idle is acting funny at start up

[Jibit]

Ever since I replaced my fuel pump I have had two problems. One, I have to let the fuel pump prime the rails before I turn the engine over. Otherwise the car will crank for about 5-8 seconds before it kicks over (pressure on rail is 40psi max). Second, on cold starts the idle that fluctuates from 800 to 1200 RPMS. I give the gas a quick kick at the idle stabalizes when it comes back down. The dealership says the fuel pump is bad because it should have a valve that maintains the pressure in the line. It didn't throw any codes when at the dealer. I thought that there was something in the rail that held the pressure. Any suggestions???

 

[Joeychgo]

sounds like the fuel pump to me.

 

[Jibit]

Response is fine though and I have no problem adjusting the pressure (when it was first installed I was reading 65psi!). Anyone no the internals to a pump and whether or not is has some kind of valve to hold the line pressure.

 

[driller]

...Anyone no the internals to a pump and whether or not is has some kind of valve to hold the line pressure.

The fuel pump has a check valve to prevent pressure loss. The injectors and regulator are the other two components holding pressure in the system. It is unlikely the injectors leak off enough to cause problems. Assuming a new fuel pump, I would guess the fuel regulator is the next suspect.

Disconnect the return line from the regulator, fashion a hose attachment from the return line fitting at the regulator. Install a pressure guage at the schrader valve on the fuel rail. Turn the key on, let the system pressure up and the fuel pump will then shut off. Monitor the gauge for a pressure drop and monitor for fuel at the container after the pump has shut off. You may need to cycle the test a few times to be certain of the results. If the pressure drops with no fuel loss from the regulator - look at the fuel pump. If you have pressure loss in sync with fuel loss at the regulator - you may need to replace the regulator.