Fuel Selector Valve - Electric GMC Cab & Chassis S15

COMPONENT TESTING

Note. Specific component testing information not available. Refer to any tests performed during REMOVAL & INSTALLATION or OVERHAUL procedures

DESCRIPTION

System consist of main and auxiliary fuel tanks, tank selector valve, tank selector switch, fuel lines, and electrical wiring.

OPERATION

Instrument panel-mounted switch controls both fuel selector valve and fuel gauge indication. Six-port fuel selector valve is electrically-actuated. Depressing upper and lower halves of switch feeds fuel from right and left side fuel tanks respectively.

Scheme 72

1. Ensure all electrical and ground connections are clean and tight. Disconnect selector valve harness at firewall, just right of steering column. (Scheme 72) With ignition on, connect a 12-volt test lamp to one terminal of female harness connector.
2. Connect other end of test lamp to remaining terminal. Test lamp should light in both switch positions. If okay, go to step 5. If test lamp does not light, go to next step.
3. Check for proper ground connection (Black or Black/Pink wire) at bus bar. Check for proper connection to ignition receptacle at fuse block. (Scheme 72) (Scheme 72): Selector Valve Wiring Harness
4. If ground and power connections are okay, check for proper connection at selector valve switch. Check for bent terminals on back of switch and in switch connector. Check "B" on Pink wire and ground on Black wire in switch connector. Repeat step 2. If okay, go to next step.
5. With ignition on, connect test lamp to ground and probe Lt. Green wire of female firewall connector. Test lamp should light (in one switch position only). If okay, go to «SELECTOR VALVE HARNESS»(/gmc/cab-chassis-s15/1985-1988/remont/testing-diagnostics/#fuel-selector-valve-electric__selector-valve-harness-test) test. If lamp does not light in either position, replace selector valve switch. Repeat step 2.
6. If test lamp does not light, there is an open in harness between switch and firewall connector. Repair or replace as necessary. If conditions are corrected in steps 2 through 5 and a problem still exists, go to «SELECTOR VALVE HARNESS»(/gmc/cab-chassis-s15/1985-1988/remont/testing-diagnostics/#fuel-selector-valve-electric__selector-valve-harness-test) test.

SELECTOR VALVE HARNESS TEST

1. Fill one tank with 10 gallons of fuel, and other tank with 5 gallons. Remove harness connector from fuel selector valve and connect a good selector valve. Turn ignition on and depress selector valve switch. Note gauge reading for right and left tanks.
2. If reading is different between tanks, replace selector valve. If no difference is shown, repair open circuit(s) in harness between selector valve and firewall connector. If fuel gauge operates, but not accurately, check fuel gauge.

Disconnect battery negative cable. Remove hose shield and brace. Remove harness connector from selector valve. Remove fuel and vapor hoses, noting locations for reassembly reference. Remove 2 screws holding valve to frame, and remove valve. To install, reverse removal procedure.

See also:
• SELECTOR VALVE HARNESS