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Home >> Mazda >> 1991 >> 929 S >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - Basic Testing >> Fuel System (Fuel Injection) >> Fuel Pressure
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Fuel Pressure

WARNING: ALWAYS relieve fuel pressure before disconnecting any fuel injection related component. DO NOT allow fuel to contact engine or electrical components.
  1. On RX7, disconnect fuel pump connector at shock tower in trunk. On all others, disconnect circuit opening relay. See CIRCUIT OPENING RELAY LOCATIONS TABLE.
  2. To bleed down fuel in system, start engine (if possible) and allow to die. Connect pressure gauge to fuel line at fuel filter. Reconnect circuit opening relay.
  3. On Navajo, install EFI Pressure Gauge (T80L-9974-B) to relief valve. Relief valve is located on fuel supply manifold.
  4. Turn ignition on. Using a jumper wire, connect terminals of Yellow fuel pump check connector together. See FUEL PUMP CHECK CONNECTOR (YELLOW) LOCATIONS TABLE  . On Miata, Navajo, Protege and 323, jump test connector terminals Fp and ground. If pump runs, check fuel pump circuit, circuit opening relay, and fuel pump resistor (RX7).
    FUEL PUMP CHECK CONNECTOR (YELLOW) LOCATIONS

    Application Location
    B2600i, Miata, MX-6, 323 & 626 On Firewall, Near Windshield Wiper Motor
    MPV, RX7 & 929 Near Airflow Sensor
    Navajo At Right Inner Fender Panel
  5. If possible, start engine. Check fuel pressure with vacuum connected to and disconnected from pressure regulator. Turn engine off and disconnect jumper wire at fuel pump check connector. Wait 10 minutes and ensure residual pressure is at least 21 psi (1.5 kg/cm2 ).
  6. Operate fuel pump by jumpering fuel pump test connector. Check fuel pump performance. Pinch hose between pressure gauge and fuel filter. Do not hold longer than necessary to check pressure. See FUEL PUMP PERFORMANCE TABLE. If pump does not meet specifications, check fuel pump circuits, fuel pump, fuel tank, fuel filter or replace fuel pump.
FUEL PUMP PERFORMANCE

Application Pressure
All Models (1) (2) 64-85 psi (4.5-6.0 kg/cm2 )
(1) 4WD Protege, transfer pump pressure is more than 6.0 psi (0.4 kg/cm2 ).
(2) Minimum volume in 30 seconds is 1.0 pint (.47L).
REGULATED FUEL PRESSURE (AT IDLE)

Application W/Vacuum: psi (kg/cm2 ) W/O Vacuum: psi (kg/cm2 )
B2600i, Miata, MPV, Protege, 323 & 929 31-38 (2.2-2.7) 38-46 (2.7-3.2)
MX-6, RX7 & 626 27-33 (1.9-2.3) 34-40 (2.4-2.8)
Navajo - 34-46 (2.4-3.2)
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