DJ_USMC

Thanks for the guidance in advance. I've read far and wide regarding C5 fuel pump, but can't seem to find an answer.

This started 3-4 weeks ago. My car runs fine and starts normally most of the time. The problem only occurs when its been sitting for hours such as over night. It will turn over properly, but it turns for 3 seconds or so before it fires. If I roll the key to "on" to start the fuel pump a second before I try to start it gets better. If I roll the key on and off a couple of times it fires as soon as I turn the key.

I had an old ford pickup that started so much better when I "primed" the fuel pump by toggling the key. Eventually the fuel pump went out.

The filter is a year or two old, but more than willing to start there if thats what you guys think.

Thanks again.

DJ

Kevin Kuse

System Description
When you turn ON the ignition switch, the Powertrain Control Module (PCM) turns ON the in-tank fuel pump. The in-tank fuel pump remains ON as long as the engine is cranking or running and the PCM receives reference pulses. If there are no reference pulses, the PCM turns the in-tank fuel pump OFF 2 seconds after the ignition switch is turned ON or 2 seconds after the engine stops running.

The electric fuel pump attaches to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies fuel through an in-pipe fuel filter/fuel pressure regulator assembly to the fuel rail. The fuel pump also supplies fuel to the right fuel tank siphon jet pump in order to transfer fuel from the right fuel tank to the left fuel tank. The fuel pump provides fuel at a pressure above the pressure needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel returns to the left fuel tank by a separate fuel return pipe.

Test Description
The numbers below refer to the step numbers on the diagnostic table.


The left fuel sender voltage will be low if the left fuel tank is empty.
When the ignition switch is ON and the fuel pump is running, the fuel pressure indicated by the fuel pressure gauge should read 380-420 kPa (55-61 psi). The spring pressure inside the fuel pressure regulator controls this pressure.
A fuel system that can not maintain a constant fuel pressure has a leak in one or more of the following areas:
The fuel feed rear pipe check valve (Check valve stuck open)
The fuel pump fuel feed pipe
The valve or valve seat within the fuel pressure regulator
The fuel injector(s)
Fuel pressure that drops-off during acceleration, cruise, or hard cornering may cause a lean condition. A lean condition can cause a loss of power, surging, or misfire. You can diagnose a lean condition using a scan tool. If an extremely lean condition occurs, the front heated oxygen sensors will stop toggling. The heated oxygen sensor output voltages will drop below 300 mV. The fuel injector pulse width will increase.
Important : Make sure the fuel system is not operating in the Fuel Cut-Off Mode. This can cause false indications by the scan tool.



A rich condition may result from the fuel pressure being above 420 kPa (61 psi). A rich condition may cause DTC P0132, DTC P0152, DTC P0172 or DTC P0175 to set. Driveability conditions associated with rich conditions can include hard starting followed by black smoke and a strong sulfur smell in the exhaust.
This test determines if the high fuel pressure is due to a restricted fuel return pipe or if the high fuel pressure is due to a faulty fuel pressure regulator.
A lean condition may result from the fuel pressure being below 380 kPa (55 psi). A lean condition may cause DTC P0131, DTC P0151, DTC P0171 or DTC P0174 to set. Driveability conditions associated with lean conditions can include hard starting when the engine is cold, hesitation, poor driveability, lack of power, surging, and misfiring.
Restricting the fuel return pipe with the J 37287 fuel pipe shut-off adapter causes the fuel pressure to rise above the regulated fuel pressure. Using a scan tool to pressurize the system, the fuel pressure should rise above 420 kPa (61 psi) as the valve on the fuel pipe shut-off adapter connected to the fuel return pipe becomes partially closed.
Notice: Do not allow the fuel pressure to exceed 517 kPa (75 psi). Excessive pressure may damage the fuel pressure regulator.



The fuel pump runs for 2 seconds each time you command the pump ON with the scan tool. Enable the fuel pump several times in order to achieve the time specified in the diagnostic table. This test checks the supply of fuel to the right fuel tank siphon jet pump.
The fuel pump runs for 2 seconds each time you command the pump ON with the scan tool. Enable the fuel pump several times in order to achieve the time specified in the diagnostic table. This test checks for a restriction in the fuel sender fuel feed pipe (jet pump to left tank).
The fuel pump runs for 2 seconds each time you command the pump ON with the scan tool. Enable the fuel pump several times in order to achieve the time specified in the diagnostic table. This test checks the siphon jet pump output. If the siphon jet pump becomes plugged, is cracked, or if the tube is kinked, the jet pump will not transfer fuel from the right tank to the left tank.
Check the spark plug associated with a particular fuel injector for fouling or saturation in order to determine if that particular fuel injector is leaking. If checking the spark plug associated with a particular fuel injector for fouling or saturation does not determine that a particular fuel injector is leaking, use the following procedure:
Remove the fuel rail, but leave the fuel pipes connected to the fuel rail.
Lift the fuel rail just enough to leave the fuel injector nozzles in the fuel injector ports.
Caution: In order to reduce the risk of fire and personal injury that may result from fuel spraying on the engine, verify that the fuel rail is positioned over the fuel injector ports. Also verify that the fuel injector retaining clips are intact.



Pressurize the fuel system by using the scan tool fuel pump enable.
Visually and physically inspect the fuel injector nozzles for leaks.



You can put a gauge on it overnight and test your theory.

DJ_USMC

Holy moly. I will try to digest over the weekend.

Thanks for all of your help!

DJ_USMC

Thanks for all the info. It was the fuel filter/regulator allowing fuel pressure to slowly release. Replaced filter and all is well.