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Discussion Starter #1
I recently replaced the sending unit on my tank because the top tubes got rested out, causing gasonline to pool in the top depression on the tank.. I replaced it with an aftermarket one, as opposed to the $900 OEM one... Since I did this, I am no longer able to fill the tank up completely. It fills to about 7/8 and then the pump clicks off... Usually (before this work) I could easily pump 2 or 3 more bucks into it, top it up, and good to go... Now, it IMMEDIATELY spits gas back at you if you try to put more in... I can pump more gas in, 1 cent at a time, and fit another 10 bucks into it before it starts spilling out the top..

I figured I must have kinked a line or something during the work, but I looked over everything, and it all looks fine... I unhooked all the vent hoses, and blew air through them all.... I can hear air going into the canister, and I can hear the solenoid working properly.

There are no codes or lights....

Any ideas?
 

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Is it possible to connect the hoses up wrong? Possibly a vent hose is connected to a check valved fitting in error.
Also topping up a tank often leads to spilling fuel in to the evap can, causing it to be over loaded with liquid fuel as apposed to vapors . turning the charcoal inside into a solid lump requiring replacement of the evap can down the line..
Luck
 

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Premium Member
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Discussion Starter #3
Is it possible to connect the hoses up wrong? Possibly a vent hose is connected to a check valved fitting in error.
Also topping up a tank often leads to spilling fuel in to the evap can, causing it to be over loaded with liquid fuel as apposed to vapors . turning the charcoal inside into a solid lump requiring replacement of the evap can down the line..
Luck
There are only 2 hoses that go into that unit... One for the fuel to the engine, and the vent hose.

As I said, everything was perfect since the truck was new, and just started when I changed this unit.. Its an aftermarket one, I am wondering if there is something wrong/different with the vent portion? The blue thing in this picture...
339947
 

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The rusted hole in the pump top was functioning as a vent to the tank, and once you repaired it it's now relying on the actual tank vent. The tank vent connects to the EVAP canister, which vents either by a solenoid valve into the intake manifold (which is modulated open/closed during engine operation), or another solenoid valve that vents to atmosphere that is normally open. I'll guess the solenoid valve is clogged or stuck, or some hose associated between the pump and the canister vent is clogged. Another thought is the tank roll-over protection valve in line with this vent hose is stuck closed - this usually results in people getting a gas bath when filling the tank once the gas level is high enough to stop air in the tank from venting back up the fill tube.
 
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