Here's a thread on How to Diagnose Fuel Pressure Problems.
The Most Common Symptom of a Fuel Pressure Related Problem is HARD TO START/RESTART COLD
RETAINED FUEL PRESSURE
As the Fuel Pump operates when the ignition is first switched on, it primes the fuel lines to maintain FUEL PRESSURE in the fuel rail. This is known as RETAINED FUEL PRESSURE (Well it is where I come from)
When the engine is switched off the RETAINED FUEL PRESSURE should NOT DROP in the fuel rail (for ease of Starting/re-starting when cold.)
The engine usually restarts OK when Warm/Hot because of the retention of adequate Fuel Pressure.
RETAINED FUEL PRESSURE CHECK
First of all Check all the Fuel Lines from the Fuel Tank to the Fuel Rail for residual leaks. Repair any leaks evident.
Connect up a Good Quality (ABW) Fuel Pressure Gauge to the Fuel Inlet Hose, at the Fuel Rail.
While Observing the Fuel Pressure Gauge, Switch the Ignition "ON" and wait for Fuel Pump to stop priming - Approx 2-3 Seconds.
Fuel Pressure Gauge should go up to approx 260 Kpa when priming, then drop to a 230 Kpa. This will be the RETAINED FUEL PRESSURE.
Re-Check for any External Fuel Leaks at engine and surrounding areas. Repair if necessary.
With some white out, mark the F.P Gauge where the needle is.
Get Comfy, sit back, crack open a coldie and keep an eye on the F.P Gauge.
After 30 Minutes if the FP Gauge Needle has hardly budged then the RETAINED FUEL PRESSURE is considered OK. Start Looking Elsewhere fro problems.
If the RETAINED FUEL PRESSURE Drops then it is "A Process of Elimination" to locate the source of the Internal Fuel Pressure Loss.
PROBLEM 1 - IMMEDIATE PRESSURE DROP TO ZERO
If the RETAINED FUEL PRESSURE Drops Straight to Zero within 3-4 Seconds, then main culprits are the Fuel Pump Check Valve or the Fuel Pressure Regulator Check Valve.
To confirm clamp off the fuel return line, if the Fuel Pressure Drops, it will be the Fuel Pump. If the Fuel Pressure remains it is the F.P Reg Check Valve.
In rare circumstances Faulty Injectors or ECU Injector Drivers causing the Injectors to stay open can cause the problem.
PROBLEM 2 - SLOW FUEL PRESSURE DROP TO ZERO
If the RETAINED FUEL PRESSURE Drops slowly to zero then it's a matter of elimination again.
Prime Fuel Rail, clamp off Both Return & Inlet Hoses & FPReg Vacuum Hose.
If fuel pressure still drops slowly, Suspect Injectors.
If Fuel Pressure retained, Suspect FPReg Check Valve, FPReg Diaphragm or Fuel Pump Check Valve.
Eliminates Injectors.
Prime Fuel Rail, clamp off Both Return & Inlet Hoses.
If fuel pressure still drops slowly, Suspect Fuel Injectors or FPReg Diaphragm.
If Fuel Pressure retained, Suspect FPReg Check Valve or Fuel Pump Check Valve.
Eliminates Injectors and FPReg Diaphragm
Prime Fuel Rail and clamp off Inlet Hose.
If fuel pressure still drops slowly, Suspect the Injectors, FPReg Check Valve or FPReg Diaphragm.
If Fuel Pressure retained, Suspect Fuel Pump Check Valve.
Eliminates Injectors, FPReg Check Valve & FP Reg Diaphragm
Prime Fuel Rail, clamp off Return Hose.
If fuel pressure still drops slowly, Suspect the Injectors, FPReg Diaphragm or Fuel Pump Check Valve.
If Fuel Pressure retained, Suspect FPReg Check Valve.
Eliminates Injectors, FPReg Diaphragm & Fuel Pump Check valve.
This can be a long & tedious diagnosis, but at least you will definitely know whats causing your problem and eliminate replacing unnecessary parts.
If anyone has anything to add feel free to contribute.
