Fuel Gauge Problems - TCCoA Forums
 
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post #1 of 8 (permalink) Old 12-26-2003, 06:20 PM Thread Starter
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Question Fuel Gauge Problems

First off I would like to say that these forums are and excellent resource for usefull info!
I just bought a 94 t-bird Lx and I'm trying to iron out the problems that it has. The one that I'm getting hesitant about is the fuel gauge not working. It was pinned far to the right and was told by the previous owner that it did not work. I've done some reading on this and know how th test the sending unit(different resistance for different levels) but I don't know if there is a way to test the gauge itself short of swapping it out. Both the gauge and the sending unit are not exactly cheap and I don't really have the money to throw at something that isn't broke. I also had a problem putting gas in after I bought it. The pump would stop after only a couple of seconds, I'm guessing that there is a problem with the vent tube but that is only a guess. It was also the only time I have gotten gas at that particullar station(maybe stations problem?). Maybe the tank was removed by a previous owner and not installed correctly. I don't know if these problems are connected, seems like it is not uncommon for the gauge to let go. Any help or suggestions would be awesome, Thanks!

Adam
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post #2 of 8 (permalink) Old 12-27-2003, 10:30 AM
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Welcome to the forums.

The 1994 Service Manual states the following as possible causes for the fuel gauge reading erroneously:

Open or shorted circuitry
Faulty fuel gauge
Faulty instrument cluster printed circuit
Fuel pump or sender problem

Have you ever seen the "Low Fuel" indicator light up? You may want to replace the bulb on that (testing that bulb is one of the step in the diagnostics routine).

Try a search on this subject - I vaguely recall someone mentioning something about the float being stuck...you may find some good information on that.

Good luck to you!
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post #3 of 8 (permalink) Old 12-27-2003, 10:58 AM Thread Starter
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Yes that light has been on. Could you post that diagnostic routine?
Thanks,
Adam
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post #4 of 8 (permalink) Old 12-27-2003, 11:33 AM
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I've never had to test this myself, so I don't know if there's any shortcuts. At any rate, here is the diagnostics routine (from the 1994 service manual):

B1 VERIFY POWER AT FUSE PANEL (LOAD SIDE)
Use voltmeter to verify system voltage at load of Cluster Fuse (15A).
Is voltage present at load side of fuse?

Yes
GO to «B3».

No
GO to «B2».

B2 VERIFY POWER AT FUSE PANEL (FEED SIDE)
Use voltmeter to verify system voltage at feed side of Cluster Fuse (15A).
Is voltage present at feed side of fuse?

Yes
REPLACE fuse. RESTORE vehicle.

No
SERVICE wiring to fuse panel. RETEST system.

B3 VERIFY POWER AT CLUSTER
Instrument cluster connectors installed.
Partially remove instrument cluster.
Check for voltage at instrument cluster connector and gauge terminal.
Use Rotunda Digital Volt-Ohmmeter 007-00001 or equivalent.
Is voltage at instrument cluster connector gauge terminal?

Yes
GO to «B4».

No
SERVICE Circuit 640 (R/Y) for open circuit. RESTORE vehicle. RETEST system.

B4 VERIFY GROUND CIRCUIT AT CLUSTER
Use Rotunda Digital Volt-Ohmmeter 007-00001 or equivalent to check continuity of instrument cluster and gauge ground circuits.
Is there continuity?

Yes
GO to «B5».

No
SERVICE Circuit 359 (GY/R) for open circuit. RESTORE vehicle. RETEST system.

B5 CHECK TEST BOX (LOW)
Turn ignition switch to OFF position.
Insert Rotunda Instrument Gauge System Tester 021-00055 or equivalent in sender circuit.
Access and disconnect the 18 pin instrument cluster connector and connect tester to cluster side of connector.
Set tester to 22 ohms.
Turn ignition switch to RUN position, wait 60 seconds and read fuel gauge (9305).
Does fuel gauge read EMPTY?

Yes
GO to «B8».

No
GO to «B6».

B6 CHECK TEST BOX (RETEST)
Turn ignition switch to OFF position.
Turn ignition switch to RUN position.
Tap lightly on instrument panel, wait 60 seconds and read fuel gauge.
Does fuel gauge read EMPTY?

Yes
GO to «B8».

No
GO to «B7».

B7 INSTRUMENT CLUSTER GAUGE AMPLIFIER BYPASS TEST (EMPTY)
Turn ignition switch to OFF position.
Remove instrument cluster and inspect flexible circuit.
Remove instrument cluster gauge amplifier (10E849) and connect a jumper wire from Gauge Tester directly to fuel gauge 'SIG' terminal.
Install instrument cluster.
Turn ignition switch to RUN position and read fuel gauge.
Does fuel gauge read EMPTY?

Yes
REPLACE instrument cluster gauge amplifier. RESTORE vehicle. RETEST system.

No
REPLACE fuel gauge. INSTALL instrument cluster gauge amplifier. RESTORE vehicle. RETEST system.

B8 CHECK TEST BOX (HIGH)
Turn ignition switch to OFF position.
With Rotunda Gauge System Tester 021-00055 or equivalent connected as in Step D1, set tester to 145 ohms.
Turn ignition switch to RUN position.
Wait 60 seconds and read fuel gauge.
Does fuel gauge read FULL?

