that-son Posted August 30, 2014 Report Share Posted August 30, 2014 what the heck is going on? it was running great until the intake wire to cylinder 1 started misfiring. pulled that out, replaced it with the wire from cylinder 4 exhaust and the misfire stopped. so bought a new set of wires, replaced I1 wire but E4 started misfiring. figured maybe it was so cheap it broke after i swapped it with I1. so i replaced e4 but it's still misfiring. and now it's backfiring too from the carb and exhaust. i leaned it out but it's still backfiring from the exhaust. but not all the time. it seems like it runs better when the rpm is above 900 or so. at 800 it seems to just luuuug. anyway i only had a chance to check the ignition coil... both primary and secondary coils. secondary for 1st was 11k and 11.5k for the 2nd. primary was 2.5 and 3 ohms. manual says it should only be around 1.5 or something. could this have something to do with it? Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 Because you have removed wires it's time to check every one goes to the correct side and cylinder. No sense chasing a problem that does not exist. Put an old plug in each coil wire and lay on a grounded surface and crank the engine over. Confirm that BOTH coils are firing. If the exhaust side coil is not firing replace the fuse on the far left hand side of the fuse box. Coils almost NEVER go bad. To check the coil resistance it must be disconnected from anything that could alter the reading. Primary resistance is approximately 1 to 1.25 ohms. Secondary resistance is 8-12K ohms. If you check for spark above you don't have to check the coils. Either they work or they don't. All voltage will seek the shortest and easiest path to ground. This is why the rotor, wires, distributor cap and spark plugs must be in good condition so that the easiest path to ground is the gap on the spark plug. Wait until very dark and fire it up. Rev the motor quickly and watch the ignition wires, cap and the coil. Any really obvious arcing will be visible as a blue flash. 1 Quote Link to comment
that-son Posted August 30, 2014 Author Report Share Posted August 30, 2014 "Because you have removed wires it's time to check every one goes to the correct side and cylinder. No sense chasing a problem that does not exist." lol... can we delete this thread now? i was so convinced i did not get the two mixed up. i really do have a bad wire though. the way it was previously wired was all intake wires are on one side and all exhaust wires on the other. none of the wires are routed behind the engine. does it matter? also, while we're on the subject of ignition... what do you think about high energy ignition? thinking about two msd blasters and maybe a 6a later on. Quote Link to comment
datzenmike Posted August 30, 2014 Report Share Posted August 30, 2014 It happens. The intake coil fires all the plugs on the carb side, the exhaust coil fires all the plugs on the exhaust side so yes there are two separate systems but the two coils fire together. Save your money. The 720 already has a high voltage EI (electronic ignition) system that is way more than what is needed. Products like MSG take advantage of the placebo effect. Which is... the more expensive and shiny a product is, the more you believe the better it works. 3 Quote Link to comment
that-son Posted August 31, 2014 Author Report Share Posted August 31, 2014 truck runs great. no more surprises so far. thanks for all the help!!! Quote Link to comment
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