Tried everything: engine doesnt start.The case of deceiving coil to rotor cable

[SeaLord]

I have been bugged for almost a year by my 2001 5.7gl randomly not starting especially when for some days left at the mooring.
All the times everything was checked including the sparks coming from the coil into the distributor. A very sound and high voltage spark I hardly could hold the cable. Could not be it right ? Items checked to the next step to find nothing.
By exasperation I thought problem must have been around the coil despite the above mentioned fact.
So I substituted the coil. Nothing.
Then the electrician that was helping me thought he should try his own connection from the coil to the distributor. Bang! engine started. just to make sure I then installed my old ignition coil. yessss! put back the old cable. Nothing.
Substituted the old set of cables connecting distributor caps to sparks and ignition coil with a new set.

A year ago when I dedicated quite a few parts to substitute the old, I decided to bypass the recommended substitution of rotor, rotor cap and cables because everything looked nice, sparks were bright and strong then... what the heck....just kept the bought spares for a later event.

Wrong and undetectable. Lesson learned (comments would be highly appreciated though)

 

[Saline Marina]

This type of tool is very handy in troubleshooting ignition health.

Google search "spark gap checker" for many variants on the same theme. The HEI will jump a 1/2" gap when cranking the engine over (its easier in free air, becomes more challenging to ionize under the compression pressure, but still a *lot* of energy being delivered)

Ignition and fuel systems are somewhat tricky because they require abstraction to fix. You can do a few measurements in troubleshooting, but a lot of it ultimately you cannot directly visualize and then it boils down to "swaptronics". Also having a good understanding of the system helps too.

Really good find, it is quite satisfying to find the root cause of the trouble, without any shred of doubt!

 

[jeffnick]

If you put the new parts in and use the old ones as spares you'll know for sure that the spares will work properly. You'll also be familiar with the swap and know you have the right tools on hand. This isn't real critical for weekend boaters, but it's a real bummer when you're a couple days offshore and find out that your new part isn't the right one or you don't have the correct wrench to get the old part off.