Cheers
Geoff
F22-GURU
The Most Common Symptom of a Fuel Pressure Related Problem is HARD TO START/RESTART COLD
RETAINED FUEL PRESSURE
As the Fuel Pump operates when the ignition is first switched on, it primes the fuel lines to maintain FUEL PRESSURE in the fuel rail. This is known as RETAINED FUEL PRESSURE (Well it is where I come from)
When the engine is switched off the RETAINED FUEL PRESSURE should NOT DROP in the fuel rail (for ease of Starting/re-starting when cold.)
The engine usually restarts OK when Warm/Hot because of the retention of adequate Fuel Pressure.
RETAINED FUEL PRESSURE CHECK
First of all Check all the Fuel Lines from the Fuel Tank to the Fuel Rail for residual leaks. Repair any leaks evident.
Connect up a Good Quality (ABW) Fuel Pressure Gauge to the Fuel Inlet Hose, at the Fuel Rail.
While Observing the Fuel Pressure Gauge, Switch the Ignition "ON" and wait for Fuel Pump to stop priming - Approx 2-3 Seconds.
Fuel Pressure Gauge should go up to approx 260 Kpa when priming, then drop to a 230 Kpa. This will be the RETAINED FUEL PRESSURE.
Re-Check for any External Fuel Leaks at engine and surrounding areas. Repair if necessary.
With some white out, mark the F.P Gauge where the needle is.
Get Comfy, sit back, crack open a coldie and keep an eye on the F.P Gauge.
After 30 Minutes if the FP Gauge Needle has hardly budged then the RETAINED FUEL PRESSURE is considered OK. Start Looking Elsewhere fro problems.
If the RETAINED FUEL PRESSURE Drops then it is "A Process of Elimination" to locate the source of the Internal Fuel Pressure Loss.
PROBLEM 1 - IMMEDIATE PRESSURE DROP TO ZERO
If the RETAINED FUEL PRESSURE Drops Straight to Zero within 3-4 Seconds, then main culprits are the Fuel Pump Check Valve or the Fuel Pressure Regulator Check Valve.
To confirm clamp off the fuel return line, if the Fuel Pressure Drops, it will be the Fuel Pump. If the Fuel Pressure remains it is the F.P Reg Check Valve.
In rare circumstances Faulty Injectors or ECU Injector Drivers causing the Injectors to stay open can cause the problem.
PROBLEM 2 - SLOW FUEL PRESSURE DROP TO ZERO
If the RETAINED FUEL PRESSURE Drops slowly to zero then it's a matter of elimination again.
Prime Fuel Rail, clamp off Both Return & Inlet Hoses & FPReg Vacuum Hose.
If fuel pressure still drops slowly, Suspect Injectors.
If Fuel Pressure retained, Suspect FPReg Check Valve, FPReg Diaphragm or Fuel Pump Check Valve.
Eliminates Injectors.
Prime Fuel Rail, clamp off Both Return & Inlet Hoses.
If fuel pressure still drops slowly, Suspect Fuel Injectors or FPReg Diaphragm.
If Fuel Pressure retained, Suspect FPReg Check Valve or Fuel Pump Check Valve.
Eliminates Injectors and FPReg Diaphragm
Prime Fuel Rail and clamp off Inlet Hose.
If fuel pressure still drops slowly, Suspect the Injectors, FPReg Check Valve or FPReg Diaphragm.
If Fuel Pressure retained, Suspect Fuel Pump Check Valve.
Eliminates Injectors, FPReg Check Valve & FP Reg Diaphragm
Prime Fuel Rail, clamp off Return Hose.
If fuel pressure still drops slowly, Suspect the Injectors, FPReg Diaphragm or Fuel Pump Check Valve.
If Fuel Pressure retained, Suspect FPReg Check Valve.
Eliminates Injectors, FPReg Diaphragm & Fuel Pump Check valve.
This can be a long & tedious diagnosis, but at least you will definitely know whats causing your problem and eliminate replacing unnecessary parts.
If anyone has anything to add feel free to contribute.
Cheers
Geoff
F22-GURU
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