95 F355 No spark on cylinder #1

pull boot heads and use an ultra loe impedence VOM...an expensive one...
back probe for triggrer signals to ign mods...if none, board in Motronic opr boot connectors are a problem...try and wiggle boot head carefully-a known problem 0n 2.7 version systems(not limited ti ferrari only) especially where ecus are located in engine bay heat soak area...

 

You could swap the motronic computers from side to side and see if the problem moves. Otherwise I'd suspect a connector issue as above.

 

355,since your knowlegable about plugs-is it detrimental to use platinum or iridium plugs in older V12s which were originally made for regular plugs ( ie 456)? Is there any advantage?

 

the purpose is to withstand higher heat ranges with a highewr voltage at the firing line...
Platinum is, IMO, more costly than is iridium, therfore the change in materials...
the wire tipped electrodes is to reduce the thermal mass of the electrode, thus rteduciong the liklihood of it acting as a "heatsink" and potentially promoting a glowplug effect which would result in pre-ignoition, detonation, pinging, etc....those explosion forces-when compared to the forces exreted upon the piston crown via a controlled "f;lame front' differ in the order of 20X-30X...thus it is a materially signioficant design consideration

 

On a normal ignition coil one end of the secondary winding is grounded and the other end fires the spark plug.

Typically the way a coil with twin outputs works is that one end of the secondary winding fires the plug on the compression stroke and the other end of the secondary winding fires the plug on the exhaust stroke (wasted spark), and effectively is the ground. The polarity of one spark will be reversed from that of a normal coil as the spark is going is a different direction. You can see that the plug electrodes of the paired spark plugs will wear differently due to this polarity (the ground electrode of one plug will wear and the center electrode of the other plug will wear).
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On the twin output coil, if you disconnect and isolate/insulate one of the outputs of the coil from ground, you will have no spark at the other paired terminal. The coil needs to have good wires/plugs on both ends of it in order to have a complete secondary circuit.

Are you sure that you have no spark at the #1 spark plug. Using a timing light is not a good way to check for spark. A spark tester tool, where you can actually see the spark jumping a gap is the only way to be sure that you have no spark.

The other issue about using a timing light, is that some lights are sensitive to the direction of the spark and have "Spark plug" marked on one side of the pickup. Since the polarity is reversed on a twin spark coil, the timing light pickup may have to be installed backwards for it to work.

If you don't have a spark tester tool, you can just pull the spark plug connector off of the plug while the engine is running, and you should be able to hear the spark arcing down inside the spark plug well. Try it on both paired plugs, #1 and #4 and see what happens. Don't remove the spark from either cylinder for too long, as the fuel injector will be spraying raw fuel into the cylinder, which could cause the catalytic converter to overheat.

My guess is that you have spark at #1 and there is another problem causing the miss (plugged injector, no compression, etc.). Check for spark at cylinder #1 with a spark tool or even a spark plug just plugged into the connector held against the cam cover with some insulated spark plug pliers. I would be very surprised if you don't have spark there. Let me know what you find and we can go from there.

Good luck!
Brian Brown
Patrick Ottis Co.