At 00:50 10/5/2004, Joy Hecht wrote:
>- check fuel pressure while driving.  Too high, 40 (units?) while driving.
>Running too rich, black smoke coming out, lots of misfiring and lurching and
>stuff like that.

Fuel pressure is supposed to be 2.5 bar higher than manifold absolute
pressure.  If you put the gauge inside a box with a line into the manifold
it should read a constant 2.5 bar or 36.25 psi.  That's awkward to do, of
course.  But here are some conversions from inches(Hg) of vacuum to fuel
pressure gauge readings:

In Hg           (MAP)*          Fuel pressure.          *at sea level, will
reduce ~ .49 psi per 1,000 ft altitude

0               14.7 psia       36
5               12.25           33.5
10              9.8             31
15              7.35            28.5
20              4.90            26
25              2.45            24

So at full throttle you might see 36 and with closed-throttle deceleration
down around 25.  If you don't see this variation then the regulator isn't
working.

>- replaced heat sensor near fuel injectors, which was no good (he said).
>Made no difference.

Temp II sensor -- should show about the same voltage between terminals as
the T I sensor in the AFM when both are cold, and near zero volts when
warmed up and running.  If not, ECU will never get out of cold-enrichment
mode.

>I think that was it for today, as far as I can recall.  The next hypothesis
>is that I need a new fuel temperature regulator.  Rocky ordered one of
>those, and also a new fuel pump, just in case either fixes it.  So that's
>where we start tomorrow morning.

If you're running rich, the fuel pump can hardly be the problem, eh?  First
thing to begin making sense of what's happening is to monitor the O2 sensor
during warmup, preferably with a scope or fast meter.  Does it follow the
normal pattern?  Should be ~ half a volt cold when connected to ECU, rises
as the sensor warms up and begins showing a rich mixture, then alternating
above and below a half volt as the ECU shifts into closed-loop mode.  If
it's not close to a half volt when everything is cold, the sensor has troubles.

Assuming that's ok -- UNHOOK it and leave it unhooked until the engine is
running right.  You can read it with a voltmeter, but don't let the ECU see it.

If it's suddenly ok -- sensor problem, leave it unhooked and deal later or
replace now.

If it's still running rich -- fuel pressure regulator leaking into manifold
through vacuum connection will certainly do it to you.  Not to mention
sometimes causing hydro-lock.

Stuck injector...

If a momentary (half-second) ignition shutoff cures it temporarily, I would
expect the ECU is getting confused by some intermittent input and shifting
into panic mode.

Just some thoughts...
david

--
David Beierl - Providence RI USA -- http://pws.prserv.net/synergy/Vanagon/
'84 Westy "Dutiful Passage," '85 GL "Poor Relation"