Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET1987FORWARD CONTROL 4.8 T, AUTOMATIC, 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMFUEL INJECTION SYSTEM - TBITESTINGFUEL SYSTEM PRESSURE TEST
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Fuel System Pressure Test
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Fuel System Pressure Test
- Turn engine off and relieve fuel pressure. See FUEL SYSTEM PRESSURE RELIEF . Remove air cleaner and plug air cleaner (THERMAC) vacuum port (model 700 TBI unit only).
- Disconnect fuel line between throttle body and fuel filter. Install Fuel Pressure Gauge (J-29658A) between throttle body and in-line fuel filter. Start engine and observe fuel pressure reading.
- Fuel pressure should be 9-13 psi (.6-.9 kg/cm2 ). If not, see CHART A-6 FUEL SYSTEM PRESSURE TEST in GENERAL MOTORS COMPUTER COMMAND CONTROL article in COMPUTERIZED ENGINE CONTROLS section.
- After testing, relieve fuel pressure. Remove fuel pressure gauge and connect fuel line to fuel filter. Start vehicle and check for leaks. Remove plug from throttle body vacuum port (model 700 TBI unit). Install air cleaner.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.