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.
1991 Toyota Camry Base, AutomaticFACTORY OEM SERVICE PROCEDURE
Fuel Pressure-Up System
- Ensure coolant temperature sensor, air temperature sensor (in airflow meter) and circuits are operating correctly. See ENGINE SENSORS & SWITCHES .
- Fuel pressure-up system is controlled by ECU through a vacuum switching valve. The vacuum switching valve is fed current through the EFI main relay when the ignition is turned on. ECU controls the ground circuit. ECU will activate vacuum switching valve for 90-180 seconds when restarting engine at normal operating temperature.
- Vacuum switching valve is located on lower side of intake manifold runners. Remove vacuum switching valve from vehicle. Check for continuity across valve wiring terminals. Resistance should be about 33-39 ohms at room temperature. There should be no continuity between each terminal and body of valve. To check operation, see Fig 1.
Factory Service Tools
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
Disclosure: Verified tool recommendations may earn an affiliate commission at no cost to you.
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.