Fuel gauge woes

501 Views 5 Replies 3 Participants Last post by 15cruzediesel, 2 mo ago

oilburner15

Discussion Starter · 2 mo ago

Speedometer Gauge Odometer Car Trip computer

I am having an issue where my fuel gauge gets stuck between the first and second mark above empty, even with a full tank. I’ve replaced the fuel level sensor in the tank with a new GM one and still the same problem. After a fill up, I can drive ~100ish miles and it’ll start reading correctly. Anyone seen anything like this?

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revjpeterson

· #2 · 2 mo ago

oilburner15 said:
I am having an issue where my fuel gauge gets stuck between the first and second mark above empty, even with a full tank. I’ve replaced the fuel level sensor in the tank with a new GM one and still the same problem. After a fill up, I can drive ~100ish miles and it’ll start reading correctly. Anyone seen anything like this?

If you switch over to the screen with speed, distance remaining, and instant fuel economy (one screen up from the one displayed on your DIC in the picture), does it go up when you fill the tank, even though the needle stays stuck?

If the DIC distance remaining is accurate, but the needle is wrong, you most likely have a problem with the stepper motor in your instrument cluster.

If the DIC distance remaining is inaccurate in a way that corresponds to the stuck needle, you most likely have a problem with the level sensor in the tank.

If neither of those is the source of the problem, then there's probably an intermittent wiring fault between the level sensor and the ECM.

Since it always sticks at the same spot, I'm heavily inclined to think it's the stepper motor behind that fuel gauge on the instrument cluster. There's probably a dead spot in that stepper motor, and a jolt from a bump or a surge of power jars it loose until you get back to that spot and it sticks itself again.

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oilburner15

Discussion Starter · #3 · 2 mo ago

revjpeterson said:
If you switch over to the screen with speed, distance remaining, and instant fuel economy (one screen up from the one displayed on your DIC in the picture), does it go up when you fill the tank, even though the needle stays stuck?

If the DIC distance remaining is accurate, but the needle is wrong, you most likely have a problem with the stepper motor in your instrument cluster.

If the DIC distance remaining is inaccurate in a way that corresponds to the stuck needle, you most likely have a problem with the level sensor in the tank.

If neither of those is the source of the problem, then there's probably an intermittent wiring fault between the level sensor and the ECM.

Since it always sticks at the same spot, I'm heavily inclined to think it's the stepper motor behind that fuel gauge on the instrument cluster. There's probably a dead spot in that stepper motor, and a jolt from a bump or a surge of power jars it loose until you get back to that spot and it sticks itself again.

Car Speedometer Gauge Odometer Automotive design

It’s consistent with the gauge reading. The gauge sweep when I start it is normal and smooth.

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revjpeterson

· #4 · 2 mo ago

oilburner15 said:
It’s consistent with the gauge reading. The gauge sweep when I start it is normal and smooth.

Sounds like that rules out the stepper motor, then. I'd bet there's a dead spot in the level sensor in the tank, then. The 100 miles is probably how long until the float gets past the dead spot and starts communicating again. On the way down, does it seem to hang up for a while before it gets down to the sticking point, then jump straight to the sticking point? If so, I think that would all but confirm this is the case.

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oilburner15

Discussion Starter · #5 · 2 mo ago

revjpeterson said:
Sounds like that rules out the stepper motor, then. I'd bet there's a dead spot in the level sensor in the tank, then. The 100 miles is probably how long until the float gets past the dead spot and starts communicating again. On the way down, does it seem to hang up for a while before it gets down to the sticking point, then jump straight to the sticking point? If so, I think that would all but confirm this is the case.

It has a brand new GM sensor in it. I’m assuming a wiring issue at the point.

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15cruzediesel

· #6 · 2 mo ago

Gauge sweep indicates it is not the gauge for sure.

ECM is getting bad information from the float at times.

So you replaced the float assembly and it has the same issue or did you replace the entire fuel pump module and float assembly?

I would first inspect the wire harness connector at the tank. Looking at the pins for corrosion, a pin pushed in and any female socket that appears to not have good retention of the male pin. (Hard test to perform if you don't have a similar male size pin to test it with)

Next I would do the same test at the ecm.

Trick to both is having the wire diagrams.

You might have to drop the tank and inspect the electrical connection at the pump inside where the float plugged in and while it is out move the float up and down and watch the fuel guage.

Also inspect all ground connections associated with the tank wiring.

There is more in depth electrical testing but without a service manual it is tough to do. It is just a resistance and a voltage telling the ecm fuel level status.

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