re. More 86 5KCS Sudden Death

[Ben Swann]

Steve,

Check/replace the O-rings on the system pressure regulator.  The assembly
comes out with a 14mm wrench.  The two inner O-rings for check valve and
system pressure are relatively easy to change.  The outer one is for
control pressure, and is more of a pain.  You need to remove the allen
screw, and there is a tiny snap ring holding the spring and outer o-ring
assembly into place. BE VERY CAREFUL not to lose that snap ring, which will
come off with tiny needlenose, and also fly into unintended places.

Per above, it sounds like this may be the culprit, not sealing correctly
and causing your system and control pressures to jump all over the place.

Regarding the resistance on the airflow plate, some is normal, as that is
what control pressure is for.  If your control pressure is still too high
after R&R the check valve, you may have a gummed up Warmup/Control Pressure
Regulator.

These were some of the items that plagued me after I rebuilt the engine and
put in a hotter cam, which is apparently not as mixture tolerant.

Ben

[Thanks to all for the suggestions...

Good news is the timing belt is fine with good compression all around,
so no bent valves.  Although there is a small leak from the water pump,
so that will need to be replaced. It does seem (fortunately) that the
leaky water pump was coincidental with some other problem(s) that are
keeping the engine from starting/running.  However more immediate things
first, figuring out why the thing does not start/run...

The engine does not start (typically), but will start and run if I feed
it starting ether... so looks like a  fuel problem/vacuum leak.  I have
gone thru all the hoses and think I can eliminate the vacuum leak
possibility.  But while I had the air filter out I did notice something
funny:

The air mass sensor plate was very hard to move, in fact it felt like it
had a spring pushing it back down with 4-8oz of force.  If I bled the
fuel pressure (loosen the banjo at the fuel filter) then this downward
pressure went away, and the air mass plate was free to move up and down
(although it did seem like the plunger would not follow it down right
away?).  I tried starting the car (with air intake hoses off) and
manually pushing the air mass sensor up while the throttle plate was
worked.  That seemed to help but did not get to a working/running
engine.

My question for those who are more familiar with the CIS system is, what
does this mean?  Is the fuel distrib gone?  Is the Control pressure
regulator gone?  Is the fuel pump supposed to be self regulating
pressure-wise?

Is there anything else I can so without the Shop pressure test
equipment, or is it take it to the shop time?

TIA

Date: Sun, 05 May 2002 19:00:38 -0600
From: Steve Sherman <spsherm at attglobal.net>
Reply-To: spsherm at attglobal.net
To: quattro <quattro at audifans.com>
Subject: CIS Diagnostic, help

A bit more info on my 86 5KTQW that won't start (or stay running the few
times it does catch)...

Starts/runs if you feed it ether.  Checked for vacuum/hose leaks, but
did not find any.  Spark plugs are sooty, from too much fuel not oil.
Good compression, and crank, valves and dist are all in sync. Fuel pump
works, but when I took a pressure reading, I got 40-50#'s; with quite
alot of jumping around (that is it did not settle down at a steady
pressure).  This is with the engine off and the fuel pump jumpered to
run.  And FWIW, the air plate in the fuel distributor seems hard to move
up, but comes down easily; up resistance goes away when fuel pressure is
removed.

I'm trying to add these all up to come up with a likely diagnosis, but
seems like they are pointing in different directions...  The low/erratic
fuel pressure would seem to say clogged fuel filter or bad pump.  But
the sooty plugs and up pressure on the air plate seem to point to too
high a fuel pressure.

Anyone in list land an expert on the CIS system?  Could low or erratic
fuel pressure cause rich running sometimes (sooty plugs) and no fuel
situation others?  Other possibilities that fit these symptoms?

TIA

Steve]