Fuel Guage Inquiry

[Merv]

Alright. Who here can dumb down the fuel guage process for me.

The gauge in my Binder no worky. Wires are hooked up, traced them to the firewall. They plug into a multi pin plugin from there. All the dash light and other gauges work.

Are there any ways to test if it is the fuel pick-up specifically or do i have to rip the dash apart and get to the gauge specificaaly?

 

[cybrfire]

Alright. Who here can dumb down the fuel guage process for me.

The gauge in my Binder no worky. Wires are hooked up, traced them to the firewall. They plug into a multi pin plugin from there. All the dash light and other gauges work.

Are there any ways to test if it is the fuel pick-up specifically or do i have to rip the dash apart and get to the gauge specificaaly?

You can test the sending unit. You should be able to put an ohm meter across the connection on the sending unit and a ground. Have to pull the sending unit out of the tank or be able to tip the tank upside down so the float can move through its range.

take those readings and compare to the Ohm range of what your sending unit should be and know whether its working or not. For instance a GM sending unit is 0-90 ohms.

 

[Metrodps]

I did not read all of this but here is a link.
http://members.cox.net/vipir14/gmgauges.html

General Motors 0-90 Ohm Gauge Diagnosis Procedure

Especially as cars age, it is often somewhat difficult to pinpoint the root cause of instrument cluster gauge failure, thanks to questionable wiring, normal wear and tear, and sometimes even incorrect diagnosis procedures. The following diagnosis procedure is the method that GM publishes in it's shop manuals, will work on oil pressure, temperature, and fuel gauges, and should apply to all but the most recent GM-made vehicles with computerized gauges.
Before You Begin

You will need either Kent-Moore tool J-24538-A, if available, or tool JG-GM-1, a homemade GM gauge testing jumper. To build tool JG-GM-1, you will need the following materials:

• 1 Jumper wire with alligator clips (about $2 US from Wal-Mart)
• 1 220 ohm, 1/2W resistor (Radio Shack #271-1109, pack of 5, $0.99)
• 1 150 ohm, 1/2W resistor (Radio Shack #271-1111, pack of 5, $0.99)
• about 1" of 1/4" heat-shrink tubing, or vinyl electrical tape

Construct the jumper as follows:

1. Cut the jumper wire in half, and strip about 1/8" of the insulation off of the cut end of each wire. Tin the bare wires using a soldering iron.
2. Take both resistors and twist their leads together on each end, so that the resistors are joined in parallel. Twist the leads tightly, cut off the excess, and tin the twisted leads. If using heat-shrink tubing, make sure that the resistor assembly is about half the length of the tubing, or less.
3. If using heat-shrink tubing, slip the tubing over one of the jumper wire halves.
4. Solder each half of the jumper wire onto the opposite ends of the resistor assembly.
5. If using heat-shrink tubing, slide the tubing over the resistors and solder joints and shrink using a low-temperature flame or hair dryer. If using electrical tape, tightly wrap the tape around the resistors and solder joints, ensuring that the solder joints are completely covered.

Diagnosis Procedure

1. Disconnect wire from sending unit, and connect tool JG-GM-1 from the wire connector to ground.
2. Turn ignition ON.
3. If the gauge being tested reads at the high end of the scale (i.e. full for gas, 60psi for oil, etc.), the sending unit is at fault and must be replaced. Retest after sending unit replacement.
   Else, go to step 4.
4. If the gauge responds, but not accurately, go to step 5.
   If the gauge does not respond at all, go to step 7.
5. Disconnect engine harness connector at firewall bulkhead. Connect tool JG-GM-1 from ground to bulkhead connector lead that goes to gauge. If the gauge now responds accurately, check the wiring between the sending unit connector and the engine harness connector, repair any faults, and retest.
   Else, reconnect the engine harness connector, and go to step 6.
6. Remove the gauge from the instrument cluster and check the speed nuts holding the ceramic shunt across two terminals on the back. If they are loose, tighten them and retest gauge; if tight, the gauge is at fault and must be repaired or replaced.
   NOTE:You might be able to repair the gauge with a kit from Fix-A-Gauge, and/or you might be able to manually reposition the needle where applicable. Retest after repair.
7. Remove the instrument cluster and check for bad connections at the gauge terminal clips, instrument cluster connector, and both the instrument cluster and sending unit ground. If the connections are good, inspect the wiring from instrument panel to firewall harness connector, and repair any faults if found; if bad, repair the connections, reinstall gauge, and retest. If the connections and wiring are both good, the gauge is at fault and must be replaced.
   NOTE:A gauge diagnosed as bad through this step most likely can not be repaired.

From the GM Service manual for 10-30 series 1987 Light Duty Trucks
page 8C-4 Instrument Panel
Gauge Reads Between 1/4 & 1/2 with 90 OHMS from J-24538-A (their tester)

page 8C-2 Instrument Panel
Fuel Gauge
The fuel gauge is an electrical, current sensing type of indicator. It has two coils in it. One coil sets up a constant magnetic field. The other coil has a varying magnetic field which is varied by the reostat attached to a float in the fuel tank. A magnet, attached to a pointer, is located between the two coils. The magnet will establish a position which is controlled by the magnetic fields of the two coils. Refer to figure 2 for diagnosis.

It just says to take wire off check this and check that. The only major thing is what I listed above (page 8C-4 Instrument Panel) it all basically says if all else fails replace gauge.