fuel gauge
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Junior User
Joined: Jun 2002
Posts: 79
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fuel gauge
on my 72 f100, when the tank is filled. the gauge shows 3/4 full. when filling up when on empty, i can only get 14.50 gallons in the tank. i should be able to put 4 more gallons in the tank. why isn't the gauge showing an accurate reading?
Fleet Mechanic
Joined: Sep 2003
Posts: 1,279
Likes: 1
From: savannah,ga
most likely the float has allowed gas inside and giving a false reading. carry a gallon can of gas when reading E. when it stops then your empty. add the gallon then fill it up to get accurate
tank capacity. if its still 14.5 then the gauge is correct.
if not then you will need to diagnose the gauge circuit.
pull the wire to the float at the tank and ground it to see if the
dash gauge goes to full. if it does then the problem is the float
run until tank is empty and then get it home with one gallon of gas. drop the tank and pull the float unit out to check the float ball
most dealers still stock this part
tank capacity. if its still 14.5 then the gauge is correct.
if not then you will need to diagnose the gauge circuit.
pull the wire to the float at the tank and ground it to see if the
dash gauge goes to full. if it does then the problem is the float
run until tank is empty and then get it home with one gallon of gas. drop the tank and pull the float unit out to check the float ball
most dealers still stock this part
Senior User
Joined: Jun 2003
Posts: 281
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From: Bearspaw (near Calgary)
Like MHG said it's probably the float. My gauge was doing the same thing. I pulled the float and sure enough it had a rusted pinhole leak in it. That allowed the float to fill with gas and not register properly. I just emptied it, sealed it with some seal-all and reinstalled it. Now it works fine.
Moderator
Joined: Dec 2003
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From: Saskatoon, Saskatchewan
Originally Posted by rrawlins
Like MHG said it's probably the float. My gauge was doing the same thing. I pulled the float and sure enough it had a rusted pinhole leak in it. That allowed the float to fill with gas and not register properly. I just emptied it, sealed it with some seal-all and reinstalled it. Now it works fine.
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Junior User
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i replaced the sending unit including the float and it didn't make a difference to the guage. what should i do now?
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Joined: Jan 2004
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From: Spokane, WA
Check the IVR (internal voltage regulator) it's behind the dash gauge panel. Like others have said clean all the connections and check the wiring for grounding/shorting. Also check the gauge itself. I also installed a new sending unit in my 70 F250 and changed out the internal voltage regulator with no noticible difference it still reads 3/4 with a full tank. My next step will be to clean all terminals at the gauge/sender and switch (dual tank setup) Making sure that there is a good ground.
Good luck.
Good luck.
Senior User
Joined: Jul 2003
Posts: 276
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From: Lacey
Can the sending unit be tested with a mutli-meter? If I moved the float up and down could I read the resistance on a multi-meter? I think I have read they are supposed to read from 73 to 12 ohms up to 1989.
