1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

Boat came in shop backfiring severly and unable to keep running.Customer had someone build carb earlier-not a fuel issue . went to do test now no spark at all . I followed the oem manual per diag chart bat v @ 13.3 , 12v @ coil,11.24 @ wh/rd dist ,no spark grounding tapping wh/gr . substiuted a new ign coil. no spark -Per manual replaced ign module ( very spendy for customer ) . no spark still . disconnected gray wire @ tach . no spark,had a good thunderbolt IV switched out ign sensor, no spark. out of the blue while cranking I had good strong spark then no spark after 5 sec of cranking.I could shut off the ignition and re crank for 5 secs and have spark then none. located remote box kill wire yellow / red cut them and put together .Heres what it has - new spark plugs / cap / rotor ( prior of no spark and rough running as the customer stated.) new ign module ( per manual ) , good take of ign sensor , new ign coil ., even new battery after cranking so much and battery was junk had to kept charged to do test. 97 4.3 LX , ser# 0K026737 , carb ( not efi ) , thunderbolt V distributer , none knock sensor model Found problem- disconnect the 2 leads from the shift interupter switch and fired up. Also had a faulty new ign module that created a bunch of stress.Reiinstalled customers orig module and boat runs great.Took it on the lake and runs great.Note make sure cables are adjusted correctly,we had to replace the shift cable do to out of specs.Someone should re write these manuals because these parts arn't cheap to be throwing parts as the manual states when all it was a faulty 60.00 switch.

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

anyone have any ideas ?

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

what did you ever come up with? my boat is doing the same thing and i have done all the same things except the ignition module replacement but i don't think that is the problem because i get the spark for the 5 secs when i first try cranking...

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

Just for giggles, remove the dist cap, crank the motor and see if the dist is TURNING correctly. Worn cam chain/sprockets may be slipping, initially causing backfiring from altered timing and since gotten so bad the dist is barely turning.

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

its turns like it should, with every roatation of the engine its spinning... just don't understand why i have spark everytime the key is off and turnt back on again. but if i leave it in the on position and try and crank nothing... mine is a thunderbolt V system though

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

nate_1503 said:

its turns like it should, with every roatation of the engine its spinning... just don't understand why i have spark everytime the key is off and turnt back on again. but if i leave it in the on position and try and crank nothing... mine is a thunderbolt V system though

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I did get it running.I replaced the shift interupter switch diconnect the 2 wires from the switch then start it.I did find other issues but as soon as I disconnected the shift switch it ran.

Re: 1997 4.3 lx no spark ,now spark 5 secs, no spark after cranking 5 secs ???????

did you run a jumper wire between them, or just disconect them?