Blazer addict
out to lunch
Does anyone have a diagram for a 74' k5 fuel system?
CK5
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74' K5 fuel diagram
- Thread starter Blazer addict
- Start date
Probably not, but what do you want to know
Blazer addict
out to lunch
How they vent, we tried to fill the tank with a 5 gal. can and it won't let the gas go down the filler tube and we let it sit for a while and when we tried it again we opened the cap and the pressure was building to the point that the gas in the tube spilled out on the ground. It's only got about 5 gals. in the tank .
Well the filler neck has its own vent tied in to it that vents the tank to the upper portion of the filler neck, you can see it from under the truck. The cap vents the tank. Also a 5/16 line from the tank sender unit up to the vapor can and then to the carb. The 3/8 line from the sender unit feeds the fuel pump.
Sounds like Something is in the lower portion of the filler neck blocking it and/ or the filler vent line is clogged.
Make sure all the lines are clear and not capped off, can you blow thru them. You may have to take the filler neck off and look for an obstruction.
Did this just start or what?
Sounds like Something is in the lower portion of the filler neck blocking it and/ or the filler vent line is clogged.
Make sure all the lines are clear and not capped off, can you blow thru them. You may have to take the filler neck off and look for an obstruction.
Did this just start or what?
If the cap is indeed the vent on these (no idea when that changed to a non-vent cap setup, I guess with EVAP?) take the cap off and see if you can blow and suck air through it freely.
I had an older cap that was vented, for some reason however the little valves work, they quit working, and started building pressure. With a tiny bit of effort you can take the later "high pressure vented" (like 16PSI) caps and simply wedge the little rubber valves open...when air moves freely through it, you are good to go.
The overflowing with the fuel can is a different problem, air has to vent out around the nozzle somehow. In this picture, it's the two punched out slits above the little flap where the nozzle goes: https://lh5.googleusercontent.com/-obDsIrhtb2s/UZ_oPeUyyWI/AAAAAAAABAE/kh9Dfh7H8Xg/w885-h664-no/20130524_181728%255B1%255D.jpg Not sure if there are different fill neck designs in regards to this venting.
Pretty difficult for the vent tube to be screwed up, but if disconnected or if wasps had a chance to build a nest in it at some point, could also be the problem.
I had an older cap that was vented, for some reason however the little valves work, they quit working, and started building pressure. With a tiny bit of effort you can take the later "high pressure vented" (like 16PSI) caps and simply wedge the little rubber valves open...when air moves freely through it, you are good to go.
The overflowing with the fuel can is a different problem, air has to vent out around the nozzle somehow. In this picture, it's the two punched out slits above the little flap where the nozzle goes: https://lh5.googleusercontent.com/-obDsIrhtb2s/UZ_oPeUyyWI/AAAAAAAABAE/kh9Dfh7H8Xg/w885-h664-no/20130524_181728%255B1%255D.jpg Not sure if there are different fill neck designs in regards to this venting.
Pretty difficult for the vent tube to be screwed up, but if disconnected or if wasps had a chance to build a nest in it at some point, could also be the problem.
Blazer addict
out to lunch
The sending unit has 2 lines, no vapor can, they are supply and return. the gas pump fills it but a gas can just spills over. the 5/8 vent isn't plugged. my question is where does the air enter the tank as the gas gets consumed? the cap has no vent and the filler neck has no unleaded restrictions (it's wide open).
The cap should be vented to allow air in as fuel is used, as stated prior non vented caps came later with evap systems.
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Shouldn't matter if your filling with a pump or can it vents the same way while filling unless your blocking the filler with can and it can't vent. (Edit)Disconnect the 5/8 line from the filler and see if it makes a difference with the can.
Return system with 2 lines, 1 supply and 1 return from the pump. With that set up if your tank wasn't vented the return will pressurize the tank.
My 74 has the 2 lines also but uses vapor canister not the return system and my pump doesn't have the 1/4 return line.
Return system with 2 lines, 1 supply and 1 return from the pump. With that set up if your tank wasn't vented the return will pressurize the tank.
My 74 has the 2 lines also but uses vapor canister not the return system and my pump doesn't have the 1/4 return line.
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Blazer addict
out to lunch
He's driving now with a new vented cap so we'll see tomorrow in the heat of the day if it's working,and thanks everyone for the advice.
