Frustrations set in.. prematurely? (SAME 84 start issue)

[Ben Swann]

Johnny,
 
Now I'm not trying to talk you out of doing a fuel pressure test entirely, but do think
you are not at the point of justifying doing it yet.  I do think it is necessary to
understand what you are or will be doing and for what reason.  If you analyse, you may
come to same conclusion as Huw, myself and others - that fuel pressure testing might be
a complete waste of time and money.  For sure a complet review of the procedure is in
order before going there.   Fuel pressure testing is a valuable test when used for the
right purpose  - I simply don't think this is it.
 
Why test Fuel pressure?- You want to make sure there is adequate fuel pressure getting
to the CIS metering assembly to and through the fuel pressure regulator.  You might also
want to make sure that the pressure is being regulated through the system.  We would do
this if all other tests did not pan out - you have not done this yet as best as I can
tell.  Again, point overall is don't make life more difficult when there are more simple
ways to cut to the chase.
 
Tests you need to do beforehand:  Injector spray pattern - remove injectors from the
head but keep attached to the lines.  Place injectors over a test basin - trash can lid
works fine, or if you really need to spend the money and get fancy you can buy special
graduated cylinder transparent containers that also let you measure flow rate as well.
Run the pump - lift airflow plate and check fuel spray pattern.  If all look fine and
there is nice atomized conical spray pattern and no dripping, then you probably don't
have a problem with fuel delivery or pressure.  Have you done this yet?
 
You can also do fuel delivery tests - one way is to measure injector flow both all
combined and individually.  I rarely get this far, since these tests are merely to
answer if there is fuel getting to the injectors or not.  A hard block in the metering
head or DPR will make it difficult to lift the air plate and no fuel will be delivered.
You will feel the problem!   I do still suspect DPR as potential culprit and don't think
you have ruled this out yet.  I'll often run the pump with DPR removed to expel fuel
into container and make sure there is no blockage.  This has cleared problems in about 5
out of 20  CIS-e cars for me.
 
Is pump delivering enough fuel  flow?  Don't need a guage for that - procedure is in the
book, but this is basic/simple.  Disonnect the feed line and measure how much fuel goes
into measuring cup or that expensive graduated cylinder  if you need to spend the $.  If
you want to put a guage in line, you might want to do it just after the fuel pump
regulator - that should give you a baseline on system pressure, but really you need to
know if the pump is putting out correctly..
 
At this point you should have a good idea if the pump is delivering fuel adequately or
not.  The filter usually won't cause low pressure problems, but might result in low fuel
flow.  You should have that area ruled out  since you replaced accumulator, filter and
pump check valve.  The only other item that would effect fuel pressure into the CIS
metering assembly at this point is the regulator - If I recall this is a vacuum
controlled pressure regulator. Anyway no need for expensive guage if you can put one in
line permanently here.  I've just never had to do it and my experience with fuel
regulators is they are leaking fuel when they no longer work, but maybe yours is a
problem
 
Cold start injector is an easy test - just remove the dang thing and verify it pulses
fuel spray when engine is cold and cranking.  If no spray then make sure there is an
electrical pulse at the injector connection.  I suppose you can plumb in a replacement
injector to rule out CS injector.  I may have replaced on or two of these in hundreds of
cars, so not a common problem
 
Before pressure testing, you would be best served by making sure timing is spot  on,
timing belt is installed properly (no slop).  Is the timing advance mechanisme working
inside the distributor.   Test with a mityvac - bet it's locked up solid.
 
Get your mixture and idle in the ballpark too - this makes a big difference in start and
driveability.  Also, rock solid idle can be a typical problem with engine having a
sizeable air leak.
 
