fuel tank question
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Junior User
Joined: Feb 2005
Posts: 54
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From: GA.
fuel tank question
here it is, i have two tanks on my 89 f350 7.3na not sure what size they are, so this the crazy thing, if i run either one of the tanks below 1\2 a tank the mpg's drops to around 14mpg's and if i fill up before they get below 1/2 a tank the mpg's stay around 18 and 19mpg's. so... what gives, is it the fuel tank pick up lines are cracked or something else?
thank's for any help.
austin
thank's for any help.
austin
Fleet Mechanic
Joined: Sep 2005
Posts: 1,509
Likes: 3
From: Ladner, British Columbia
I noticed on my 91 F350 that the Fuel Gauges are not very accurate.
I will do 200 miles on 1/2 a tank and then barely get another 100 miles on the rest of the tank.
I believe mine are 20 gallon tanks, I would have to check the book.
I will do 200 miles on 1/2 a tank and then barely get another 100 miles on the rest of the tank.
I believe mine are 20 gallon tanks, I would have to check the book.
Freshman User
Joined: Mar 2006
Posts: 32
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I have a 92 with the dual tanks, when the needle is on E on the guage. I still have 5 gals of fuel left in the front tank, and about 7 gals in the rear. the tanks on the truck are 20 gals in the mid-ship and 18 gals in the rear. the gas guages in the dual tanks from ford are very inaccurate, I have an 83 gas 300 six with the same dual tanks and the guage works about as good as the diesel's does.
the way I found out how much the tanks held was to run them dry(one at a time of course) and just fill them up to see how much they hold empty. both of my trucks hold the same amount of fuel , however I have read and was told by my local dealer they should not be the same. so , it may not be the best way, but it will get the job done.
V/R
John
the way I found out how much the tanks held was to run them dry(one at a time of course) and just fill them up to see how much they hold empty. both of my trucks hold the same amount of fuel , however I have read and was told by my local dealer they should not be the same. so , it may not be the best way, but it will get the job done.
V/R
John
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Junior User
Joined: Feb 2005
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From: GA.
Guatman, yes by filling up. i should of said that in the first post, if i run the truck around about 120 miles on one tank and 120 miles on the other for a total 240 or 250 miles, the mpg's stay about 17 to 19, and if i run the miles up 350 or more the mpg's drop down to about 14 to15. sorry that i was not clear before. i know that the fuel guages are not very accurate, heck one of them does not even work.
thanks for the replys and the help.
i will try and be more clear with my post.
thanks for the replys and the help.
i will try and be more clear with my post.
Freshman User
Joined: Sep 2005
Posts: 38
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From: Guatemala
I agree with Dave on this one, sounds like you may have a air leak in the dip tube. Do you have any trouble starting it when the tanks are low?
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Junior User
Joined: Feb 2005
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From: GA.
No, not that i can remember. have not had hard starts in a long time. i just hate to drop the tanks and that not it. what i mean is i don't want to drop the tanks at all. but it looks like there is no way around it. thanks for the help everyone, i need all of it that i can get.
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Post Fiend
Joined: Nov 2003
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From: Nutter Fort, WV
The bad thing about a small leak like that is it will be almost impossible to see.
To find it you will probably have to use low air pressure into the pickup tube with your finger over the other end while holding it under water.
Bad thing is the leak could also be in the line anywhere between the tank and fuel pump. It does not take much air to mess up a diesel.
The only reason I say it is an air leak is for the performance to drop off as the fuel pump has to lift the fuel farther just sounds like a small air intrusion problem.
To find it you will probably have to use low air pressure into the pickup tube with your finger over the other end while holding it under water.
Bad thing is the leak could also be in the line anywhere between the tank and fuel pump. It does not take much air to mess up a diesel.
The only reason I say it is an air leak is for the performance to drop off as the fuel pump has to lift the fuel farther just sounds like a small air intrusion problem.
Lead Driver
Joined: Jan 2005
Posts: 7,782
Likes: 221
From: Huntington Indiana
Before doing the extreme. check the fuel lines on the frame to see if they are corroded badly. Could be getting air in there. Mine was - but it started badly.
Last edited by bigredtruckmi; Jul 6, 2006 at 08:05 PM.
