Fuel gauge acting up!! - Team Camaro Tech
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post #1 of 5 (permalink) Old Jan 9th, 06, 07:30 PM Thread Starter
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Darren
 
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Location: Inman, S.C.
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Question Fuel gauge acting up!!

I have a 69 prostreet with a stock fuel gauge in the dash. I have a 12 gallon fuel cell hooked to it. My question is my gauge is buried on E and want move at all until i am in the car and going down he road as soon as get on the gas hard it rises like if it was my tachometer. thejn goes back down as the rpm's go down. can you help me or maybe tell me where and what to start checking
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post #2 of 5 (permalink) Old Jan 9th, 06, 08:16 PM
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Jim
 
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Re: Fuel gauge acting up!!

Disconnect the sending wire off of the sender that goes to the gauge and see what happens. If it reads and stays above full then the wire forward should be ok but for another test after that to further verify the gauge and that wire are OK would be to ground the wire off of the sending unit that goes to the gauge and the gauge now should read empty and stay there. If this is how it works then the problem is in the sending unit, the ground for the sending unit, or the lack of a baffle or foam inside the fuel cell.

Jim

1974 Spirit Of America Nova (being restored), 1973 Nova Custom, 1968 Chevy II (Garage Find 2012)

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post #3 of 5 (permalink) Old Jan 10th, 06, 04:31 PM Thread Starter
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Darren
 
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Re: Fuel gauge acting up!!

Hey i did everything you said and when i unplugged the sending unit my gauge shot way past full. Then i grounded that same wire and flew back down to empty. So i guess all the wiring and gauge are okay. I looked to see if there is ground on the fuel cell but don't see one. where would you usually ground it at? Also my fuel cell doesn't have any foam in it why would that cause a problem? If i pull my sending unit out how would i go about checking that?
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post #4 of 5 (permalink) Old Jan 10th, 06, 05:00 PM
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Jim
 
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Re: Fuel gauge acting up!!

if the test passed, but the guage still goes to empty when you hook the wire up, there is a problem with the sender itself... With a fuel cell, it's hard to say from here whats in there...take the sender out, hook the wires back up, and see what the guage does when you move the float manually. Disconnect the wires and hook an ohmeter to the sender. It should read zero ohms float down, and 90 up. Could be simply the wrong sender, many oither makes use senders 200 ohms or more. No baffles could cause some sloshing which would move the guage, but when the tank is full the guage should say so.





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post #5 of 5 (permalink) Old Jan 10th, 06, 05:07 PM
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Jim
 
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Re: Fuel gauge acting up!!

Quote:
Originally Posted by Adaz71
Hey i did everything you said and when i unplugged the sending unit my gauge shot way past full. Then i grounded that same wire and flew back down to empty. So i guess all the wiring and gauge are okay. I looked to see if there is ground on the fuel cell but don't see one. where would you usually ground it at? Also my fuel cell doesn't have any foam in it why would that cause a problem? If i pull my sending unit out how would i go about checking that?
Ok with the two tests you did the gauge and the wire from where you disconnected it are fine so your guess is right on.

There should be a ground wire off of the sending unit and also the fuel cell to pass most racing rules and to keep from arcing with static electricity when refueling (there used to be some fires years ago with people filling plastic gas cans in the beds of the trucks that had the plastic liners in them).
Most of the time you can use one of the mounting bolts that hold the sending unit into the fuel cell by taking it out and putting a ring terminal on the bolt and putting the bolt back in and then on the other end of the wire put on another ring terminal and use a screw (nut and bolt would be betst with a lock washers or two) to attach it to a clean, bare metal spot on the car.

With no foam or baffles in the tank the fuel is sloshing back and forth, side to side and this makes the float arm of the sending unit go up and down and makes the gauge read high and low. When you are sitting still the fuel slowly levels itself out and the gauge does not fluctuate as much. Some gauges are designed to read slow even though the sending unit might be going from one extreme to the other or with a little bit of sloshing of fuel in the tank. I doubt by swapping to a different style sender would do anything for the fluctuating gauge up front. You just need to control the sloshing and movement of the fuel inside the cell. I have seen and installed aftermarket senders that are in a hollow tube and those work the best with a foam filled fuel cell as you cannot really use a stock swing arm style sender with the foam as you would have to remove a fair amount of the foam to keep it from interfering with the swing of the float arm off of the sending unit. What would be cut away would still allow fuel in that area to slosh around and would still make the gauge fluctuate more than it should.
I would think Jaz or the other fuel cell companies would sell the foam. Just make sure it's compadible with the fuel you are using (gas and alcohol may take different foams). Once you get the foam remove the swing arm type sender and then install the foam. Now by using a large straight knife go through the hole where the sender was at and cut out the foam directly below it and then install the tube style sender.

Jim

1974 Spirit Of America Nova (being restored), 1973 Nova Custom, 1968 Chevy II (Garage Find 2012)

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