What happens when you force the ISV to actuate?  Turn the throttle idle way closed and
ensure that the ISV is attempting to recover RPM.  If I recall in this engine you can
turn the idle down enough to kill or make ISV hunt, wheras on CIS-E3 idle screw is
supposed to be completely closed.  Make sure the ISV hose is not collapsing and that you
don't hear a hissing noise- inside or outside those hoses.  This is another place I
think you may have problem - in fact maintain my hunch your problem is in this area -
throttle, ISV, associtated hoses and crankcase ventilation.  Some tests that may reveal
information - what happens when you disonnect the idle switch connector when engine
idleing..and when you rev. it with connector unplugged?
 
Have you driven the car for awhile now after purging old fuel and running new fuel?  Run
fuel injector/fuel system cleaner though - at least one tank full?   Given it a nice
long drive - often referred to as an Italian tunup.  This sometimes will get rid of
varnish deposits and literally run the fuel system clean.  
 
You say you have no technical know how, then definately don't do fuel pressure testing.
It is messy, requires certain equipment and can be dangerous.  Don't start running tests
because you are frustrated and willing to try anything.    Furthermore on this engine I
just can't see why you need to do it - I never have even when starting with engines that
had been sitting for close to a year with old fuel turned to varnish.  I have come to
the conclusion that many tests are in the Bentley so the shop mechanics could charge
more money for the time and equipment, some were just holdovers from earlier/different
model cars/engines.
 
CIS pressure testing does make more sense in a CIS system like the one in the Ur Quattro
or 5000 Turbo Quattro that have warmup regulator, but even there I have found this a
last resort type of thing and usually for verifying that the WUR is not blocked.
 
In a nutshell, I don't think you have ruled out the silly simple stuff yet.  Although a
previous maintenance history may be helpful, I would not go by what prior owner has told
you outright - you already found and resolved at least one problem he didn't and that
changes everything.  Verify things yourself and use others suggestions as possible
clues.
 
Ben
 
  _____  

From: Johnny B [mailto:pre95 at live.com] 
Sent: Monday, August 16, 2010 9:52 AM
To: josh at spiny.com; cody at 5000tq.com
Cc: benswann at verizon.net; quattro at audifans.com
Subject: Frustrations set in.. prematurely? (SAME 84 start issue)


Well at this point I really have no choice but to rip in to the fuel system with a
pressure tester. This start issue absolutely makes zero sense to me and I really have no
other direction to go in. To be honest, I give it two weeks before I tear this bitch
down for parts on my ur-quattro (as at this point I dont think I'll find the problem.
The PO noted 12 years of trying to find this, countless tests and the guy was no dummy,
several of the ur-q owners know him quite well). Sorry to get so disgruntled but I have
literally crawled to hell and back again on this thing and found absolutely no problems,
and the symptoms continue. Without technical know-how, or the budget to support
replacing everything fuel related, I'm totally lost. 

So, just to recap: Cold start takes 3-4 tries before firing. Warm start will take 1 or 2
tries before starting. Both have the same symptoms once started: Bogs when you throttle,
will not allow you to drive. When warm this lasts 5-10 seconds, when cold this lasts a
bit longer, 30-40 seconds. Symptoms are the same if you drive for 30 mins, shut the car
off, and fire right back up 30 seconds later. Same bogging, same symptoms, no change.
The issue is lean, for whatever reason it does not get enough fuel. 

Screams vacuum leak right? Well, considering my idle is 100% rock solid just shy of 1k,
never wonders, good power through to red line, and after a complete soak down of
chemtool, I dont think this is my problem. That is, unless there is a hidden massive
vacuum leak that takes 5 seconds to re-close when already hot. Not likely, and I really
dont know where else to look. 

Cold start valve would not effect throttle once started. The coolant temperature sensor
for the ECU has been replaced. The idle & WOT switches have been tested. The injectors &
seals are new, all vac lines & connections have been replaced, full tune up performed +
a fresh rebuild on the engine less then 30k ago. Accumulator & check valve have been
ruled out with bypassing the FP relay. This all does not compute with my starting issue.


Shit. Any suggestions on where to drop this off in Norcal appreciated. 

Johnny