Hot no start- "hns"
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Joined: Oct 2012
Posts: 243
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From: Tallahassee Florida
Year: 89
Model: Cherokee
Engine: 4.0
My most recent attempt to solve the riddle.. I picked up the BOSCH fuel pump,strainer,filter today.
MPI Fuel Pressure Leak Down Test with Engine Off
If abnormally long periods of cranking are required to restart a hot engine after the vehicle has been shut down for a short period of time, fuel pressure may be bleeding past the fuel pressure regulator or the check valve in the outlet end of the fuel pump.
If this doesn't work she's goin up in smoke...........
MPI Fuel Pressure Leak Down Test with Engine Off
If abnormally long periods of cranking are required to restart a hot engine after the vehicle has been shut down for a short period of time, fuel pressure may be bleeding past the fuel pressure regulator or the check valve in the outlet end of the fuel pump.
- 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.
- Start the vehicle and let engine idle. Check fuel pressure reading on gauge. Fuel pressure should be within specifications. Refer to MPI System Fuel Pressure Test.
- Shut engine off. Note fuel pressure reading on gauge. Leave fuel pressure gauge connected. Allow engine to set for 30 minutes and then compare fuel pressure reading on gauge to 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.
- If fuel pressure drop is within specifications, the fuel pump outlet check valve and the fuel pressure regulator are both operating normally.
- If fuel pressure drop is greater than 138 kPa (20 psi), restart the vehicle and let engine idle. 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.
- Momentarily pinch shut the hose section of the fuel return line and shut engine off. Note pressure reading on gauge. Allow engine to set for 30 minutes. Compare fuel pressure reading to reading taken when engine was shut down. If fuel pressure drops approximately 138 kPa (20 psi), replace the fuel pressure regulator. If fuel pressure has dropped considerably more than 138 kPa (20 psi) fuel pressure is bleeding off past the outlet check valve in pump and the fuel pump must be replaced.
If this doesn't work she's goin up in smoke...........
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