🚀 go-pugleaf

I have more experience than I wished in low cost debugging of this type
of injection system.  As you implied, you HAVE to measure the pressure to
know what is going on.  If you are willing to not measure the pressure to
the accuracy all the manuals say is necessary then the following is one way.

Find one of those cheap foot operated tire pumps with a dial type guage on 
it.  Unscrew the guage, connect it to a piece of fuel line and, using a 
T fitting (I used a plastic one designed for vacuum lines-metal would surely
be better) insert it in the fuel line.  The guage covers the right range
(I recall something like 40 or 50 psi).  You can read it to about 2 psi and
the accuracy is probably 2 or 3 psi (the manuals say you need to know to 1
psi).  In my case the mechanical regulator failed stuck open allowing full
(electric) fuel pump pressure (about 100 psi).  Replacing the regulator fixed
the problem.  The shop manual implied that failure usually resulted in low
pressure, which seems to be what you have.  As you have no doubt found out,
the cheap fuel pressure gauges cover much lower pressures and are designed
for mechanical fuel pumps in non fuel-injected systems.  My experience is on
a 280 Z, but the system is simile2to yours.  Good luck!
	Jack Buchanan
	UNC-Chapel Hill
	{decvax, akgua}!mcnc!jwb
 

In article <476@harvard.ARPA> friedell@harvard.ARPA (Mark Friedell) writes:
>I'm trying to debug the fuel injection on my '78 Rabbit and I've discovered
>that I need about $10,000 in diagnostic equipment to do it.  In particular,
>I'd like to get a reading of the control pressure between the control-pressure
>regulator and the fule distributor.  The shop manual claims that this is
>a piece of cake -- just connect your special VW CIS control-pressure guage.
>And of course... to adjust the fuel mixture... just connect your home
>exhaust-gas analyzer.

Heathkit sells an exhaust-gas analyser (CO meter) for something like
$100.  You can make your own gauge with a pressure gauge that will
handle the 60-70 psi, a valve, and some high-pressure fuel line
with banjo fittings.  (A friend of mine did this, it works.)

If you do this, make sure that all the parts you use can handle
the pressures involved.  Let's not go spraying gas all over that
nice hot exhaust manifold!

Snoopy (ECS Ronin #901)
tektronix!tekecs!doghouse.TEK!snoopy