Fuel Tank Sending Unit Problems???
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Tuned
Joined: Oct 2003
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From: Grayling, MI
Fuel Tank Sending Unit Problems???
I have a 1977 Bronco that I got last fall. I pulled the tank today to check out why the gauge wasn't reading right. The tank is a plastic tank and it looks like it has a newer sending unit in it also. I took the sending unit out and it reads 50ohms empty and about 50ohms full when I move the float up and down. I hooked it to the Bronco and moved the float out of the tank and the gauge reads right. When I put the tank back in with no gas in it the gauge reads about 3/4 tank. I put the gas in that I took out before I took it out and it shows full with about 7-8 gallons in it. It is the same as it was when I took it out.
Has anyone had this problem before? Anyone have any ideas on what the problem is? I would appreciate any help.
Steve
Has anyone had this problem before? Anyone have any ideas on what the problem is? I would appreciate any help.
Steve
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The simple diagnosis I have always heard is you take the wire off the sending unit from the harness and ground it. The the gas guage reads full you replace the sending unit. If the guage does not read full, you replace the guage.
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Tuned
Joined: Oct 2003
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From: Grayling, MI
Yeah, I have heard that before too, but like I said it worked fine out of the tank when I had it hooked to the Bronco. That is what has me stumped. It works fine out of the tank, but not in the tank.
Steve
Steve
Ford Parts Specialist
Joined: Nov 2006
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From: Simi Valley, CA
Did you happen to shake the float to discover if there was gas inside? The float is made from 2 pieces of copper soldered together. Solder breaks down, gas seeps into float, float settles slowly to the bottom of the tank.
The float, sender gasket and the plastic mesh filter screen that slides over the end of the pickup tube are available separately from Ford. The float fits every Ford fuel sender, car & truck from 1957 thru 1979.
C0AZ-9202-B .. Fuel Sender Float
C0AF-9276-A .. Fuel Sender O Ring Gasket
D1AZ-9A011-A .. Plastic Mesh Filter Screen
The float, sender gasket and the plastic mesh filter screen that slides over the end of the pickup tube are available separately from Ford. The float fits every Ford fuel sender, car & truck from 1957 thru 1979.
C0AZ-9202-B .. Fuel Sender Float
C0AF-9276-A .. Fuel Sender O Ring Gasket
D1AZ-9A011-A .. Plastic Mesh Filter Screen
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Tuned
Joined: Oct 2003
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From: Grayling, MI
That was one of the first things I checked after I got it out of the tank. There wasn't anything in the float. I think that the sender in an aftermarket unit though. I didn't see any Ford part numbers on it anywhere.
Maybe I should just buy another sender. They are like $50 from Bronco Graveyard. I think I will drop the tank again and check things out before I do that though. See if I missed something.
Steve
Maybe I should just buy another sender. They are like $50 from Bronco Graveyard. I think I will drop the tank again and check things out before I do that though. See if I missed something.
Steve
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Just buy another sender. If it doesn't work in the tank, it doesn't work.
Make sure the gas guage reads full when the lead is grounded. Drive it with the line grounded for while and see if the guage still says full. What you are really looking for in that test is making sure there is not a bare spot on that wire to the sender in the harness that's messing with your reading.
Make sure the gas guage reads full when the lead is grounded. Drive it with the line grounded for while and see if the guage still says full. What you are really looking for in that test is making sure there is not a bare spot on that wire to the sender in the harness that's messing with your reading.
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Tuned
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From: Grayling, MI
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From: Colville
The Early Bronco gauges don't work off of 12 volts there is a resistor that drops the voltage to about 2.5 volts (I don't remember exactly). Having a good ground is extreamly important for the gauge to work corectly. I would run a wire to the sending unit from a very good ground to check to see if that is the reason the gauge works out of the tank and not when it is installed.
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Ford Parts Specialist
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From: Simi Valley, CA
Originally Posted by velcro7279
That was one of the first things I checked after I got it out of the tank. There wasn't anything in the float. I think that the sender in an aftermarket unit though. I didn't see any Ford part numbers on it anywhere.
Maybe I should just buy another sender. They are like $50 from Bronco Graveyard. I think I will drop the tank again and check things out before I do that though. See if I missed something.
Steve
Maybe I should just buy another sender. They are like $50 from Bronco Graveyard. I think I will drop the tank again and check things out before I do that though. See if I missed something.
Steve
Last edited by NumberDummy; Jul 27, 2007 at 06:42 PM.
Thread Starter
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Tuned
Joined: Oct 2003
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From: Grayling, MI
Originally Posted by 68 351 bronc
The Early Bronco gauges don't work off of 12 volts there is a resistor that drops the voltage to about 2.5 volts (I don't remember exactly). Having a good ground is extreamly important for the gauge to work corectly. I would run a wire to the sending unit from a very good ground to check to see if that is the reason the gauge works out of the tank and not when it is installed.
Numberdummy, thanks for the info on the part numbers. Another reason I thought it was aftermarket is that it is chrome. All of the other Ford senders I have seen were like galvanized or zinc plated.
Steve
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From: torrance
Originally Posted by Boba Fett
The simple diagnosis I have always heard is you take the wire off the sending unit from the harness and ground it. The the gas guage reads full you replace the sending unit. If the guage does not read full, you replace the guage.
Thanks,
Chuck
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Joined: Jul 2002
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From: torrance
Originally Posted by slammercb
Where that wiring harness goes into the firewall there are three plugs. I think I know which plug it is but don't know which wire to ground. Anyone know the wire color? 86 F150
Thanks,
Chuck
Thanks,
Chuck
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