Wrangler L4-150 2.5L VIN P MFI (1993)
Fuel Pressure: Testing and Inspection
Fuel Pressure Leak Down Test
FUEL PRESSURE LEAK DOWN TEST- WITH ENGINE OFF
NOTE: Abnormally long periods of cranking to restart a hot engine that has been shut down for a short period of time may be caused by:
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Fuel pressure bleeding past the fuel pressure regulator.
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Fuel pressure bleeding past the check valve in the outlet end of the fuel pump.
Fuel Pressure Test
PROCEDURE
1. With the engine off, connect an accurate 0-689 kPa (0-100 psi) fuel gauge to the pressure test port fitting on the fuel rail.
2. Start the vehicle and let engine idle. Check fuel pressure reading on gauge. Fuel pressure should be within specifications. Refer to Fuel System
Pressure Test.
3. Shut engine off. Note fuel pressure reading on gauge. Leave fuel pressure gauge connected. Allow engine to set for 30 minutes and then compare
the fuel pressure reading on the gauge with the reading taken when engine was shut down. A pressure drop up to 138 kPa (20 psi), to a range of
131-269 kPa (19-39 psi) is within specifications.
4. If fuel pressure drop is within specifications, fuel pump outlet check valve and fuel pressure regulator are both operating normally.
5. If fuel pressure drop is greater than 138 kPa (20 psi), restart the vehicle and let engine idle.
Fuel Return Line
6. Momentarily pinch shut the hose section of the fuel return line and shut engine off.
CAUTION: Fuel pressure will rise to as much as 95 psi when the fuel return line is pinched shut. Shut engine down immediately after pinching
off fuel return line.
Note pressure reading on gauge. Allow engine to set for 30 minutes. Compare fuel pressure reading to reading taken when engine was shut down.
