key switch ?

[Tnash542]

Hey guys i been trying to figure out for about 2week why my rv lost. Spark will turn
Over but no fire . I tried. All the suggestion. You all gave.still no go but today i
Think i have new info.it seems it will spark only when it is being put in the off position.
(Only when the keu is being going from acc to off it will fire like. One time.so my ?is do you think
Its key doing that or the harness.  I just excited to finally see spark again

 

[catblaster]

I had that situation on a Cadillac engine in an airboat, It had the HEI distributor and would not fire until let off of the switch. I finally figured it was a voltage problem since the coil fired the instant that the starter was out of the system. In other words, with the starter engaged there was not enough voltage available to the coil. It seems that HEI distributors are very sensitive to low voltage. I had changed coils and modules but the problem persisted. My situation is different because I have a 6ft prop that provides enough momentum to turn engine over after starter is disengaged


This was several years ago and I cant recall if it was fixed when I sold the boat but the new owner has no problems with it since he put a new battery in.