Originally Posted by Concillian
You can disconnect the reference line, but you don't NEED to. Turn the ignition on, but don't crank the car. The pump comes on for a few seconds to prime the fuel system. At this point in time, the pressure in the manifold is at atmosphere, so will give the same results as disconnecting the reference line.
If your pump is hard-wired, you can simulate this by letting it run for 5-10 secs, then pulling the fuse.
What does fuel pressure do? How fast does it decay after prime (should bump up to ~43-44 psi and take a long time to decay. Barely noticeable decay unless you go away and come back 30+ minutes later.)
Just tested see below:
- Ignition on / fuel pump prime = 3.3 BAR ( 47.8 PSI )
- Once its stopped priming = 2.9 -3.0BAR ( 42 - 43.5 PSI )
It holds 42-43PSI for 1min
From there every 3 - 4mins it drops - 2PSI