CIS Problem?--AGAIN!!!

Ben Swann benswann at
Mon Jun 26 16:01:39 EDT 2006

Not sure what the specific question is.

As I mentioned, old leaking injectors can and will cause hard starting.  I
have had this problem on just about every 5kTQ that I have owned or worked on
and other CIS cars as well.  Usually among the contributing reason folks get
rid of the cars.  One thing leads to another and the leaking injectors causes
a domino effect on things - too much draw on starter and wiring leading to
other failures, etc.

I know in theory - the fuel leaked into your engine, but that leaked fuel is
now condensed on the manifold, and the line pressure has leaked down.
Therefore no spray.  It can take 10-15 seconds of cranking to get them charged
up again.

The fuel pump valve and accumulator will cause a loss of system pressure if
they are defective, and can also result in line leakdown, but usually this is
not the problem.  If you replace your injectors and that does not fix then
look at doing these.  

Fuel pressure and leakdown tests can tell you something, but hard to do and
difficult to prove a leakdown is not happening with the test equipment.

O-Rings go along with this fix and the combination does wonders.  Of course
getting at all those old vacuum lines may help as well.


-----Original Message-----
From: L DC [mailto:ldc007usa at] 
Sent: Monday, June 26, 2006 12:46 PM
To: L DC; Cody Forbes; Ben Swann
Cc: quains at; quattro at
Subject: Re: CIS Problem?--AGAIN!!!

Sorry, I did not get a response so I'm reposting this.

Many Thanks again Cody!!

Could you please clarify a few things?

Cody Wrote:

< You are correct on leaking fuel into the combustion
> chamber, which is why I don't think you have bad
> injectors.

So, if the car had leaky fuel injectors, the car would
still start, but it would run crappy, right?

I mean, fuel + air + spark in the combustion chamber
will make the car start, albeit crappy perhaps and
might shut off if the combination is not right.

> Other possible pressure leak-downs occur at the
check > valve on the fuel pump....

So far I'm ruling this one out given the fuel pump,
Pierburg, came with a brand new check valve.

>...and the pressure accumulator in front of the right
rear wheel under the car.

This could be a possibility as I would bet this car,
as most its era, has the original pressure accumulator

This a pic of the accumulator from your web site,
right Cody?

Do you know if a part from an Audi non T, not Q from
either a 5K or 100 is interchangeable with that of the

In what other places could there be a pressure
leak-down, aside from the obvious fuel lines running
under the car or engine bay?

But even with a pressure leak-down, isn't there still
enough pressure being built by the fuel pump to at
least make the car start? 

It almost seems to me that the car is simply not
getting fuel delivered to the combustion chamber. 

Maybe I'll disconnect the fuel line leading to the
fuel filter and if I get fuel there and I will pull
one of the fuel injectors to see if spraying. 

So which do you recommend Cody, option 2 or 3?

> Option 2:
> Factory wiring. You can use the much safer method of
> using the factory wiring so the pump automatically 
> turns off if the engine stops (ie. in event of an
> accident). This is the most simple method, but it
> does leave the OEM fuel pump fuse and relay in the 
> way in case they go bad. For this method follow the 
> diagram I made exactly.

>EOM fuel pump.... meaning if anything goes bad in
that wiring, the pump won't run, right?

Also, by taking this route I assume I will be using
the "green and yellow" wire that comes from the OEM
fuel p relay and not from any nearby hot wire,

> Option 3:
> Direct to ECU. You can run a whole new wire all the 
> way to the ECU. 
> It's alot more work, but I recomend the second
> choice.With this choice it's actually slightly
> different then the wire diagram I made. The ECU 
> turns the GROUND on and off, not the positive, so 
> you have to run the wire from the ECU to the new
> relay (where I labeled "from green and yellow wire),

> then the other wire from the coil of the relay 
> (where I labeled "Chassis Ground")goes to the
> battery positive. The other two go exactly how I did
> the diagram. 
> The pin on the ECU connector is pin #21 

For this method, I assume the relay labeled "From
Battery + " would then go to a chissis ground, right?

Would the wire running from the new relay to pin 21 on
the ECU hook up easily or would it require soldering? 

Just curious, what happens to the other wires that the
fuel pump hook up to?

One is a ground, the other would hook up to the wire
(hot) running from the new relay, what about the other
2? I know 1 of those other 2 wires is a hot wire also,
can't recall on the other.

Thanks again Cody,


More information about the quattro mailing list