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Discussion Starter #1
since i modified the smog set up off the tank, my California Cougar fuel tank has been getting really full at the pump, well past the "F".

seems that when the tank is that full and i go up a hill, the fuel in the tank blocks the vent at the top of the tank and prevents air from entering the tank to replace the fuel that leaves. which of course causes a significant loss of power.

obvious answer is to not fill it up all the way. i can do that. just curious if there might be another fix. can i fix the tank? why doesn't the float in the tank prevent the tank from getting that full? thanks-

billy
351W California Cougar
 

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What did you do to the tank when you modified it?

I am NOT aware of a California Cougar fuel tank set up, but the only float I am aware of is the FUEL GAGE SENDING UNIT, and it has nothing to do with how much fuel goes in the tank, it only tells you how full the tank is. Did you have the FLOAT out of the tank when you modified the smog system?

Dale in Indy
 

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Did yo take out the 20 gallon California only tank and replace it with the 49 state 22 gallon tank? What about the gas cap? Did you use the 49 state vented one? The smog (Vapor return) tank used the vapor return system to vent the tank the 49 state tank uses a vented cap. I'm not sure what is causing the problem.
 

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Discussion Starter #4
Did yo take out the 20 gallon California only tank and replace it with the 49 state 22 gallon tank? What about the gas cap? Did you use the 49 state vented one? The smog (Vapor return) tank used the vapor return system to vent the tank the 49 state tank uses a vented cap. I'm not sure what is causing the problem.
i used the same 20 gallon tank. the smog system consisted of four lines attached to the top of the tank. those lines were in turn plumbed in the trunk in a crazy way that didn't make a lot of sense to me, took up a lot of room, made the trunk area quite lumpy, and in the end, was more of a band aid to make someone feel good that they were doing something positive for the environment. i am all for that, but it really didn't do much.

all i did was get rid of 90% of the system, but retained one line to vent to the ambient air so the tank could suck and blow when it needed to. the filler neck is a different size on the 20 gallon vs the 22 gallon so there is no vented cap that will fit the beast. so i use the standard non-vented cap. the problem is the tank is getting overfull and when the car is going up a hill, the fuel is blocking the hole to the line i am using for venting.

so maybe the question is why is the tank getting overfull? does it matter which of the four lines is used to vent? or is it just a coincidence that i messed with the system and now it overfills? i did not mess with the tank float or anything inside. the easy answers are - don't fill it all the way, or replace the tank with a standard 22 gallon tank and vented cap. but you know how we are - we like solving puzzles!!
 

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I take it you have tried running less gas and you don't have the problem?

Maybe you could make your own vented cap...:flamer:

I'd use a drill though! ;>) start small and work your way up.
 

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Discussion Starter #6
I take it you have tried running less gas and you don't have the problem?

Maybe you could make your own vented cap...:flamer:

I'd use a drill though! ;>) start small and work your way up.
thought about making my own cap from a stock non-vented cap. i think the problem would still remain - with an overfull tank, going up a hill, the fuel would fill some or part of the filler neck and again there would be no way to suck air into the tank, since the fuel would be up against the back side of the cap.

i am working my way through this tank of gas to trouble shoot when it gets down below 3/4 or so. however, maybe related maybe not - although it does great with a full tank on level ground, with and without secondaries kicking in- it does start to break down above 75-80 mph. ok, i am rarely there, but in the interest of trouble shooting i did get it up there and it starts to sputter. again, could be sucking air like it is supposed to but not at a high enough rate to replace the fuel leaving at that kind of demand. or could be the fuel pump unable to keep up.

any thoughts on that? thanks-

billy
 

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Yeah I wondered about that too, but I think what may be happening is that the fuel moving around could be creating a vacuum more so than anything else when there is only one area to relieve pressure. By adding a secondary source it should be a push/pull thing and not create as much vacuum when sloshing around. At least that sounds goo in theory --- right? I bet your fuel pump is ok. Just a matter of finding the right balance. I wonder if they make such a thing as a one way valve you could replace one of the cutt off hoses with? (fuel resistant of course)
 

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Yeah I wondered about that too, but I think what may be happening is that the fuel moving around could be creating a vacuum more so than anything else when there is only one area to relieve pressure. By adding a secondary source it should be a push/pull thing and not create as much vacuum when sloshing around. At least that sounds goo in theory --- right? I bet your fuel pump is ok. Just a matter of finding the right balance. I wonder if they make such a thing as a one way valve you could replace one of the cutt off hoses with? (fuel resistant of course)
does sound good in theory. but if that is true, how does a regular tank vent? just through the vented cap, or does it have a secondary source? gotta' be a lot of non-Cali fuel tanks out there. is the cap the only vent source?
 

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I was thinking charcoal canister....but now that you mention it - I don't think mine has/had one..? Hmmm - good question. I sumped my tank many years ago, so the factory stuff went out the window. I can't recall if it did for sure, but it doesn't have one now. But I am running electric pump as well. I guess it couldn't hurt to check your fuel pump volume. If I remember right the rule was it should fill up a pop bottle (12 oz) in 3 pumps when you turn it over (make sure it doesn't start! LOL) If running less gas solves it, then you are back to square one. Would the fill kneck angle be different on a Cali I wonder? Curious to see what you figure out.....
 
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