Testing Sending unit/fuel guage
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Testing Sending unit/fuel guage
OK, I just put a new sending unit in my rear tank and the tank is working fine, but the fuel gauge still doesnt work. When I unplug the electrical connector that connects the sending unit and put a wire tester on it it blinks. According to the information that I have, that is what it is supposed to do. So I believe that tells me that I have power going to the unit like it is supposed to be. So, I am beginning to assume that the connector itself is worn out. Does this make sense? I thought about simply going to Autozone and picking up a couple of round female connectors to atleast test it with. Any ideas/suggestions?
Cargo Master
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From: Ideeho
Like bullit said.................If you ground the wire coming from the guage back at the connector for the tank and the guage pegs............you have virtually eliminated any other problems from that connector forward to the guage............If that checks out good its from the connector to the sending unit or the sending unit itself......
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OK...so here is what I have. If I put a test light on the wire coming from the gauge the light blinks strong. If I hook a ground wire up to the wire coming from the gauge the gauge doesnt move. Does that mean the gauge is bad? I am going crazy here! Neither tank has much fuel in it, but should be enough to register on the gauge. I am considering going down and dumping more fuel in both tanks to ensure the gauge still does work for the front (it was working fine). OK, so the gauge works just fine on the front tank. Am I to assume the brand new sending unit that I just bought is bad? OK...figured it out finally. I just didnt have a good enough ground so I made a brand new ground straight off the frame.
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Are you testing at the gauge, the switch, the valve or at the sending units?
Green/Red should be rear tank
Black is front tank
Brown with white tracer is the valve.
AT THE SENDING UNIT if you ground either wire with the switch in the correct position it SHOULD pef the gauge to FULL.
If it doesn't work at the sending unit that is when you start working your way back to the switch on the heater control panel.
Or do you have an aftermarket style? Some of those are mounted on the floor board by the seat.
Josh
Green/Red should be rear tank
Black is front tank
Brown with white tracer is the valve.
AT THE SENDING UNIT if you ground either wire with the switch in the correct position it SHOULD pef the gauge to FULL.
If it doesn't work at the sending unit that is when you start working your way back to the switch on the heater control panel.
Or do you have an aftermarket style? Some of those are mounted on the floor board by the seat.
Josh
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It is all fixed now. I was testing it back at the rear tank since the front tank worked fine. It turned out I just had a bad ground. I sanded the frame nice n clean and put a new ring terminal on the frame cross member and now it works perfect.
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From: SWPA
Are we talking about grounding the tank itself?
Both my 97 and 92 have front tank gauge issues. Both tanks work, but the gauge reads "E" on both even when they are full. If it's a short the gauge goes past "E", sending unit problem it just goes "to" E, correct?
Cargo Master
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From: Ideeho
There are two wires that come off of the sending unit. One runs up to the guage, the other is a ground that hooks to the frame. I beleive he is referring to the ground that attaches to the frame.
MSEE
Joined: Apr 2004
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From: Austin, TX
I'm fairly positive that sometime after the 73-79 generation (not sure how much later), the sending unit direction was reversed. You should post these questions in the Electrical forum or the forums for your '92 and your '97, as the principles for 73-79 won't apply.
1st Gear
Joined: Nov 2022
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79 F250 Rear fuel tank
I have a similar problem. The front tank reads accurately. the rear tank has a new sending unit and after fill up (19 Gal) it shows full. then after 25 miles it shows half full...?? i go back to the filling station and it only needs 3 gal. I did clean the ground wire connection to the frame thoroughly and still have the same problem.
Any ideas , suggestions to help me work out this glitch
many thanks to all
Any ideas , suggestions to help me work out this glitch
many thanks to all
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