fuel tank anomaly....
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More Turbo
Joined: Feb 2005
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From: Orange, CT
fuel tank anomaly....
Here's a brainteaser:
I've run out of gas a few times now (thank God I have the saddle tanks) because my main tank stops feeding after it has fed about 8 gallons. I can fill it up, and after about 8 gallons have been used (somewhere under 100 miles), the tank "goes dry". Then I fill it, and it only takes about 8 gallons!
What's up with that? I know it's filling to the top, because you can hear it sloshing around.
Could the feeder tube somehow be standing that high in the tank that it never uses the lower part of the tank?
I've given up (for now) using the main tank, and just run on the saddle tanks until they go dry, then swith to the main for a spare.
Any ideas?
I've run out of gas a few times now (thank God I have the saddle tanks) because my main tank stops feeding after it has fed about 8 gallons. I can fill it up, and after about 8 gallons have been used (somewhere under 100 miles), the tank "goes dry". Then I fill it, and it only takes about 8 gallons!
What's up with that? I know it's filling to the top, because you can hear it sloshing around.
Could the feeder tube somehow be standing that high in the tank that it never uses the lower part of the tank?
I've given up (for now) using the main tank, and just run on the saddle tanks until they go dry, then swith to the main for a spare.
Any ideas?
Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
I had a similar problem with a Clients 65 Dodge truck with the tank behind the seat. I discovered the draw tube had corroded/ rusted so a few pin holes part way down the tube.
Once fuel level dipped below holes in the tube, fuel pump sucked froth or air through the line. The engine would not run. I could not buy another fuel tank sender unit so I slid a piece of tubing over the OEM tube & silver-soldered ****' ends closing them on the outside of the OEM tube. A lot of hassle but seemed to work fine.
The truck sat unused for a number of years before I ever worked on it. I figure some condenstaion caused that problem over the years it sat unused.
FBp
Once fuel level dipped below holes in the tube, fuel pump sucked froth or air through the line. The engine would not run. I could not buy another fuel tank sender unit so I slid a piece of tubing over the OEM tube & silver-soldered ****' ends closing them on the outside of the OEM tube. A lot of hassle but seemed to work fine.
The truck sat unused for a number of years before I ever worked on it. I figure some condenstaion caused that problem over the years it sat unused.
FBp
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More Turbo
Joined: Feb 2005
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From: Orange, CT
Hmmmmm,
I'll bet mine sat for a long time in it's past, so maybe you're on to something. But isn't the draw tube inside the tank really short, like standing up above the bottom just enough to empty the tank, but still leave sludge sloshing around? How can a draw tube stop drawing with over a half tank left?
Saturday in the mail I got my 4-volume official Ford Service Manual set. I'll look in the Fuel section and see if it gives me some kind of clue.
Thanks!
I'll bet mine sat for a long time in it's past, so maybe you're on to something. But isn't the draw tube inside the tank really short, like standing up above the bottom just enough to empty the tank, but still leave sludge sloshing around? How can a draw tube stop drawing with over a half tank left?
Saturday in the mail I got my 4-volume official Ford Service Manual set. I'll look in the Fuel section and see if it gives me some kind of clue.
Thanks!
Postmaster
Joined: Sep 2004
Posts: 3,166
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From: wi
if the tube has a pin hole in it it will draw air instead of gas try a lil experiment next time ya get a coke at some fastfood place bend the straw a couple times so it gets a small hole in it youll only drink half your coke
Senior User
Joined: Apr 2004
Posts: 289
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From: Raleigh, NC
Brider,
FordBoyPete is saying there is a hole in the tube half way down (or up). When the fuel level gets to the hole it stops using fuel from the tannk and starts sucking air.
edit - Dang, wizzard beat me to it...
FordBoyPete is saying there is a hole in the tube half way down (or up). When the fuel level gets to the hole it stops using fuel from the tannk and starts sucking air.
edit - Dang, wizzard beat me to it...
