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gsxrken gsxrken is offline
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Join Date: Sep 2002
Location: Westchester County, NY
Posts: 1,702
Garage
More progress, and setbacks. I was able to reseat the wastegate so that it does not leak at idle. While I was under the car, I noticed that cylinder #4's tubing was not turning a nice golden hue like the other 5 cylinders were. I could touch the pipe and it was cold.

First I put a spare spark plug on the end of the ignition wire, held to ground, and observed spark. (more on this later). I installed a different used plug in #4, but still dead.

Then I pulled the injector and observed fuel spraying when I pushed the air plate down. I switched the injector with #5 for the hell of it, but still dead.

So having fuel and spark, I convinced myself that my valve adjustment may have left one of the valves too tight (it is an unheated garage, so the engine is COLD). But I rechecked 4-5-6 intake and exhaust and they were fine. #4 still dead.

So I pulled all the plugs, and conducted a compression test- between 115-125 across the boards, number 4 had 125.

What the heck- fuel, spark, compression and it won't fire even once? The header tube can be touched while the others are scalding hot in 20 seconds of idling. So back to the spark- I did have spark but the spark itself was not too impressive, almost hard to see in a pretty dark garage. More searching on PP and I learn a weak spark can jump across a plug in free air but potentially not fire under tension in a compressed cylinder. So I pulled wire #4 (Clewett wires with 14k on them) and got 2700 ohms of resistance, where I was looking for about 1500 [500 ohms per foot of wire].

I decided to use the dead cylinder #4 wire on the #5 plug, and put #5's working wire on the problem #4. AND GUESS WHAT? Now #5 doesn't fire (cold tube), so it must be the ignition wire, right??? But #4 still doesn't fire!!! So if I had a bad wire, I should have been able to "move" the problem to cylinder #5, which I did, but I would expect #4 to fire now.

If anyone is still reading this, you may be as frustrated as I am. The entire house reeks of insanely rich exhaust from all the retests, despite the garage doors being open since the car is backed in. I am done and moving into diagnosis by credit card mode- I've ordered a set of magnecor wires, cap, rotor, and plugs from our host on the prayer that some weirdness is going on with one of my wires and then (after all the manipulation) another one of my wires either crapped out or my distributor cap has something going on with the #4 post.

I am simply out of ideas. The parts should arrive Friday (CA-to-NY) for our host and I get another crack at this next weekend.
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1986 930, 1969 Mach1, 2003 540 Sport, 2016 R1200RS

Last edited by gsxrken; 01-24-2010 at 07:26 PM.. Reason: clarity
Old 01-24-2010, 07:23 PM
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