1993 7.4L / Bravo 1 - Thunderbolt IV Will Not Start

[NautiNights]

I have a 1993 Crownline with a 7.4L/Bravo 1 with the Thunderbolt IV ignition system. The coil, ignition sensor, distributor cap and rotor are brand new and the timing chain has been verified and is in the right position. The engine will not start. It has spark at coil and at spark plug wires but they appear weak. When turning over, the engine sometimes seems like it wants to start but then either backfires back through carburetor or stops turning over like it's compression locked similar to an engine with too much advance. It was running like a champ on a Friday and then went back to go out on a Saturday and it wouldn't start? Why won't the engine start? Is it the ignition module going bad?

 

[guyjg]

perform these procedures

Tests forThunderbolt Ignition:
W/ignition key on AND BILGE WELL VENTILATED OF GAS FUMES!!!

#1 - Connect your voltmeter neg. lead to the engine ground and pos. lead to thewhite/red wire terminal at the dist. It should read 12 volts.

#2 - If 12 volts is present, remove the coil spark wire from the distributorand connect it to a spark gap tester to ground. Remove the white/green leadfrom the dist. terminal. Turn the ign. key to on and strike the white/greenlead to ground. If there is spark, replace the ignition sensor in the dist.

#3 - If there is no spark, substitute a new coil and repeat test #2. Now if youget spark, install a new coil. NO SPARK, replace ign. amp.

#4 - In #2, if there is No voltage present, disconnect the white/red wire andcheck it again for 12 volts. If 12 volts is present, replace the ignitionsensor inside the dist. cap. If no 12 volts present w/it disconnected--ignitionamplifier is shot and must be replaced.

 

[Docksidemarineservices]

I have a 1993 Crownline with a 7.4L/Bravo 1 with the Thunderbolt IV ignition system. The coil, ignition sensor, distributor cap and rotor are brand new and the timing chain has been verified and is in the right position. The engine will not start. It has spark at coil and at spark plug wires but they appear weak. When turning over, the engine sometimes seems like it wants to start but then either backfires back through carburetor or stops turning over like it's compression locked similar to an engine with too much advance. It was running like a champ on a Friday and then went back to go out on a Saturday and it wouldn't start? Why won't the engine start? Is it the ignition module going bad?

Weak spark, replace the coil with a non resisted coil.