Question about 1988 Ford F 150

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I have a 1988 F-150 p/u with dual tanks.fuel gauge on both tanks do not work. one reads below empty all the time the other reads above full all the time.

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  • xtreme9898 Mar 22, 2009

    i have a 1990 ford f-250 with the same problem. the front tank always says its empty and the rear tank always says it full. im thinking the floats in the tanks are stuck... i dunno?

  • Anonymous Mar 29, 2009

    I have a 91 f150 with the same problem....

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I have the same problem and i replaced the shuttle valve and i fixed the problem it is located on the drivers side frame rail just behind the the main high pressure fuel pump it should have 6 lines going into it and out it is a mechanical part so its not repairiable hope this helps

Posted on Mar 31, 2009

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1 Answer

Why would Fuel gauge fluctuate erratically then shake at blinding speed?


Bad sending unit, bad ground, bad gauge, I have seen sending unit go bad they will work part way.

Jan 02, 2016 | Cars & Trucks

1 Answer

Fuel gauge not working


You will need to test a number of things, the fuel gauge is part of a rather simple circuit.

Battery -> gauge -> tank sensor -> chassis ground to battery

If the circuit is broken at any of the steps, your gauge will read "empty". If the tank sensor is bad, it could read empty, or if the float in the tank has sunk, it will read empty.

I start at the gauge with a "test light" that glows when it sees battery voltage. Get a light at the connection to the gauge? Good. find the sensor connection, usually on top of the tank, accessible in the trunk. Probe with test light. Light on? Good. Connect wire to ground, gauge should read "full". If all that is as I said, then the tank sensor is bad. If you don't read battery at any step, you know where the problem is.

Nov 13, 2015 | Cars & Trucks

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I have a 1992 Mercury Grand Marquis Ls with a fuel gauge that does not work (gauge may be reversed)??? help please.


The fuel level indicating system is a magnetic type system, which consists of the sending unit located in the fuel tank, an anti-slosh module located on the back of the instrument cluster, and a fuel gauge located in the instrument cluster. The sending unit changes resistance according to the level of fuel in the fuel tank, which varies the current flow through the gauge.The pointer position varies proportionately to the current flow. In this system, the sending unit resistance is low (22 ohms) when the fuel level is low and high( 145 ohms) when the fuel level is high. The pointer of the magnetic gauge remains in position when the ignition is turned to the Off position. On some models, an anti-slosh module is used to dampen out fluctuating fuel signals from the sender. Some vehicles are equipped with a low fuel warning indicator. The anti-slosh module will also actuate the low fuel indicator when the fuel level in the tank reaches 1/16 to 1/8 full.


Do your other gauges/warning indicators work properly with the ignition on? If not, check for power at the fuse panel/fuses.

If they do then partially remove your cluster with connector still installed and check for voltage at cluster connector and gauge. Check continuity of cluster and gauge for ground.

Sometimes the anti-slosh module (if installed) goes bad in the Grand Marquis but not likely.

Sender troubleshooting:
  1. Perform test with resistors as follows:
    1. Disconnect wiring connector at sender unit, then connect resistor between gauge lead and a suitable ground.
    2. Turn ignition switch to On position.
    3. With 145 ohm resistor, the gauge pointer should contact the Full mark.
    4. With 22 ohm resistor, the gauge pointer should contact the Empty mark.
  1. Perform test with fuel sender of known quality as follows:
    1. Turn ignition to Off position.
    2. Disconnect wiring connector from sender and connect it to test sender.
    3. Move float rod away from fuel filter against Full stop position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or above the Full mark.
    4. Move float rod toward fuel filter against Empty stop position. Turn ignition switch to Off position. Wait approximately 30 seconds, then turn ignition switch to On position. The gauge should read on or below the Empty mark. If gauge works properly replace sender, which involves dropping fuel tank.

Mar 23, 2013 | 1992 Mercury Grand Marquis

1 Answer

I have a 2000 gmc 3500hd,the fuel gauge stopped at half way and i run out of fuel. the rear tank is not sending fuel to the front tank?


