Re: 84 force 85hp Ignition problems--HELP!--
These engines have one itty-bitty ground wire coming off the electronic mounting plate to the block and all components are grounded to the plate. Before you go crazy, run a separate ground wire daisy chain fashion from all three coils and both electronic boxes to the terminal block on the other side of the engine. double check the ground for #3 coil. if all grounds are OK, since you have replaced all other components, and since it only happens on #3 cyl, then the trigger is a suspect. Check the trigger connection with only two wires, (that's #3) and check the wires under the flywheel: these wires move with the trigger and it is not unlikely that one of them broke. possibly internally from flexing. I don't remember the resistance, but the triggers are coils that produce about 1/2 volt signal voltage. So you should be able to check #3 against the other two with an accuate voltmeterwhile cranking the engine. If you show 0 volts at the connector, there's your culprit.
FYI:1 and 2 cyl are fired by the first box, 3 is fired by one side of the second box. So, if one half of a box fails, use the good half on #3 and the good box on 1 and 2. save a little money that way. White wire from boxes is shut off, black wire is ground. both connect to ground when engine is shut down. However, if you have a bad ground on the black wire, the box will not fire the coil.
