crank it while I chacked for spark. It came to life! FINALLY!

Now to tune it, she is running but like a dog. That's not unusual.

Thanks all
Ian
Old 12-22-1999, 03:38 AM
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