***Car starts w/in a second of turning key and lacks no power, but is this nornal?***

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*Prime the pump, and i get about 43 psi.
*Let the car sit, and it dropps to about 20 in an hour.
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*If i start the car, pressure is about 35-40 psi at idle
*Rev it, jumps to about 45 psi.
*Turn the car off, pressure drops to just under 40 psi, and will also drop to about 20 in a couple hours.
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--My fuel pump has been changed, did that about 10 mos ago. THen, the problem was so sever, I would get max 25 psi, and it wouldn't start often, run poorly, etc...

My question is, what are you fuel pressure readins at idle? what about a couple revs? How long do yur lines hold pressure for? If my problems are really problems, what could cause this? Does the fuel pressure regulator play any role in HOLDING pressure when the engine is off? Don't think so, but then we're going back to the pump I just replaced...

OR, should I not worry until I actually notice this affecting anything?

Thanks.

 

The pressure is held in the line when the pump shuts off, by the diaphragm in the fuel pressure regulator blocking off the return line, and the check valve in the pump blocking off the supply line. Dropping to 20psi in an hour doesn't sound all that bad.

And your pressures sound fairly normal. First start the engine, and pull the vacuum line off the pressure regulator (plug the end of the line). Fuel pressure should be 43.5psi, plus/minus 2.5psi.... so any reading in the range of 41-46psi is OK.

Then reconnect the vacuum line to the regulator. Pressure should drop proportional to intake manifold vacuum. With a stock cam that could be as much as 8 or 9psi reduction from the "no vaccum" pressure. With a more radical cam, it might only drop 4 or 5psi.

When you suddenly open the throttle blades at idle, the intake manifold vacuum diappears, so the pressure should rise to the "no vacuum" value. As the throttle snaps closed, the intake manifold vacuum will spike, and the pressure will very briefly drop below the "idle with vacuum" setting.

The critical value is what happens at WOT/max RPM/full load - the pressure should hold within a couple psi of the "no vacuum" value.

Your system doesn't sound abnormal.