a strange spark plug wire problem...
Thread Starter
Burning Brakes
Joined: Sep 2008
Posts: 753
Likes: 0
a strange spark plug wire problem...
Before I go there making tests and try to fix the problem...
is it possible that a spark plug wire that measures correct resistance, actually it doesn't work?
I explain.
on cyl n 5 the spark plug is soothy, looks like not burning the gas.
But the 5 and 7 wires are correctly routed ( far one from the other) and the wire's resistance correct , about 600 ohms .I haven't realized earlier the problem because with former heads I had a certain oil leak due to worn valve guide exhactly at cyl 5 only, but now the problem is still there also with new heads.the bore of cyl 5 is also more worn ( ridge) at the top. all the other are OK
Of course , I'll make soon various tests to check if the plug is actually firing or not, but is it possible that the wire is failing to conduct under load , with heat...?
MSD 6A ignition and the distributor works fine
p.s.
wires are 7 years old Taylor spyro pro. I think they have seen lot of underhood heat and a couple of them were not in great shape at the spark plug end but I restored them ( cut and placed suitable angle boots). all spark plugs work fine less the number 5
is it possible that a spark plug wire that measures correct resistance, actually it doesn't work?
I explain.
on cyl n 5 the spark plug is soothy, looks like not burning the gas.
But the 5 and 7 wires are correctly routed ( far one from the other) and the wire's resistance correct , about 600 ohms .I haven't realized earlier the problem because with former heads I had a certain oil leak due to worn valve guide exhactly at cyl 5 only, but now the problem is still there also with new heads.the bore of cyl 5 is also more worn ( ridge) at the top. all the other are OK
Of course , I'll make soon various tests to check if the plug is actually firing or not, but is it possible that the wire is failing to conduct under load , with heat...?
MSD 6A ignition and the distributor works fine
p.s.
wires are 7 years old Taylor spyro pro. I think they have seen lot of underhood heat and a couple of them were not in great shape at the spark plug end but I restored them ( cut and placed suitable angle boots). all spark plugs work fine less the number 5
Last edited by elle88; Apr 24, 2009 at 11:16 AM.
Le Mans Master
Joined: Dec 2003
Posts: 5,727
Likes: 38
From: Fremont CA
If your checking wire with a Ohm meter, your putting in 9 volts into it. When the secondary voltage is present there is 20,000+ volts in the wire so YES the wire can read OK but be leaking voltage at running conditions. Wire sets are pretty cheap, I would buy at least a replacement wire and swap it too isolate the problem. Cracked distributor cap, cracked plug porcelin are other possible problems.
Le Mans Master
Joined: Oct 2006
Posts: 7,123
Likes: 433
From: Gladstone MO
C3 of Year Finalist (appearance mods) 2019
Wait until dark- start it and get it warm enough to idle, then spray the plug wires/secondary ignition with water. If there's a high voltage leak, it's going to show up. Guaranteed.
