So I just installed an accel adjustable fuel pressure regulator on my z and now the car is really hard to start it cranks and cranks and cranks before it fires up and then the idle seems a little low any ideas?

 

Why did you put an adjustable regulator on? What did you set the pressure for?

 

old regulatoir was bad I just went a checked the psi it was at 60 I set it back down to 43 psi, would fouled plugs cause it to hard start? I'm thinking maybe it was running so rich it fouled the plugs maybe

 

The injectors were functioning as over 28lbs at that pressure. I would change the plugs and oil because it is likely rather fuel contaminated.

 

43 psi is the stock pressure with the vacuum line disconnected.

 

whats the stock psi with the vacuum line on?

 

Stock pressure without the vacuum line is 43.5psi. GM accepts anything from 41-47psi. When you reconnect the vacuum line, pressure drops proportional to intake manifold vacuum. In an LT1 with a stock cam you might see the fuel pressure drop 8psi. With a more aggressive cam, pressure will drop less.

Set the pressure with the vacuum line off (and plugged). That's the correct way to do it, not with the vacuum line connected.

 

To expand on Fred's comments. The regulator basically keeps the pressure diferential between the fuel rail and inside of the intake constant.

As a grossly simplified example. Say you had a boosted motor running 15psi and had a 15psi fuel injection system, if the pressure of the fuel system did not rise at all the inectors would not spray any fuel when the motor was at 15psi because the pressures would be the same.
On our cars it is more a matter of the very low pressure/high vacuum at idle would suck fuel out of the injectors making them act larger than they are, the factories solution was simply to always keep the pressure differential the same, yes that results in different system pressure but the injectors don't know that.

 

thanks for the info guys so basically, it was at 60psi with the vacuum line on I adjusted it down to 43 with the vacuum line on so I guess it's still to rich then, I'll tweak it tomorrow when I get off work hopefully that'll fix the hard start issue.

 

should i test pressure at idle or with the car off and the key turned on?

 

At idle is better. If you start the pump without the engine running, the pump will only run for two seconds and shut off. Then pressure may start to drop before you can set it correctly.

 

set this psi to 43 today with the car at idle and the vacuum line off car runs fine but still has to crank for about 10 seconds before it starts, do you think it's the plugs being fouled or is there something else I'm missing?