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#1 |
Registered User
Join Date: Nov 2011
Location: USA
Posts: 387
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Trying to figure out why my fuel gauge doesn't read correctly
On my 1968 Chevy C10 the fuel sending unit had already been replaced with a new one by the previous owner but that did not fix the problem of the fuel gauge not reading correctly. The gauge reads empty with the key on however when you turn the key on and then remove the wire to the sending unit the needle for the fuel gauge instantly moves to the 3 oclock posiition and stays there but when you put the wire back on the needle then goes right back to the empty fuel location.
Anybody have any ideas on what could cause this? Last edited by LockDoc; 06-30-2019 at 12:11 PM. |
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#2 |
Msgt USAF Ret
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Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Trying to figure out why my fuel gauge read correctly
Your fuel gauge sending unit wire is grounded to the frame and is not going through the sending unit resistor. Trace the wire from the sending unit back to the gauge and you will find where it is touching the cab or frame. If you can get to wire where it runs under the door sill you'll probably find it is worn through the insulation and is touching bare wires to the metal.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#3 |
Registered User
Join Date: Feb 2019
Location: So Cal, CA
Posts: 108
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Re: Trying to figure out why my fuel gauge read correctly
Do I have the same problem if my gauge stays at 3 o clock all the time? I've found your older post about the fuse, but my fuse box did not look like the picture
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#4 |
Senior Member
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Location: Portland - OR
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Re: Trying to figure out why my fuel gauge read correctly
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#5 |
Registered User
Join Date: Feb 2019
Location: So Cal, CA
Posts: 108
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Re: Trying to figure out why my fuel gauge read correctly
I just pulled up that will trying to reach my selector valve I will be replacing soon. I will look for that wire
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#6 |
Registered User
Join Date: Apr 2011
Location: Fairview Park, Ohio
Posts: 1,031
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Re: Trying to figure out why my fuel gauge read correctly
Just by pass the old wire with new wire rather than tracking down the area of the short.
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My build page http://67-72chevytrucks.com/vboard/s...d.php?t=764662 My cabinet building site http://www.cbcabinets.com |
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#7 |
Senior Member
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Location: Studio City, Calif.
Posts: 2,873
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Re: Trying to figure out why my fuel gauge read correctly
If he has a short somewhere along that wire then why would disconnecting the sender change that? I don't get your thinking. I think more likely he has a short in the sender.
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'69 GMC C2500 Custom Camper, 8 1/2' bed, New GM 350, NP 435 Close Ratio 4spd. Trans., 3.73 Dana-60 open.Camper and Trailer wiring, PS, PB, AC, tach , three gas tanks, stereo speakers, 2nd owner, Work-Truck supreme. |
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#8 |
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Re: Trying to figure out why my fuel gauge read correctly
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Thanks to Bob and Jeanie and everyone else at Superior Performance for all their great help. ![]() RIP Bob Parks. 1967 Burban (the WMB),1988 S10 Blazer (the Stink10 II),1969 GTO (the Goat), 1970 Javelin, 1952 F2 Ford OHC six 4X4, 29 Model A, 72 Firebird (the DBP Bird). 85 Alfa Romeo If it breaks I didn't want it in the first place The WMB repair thread http://67-72chevytrucks.com/vboard/s...d.php?t=698377 |
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#9 | |
Msgt USAF Ret
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Location: Kalamazoo, Michigan
Posts: 8,714
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Re: Trying to figure out why my fuel gauge read correctly
Quote:
Reading his post I answered his question about the zero reading. I also assumed that he was disconnecting the sending wire at the gauge, but you are correct that if he disconnected the sending wire at the sender he would be removing the path to ground for the gauge. If the sending unit is grounded, an ohms check between the terminal and the flange would show that, provided there is fuel in the tank.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#10 | |
Registered User
Join Date: Nov 2011
Location: USA
Posts: 387
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Re: Trying to figure out why my fuel gauge read correctly
Quote:
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#11 | |
Msgt USAF Ret
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Location: Kalamazoo, Michigan
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Re: Trying to figure out why my fuel gauge read correctly
Quote:
Here is the diagram or how it's wired.
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. |
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#12 | |
Registered User
Join Date: Nov 2011
Location: USA
Posts: 387
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Re: Trying to figure out why my fuel gauge read correctly
Quote:
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#13 | |
Msgt USAF Ret
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Location: Kalamazoo, Michigan
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Re: Trying to figure out why my fuel gauge read correctly
Quote:
What I'm seeing from this reading is that you don't have even 1 ohm of resistance when you should be seeing 90. Basically its a short to ground which is causing your gauge to read empty. So your sender is bad. You can check this if you can wire some kind of resistor in series with the sending unit wire and the terminal on the tank sender. It should cause the gauge to read higher than empty. Or you could just pull the sending unit and install a new one with a new filter sock since yours is probably deteriorated after all these years. I got mine from Parts Geek .com and it's a beauty. Works great. https://www.partsgeek.com/catalog/19...ding_unit.html
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VetteVet metallic green 67 stepside 74 corvette convertible 1965 Harley sportster 1995 Harley wide glide Growing old is hell, but it beats the alternative. Last edited by VetteVet; 07-01-2019 at 03:51 PM. |
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#14 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,216
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Re: Trying to figure out why my fuel gauge doesn't read correctly
The float on the end of the sending unit is probably full of gas.
George |
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#15 |
Registered User
Join Date: Dec 2017
Location: Elkhart, Texas
Posts: 1,706
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Re: Trying to figure out why my fuel gauge doesn't read correctly
That's a very good possibility.. I've had 4 float failures within the past year on my new sending unit.. Each failed at the solder seam joining the two float halves.. The float fills with gas, causing the float to sink to the bottom.. the sending unit goes low ohms resistance and the needle points to "E"..
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