Bad fuel gauge??
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Senior User
Joined: Feb 2003
Posts: 395
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From: South Carolina
Bad fuel gauge??
Any ideas on a fuel guage that only goes to 3/4 when the tank is full? Bad guage, sending unit, float??? I replaced the float out my parts truck (it worked fine when I parked the truck about 3 years ago). That didn't fix it, though. I noticed that there are two wires on top of the float assembly... is this part of the sending unit? Also, if the guage only goes to 3/4 on fillup... reckon that means that when it gets to E that there is 1/4 left? 
Senior User
Joined: Aug 2001
Posts: 211
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From: Houston, Tx
Bad fuel gauge??
My gauge does the same thing. However, I am using a 67 mustang gas tank and sender. If yours is really like mine, you should run out of gas just as the needle hits "E". I think that most trucks without this problem can go a while on "E".
Freshman User
Joined: Jan 2003
Posts: 36
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From: Long Beach
Bad fuel gauge??
Time to check the float. I don't know how many cars I have looked at that had microscopic holes in the gas gauge sending unit float. Gas will slowly seep into the float until it's weight will not permit it to rise to the top of the tank. Eventually it will not rise at all and will sink to the bottom. The brass float is as thin as crepe paper and the leaded seam tends to get leaks around it and the brass. Pull out the unit, and take off the float VERY CAREFULLY. Give it a shake and see if you feel or hear gas inside it. Get a new float for a couple of bucks, the plastic ones won't give you a lick of problems. Beats a half filled up old float submerged like a submarine in your gas tank. Oh by the way, once you have pulled out the float and removed the unit, now is the time to paint that rusty steel float arm so it wont rust in half and break while you out in the middle of nowhere!
New User
Joined: Mar 2003
Posts: 19
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Bad fuel gauge??
The problem probably lies in you instrument cluster. If you remove the gauge bezel there is a small electrical unit 1/2 inch by an inch. Im not sure what it does but it affects all the guages. I replaced my sending unit, float and my gauge only went to 1/2 way. I replaced this little box and walla it worked again.
Just something you might want to look at.
Later, jaret
Just something you might want to look at.
Later, jaret
New User
Joined: Mar 2003
Posts: 14
Likes: 0
From: Seattle, WA USA
Bad fuel gauge??
Is there anywhere online to read how to perform the test? Both of the gas guages are dead on my 69 f250, and I suspect it is the IVR (I have yet to find myself a set on manuals). What is the best place to get a replacement IVR?
Thanks a lot!
Update: Sorry, I just searched past posts and I found the info I needed, so nevermind. I'll do that first next time
Thanks a lot!
Update: Sorry, I just searched past posts and I found the info I needed, so nevermind. I'll do that first next time
Last edited by 69GasHog; Mar 20, 2003 at 12:18 PM.
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Bad fuel gauge??
This also works for the fuel gauge.
*NOTE*
If the other gauges work properly,The Voltage reg is NOT the problem.
To check the gauges with the key off:
Take the connector for the oil pressure sending unit off
put a cotter pin it, now attach it to a good ground,go back and turn the key to ON > If the gauge pins to the high side the gauge is good.
Now do the same with the temp sending unit.
If the gauge DOESN'T pin, there is either something wrong with the gauge,wiring,or IC V reg.
To check the IC V.Reg with key ON:
Take a test light and attach it to the sending units wiring.
You should have a PULSING light.
If so, the IC V. reg is Okay.
If Not,either the wiring is bad or the V reg. is bad.
The IC V.reg is located on the back of the Instrument cluster.
So,If you have a gauge that Pins and a Connector that Pulse flashes : the problem is with the sending unit.
Check the S.U. for teflon tape wrapped around the threads.
If so,remove it and check it again for gauge reading.
Always use the proper sealant for sending unit threads.
Teflon tape is insulator so use the minimum amount to make sure the metal touches
You ca also use a conductor sealant.
*NOTE*
If the other gauges work properly,The Voltage reg is NOT the problem.
To check the gauges with the key off:
Take the connector for the oil pressure sending unit off
put a cotter pin it, now attach it to a good ground,go back and turn the key to ON > If the gauge pins to the high side the gauge is good.
Now do the same with the temp sending unit.
If the gauge DOESN'T pin, there is either something wrong with the gauge,wiring,or IC V reg.
To check the IC V.Reg with key ON:
Take a test light and attach it to the sending units wiring.
You should have a PULSING light.
If so, the IC V. reg is Okay.
If Not,either the wiring is bad or the V reg. is bad.
The IC V.reg is located on the back of the Instrument cluster.
So,If you have a gauge that Pins and a Connector that Pulse flashes : the problem is with the sending unit.
Check the S.U. for teflon tape wrapped around the threads.
If so,remove it and check it again for gauge reading.
Always use the proper sealant for sending unit threads.
Teflon tape is insulator so use the minimum amount to make sure the metal touches
You ca also use a conductor sealant.
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