Yes
GO to «B10».

No
GO to «B9».

B9 INSTRUMENT CLUSTER GAUGE AMPLIFIER BYPASS TEST (FULL)
Turn ignition switch to OFF position.
Remove instrument cluster gauge amplifier and inspect flexible circuit.
Remove instrument cluster gauge amplifier.
Connect a jumper wire from tester to fuel gauge 'SIG' terminal.
Turn ignition switch to RUN position and read fuel gauge.
Does fuel gauge read FULL?

Yes
REPLACE instrument cluster gauge amplifier. RESTORE vehicle. RETEST system.

No
REPLACE fuel gauge. RESTORE vehicle. RETEST system.

B10 INSPECT FUEL TANK
Inspect fuel tank (9002) for damage or distortion.
Is there damage?

Yes
REPLACE fuel tank. RESTORE vehicle. RETEST system.

No
GO to «B11».

B11 CHECK TEST BOX--EMPTY STOP
Connect one lead of Digital Volt-Ohmmeter 007-00001 or equivalent to the fuel sender signal lead and the other lead to the ground.
NOTE: Float rod is against empty stop (closest to filter).
Does ohmmeter read between 14-18 ohms?

Yes
GO to «B12».

No
REPLACE fuel sender. RESTORE vehicle. RETEST system.

B12 CHECK TEST BOX--FULL STOP
Connect one lead of Digital Volt-Ohmmeter 007-00001 or equivalent to the fuel sender signal lead and the other to sender ground.
NOTE: Float rod is against full stop.
Does ohmmeter read between 155-165 ohms?

Yes
GO to «B13».

No
REPLACE fuel sender. RESTORE vehicle. RETEST system.

B13 CHECK FLOAT ROD LEVEL
Connect one lead to Digital Volt-Ohmmeter 007-00001 or equivalent to the fuel sender signal lead and the other to sender ground.
Slowly move float rod from full stop to empty stop.
Does ohmmeter reading slowly decrease?

Yes
GO to «B14».

No
REPLACE fuel sender. RESTORE vehicle. RETEST system.

B14 CHECK LOW FUEL WARNING
Turn ignition switch to the OFF position.
Connect Rotunda Instrument Gauge System Tester 021-00055 or equivalent in sender circuit.
Access and disconnect the 18 pin instrument cluster connector and connect tester to cluster side of connector.
Set tester to 56 ohms.
Turn ignition switch to the RUN position, wait 60 seconds.
Is low fuel indicator on?

Yes
REPLACE instrument cluster gauge amplifier. RESTORE vehicle. RETEST system.

No
GO to «B15».

B15 CHECK GAUGE AND INDICATOR
Turn ignition switch to the OFF position.
Reset tester to 33 ohms.
Turn ignition switch to the RUN position.
Wait 60 seconds.
Is indicator on, and gauge showing 1/8 tank?

Yes
Instrument cluster gauge amplifier operating properly. RESTORE vehicle. RETEST system.

No
GO to «B16».

B16 CHECK INDICATOR
With ignition switch in the ON position, ground indicator circuit between indicator and low fuel module.
Is indicator on?

Yes
REPLACE instrument cluster gauge amplifier. RESTORE vehicle. RETEST system.

No
GO to «B17».

B17 CHECK INDICATOR BULB
Turn ignition switch OFF.
Remove instrument cluster as outlined.
Remove indicator bulb using an ohmmeter. Check bulb continuity.
Does bulb test OK?

Yes
REPLACE instrument cluster printed circuit. RESTORE vehicle. RETEST system.

No
REPLACE damaged indicator bulb. RESTORE vehicle. RETEST system.



Whew!
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post #5 of 8 (permalink) Old 12-27-2003, 11:47 AM Thread Starter
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Awesome, Thank you very much. It is exactly what I was looking for!
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post #6 of 8 (permalink) Old 12-27-2003, 12:49 PM
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Glad to be of assistance. I've benefitted from the knowledge at this site, so I try to assist when I can.

I located the 1993-1994 Service Manual on CD at an eBay auction, and won the auction for a whopping six or eight dollars (shipping included). That was over a year ago, but you can still located manuals at that auction site. It's been a very valuable tool.


--Pete
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post #7 of 8 (permalink) Old 12-27-2003, 01:08 PM
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As far as the issue with filling the gas tank at the filling station, I've had the same problem before. It happens every now and then, and I usually just have to mess with the gas pump a little (pushing down on it usually works). It's probably not a problem with your car.

-Rod

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post #8 of 8 (permalink) Old 12-27-2003, 01:49 PM Thread Starter
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Well I pulled the dash out and started testing things and got the gauge to work. I don't know if the gauge was just stuck or maybe a connection was loose. As for the filling problem I traced the vent tube as much as I could and I didn't find any kinks in the line so it probably was the station or the way I was putting gas in. Half to wait til I get the car on the road. My K&N filter is coming in to finish my CAI and my catback system should be in on Monday. I think I'm going to like this car!
Thanks for the help guys, this site Rocks!
Adam
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