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Discussion Starter · #1 ·
So bit of a problem here, done a lot of work to this truck and been through three months of bullshit with it. Took out on the road for the first time today and when i got back and shut it off it shot gas straight out the top of the air cleaner. smoking and clicking like crazy too. It's the 318 and with the two barrel holley carburetor if that has any significance. I read somewhere that fuel pressure being to high can cause it to flood like that and I have an inline electric pump instead of the mechanical pump if that could cause it. I just need someone to point me in the right direction as to how to fix this
 

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If the carb has not been rebuilt in the last 10 to 20 years, the valve for the float could be bad, and it can do that with a regular pump.

Yes, too high a pressure can also do that. You mention an electric pump, are you turning it off first?
 

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You may need a regulator between the pump and carb.  They only want like 3-5 psi.  much more than that, and they flood like crazy.  but yeah, it could just be some garbage in the needle/seat.  easy fix, if thats all it is

 

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Discussion Starter · #5 ·
Hey guys I appreciate the help. I've got a new carburetor coming in soon, picked it up for about 70 bucks. Other than that I think I'm going to test just how much pressure I have in the fuel line and replace some other things. Thanks for the help again
 

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Discussion Starter · #7 ·
Ok, so I pulled the return line and it is bone dry, there's a lever with a rubber cap on it that seals it the return shut inside of the carburetor. How should this work?
 

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did this gas shooting out and "clicking" noise happen when you got back and SHUT it OFF ?  I so I suspect it did something called "ran on" or dieseled , means it ran from HOT spots in cylinders not the ignition usually caused  by the throttle plate not closing far enough when the key is shut off ( too much air ) and /or a hot engine temp  NOT by the float  or pump pressure . IF you have a mechanical  fuel pump bolted to operated by the engine , the pressure is not the problem IMO .
 

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Vendance said:
Ok, so I pulled the return line and it is bone dry, there's a lever with a rubber cap on it that seals it the return shut inside of the carburetor. How should this work?
That is just a vent, that closes when the engine is idling, or shut off. With the crap gas now days, it is a good thing to have, it helps keep the gas in the carb bowl from evaporating. Should not have any gas in it, just fumes.
 

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Discussion Starter · #10 ·
So this issue has been fixed. She dieseled a bit when I shut it off but I've since replaced the radiator and the carburetor. Only problem now is she smokes like crazy. I want to say that it's just burning carbon because if I step on the gas itll leave a massive black spot in the grass but the oil and water levels never seem to go down.
 

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Vendance said:
So this issue has been fixed. She dieseled a bit when I shut it off but I've since replaced the radiator and the carburetor. Only problem now is she smokes like crazy. I want to say that it's just burning carbon because if I step on the gas itll leave a massive black spot in the grass but the oil and water levels never seem to go down.
Respectfully, you need to stop guessing and stabbing in the dark at problems. You need to slow down and get some books and learn how your truck works and learn how to properly diagnose the problems it is having.

Black soot on the ground means the engine is running too rich. White smoke = coolant or morning condensation. Blue smoke = burning oil. Black smoke = unburned fuel.

I recommend you get a factory service manual for your specific year of truck as well as these two books:

Stockel and Stockel, "Auto Mechanics Fundamentals". These are always plentiful and cheap, since they were the standard textbook for just about every auto shop class ever taught in North America. Numerous printings; most any will do, but it's best to find one printed a couple years after your car was built.

Petersen's Automotive Troubleshooting & Repair Manual, 1975 (or thereabouts; there were a few print runs of this book. 1974, 1975, 1977 at least.)

Then read those books until you know what is going on with your truck. It will be cheaper and much less frustrating in the long run than throwing money at it and complaining to peopl eon the internet and asking them to diagnose your truck without being able to even see it.

I say this all respectfully and not intending to insult you or start some kind of flame war.
 

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Discussion Starter · #12 ·
I appreciate it. I've got one somewhere I was just trying to get people's opinions on what it could be or where to start checking. I've found the cheat sheet thread and I've got plenty of ideas there too. Even if I wind up replacing things that dont necessarily need to be replaced I'm not too concerned with it because it's an old truck and eventually it will need it.
 

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Vendance said:
I appreciate it. I've got one somewhere I was just trying to get people's opinions on what it could be or where to start checking. I've found the cheat sheet thread and I've got plenty of ideas there too. Even if I wind up replacing things that dont necessarily need to be replaced I'm not too concerned with it because it's an old truck and eventually it will need it.
Replacing worn out parts is all well and good, but if you load up the parts cannon to fix a problem, it'll be frustrating and incredibly expensive. Learning to troubleshoot is a critical skill, especially when one is running a carbureted engine. Fuel injection takes a ton of guesswork out of vehicle tuning, because the computer does the work. Carburetors will actively search for ways to punish poor tuning, and it gets worse as problems build up. Learn to troubleshoot!!!

Your stress levels and pocketbook will thank you.
 

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Discussion Starter · #14 ·
It's all a learning experience. So far I've done so much to the truck and it's been fun learning all of the new things that come with something so old. I was looking around and realized that the stock fuel filter has a return line and I was wondering if it acts as a pressure regulator in itself. If anything I'm going to pick one up and see what happens. I work at a napa so cost isnt really that bad for me to load up the parts cannon.
 

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Vendance said:
It's all a learning experience. So far I've done so much to the truck and it's been fun learning all of the new things that come with something so old. I was looking around and realized that the stock fuel filter has a return line and I was wondering if it acts as a pressure regulator in itself. If anything I'm going to pick one up and see what happens. I work at a napa so cost isnt really that bad for me to load up the parts cannon.
Yes, that's essentially what it does. It's acts as a semi-calibrated fixed bleed-off regulator. The float needle in a carburetor acts as another.
 

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the way a mechanical fuel pump works , the arm pushes a diaframe one way , a spring pushes it back . when the amount of fuel pumped is more than needed , the spring can't return the diaframe , the pump stops pumping , that return on the filter , allows the pump to keep fuel flowing , somewhere , so there is no clatter from the pump , and fuel is always right there when needed by the carb . An additional benefit is the flowing fuel does NOT have a chance to get hot and "boil" in the line , causing something called VAPOR lock to happen .  IT does NOT act as a pressure regulator , no . 
 

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dodge82273 said:
the way a mechanical fuel pump works , the arm pushes a diaframe one way , a spring pushes it back . when the amount of fuel pumped is more than needed , the spring can't return the diaframe , the pump stops pumping , that return on the filter , allows the pump to keep fuel flowing , somewhere , so there is no clatter from the pump , and fuel is always right there when needed by the carb . An additional benefit is the flowing fuel does NOT have a chance to get hot and "boil" in the line , causing something called VAPOR lock to happen . IT does NOT act as a pressure regulator , no .
The filter design allows a return loop, but the size of the return port certainly acts as a local regulator. If the return hole were too large, the pump stroke would take the path of least resistance - i.e. all go back the return line since the needle float valve would have more resistance.
 

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ToxicDoc said:
The filter design allows a return loop, but the size of the return port certainly acts as a local regulator. If the return hole were too large, the pump stroke would take the path of least resistance - i.e. all go back the return line since the needle float valve would have more resistance.
I run a return line off of my main fuel line. I just teed into it.
It's a 1/4" line... BUT I restrict it right at the fuel tank with a main jet off of a Holley carb.
It helps tremendously on hot days here in the desert.
No issues with vapor lock whatsoever.
I can actually hear it squirting fuel back into the tank after I shut off the engine.
 
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