??? Gas Filter???

[ammcf1]

94 3-cyl, 1.0 liter. Automatic.

I noticed the chart on the underside of the hood shows a "gas filter" - and tracing it down I find it is a small, white plastic, round thingie attached to the firewall of the car on the left-ish side (looking at the car from the front). It has a line coming out of each end (top and bottom). I've already replaced the actual "fuel filter" underneath the car... what is THIS THING?

[GM Line Rat]

While the underhood sticker DOES refer to the "White Round item with the vacumm hoses going to it in the pic below as a "Gas Filter" (???).......It's not an actual fuel filter. This part is a vacumm "Check Valve" that runs between the throttle body and the MAP Sensor that's mounted on the firewall bracket. The only actual inline fuel filter on your Geo Metro is located just behind the drivers side rear wheel, on the inside of the frame of the car.

1994 Geo Map Sensor and Check Valve.




Fuel Filter, Location and service/repair

REMOVAL:




1. Disconnect the negative battery terminal.
2. Relieve fuel system pressure. Refer to MAINTENANCE PROCEDURES/FUEL SYSTEM PRESSURE RELIEF.
3. Raise vehicle on hoist.
4. Place an appropriate fuel holding container under fuel filter.
5. Disconnect inlet hose from the fuel filter.
6. Remove fuel filter, mounting bracket, and outlet hose as an assembly from the vehicle.
7. Disconnect outlet hose and bracket from the fuel filter.

INSTALLATION:



1. Connect mounting bracket to fuel filter.
2. Reconnect outlet hose to fuel filter outlet port.
3. Install fuel filter, mounting bracket, and outlet hose as an assembly to the vehicle.
4. Install filter outlet hose and clamp to fuel feed line.
5. Reconnect fuel filter inlet hose and clamp to the filter. Lower vehicle.
6. Reconnect the negative battery terminal.
7. START vehicle and check for fuel leaks.

[ammcf1]

Thanks GM LineRat...

Tell me, what symptoms would show that this check valve or the MAP sensor (what is a MAP sensor, by the way) are going bad or needed to be replaced?

And another while you're at it. Where is the thermostat located and how would you go about replacing it? (I have a suspicion mine is going out - takes LOOOONNNNNGGGG time for my temp gauge to rise to normal levels).

Thanks

[91Caprice9c1]

Originally Posted by ammcf1

Tell me, what symptoms would show that this check valve or the MAP sensor (what is a MAP sensor, by the way) are going bad or needed to be replaced?

Where is the thermostat located and how would you go about replacing it? (I have a suspicion mine is going out - takes LOOOONNNNNGGGG time for my temp gauge to rise to normal levels).

Thanks

If you follow the top radiator hose to the motor you will find this assembly.

Object 3 is the thermostat, you must remove the two bolts holding (4) in place. Be sure to replace the gasket as well, they don't usually come with one.

The check valve is for backfire protection and does not interfere with performance unless it is somehow plugged. Symptoms of poor MAP input are hard starts, poor/no idle, miss-fire, and a check engine light. If you are so inclined you can: Remove the hose end from the MAP sensor, then remove the hose end at the intake manifold/throttle body. With the two hose halves and check valve assembly in hand, you should be able to blow one way, and not the other. The proper flow of air is FROM the MAP TO the engine.

-MechanicMatt