Senior User
Joined: Sep 2004
Posts: 446
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From: Texas
the Dodge was drawing fuel from the top through a tube that went down. our fords draw off the bottom, so the tube can't be the problem.
If the tank has baffles, one of them may be plugged, so it's not letting fuel flow to the other side.
If the tank has baffles, one of them may be plugged, so it's not letting fuel flow to the other side.
Laughing Gas
Joined: Jun 2003
Posts: 1,218
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From: Parkville, MO (KC)
Ehhh... 66beater, you talking about the "main" tank behind the seat, right? That one at least draws from the TOP, just as everyone is trying to explain.
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Posting Guru
Joined: Jul 2003
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From: East Central Florida
66 beater,
What sort of fuel tank do you have? And where is your Fuel Gauge Sender located?
OEM Behind the seat fuel tanks, in fact all FoMoCo fuel tanks I ever saw draw from the top with their pick-up tube extending down into tank & fuel load. The fuel gauge sending unit is also mounted on that assembly (tube). Like Steve says there's a soda straw effect of fuel extraction. Fuel goes up before going down & exiting through cab floor, or at least it did/ does in OEM set ups.
I don't think a cap can be the problem. 8 gallons is a lot of fuel. It doesn't take that much to "vacuum lock" a fuel line in a non vented system. He's talking about -8 gals from full. If he had a nearly empty tank it would take longer because there is greater expansion of air vs fuel, but in a full tank there is little to no air to expand. It Would Vacuum Lock before the 1st gallon was drawn off. . . .
The way to find out is pull sender unit & fuel draw tube from the tank & look.
FBp
What sort of fuel tank do you have? And where is your Fuel Gauge Sender located?
OEM Behind the seat fuel tanks, in fact all FoMoCo fuel tanks I ever saw draw from the top with their pick-up tube extending down into tank & fuel load. The fuel gauge sending unit is also mounted on that assembly (tube). Like Steve says there's a soda straw effect of fuel extraction. Fuel goes up before going down & exiting through cab floor, or at least it did/ does in OEM set ups.
I don't think a cap can be the problem. 8 gallons is a lot of fuel. It doesn't take that much to "vacuum lock" a fuel line in a non vented system. He's talking about -8 gals from full. If he had a nearly empty tank it would take longer because there is greater expansion of air vs fuel, but in a full tank there is little to no air to expand. It Would Vacuum Lock before the 1st gallon was drawn off. . . .
The way to find out is pull sender unit & fuel draw tube from the tank & look.
FBp
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Joined: Feb 2005
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From: Orange, CT
Hey guys- it's ME, brider, who has the problem, NOT 66beater.
So I am now educated as to how the main tank draws, thru a tube extending DOWN, not thru a tube extending UP, as I assumed. That explains everything! ( I suppose I would have learned this if I had just pulled the sender).
My gas guage ALSO does not work, so I knew I had to pull the sender sometime, but for now I've been lucky, operating off the saddle tanks and using the main as a spare.
Thanks for all the help, I'm sure my problem is the "straw effect".
So I am now educated as to how the main tank draws, thru a tube extending DOWN, not thru a tube extending UP, as I assumed. That explains everything! ( I suppose I would have learned this if I had just pulled the sender).
My gas guage ALSO does not work, so I knew I had to pull the sender sometime, but for now I've been lucky, operating off the saddle tanks and using the main as a spare.
Thanks for all the help, I'm sure my problem is the "straw effect".
Posting Guru
Joined: Jul 2003
Posts: 2,222
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From: East Central Florida
Brider, a couple posts up 66 beater said MoPaR may empty from top but Fords "MT" by draining down, and they don't. They also draw up using a draw tube we're talking about. It's the one that comes out the top of in cab tanks, where sender wire connects. . . To state draining or "MT"ing from the bottom confuses the issue.
Look closely where rheostat housing is "spotted" onto draw tube, most likely that's where the "fault" will be.
FBp
Look closely where rheostat housing is "spotted" onto draw tube, most likely that's where the "fault" will be.
FBp
Last edited by FordBoypete; Jun 28, 2005 at 11:21 AM.