Fuel metering device location ? - 1990 Lexus LS 400

check the ground wire for your fuel gauge, or it would be a bad fuel level sensor which is located on the pump assembly itself, located IN the fuel tank.

Probably need a new sending unit which is located in the tank.

Could be a bad oh tew sensirrrr, an air fuel metering device. A bad air fuel metering device can cause a vehicle to run too rich which means that it is dumping too much fuel which in tern is causing bad fuel economy okie dokie

The most common cause of the fuel level meter not working is that the fuel level meter sending unit located inside the gas tank is defective.

The fuel tank has the Rheostat that has a float and on which the float moves up to change the resistance to the gauge which is a volt meter.
So you need to locate the fuel tank to see the fittings here, removal of the wires to the rheostat will change the fuel readings, so as to confirm the gauge.
If so remove rheostat and move float on the outside with the connection of ground and lead externally to confirm as you will notice the change on the meter.

try to open your car hood and locate the wiring that is connected to the fuel meter. Normally, these wires are connected separately towards their respective meters (fuel, speed, temp). Just have an assistant to check the meters and you will disengage/reengage the wires and he will verify if that meter functions well or not..

REMOVAL & INSTALLATION

See Figures 1, 2, 3 and 4
Before performing any service on the front or rear TBI unit, you must place the unit in a suitable holding fixture such as J-9789-118, BT-30-15, or equivalent. If you dont place the unit in a suitable fixture, the throttle valve may be damaged.

1. Disconnect the negative battery cable.
2. Remove the TBI unit from the vehicle, and place it in a suitable holding fixture.
3. Remove the fuel meter cover, as follows:
   1. Remove the 5 fuel meter cover attaching screws and lockwashers.
   
   

Fig. Fig. 1: Exploded view of the fuel meter cover attachment

1. Lift off the fuel meter cover with the fuel pressure regulator (rear unit) or accumulator (front unit), noting their positions for reassembly.
2. Remove and discard the fuel outlet passage only. Leave the fuel meter cover gasket on the fuel meter body.

CAUTION Do NOT remove the 4 screws securing the fuel pressure regulator or accumulator to the fuel meter cover. The regulator or accumulator includes a large spring under heavy compression which, if accidentally released, could cause personal injury. The fuel meter cover is serviced as a complete assembly only. On the rear unit, the fuel meter cover includes the fuel pressure regulator which was calibrated and plugged at the factory.

Fig. Fig. 2: Bottom view of the front and rear fuel meter covers
Do not immerse the fuel meter cover (with the pressure regulator or accumulator) in any type of cleaner. Immersion will damage the internal diaphragms and gaskets.

1. Remove the foam pressure regulator sealing ring (dust seal) from the rear throttle body.

When removing the injector, be careful to avoid damaging the electrical terminals on top of the injector, injector fuel filter and nozzle. Do NOT use pliers to remove the injector, as this could cause damage. The injector cannot be disassembled and is serviced as a complete assembly only. As it is an electrical component, it should not be submerged in any type of cleaner.

1. With the fuel meter cover gasket in place to protect the casting, use a suitable prytool and a fulcrum, as shown in the accompanying figure, to carefully lift the injector until to is free from the fuel meter body.

Fig. Fig. 3: Carefully pry the fuel injector out of the fuel meter body

1. Remove the injector. If removing both injectors, make sure to mark them front and rear, so they can be reinstalled in the proper position. The injectors are NOT interchangeable and cannot be switched during installation.
2. Carefully rotate the injector fuel filter back and forth, then remove the filter from the base of the injector.
3. Remove and discard the fuel meter cover gasket.
4. Remove the large O-ring and steel back-up washer in the top counterbore of the fuel meter body injector cavity. Remove the small O-ring located at the bottom of the injector cavity.

Raise rear seats, you will see your fuel tank with two caps, you will find the wires there

thats located in the fuel injectors.

Try metering the wires to the fuel pump first with a voltage meter. If you're getting no voltage whatsoever, locate the fuel relay. Somewhere along the firewall should be at least 2 relays mounted. One of these should be the fuel relay. Meter the wires going in to the fuel relay, the the wires coming out of it. If you have voltage on the wires going to the relay, but not going from the relay to the fuel pump, then you'll have to replace the fuel relay. They're usually inexpensive at most local parts stores--usually never more than $20-25. If you have voltage on both ends of the relay, it's possible that the emergency fuel-cut-off switch has been tripped. You may have to refer to a manual to find the actual location of this switch, but on most vehicles, it's usually in an access panel in the trunk around the wheel-well on the side that your fuel door is on. If it has been tripped, all you have to do is reset the switch (Usually just have to pull the switch out...you'll understand once you locate it. Hopefully this solves your issue.