Help! 87 sun sport runs great then dies!!!

[Furball_127]

Ok this is going to get lengthy but I want to include as much relevant info ad I can. Here goes. And thanks in advance to anyone that reads this. Any and all help is GREATLY appreciated! 1987 supra sun sport. Hours unknowns but there are many on her. We have had her for 8 years and she's been a good girl up until now. We replaced the floors 2 yrs ago and the seats were redone 3 yrs ago. So she's In pretty good shape now. So this problem started last year at the end of the season. Driving across the lake running great the motor "poped" and shut off. Tried to get it running again and it almost drained the battery and after giving up all hope it fired when I pumped the heck out of the throttle. We were cursing at 25-30 mph when it cut out. We made it back home at idle speed and it ran great. We used the boat for a few more weeks and didn't have anymore problems with it. Over the winter knowing of the problem I rebuilt the carb hoping that would fix the problem. Now this year we are having the same problem but it is happening more often and sooner. Before we could cruise 8 or 10 miles down the lake before it would act up and now we can barely make it out of the bay without issues (1/2-1 mile). She's a 351 with a Holley 4 barrel, petronix pointless ignition, the cap rotor, pugs and wires are 3 years old. So far this year we have replaced the fuel filter (it was very dirty) fuel pump, and fuel lines. We ran the boat off of a external gas tank and it ran great so as we were replacing the fuel line we drained all the gas out of the tank and wiped it out as best we could (not perfect but better) when we hooked the fuel line up directly to the pump and put the hose in the hole from the sending unit on the fuel tank the thing ran great. We then finished running the line and hooked it up to the fuel filter. (Drained and cleaned it again) and then hooked up the line to take pick up tube. Went for a drive and again it idled great and cruised well then after 3/4 mile it "poped" and died. Now when it pops if I back off the gas I can save it from shutting off but if I stay I'm the gas or try to pump it it will die. This time I was impatient and we had to get a jump to get tit running cause I kept turning it over and gave it too much gas. I don't know if the pick up tube is maybe bad? We have blown out all the lines including the breather line the pick up tube and we even tried to run the boat with the gas cap off thinking it was a breather issue but no luck figuring anything out. Really hoping someone has some insight to my issue.

Thanks

Tony Schaefer
Brainerd Minnesota

[Kma4444]

Have you checked it for a spark right after it pops and shuts off. My suspicion is the ignition is letting you down, either a bad connection or electronics failure. Hard shut offs like yours where it is running fine, then something harsh happens and it stops running lead me to believe it's ignition. Think of turning off the switch while you are cruising, very harsh. Fuel issues tend to feel more gradual on carbureted engines, it would likely sort of hesitate or nose over then die, it's very unlikely starving of fuel would manifest itself in a square edged shut off like you mention. Also considering you have gone through the fuel system so thoroughly I would look elsewhere.

Check it for spark when it dies, then check power to the coil if you have no spark. You will find it, you've got to be close now.

[lively]

Go by a Noid light from cheap auto store to rule the spark out . Your ign module might be causing this , but grab a Noid light and hook it up to #1 cly and go drive it when it pops watch the light and see if it flashes out .

Also I had a carb pop before witch in my case is why I replaced my Holley with edlebrock , and my pop was cause by a lean condition , take a video of what your experiencing . Sounds , smells tell everything when diagnosing these issues


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[michael hunter]

I agree its probably ign related. While you are at it make sure the gas tank vent is clear. Call me and I will walk you through checking ignition.
Mike Hunter 678-277-8833