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360 cutting out |
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John b 
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Joined: Feb/14/2021 Location: Massachusetts Status: Offline Points: 14 |
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 Topic: 360 cutting outPosted: May/15/2021 at 11:12am |
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Hi
I have a 1980 j20 360 automatic Just completely rebuilt engine When driving after about 30 minutes the engine cuts out Have to pull over put in neutral and gently rev engine Usually doesn’t stall if put in neutral Then after a minute or so I can continue driving So long as I don’t accelerate hard May go a couple miles Seems to happen when hot and accelerating What I’ve done so far: Has edelbrock carb Did many adjustments but no change So I swapped with another carb from my other Truck that I know runs great Replaced fuel lines Checked fuel pressure 5-6 pound Then I eliminated gas tank by running fuel from 5 gallon can in bed Same results Also have tried many timing adjustments And vacuum advance is working Could it be bad coil when hot? Has new hei distributor No backfire Just cuts out intermittently I feel like I covered all fuel possibilities Thanks for reading
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Heavy 488
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Joined: Apr/27/2019 Location: In the Status: Offline Points: 3552 |
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Posted: May/15/2021 at 11:37am |
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Fuel return line hooked up at the filter or did you scrap that?
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John b
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Joined: Feb/14/2021 Location: Massachusetts Status: Offline Points: 14 |
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Posted: May/15/2021 at 11:46am |
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I eliminated fuel return , didn’t help
SoI bypassed fuel tank going to gas can I think I eliminated Any problems with the truck gas tank Everything is new Completely rebuilt engine by professional engine builder Thanks for your reply
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Softbuster
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Joined: Nov/08/2014 Location: Pennsylvania Status: Offline Points: 116 |
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Posted: May/15/2021 at 12:15pm |
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Kinda sounds like a failing fuel pump, it might make pressure but not be able to flow enough volume to meet the demand at throttle and so starve the engine of fuel. Idle a bit in neutral and it can re fill the carburetor again to go for a while. I had this issue.
It could also be that the fuel is getting too hot and boiling (vapor lock) The feedback fuel filter system is designed to send air bubbles to the gas tank and fuel to the carb, on the feedback fuel filter have the return outlet of the filter 90 degrees straight above the fuel line going to the carb, then air rises and is pushed into the tank. A failing coil would not make sense that it would work again after idling for a little in neutral. It could be something grounding out the ignition, but that would shut the engine off entirely until the wire stops making contact against whatever its grounding to. Keith
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Softbuster
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Joined: Nov/08/2014 Location: Pennsylvania Status: Offline Points: 116 |
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Posted: May/15/2021 at 12:18pm |
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Where was the fuel pump from?
New parts can be faulty sometimes, I had 2 new faulty starter solenoids so i pulled them apart and made one good one Haha.
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John b
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Joined: Feb/14/2021 Location: Massachusetts Status: Offline Points: 14 |
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Posted: May/15/2021 at 12:27pm |
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I am running a stock mechanical fuel pump
I have a spare electric pump Maybe I’ll try that it would keep fuel cooler than mechanical one So maybe it is vapor lock?
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Softbuster
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Joined: Nov/08/2014 Location: Pennsylvania Status: Offline Points: 116 |
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Posted: May/15/2021 at 12:34pm |
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Case of beer says its the fuel pump!
Vapor lock is a possibility but not super common,
a 3rd option is something clogging in the carburetor. |
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Heavy 488
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Posted: May/15/2021 at 12:38pm |
Good choice. You eliminated the line the factory installed to ward off vapor lock issues
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John b
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Joined: Feb/14/2021 Location: Massachusetts Status: Offline Points: 14 |
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Posted: May/15/2021 at 12:38pm |
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I’ll have to try fuel pump
Maybe I’m buying the beer thanks
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72gremx401
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Joined: Oct/02/2014 Location: bc Status: Offline Points: 123 |
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Posted: May/15/2021 at 4:23pm |
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my thought is vapour lock, any were the fuel line is close to exhaust?
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1972 gremlin x 401
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John b wrote: