Adjusting Fuel pressure
 

I have a 91 tpi 350 z28 with an adjustable fuel pressure regulator on it. Seems the fuel pressure may be low at idle. Not for sure though. Question is does turning the bolt on the regulator increase or decrease pressure and is it at idle or only under load ? Also is it 45psi the correct pressure ?

Re: Adjusting Fuel pressure
 

Stock is 43psi IIRC. Turning in the screw increases pressure all the time. Set the base pressure with the vacuum line disconnected. The vacuum signal will alter the fuel pressure further as necessary under load.

AFPRs are a bit of EFI dark ages hokem. It's a bandaid workaround for not having the equipment or knowledge or $$$ to properly tune the car. A little tweak can sometimes help, but by and large most people are going to set it wrong and do more harm than good. IMHO.

Re: Adjusting Fuel pressure
 

Since you're "not sure", I'm assuming that means you haven't put a gauge on it? In my experience, you can't feel/hear minor pressure differences. My TPI runs just fine anywhere from low 30s to high 40s. Tune won't be quite right if it's off, and the Dyno or dragstrip ET would see it, but it's unlikely you can just "feel" it being off, especially at idle. ...and sure, maybe some people CAN feel it, but the point is that the pressure needs to be measured properly and adjusted accordingly, and not guessed.

Measure pressure - should be mid to high 30s.
Disconnect vacuum - should read 43.
if not....set to 43.
Reconnect vacuum...should drop back to mid to high 30s.

Re: Adjusting Fuel pressure
 

I put a gauge on and it sat below 40 so I turned it up to about 43psi and also took a handheld vacuum pump to the vacuum port with the engine off just running the pump and as I increased the pressure the fuel pressure went down. Is that correct because it seems to me it should be the other way around.

Re: Adjusting Fuel pressure
 

You increased PSI or vacuum? + PSI raises pressure, vacuum decreases it.

Re: Adjusting Fuel pressure
 

Ok so the fuel pressure regulator is working properly. Apply vacuum and the fuel pressure is suppose to drop correct?

Re: Adjusting Fuel pressure
 

yes