CARBURETOR DATED

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AuroraGirl

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Joined
Sep 8, 2019
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Location
Northern Wisconsin
First Name
Taylor
Truck Year
1978, 1980
Truck Model
K10, K25
Engine Size
400(?), 350
Just a random thought but has anyone considered a drain-back issue?
I have drain back issues but i think mine are due to the diaphram on the fuel pump, the fuel lines are empty after a couple days. I put a fuel line check valve before my fuel nipple in the hose honestly no idea if its doing much or not but i thought it seemed to hold better

Cranking first, then a couple pumps, itll start everytime
 

Ricko1966

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Joined
Apr 11, 2017
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Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
wdym not possible?
Fuel comes in from the top,not the bottom it can't pull a siphon because it will suck air from the top of the float bowl.
 
Last edited:

Ricko1966

Full Access Member
Joined
Apr 11, 2017
Posts
5,323
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8,474
Location
kansas
First Name
Rick
Truck Year
1975
Truck Model
c20
Engine Size
350
I have drain back issues but i think mine are due to the diaphram on the fuel pump, the fuel lines are empty after a couple days. I put a fuel line check valve before my fuel nipple in the hose honestly no idea if its doing much or not but i thought it seemed to hold better

Cranking first, then a couple pumps, itll start everytime
The valves in the fuel pump should keep fuel in the main line. If you are running a 1406 and a 3 line pump it will probably never hold fuel long from the pump to the carb. It will drain through the return line as if there is the tiniest air leak,porosity of the fuel line,as soon as enough fuel evaporates to et the seat open a tiny amount, or if the needle and seat leak at all.With the 1406 and a return line the only thing keeping fuel in the feed line from draining through the return line is that it can't get any air, just like putting your finger on the end of a straw to hold liquid. Any air at all and your liquid runs out.Qjets with a return style pump had the needle and seat and a check valve in the fuel filter to keep fuel in the feed line. But your 1406 bowl should hold fuel to start the vehicle because the fuel bowl can't syphon.
 

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