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Yet another C4S fuel gauge issue!

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Hi All,

I went back and read all the previous C4S fuel gauge posts. I now understand that the C4S tank is saddle bag shaped and the display on the cluster is a guestimate from the measurement on one side. Below is my problem

When I fuel the car...it takes in only about 10 gallons from E to Full. Consequently, I get only 200 miles and the tank shows E again. I know that there is more gas in there but I drop to E after 10 gallons.

Took to a mechanic who replaced my fuel sending unit and did a recalibration. He said after he emptied the tank he could put around 16 gallons in it. I picked up the car and drove it and I still have the same problem. I am on E after about 200 miles....so the sending unit was not the issue(need my $$ back!!!)

Also the trip computer follows the needle pretty much....at Full it says I have 300+ miles range but the time the needle goes to E it says I have close to 0.

The mechanic said that if it is not the sending unit....it is the instrument cluster which is a $2000 part on a 2002 C4S manual.

Do I believe him? What are the chances that the cluster is bad. Its just a passive device that reads the electric current and moves the needle.

Help!!! What could be wrong here!!!


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You can not calibrate the fuel level sensor on a C4 (or C4S) without a PST2 or PIWIS -- did this mechanic have one and use it?

yes...the mechanic used the PST2 for calibration.

We changed the sending unit and re calibrated it. What else can be wrong? Could it be the instrument cluster?

Is there a way of confirming that the cluster is bad without changing it out with a brand new $2000 cluster?

I also saw a couple of TSB's on incorrect fuel reading but cannot read them on the TSB thread. How can I get to those?

Thx!!! DD

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Are you sure the calibration was done correctly? You have to take all the fuel out of the tank - then put in a measured amount. Then do the calibration.

I also saw a couple of TSB's on incorrect fuel reading but cannot read them on the TSB thread. How can I get to those?
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The calibration was done using a PST2....don't know if it was done correctly or not...have no way of verifying except for the mechanic's word.

I am taking it again tomorrow for recalibration.

He says...if that does not fix it...he will have to replace the instrument cluster. Is the computer for measuring the fuel level located in the cluster? How common is it for the cluster to go bad?

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Ok...the mechanic "recalibrated" the gauge again.

1. When I got the car, the needle was between 1/2 and 1/4. I could fill 6.2 gallons at the pump before cutoff. Forced another 0.8 to make it 7 even.

2. Went for a drive, drove 72 miles before I dropped to 3/4 tank.

3. Filled the car again. Could fill 3.2 gallons before cutoff, forced another 0.8 to make it 4 gallons.

So, from a volume prospective, looks like the issue is fixed because if quarter tank can take in 4 gallons that means the full tank can hold 16 gallons.

From a miles driven prospective...it looks promising because earlier I could get 50 miles in a quarter tank, now I got 72.

The true test would be how much gas it can take in from Empty to Full but I won't have a chance for testing that for quite some time now(leaving town on a business trip).

Sooo....how does it look so far? Do you experts think that the issue is fixed based on my testing today?


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  • 12 years later...

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