David Johnson is wrong about that. The Chevy HD dual tank has two sending units, one in each tank , one fuel pump, a fuel pump relay switch and a equalizing pump. If the truck stalls out at 1/2 tank, it is the equalizing pump. That pump, pumps fuel from the rear tank to the front. If the pump is out, the front tank empties, the truck shuts down, the guage reads half tank because the back tank is still full, but the equalizing pump won't pump the rear fuel tank load to the front. Hence the problem you listed above, not a sending unit.

Dec 15, 2011 | Cars & Trucks

1 Answer

My fuel gauge reads below the empty mark. and the tank is full. It read full the day I filled it up, but yesterday I went to start it up and it was way below the empty mark. horizontal


check for fuses, fuel sender its a common problem in GM,cars,it cost like $45 from dealers ok,of course tank need to be removed,ok,GL

Nov 25, 2009 | 2001 Buick Park Avenue

1 Answer

1987 ford f150 dual fuel tanks fuel qty gages inop.fwd tank reads empty and when aft selected reads full.


tank switch on dash could be bad, also selector valve could be bad. are the fuel gauges accurate front or rear. like you say the rear reads full, is it?? I would try the switch on the dash first.

Sep 17, 2009 | 1987 Ford F 150

1 Answer

1992 f 159 dual tanks fuel guage not working


You will need to remove the wire for the sending unit on the tank and ground it to the frame with your selector switched to the tank you are working on and the key on. If gauge comes up to full then the sending unit is bad and gauge is good. Repeat process on other tank. The fuel tank switching valve on the frame also switches the wiring signal from either tank for the gauge. If no change with first test you will want to check the valve.

Aug 13, 2009 | 1992 Ford F150 SuperCab

2 Answers

Fuel gauge not working all the time.


This is a normal concern.
The instrument cluster uses 4 different operating modes to calculate the fuel level:
Anti-slosh (default mode)
Key OFF fueling
Key ON fueling
Recovery
After a fuel fill up, the time for the fuel gauge to move from empty (E) to full (F) ranges from 2 seconds to 55 minutes depending on which operating mode the fuel gauge is in.
The default fuel gauge mode is called the anti-slosh mode. To prevent fuel gauge changes from fuel slosh (gauge instability due to changes in fuel sender readings caused by fuel moving around in the tank), the fuel gauge takes approximately 55 minutes to go from empty (E) to full (F).
The key OFF fueling mode (2 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The key must be in the OFF position throughout the entire refueling of the vehicle.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
The instrument cluster must receive a valid key ON fuel sender reading within 1 second of the key being put into the RUN position. The key ON sample readings are considered valid if the fuel sender reading is between 15 ohms ± 2 ohms and 160 ohms ± 4 ohms.
If these conditions are not met, the fuel gauge stays in the anti-slosh mode, which results in a slow to read full (F) event.
The key ON fueling mode (approximately 90 seconds to read empty [E] to full [F]) requires 3 conditions be met:
The transmission is in PARK (P).
The key is in the RUN position.
At least 15% of the vehicle's fuel capacity must be added to the fuel tank.
In key ON fueling mode, a 30-second timer activates after the transmission is put into the PARK (P) position (automatic transmissions). When the 30-second time has elapsed and at least 15% of the vehicle's fuel capacity has been added, the fuel gauge response time is 90 seconds to read from empty (E) to full (F). When the transmission is shifted out of PARK (P), the fuel gauge strategy reverts to the anti-slosh mode. The key on refueling mode prevents slow to read full events from happening if the customer refuels the vehicle with the key in the RUN position.
Recovery mode is incorporated into the instrument cluster strategy to recover from a missing fuel level input during a refueling event. Missing fuel level inputs result from intermittent opens in the fuel sender or its circuits. Recovery mode (empty [E] to full [F] approximately 20 minutes) is initiated when the following 2 conditions are met:
The instrument cluster is in the anti-slosh (default) mode.
The actual fuel level in the tank is greater than what is being displayed by the fuel gauge

Feb 18, 2009 | 1983 Mercury Grand Marquis

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