1st Generation Specific (1979-1985) 1979-1985 Discussion including performance modifications and technical support sections

Wiring for Fuel Sending Unit

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Old 04-24-08, 06:13 PM
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Wiring for Fuel Sending Unit

My gas gauge has read "E" since I've owned my car. I've just never had the motivation to mess with it. But today, I ran out of gas and that was enough for me. First, I tested the sending unit at the plug and just after it. I have 13.?? Ohms after putting gas in. I tested the guage itself and it moves when I put power to it. So my question is, does the guage itself read voltage or ohms? And I was thinking about just running new wires to the gauge, Will this work?
Old 04-24-08, 07:26 PM
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Download the FSM here. It has instructions for testing, removing and replaceing the fuel sending unit. My money is on a bad sending unit.
Old 04-24-08, 07:43 PM
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As far as I know the fuel sending unit is just a potentiometer, in which case it uses the varying resistance across the strip the arm sweeps over to send a varying voltage signal to the gauge...

So I guess both indirectly...

But I agree, your sending unit may be gone.

Try this: Check for continuity through the whole circuit; you should be able to get voltage anywhere on that circuit, if not there may have been a cut/burnt/damaged wire there.
Old 04-25-08, 07:34 AM
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In the sending unit there are three spades (on SE's anyway) The "vertical one is the ground. In three units I have played with, corrosion or whatever has broken contact and you can't get resistence readings from the gound pin. Re-established ground by soldering bit of wire between back of pin and top of sending unit, and it was good to go. I picked this up from an archived bit by Darkfrost I think it was. It includes some pictures etc. that explains it much better.
Old 04-25-08, 11:58 AM
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Here's the page with the fuel sender info:

http://frosted7.com/katrina5.html
Old 04-25-08, 02:00 PM
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I'm assuming that the sending unit is ok. I was at 13 yesterday and 27 today after driving home and back to work. That seems like its working ok. But I tested the guage itself yesterday by putting 12v to it. It went up with power supplied. So I'm still wondering about the guage. Does it read ohms or voltage? I guess I need to check the wires at the back of the guage for resistance. Are they the same colors (at the guage) as the ones running from the sending unit?

I know, this information is probably in the FSM, but reading wiring diagrams is like japanese for me.
Old 04-26-08, 09:44 AM
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Originally Posted by WorkmanGT
I know, this information is probably in the FSM, but reading wiring diagrams is like japanese for me.
Did you even look at the FSM?
Attached Thumbnails Wiring for Fuel Sending Unit-1.jpg   Wiring for Fuel Sending Unit-2.jpg  
Old 04-26-08, 03:31 PM
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I have read both of those pages of the FSM. But those do not answer the question , "Does the fuel guage read OHMS or VOLTS?".

I understand that the FSM has a ton of helpful information and I've read nearly the whole thing out of boredom. But I'm asking a question that I haven't even seen mention of in the FSM. I'm simply asking if anyone has personal experience with this. There should even be a 1st gen section on here, it should just be a link to the damn FSM since that's what everyone tells you to read for every question that is asked.

Thanks for the help everyone, I'm off to solve this my damn self.
Old 10-05-08, 09:56 PM
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Ohms
Old 10-06-08, 04:11 AM
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If the gauge ohms out in spec and the wiring is good, the gauge itself may have failed. Look at the fine white wires that are wrapped around the bar on the backside of the gauge. If there is any browning or blackening, the gauge is toast
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