Fuel System Pressure Test
- Most TBI models now have a self bleed feature which causes fuel pressure to drop when ignition is off. However, for safety reasons it is recommended that any residual system pressure be removed from system. To do this, remove fuel filler cap to relieve tank vapor pressure. Remove fuel pump fuse from fuse block in passenger compartment. Start and run engine until fuel supply remaining in fuel lines is used. Engage starter again for about 3 seconds. Turn ignition off and reinstall fuse.WARNING: Always relieve residual pressure in fuel delivery system before opening system. To prevent chance of personal injury cover fittings with shop towel while disconnecting fittings.
- Remove air cleaner and plug air cleaner (THERMAC) vacuum port on throttle body. Remove steel fuel line between throttle body and fuel filter. When removing fuel line, always use 2 wrenches to prevent damage. Install adapter and fuel pressure gauge between steel line and flexible hose.
- Start vehicle and observe fuel pressure reading. Fuel pressure should be 9-13 psi (.6-.9 kg/cm2 ). If fuel pressure is not within specification, go to appropriate GM TBI CHART A-7 in COMPUTERIZED ENGINE CONTROLS section.
- Relieve residual pressure as described in step 1). Remove fuel pressure gauge. Reinstall steel line between filter and throttle body. Start engine and watch for leaks. Remove plug from throttle body thermal vacuum port and reinstall air cleaner.
NOTE:
For additional testing and diagnosis information, see TROUBLE SHOOTING in CCC THEORY & OPERATION article in COMPUTERIZED ENGINE CONTROLS section.