Any book on troubleshooting fuel injection systems will tell you that the
first thing you need to do is measure fuel pressure. I came up with a
relatively cheap fuel pressure gauge setup this weekend that I'd like to
share. Sears sells a fuel pressure gauge that reads up to 100 psi for
$39.95. Typical pressures in the Vanagon are under 40 psi, so this gauge is
adequate for the Digijet and Digifant systems (some FI systems run over 100
psi I think). The gauge does not come with an attachment for Volkswagens so
you'll have to make one. What I did was buy 1 foot of 1/4" fuel hose (5/16"
would work better if you can find it). Be sure to get hose that's rated for
fuel injection pressures. This costs $4 or so per foot. Also get two clamps
for the hose--the solid kind not the kind with notches in the band. Unscrew
the gauge from the elbow fitting and fit it to the hose and clamp it. The
other end of the hose clamps to the T-fitting on the fuel lines in the
engine compartment.

Before attaching (and unattaching) the gauge to the fuel lines, you must
depressure the fuel lines. There are various ways to do this. On the
digifant (86 and up) you can remove the fuel pump relay and then run the
engine until it dies. The fuel pump relay is the relay on the right in the
box that's on the upper left side of the engine compartment--right above the
coil. Check the Bentley for information on depressuring fuel lines on
digijet (pre-86) systems.

-Mark McCulley