Fuel gauge was already messed up, but acting even more strange now
12-24-2011, 07:07 PM
#1
Fuel gauge was already messed up, but acting even more strange now I know my fuel sending unit was going out already. The car had to be at least 1/2 full and I'd usually have to rock the car side to side and it would read. Otherwise, if I started the car and drove it around a few miles, the gas gauge would slowly climb to the actual fuel level.
Now the gauge reads when I don't have the keys in the ignition, as soon as I put it on run or start the car, the gauge goes straight to E. THEN, as soon as I shut it off, the gauges goes right back to reading the fuel level! WTF? I haven't been able to drive the car around because I took it off insurance for the Winter!
Is it normal for your gas gauge to read the fuel level when you don't have the keys in the ignition? It's been too long since it's worked right so I don't know!
\/\/\/\/\/\/ Video
Now the gauge reads when I don't have the keys in the ignition, as soon as I put it on run or start the car, the gauge goes straight to E. THEN, as soon as I shut it off, the gauges goes right back to reading the fuel level! WTF? I haven't been able to drive the car around because I took it off insurance for the Winter!
Is it normal for your gas gauge to read the fuel level when you don't have the keys in the ignition? It's been too long since it's worked right so I don't know!
\/\/\/\/\/\/ Video
Last edited by HotWhipT/A; 12-24-2011 at 08:43 PM.
12-24-2011, 08:25 PM
#2
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i would check the ground for your sending unit and also buy a bottle of techron concentrate plus. i had fuel gauge issues in my c5z, and that techron pretty much cured it. use a bottle every time you change the oil. its def. worth a shot
12-24-2011, 08:38 PM
#3
I'll check that out.
Seriously though....somebody that has a good working gas gauge, can you check your car and see if the gas gauge is reading the fuel level with no keys in the ignition! Please
Seriously though....somebody that has a good working gas gauge, can you check your car and see if the gas gauge is reading the fuel level with no keys in the ignition! Please
Last edited by HotWhipT/A; 12-24-2011 at 11:34 PM.
12-26-2011, 01:27 AM
#4
the fingers on the sending unit have a hard time contacting the board due to slop in the bushing that holds them together......there is a youtube vid that shows this.....if you should ever pull the pump you can put more pressure on that bushing and make sure the fingers contact............very common problem in GM sending units that never gets properly identified
12-26-2011, 01:09 PM
#6
Video stops at 5:35, but I get the idea.
http://www.youtube.com/watch?v=37h9xjRdKn0
This is really really helpful too.
http://shbox.com/1/4th_gen_tech2.html#fuel_gauge
http://www.youtube.com/watch?v=37h9xjRdKn0
This is really really helpful too.
http://shbox.com/1/4th_gen_tech2.html#fuel_gauge
Fuel Gauge Operation and Testing
Most people notice that the fuel gauge does not read in a linear fashion. It will stay on the full side for a long time and then once it starts moving, it will drop rapidly. This is due to the shape of the tank and the placement of the float assembly/gauge sender unit. The tank has a bit of a wedge shape to it, that causes there to be more volume in the upper part of the tank than in the lower. The float only reacts to an up and down level and does not compensate for the tank shape.
Typically, when the gauge reads:
way past full=full tank
¾ = about half full
½ = about a quarter full
¼ = a couple gallons
E = very little on most cars (gallon or less), can be really empty on some
Tank capacity is 15.5 gallons.
Avoid running your car out of fuel! The fuel also acts to keep the pump cool. Running out of fuel can trigger a pump failure.
If you are having a problem not related to the "normal" way the gauge acts as stated above, there are some things you can check.
Locate the pump electrical connector on the rear of the floor pan under the car (above the LH axle tube). It has purple, gray and black wires going toward the fuel tank. Unplug the connector. With a meter set to ohms, read resistance between the black and purple wires going to the tank.
approximate:
88 ohms = full
60 ohms = 3/4
43 ohms = 1/2
26 ohms = 1/4
1 ohm = empty
The readings should correspond to your gauge. If the reading(s) seem accurate to what you have in the tank, the sender is ok. If they don't, the sender or wiring from that connector to the sender has a problem.
To test back to the gauge, ground the purple wire on the body side of the connector back toward the gauge (key ON). The gauge should read empty. With the connector unplugged and no ground applied, the gauge should read full.
Most people notice that the fuel gauge does not read in a linear fashion. It will stay on the full side for a long time and then once it starts moving, it will drop rapidly. This is due to the shape of the tank and the placement of the float assembly/gauge sender unit. The tank has a bit of a wedge shape to it, that causes there to be more volume in the upper part of the tank than in the lower. The float only reacts to an up and down level and does not compensate for the tank shape.
Typically, when the gauge reads:
way past full=full tank
¾ = about half full
½ = about a quarter full
¼ = a couple gallons
E = very little on most cars (gallon or less), can be really empty on some
Tank capacity is 15.5 gallons.
Avoid running your car out of fuel! The fuel also acts to keep the pump cool. Running out of fuel can trigger a pump failure.
If you are having a problem not related to the "normal" way the gauge acts as stated above, there are some things you can check.
Locate the pump electrical connector on the rear of the floor pan under the car (above the LH axle tube). It has purple, gray and black wires going toward the fuel tank. Unplug the connector. With a meter set to ohms, read resistance between the black and purple wires going to the tank.
approximate:
88 ohms = full
60 ohms = 3/4
43 ohms = 1/2
26 ohms = 1/4
1 ohm = empty
The readings should correspond to your gauge. If the reading(s) seem accurate to what you have in the tank, the sender is ok. If they don't, the sender or wiring from that connector to the sender has a problem.
To test back to the gauge, ground the purple wire on the body side of the connector back toward the gauge (key ON). The gauge should read empty. With the connector unplugged and no ground applied, the gauge should read full.
12-27-2011, 03:08 PM
#7
To test back to the gauge, ground the purple wire on the body side of the connector back toward the gauge (key ON). The gauge should read empty. With the connector unplugged and no ground applied, the gauge should read full.
I did that today and it it didn't affect the gauge no matter what I did. Well this sucks. I also got my answer on if the gauge reads the fuel level with NO key in the ignition. It's NOT suppose to read. Should be on E. I think this is causing a power drain on my battery.
My battery decided to die on me. Was at 4%. I took the alternator off and had that tested and it was fine. Was a Duralast Gold just a 2 years old. Got a new one for free though. I'm going to get a battery tender now.
