Date:         Mon, 11 May 2009 21:54:37 -0300
Reply-To:     Dave Arthur <dave.arthur@NSCC.CA>
Sender:       Vanagon Mailing List <vanagon@gerry.vanagon.com>
From:         Dave Arthur <dave.arthur@NSCC.CA>
Subject:      Digifant Fuel System Troubleshooting Experience
In-Reply-To:  <586a66170904251829w36b0c62er685918ba7b93451a@mail.gmail.com>
Content-type: text/plain; charset="US-ASCII"

I hope I never get to be one of those PO (Previous Owners). I hate it when
technicians(?) take short cuts and 'make it work'.

I've been tracking down an uneven idle and decide it was time to do a test
of the injectors. I work at a community college and borrowed an OTC kit, it
consists of a pressure gauge and an electronic device to manually fire the
injectors.

The procedure is to fit the pressure gauge into the fuel system, turn on the
ignition to pressurize the system (pump should shut off after 5 seconds),
note the fuel pressure and then fire the injector (50 pulses at 1 ms per
pulse was suggested), note the resulting fuel pressure and calculate the
drop. All the injectors should have approximately the same drop which
correlates to fuel passed through the injector. Now of course it doesn't
evaluate pattern etc. but its a fast test.

So I set up and turned on the ignition, the fuel pump runs continuously and
doesn't turn off after 5 seconds. Being a new Vanagon owner I thought that
this was normal... But I'm now suspicious.

I checked the wiring diagram and see that the pump is actually run through a
relay, that is controlled by the ECU. I removed the relay, turned on the
ignition and the pump still ran. Turns out the PO/Tech had run a wire from
terminal 15 on the coil directly to the pump. So ignition on, pump on.

This of course is a huge safety issue ...

I replaced the relay and connected the pump up properly and all was well,
until I checked the fuel pressure. As soon as the pump stopped the fuel
pressure bled down rapidly to zero (~2-3 sec). The manual expects at least
29 psi after ten minutes!

I pinched off the fuel return line and individual injectors to test for leak
down issues and concluded that the pump itself was not holding the pressure
when it stopped.

So the engine runs, but starts hard, with the pump running all the time as
before, the engine started immediately.

I guess I need to know my options. Could I put a check valve in the pressure
side of the fuel line or should I bite the bullet and get a new pump?

Dave

'86 Westy