fuel light

subaruster · #1 12-16-2009, 08:00 PM

I have a 96 SVX Lsi, 70K.

Fuel was running low on fuel on the Florida Turnpike. Stopped off, got gas. The needle started to climb to full, as it did the low fuel light remained illuminated.

As of now, I have driven it for about 150 miles with multiple starts and shutoffs in-between, low light is still on!!!

Anyone had this?

Seems like the low light sensor might be stuck.

Also while driving on the Turnpike, out of nowhere comes a vibration coming from the front of the car not affecting the steering at all. Only happens while speeding up or coasting. I have searched this problem and nothing too specific comes up.

Thanks for the help,

Joseph P

TomsSVX · #2 12-16-2009, 08:03 PM

there are two separate senders for the gauge and the low level switch. The low level switch is likely stuck down. You could learn to love it until it dislodges itself or remove the sender and move it yourself

Tom

Trevor · #3 12-16-2009, 11:48 PM

The problem reported would indicate a faulty sensor or or shorted associated circuitry. Alternatively some debris may be fouling the sensor.

The low level sensor is quite a sophisticated affair, is completely solid state and does not involve a switch or contacts. A thermistor (heat dependent resistor) is normally immersed in fuel and becomes intermittently dry when the level is low. The thermistor is simply connected in series with the indicator lamp and the wiring diagram shows that no amplifying or latching circuitry is involved.

When immersed the resistance is at maximum and the lamp connected in series is not illuminated. A switching type thermistor will be used, such that there is a near specific cut off point rather than a gradual change in resistance.

It must be presumed that the thermistor incorporated has a positive temperature coefficient, so that when the level is low and fuel evaporates from off the device, the temperature drops and the lamp illuminates. This would result in a flashing effect as the level drops and car movement causes turbulence. However if and when the tank becomes absolutely empty and remains so, the lamp will not remain illuminated.

TomsSVX · #4 12-17-2009, 04:31 PM

I never knew it was a thermo resistor... Always figured it operated on a float switch... Learn something new every day

Tom

subaruster · #5 12-19-2009, 01:10 PM

Ok thanks,I'll try and take out the sending unit and clean the one installed first before replacing. I'll let you know how it goes.

Joseph P

Quote:

Originally Posted by Trevor

The problem reported would indicate a faulty sensor or or shorted associated circuitry. Alternatively some debris may be fouling the sensor.

The low level sensor is quite a sophisticated affair, is completely solid state and does not involve a switch or contacts. A thermistor (heat dependent resistor) is normally immersed in fuel and becomes intermittently dry when the level is low. The thermistor is simply connected in series with the indicator lamp and the wiring diagram shows that no amplifying or latching circuitry is involved.

When immersed the resistance is at maximum and the lamp connected in series is not illuminated. A switching type thermistor will be used, such that there is a near specific cut off point rather than a gradual change in resistance.

It must be presumed that the thermistor incorporated has a positive temperature coefficient, so that when the level is low and fuel evaporates from off the device, the temperature drops and the lamp illuminates. This would result in a flashing effect as the level drops and car movement causes turbulence. However if and when the tank becomes absolutely empty and remains so, the lamp will not remain illuminated.

Trevor · #6 12-19-2009, 03:10 PM

Quote:

Originally Posted by subaruster

Ok thanks,I'll try and take out the sending unit and clean the one installed first before replacing. I'll let you know how it goes.

Joseph P

Kia ora Joseph,

The sensor can easily be tested.

Connect a small 12 volt, 3 watt lamp, in order to to simulate the dash indicator, in series with the sensor and a 12 volt supply. Then immerse the sensor in fuel, at which point the lamp should extinguish, to again illuminate when the sensor is removed and in free air.

Compliments of the season, Trevor.

bwb3 · #7 12-20-2009, 08:23 AM

Wecome Joseph P. Not related to this thread but, if you ever need any help with other problems, let me know. I try to keep spare parts around like MAF, sensors, etc.
Gene

subaruster · #8 12-22-2009, 05:53 PM

I have time tomorrow to do that test, Trevor. I lost my FSMs. Do I access the sending unit through the back seat or the trunk?

Quote:

Originally Posted by Trevor

Kia ora Joseph,

The sensor can easily be tested.

Connect a small 12 volt, 3 watt lamp, in order to to simulate the dash indicator, in series with the sensor and a 12 volt supply. Then immerse the sensor in fuel, at which point the lamp should extinguish, to again illuminate when the sensor is removed and in free air.

Compliments of the season, Trevor.

subaruster · #9 12-22-2009, 06:19 PM

Thanks, I do have one question and one needed part. I am starting a new thread for the question. titled "Vibration"

The part I need, I have been searching for over a year. Remote Transmitter.
Part #: SOA386R205. It has been discontinued from Subaru. Do you have it??

Quote:

Originally Posted by bwb3

Wecome Joseph P. Not related to this thread but, if you ever need any help with other problems, let me know. I try to keep spare parts around like MAF, sensors, etc.
Gene

bwb3 · #10 12-23-2009, 02:32 PM

I have an extra remote unit for the door locks with a broken case (the corners where the screws holding the 2 halves together). Worked otherwise. You can PM me if interested.
Gene

Quote:

The part I need, I have been searching for over a year. Remote Transmitter.
Part #: SOA386R205. It has been discontinued from Subaru. Do you have it??

subaruster · #11 12-30-2009, 10:08 AM

It seems the problem fixed itself. After filling the tank three times the light went out after the 3rd fill up!

Trevor · #12 12-30-2009, 03:37 PM

Quote:

Originally Posted by subaruster

It seems the problem fixed itself. After filling the tank three times the light went out after the 3rd fill up!

I pointed out --- The problem reported would indicate a faulty sensor or or shorted associated circuitry. Alternatively some debris may be fouling the sensor.

This would now appear to be what was in fact the cause of the problem.

alltrac · #13 12-30-2009, 03:45 PM

Quote:

Originally Posted by subaruster

Thanks, I do have one question and one needed part. I am starting a new thread for the question. titled "Vibration"

The part I need, I have been searching for over a year. Remote Transmitter.
Part #: SOA386R205. It has been discontinued from Subaru. Do you have it??

Correct part number is SOA386R317

subaruster · #14 12-30-2009, 07:27 PM

Quote:

Originally Posted by alltrac

Correct part number is SOA386R317

My box's part number is the one I posted. Here is the thread I posted with a picture of the transmitter:

http://www.subaru-svx.net/forum/showthread.php?t=52655

alltrac · #15 12-30-2009, 09:38 PM

Quote:

Originally Posted by subaruster

My box's part number is the one I posted. Here is the thread I posted with a picture of the transmitter:

http://www.subaru-svx.net/forum/showthread.php?t=52655

That picture is the alarm module and not the remote transmitter.

Quote:

Originally Posted by subaruster

The part I need, I have been searching for over a year. Remote Transmitter.
Part #: SOA386R205. It has been discontinued from Subaru. Do you have it??