Fuel Gauge Not Working - Third Generation F-Body Message Boards

IrocZ85 · 03-03-2008, 09:52 PM

Well guys I bought a 89 Iroc 350 auto not to long ago. Gas Gauge doesnt work though. It sits way past full at all times. I have changed the gauge and it just reads as full as it will go. Wondering if anyone has had this problem and knows what to look at. If you dont know which they are the color wires coming off the fuel tank wiring is appreciated to try and find were the problem is currently, but again any knowledge or help with fixing or diagnosing this is helpful, thanks in advance.

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John in RI · 03-04-2008, 11:24 AM

Sounds like a break in the wiring or connection somewhere. If you disconnect the plug from a the gas tank wiring with a working set-up,... the gas gauge floats all the way UP.

Your issue could be the wiring at the fuel tank pick-up, along the harness to the cluster, or the printed circuit on the cluster itself.

84redta · 03-04-2008, 11:30 AM

purple wire coming from the sending unit to my knowledge. I think it's 0 to 90 Ohms??? Can't remember but 0 is empty.

Tan is the pump and black is the ground. Make sure the ground is good on the pump harness.

IrocZ85 · 03-16-2008, 06:57 PM

Thanks for your help guys fuel gauge now fixed as off today 3/16/08

TF34MECHH · 03-17-2008, 06:19 PM

I have the same problem. What did you do to fix it? The schematic shows a ground (G304)
for the sender and shows it being on rear seat bracket. I dont have any grounds there.
Thanks
Shawn

IrocZ85 · 03-20-2008, 12:22 AM

Well I ended up actually having to change my sending unit as it was real rusty from someone changing the fuel pump and forgetting to re-install the o-ring seal

For you though I think your talking about were the wires ground out under the driverside rear seat, if your car is really rusty you might just need to change the ground to a seperate location (i suggest the seat belt bolts as they make great grounds and are hidden), That would at least be were I would start and hope this helps you

TF34MECHH · 03-20-2008, 04:46 PM

Thanks for your help. I pulled the seats and could not find any grounds. Does anyone have a pic of this ground under the back seat?
Thanks

FirenScuba · 03-25-2008, 08:50 PM

see my gauge works interminently where is teh ground for the sender because that will be my first spot to look.

84redta · 03-25-2008, 08:53 PM

three wires coming from the sending unit, tan/white stripe (power for the fuel pump), purple (power for the fuel level float to tell how much fuel you have), and black that grounds both out, you would not have fuel pump to my knowledge if you don't have fuel guage. But tracing that black wire would put you coming into the body behind the rear seats under the carpet.

84redta · 03-25-2008, 11:13 PM

just went out and checked, there is this block looking thing that is bolted to the axle hump underneath the carpet behind the rear seats. 3 wires (described above) come from the sending unit, into a plug, plug is attatched to said rivited box, box is rivited to other side of sheet metal inside the car bringing 3 wires in, purple and tan/white stripe (described above) come in and go down driver side rocker with all the other wires of the car, while the black wire grounds out to the rear seat bump (you will understand if you remove your rear driver seat), underneath the front of the bottom driver side cusion.

Purple wire should go to guages, and tan/white stripe wire breaks in two (should be under dash area???), one going to the ECU as a signal wire and one going through the firewall to the fuel pump relay in the engine compartment, towards the driver side fender against the firewall.
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Denis.V · 04-14-2008, 01:39 PM

Hi,

I'm in the same boat with my wife's Corsica.

Black wire is ground for both: fuel level & pump. Then, if you have fuel pressure (fuel pump ON), you have good ground.

Purple wire is positive fuel sender voltage. You can test with a ohmeter at the socket near to the fuel tank (You can know if the problem is IN or OUT of tank).

If you replace the fuel sender unit , be sure to use a 0 - 90 ohms sender (used for GM). Other cars uses 30 - 240, etc (I don't be sure if 0 ohms is empty or full).

Denis V.

First-Timer · 01-25-2009, 09:35 PM

i've got a 1990 iroc z and as well my fuel guage isnt working. i dropped a 350 carb motor into it. and this is what i have came up with. i have pulled the tank out and hooked the sending unit up and manually operate the float and my guage wont go past a half tank. when i unplug it from the connector it goes all the way past full. i've tested my sending unit and it passed. Anyone have any ideas what would be causing this? any suggestions would be apppreciated thx jeremy

KITT1983 · 07-15-2009, 05:32 PM

Any updates on your progress?

undertow310 · 08-11-2009, 01:43 PM

Quote:

Originally Posted by IrocZ85

Thanks for your help guys fuel gauge now fixed as off today 3/16/08

what did u do to repair your fuel gauge problem im having the same problem and it sucks running out of gas !