No Spark

[warthogcrewchief]

There's a few of you who have read/replied to my thread regarding my '89 backfiring a lot.http://www.venturerider.org/forum/showthread.php?t=45485

 

I posted a little bit about the no spark condition on the right rear cylinder. I tested the coils, and are within limits, all three other spark plugs work just fine. I tested the spark plug wire installed on the coil and the plug cap removed - got good resistance. I then tested the wire with the cap on and the cap by itself and was having a hard time getting a good resistance value. I had to turn the multimeter onto 200K ohms to get a reading. I'm thinking that the spark plug cap may be the problem. Anyone have other ideas? I've got new wires/caps on order. Hopefully that'll fix the the problem!

 

Has anyone had a no-spark condition before from the spark plug cap or the spark plug wires?

[bongobobny]

Sounds like you may have isolated the problem! Yes, I have read that the caps can cause problems...

[mbrood]

If it's a stock cap... just unscrew and clean the "guts".

 

Inside the plug end is a flat blade screw to remove... followed by a cylindrical 10K resistor, a very thin and small copper "contact plate" and then a spring... clean the contact points on all items including the bottom of the "cup" everything goes into, remeasure the resistor and if everything looks clean now, add a bit of dialectric grease and toss it all back together. Also check the screw end that the high tension wire screws onto for that green corrsion... clean as required.

[warthogcrewchief]

I had disassembled it yesterday and cleaned the resistor. There was no copper plate in there. That may be the problem. I do have new caps and plugs on order.

[mbrood]

That little copper "plate" is EASY to loose so no dobt somebody in the past has been in there. If the spring ends and the rest are clean and you get the right measurement on the resistor... toss it back together and keep checking, but... with it apart, you can Ohm from the inside "cup" on the plug holder to the ignition fuse, looking for that 13K for the coil. Since the plug wire is solid core copper, it "should" be negligable to any resistance readings. (But that green corrosion can add up many K Ohms easily)

 

Mine was running rough and #3 read 45K... just some green crud on the end of the spark wire going into the coil... 1/4" clipped off the end and it was back to smooth running.

[warthogcrewchief]

I already tried clipping both ends of the wire, and no positive results. I'm pretty sure it's not any of the coils because I tested the connecting plugs at the TCI/CDI unit. When I tested each piece, the cap was hard to get an ohm reading. Same results when the cap was tested with the assembly. All the other pieces, when tested independently seemed to be in limits.

[warthogcrewchief]

I got my new wires and caps in the other day. I changed them out yesterday and that did not solve the problem!

 

 

 

So the next thing I did was pull a spark plug off a cylinder that I knew was firing, and placed it in the faulty position... worked like a charm! Turns out the spark plugs I purchased four months ago, one was bad! Less than $3 and got spark to all four cylinders....still waiting for the darn carb sync tool...

[bongobobny]

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