Evaporative Emissions System: Testing and Inspection

1. Check all hoses and fuel tank filler cap, replacing as necessary.
2. Disconnect the vapor vent line connecting flow guide valve and vapor/liquid separator on 1971-74 except 1974 260Z or carbon canister to vapor/liquid separator, fuel tank, or check valve.
3. Connect a three-way connector, a manometer, and a cock, or an equivalent three- way change cock, to the end of the vent line.
4. Slowly supply fresh air into the vapor vent line through the cock until pressure becomes 14.5 in. H2O on all 1971-77, 1978-79 210, and 1979 310 or 15.75 in H2O.
5. Shut the cock and leave it closed.
6. After 2.5 minutes, measure the height of the liquid in the manometer. Variation of the height should remain within 1 in H2O for 1971-74, 1.1 in H2O for all 1975 and 1976-77 F10 or 0.98 in H2O.
7. When the fuel filler cap does not close completely the height should drop to zero in a short time.
8. Remove filler cap. If height does not drop to zero in a short time, repair or replace vent hose.

Flow Guide, Valve 1971-74 Except 1974 260Z
1. Disconnect all hoses from flow guide valve, noting proper connections.
2. Check that air blown in from fuel tank port flows out of crankcase port.
3. Check that air blown in from crankcase port does not flow out of other two ports.
4. Check that air blown in from carburetor air cleaner port flows from either or both of other ports.
5. Check that valve opens when inner pressure reaches 0.4 in Hg.
6. If desired results are not obtained in steps 2-5, replace valve.

Fuel Tank Vacuum Relief Valve
1. Remove filler cap, wipe clean valve housing, and place cap in mouth.
2. Inhale air. A slight resistance should be felt at first but should disappear when valve can be heard clicking.
3. If valve is clogged or no resistance is felt, replace cap.

Carbon Canister Purge Control Valve
1. Check for fuel vapor leakage in the distributor vacuum line at diaphragm of carbon canister purge control valve.
a. Disconnect rubber hose in line between "T" connector and carbon canister "T" connector.
b. Inhale air into opening of rubber hose running to vacuum hole in carbon canister and ensure that there is no leak.
2. If there is a leak, remove top cover of purge control valve and check for dislocated or cracked diaphragm. If necessary, replace diaphragm assembly which consists of a retainer, diaphragm, and spring.

Fuel Check Valve, Except 1979-8O 280ZX
1. Blow air through connector on fuel tank side. A considerable resistance should be felt.
2. Blow air through connector on engine side. Air should flow smoothly.
3. If valve is not functioning properly, replace it.

Fig. 168 - Air Vent Cleaner:

Air Vent Cleaner 1976-77 F10
1. Blow through port "T"--Fig 168. Air should flow from port "E" but not from port "A".
2. With port "E" or "9" plugged, attempt to suck air through unplugged port. Suction with slight resistance should be felt at port "A".

Vacuum Switching Valve (Some Applications)
1. Disconnect vent line hose from carburetor float chamber.
2. With engine running, inhale on vent line of carbon canister and ensure that there is no leak.
3. Check that there is a leak with engine off.