The results (WAS: Differential Pressure Regulator Checking)

[Tigran Varosyan]

Well, took my DPR to Schucks today, the guy there happened to be an
Electrical Engineering student so he helped me test for ohms. The DPR
resistance came out at 18.6 ohms, within spec....

Went home, hooked it back in and started the car again. Yanked the injector
out, plugged the intake manifold hole with my finger and watched what
happened. This time I got a pretty nice cone shape out of the spray and the
spray increased as I revved... The engine ran pretty nice (on 4 cylinders).
Then all of the sudden flow stopped and the engine died... I was like WTF?!
Felt the plate, it was not stiff (for the first time ever!!) and I stood
there wondering what happened. On my way back to the cabin to start the car
again I noticed a stream of gas coming from below the car. Looked under
there and the line going to the fuel reservoir had come mostly lose.

My explanation is that the line must have been coming lose and spraying part
of the fuel out under the car. The car ran fine at this time. Then when the
line moved farther off the connection due to the pressure it popped off and
fuel flow to the engine stopped. This is one snafu that I think helps us
troubleshoot the problem a great deal.... I will elaborate towards the end,
let me finish recounting the events...

So I hooked the line back up, this time put a hose clamp on it and went back
to crank the motor. Engine started up, ran for about a minute and stopped,
just like it has been doing the entire time. While it was running I checked
to make sure that the hose was on tightly and that I had no more fuel leaks
under the car. I went to feel the plate and yet again it was VERY stiff.
Back to our original problem...

I then went ahead to check the return line as someone recommended. I took
the braided return line that comes from a cylindrical shaped piece and goes
behind the firewall. I took that off, put it in a bottle and started the car
again. This time with all injectors in the car. (I ran out of hands... If I
took the injector out I would need to hold the manifold hole plugged, the
injector in a bottle and the return line in a bottle too.) Anyhow, the
engine ran like crap for about a minute and then started to sputter and die.
By this time my 2L bottle was getting full so I shut the motor off by
myself, but had I left it running another few seconds I am sure it would
have died. With the return line still unplugged in my hand I checked the
sensor plate. Again, VERY stiff!

I cannot check the harness going to the DPR for 2 reasons. #1 I do not have
a tool to measure duty cycle, and Schucks wants $80 for one. #2 I cannot get
the engine to run long enough to reach operating temp anyway, so even if I
had the tool to measure duty cycle of the harness I cant get the engine hot
enough to where I could.

My theory:
Due to the resistance we know that the DPR is good, right? However the car
ran perfect when the fuel line was slipping off the reservoir dumping half
of the fuel on the ground. What this tells me is that the fuel pump is
out-flowing the main Fuel Pressure Regulator. I do not know if this car has
one, or where it is but all other injected cars I have seen have a main
mechanical FPR. I can see a cylindrical thingy with 2 lines going to it from
the Fuel distributor and a single line coming out (which becomes the return
line). From the shape of it, it looks like the main FPR to me. As you may
recall I bought a generic fuel pump that says it will specifically work with
my car. Normally I would suspect that, however the stock pump did the same
thing before it died! Nothing changed between the time I had the working
stock pump and this one. This leads me to believe that there is simply too
much fuel volume going to the fuel distributor and whatever is supposed to
get rid of that fuel (like a main FPR) is not working correctly. Again, we
know its not the return line as the same problem happened with the return
line in a bottle.

Ideas, more tests, feedback wanted very badly.

Thanks,

Tyson


-----Original Message-----
From: Paul R. Cole [mailto:bdssprc at wavetech.net]
Sent: Tuesday, November 26, 2002 4:24 AM
To: Tigran Varosyan
Subject: RE: Differential Pressure Regulator Checking (WAS: New member
with bad problem)


On Tue, 26 Nov 2002 21:37:17 -0800, Tigran Varosyan wrote:

>Ok sounds good. My tester is not the 2 leg kind. Those were nearly twice as
>much... I can make that out of mine though. I happen to have a valve and a
>large T connection. Will have to buy threaded fitting from a store or
>something.
>

Just be sure the threads match. All the audi stuff is metric. Replace ANY
copper
"crush" washers you remove as they are ALL one time use units.

>Ether way, I will buy a tester and do the ohms test. Never done that
before,
>not even sure how to test for ohms but I will learn. How do I test the

OK- When you need the info let me know- My formal training is as an
Electrical Engineer and I've got waaaaaaaaaaay  to much time in on
trouble shooting Audi electricals.


>harness going to the DPR? Maybe the ECU or something is not sending the
>right signal to my DPR...
>

I sent you the relevent manual pagess. You will need to fabricate the proper
adapter harness
to allow you to measure the current UNLESS you aquire a clamp on DC ammeter
of sufficent sensitivity ( read spendy) to measure the DPR currents.

Basic electricity theory can be found on some web sites. Take a quick read
of any
begining "Ohms Law" info-  V(voltage)= I(current in amperes) X R
(resistance)
V=IxR.  You can solve for other values if you have any two ( remember your
HS
algebra?)
Another basic eq. is the one for Power ( electrical) P=IV whre I is current
and V is voltage.
you can now solve for power given any I,V,R  through simple substitution.

Any decent begining automotive electrical service text will have ALL the
info you need.
Haynes and Chilton BOTH have these troubleshooting guides at the local
FLAPS ( Friendly Local Auto Parts Store). The're pretty good at showing you
the
stuff you'll need.

HTH


>Thanks,
>
>Tyson
>
>
//************************
Paul R. Cole:
'84 Coupe (385k and still kicking )
'84 Coupe (SAR) , 85 Coupe parts car
'89 200TQ (WIP- waiting new engine)
'91 Coupe Quattro 20V 211,000+ mi(new daily driver)
'80 924Turbo ( Carrera  GTR specs)
Bloomington,MN
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