UK urQ fuel problems

[Phil@sievers.com (Phil Payne)]

In message <vines.izZ7+eXW1mA@bangate2.tek.com> scott.john.mockry@bangate1.tek.com writes:

> >>a)   Why is the quiescent position of the air volume sensor plate
>      that controls the fuel metering head given as:
> 
>                       > "1.9 + 1.1 mm" ?
> The 1.9 + 1.1mm means that the minimum height should be 1.9 mm but the max height is
> allowed up to 3.0mm, in other words the plate height should be between 1.9 and 3.0 mm

Why not give the centrepoint with a tolerance?  This would be more likely to 
give a result within bounds.

>  >>>b)   000.5147.02.00 introduces a new service tool (VAG 1348/1A)
>      >for setting up the fuel injection (it holds the air
>      >volume sensor in pre-defined positions for measuring fuel
>      >delivery volumes, etc.)  Is this _really_ a VAG tool, or a
>      >standard item masquerading under a VAG number?
> 
> I have never seen this tool available other than by the VAG number, it can be used on
> any of the CIS type injection systems. (ie VW/Audi/volvo etc). When I was a VW technician
> I never needed to use it. 

The bulletin seems to add a "full throttle" fuel volume measurement using the 
tool that is not documented before the tool was introduced.  Did you not make 
this measurement?  According to the bulletin, this is a prime way to detect 
blocked injector lines - swap the injector giving the greatest volume with the 
one giving the least and measure again.  If the result is the same as before, 
the injector line is constricted.  Etc. 

> I don't know what procedure you used to adjust the idle mixture, but the best way
> that I have found and the way I was taught as a factory VW tech is as follows:

> One  thing that is important for good cold starting/running is to have the basic 
> CO% (mixture) set correctly when the fuel system is in open loop before
> the O2 sensor warms up. The CO%  should be  checked "Upstream" of the catalytic
> convertor using the metal pipe that connects to the exhaust and is bolted to the intake
> manifold with the blue silicone rubber cap. When checking the basic CO%, the O2 sensor
> should be disconnected, 

UK specification, remember?  No cat, no O2 sensor.

> the crankcase breather hose unplugged from the valve cover (This would take the leaking
> crank seal out of the picture during the mixture adjustment) 

Absolutely.  This _isn't_ in the German microfiche and _isn't_ being done, 
either by me or BR Motorsport (who maintain the car).  I'll do it next time.

> I don't know how the evaporative canistor vapors are fed to the intake on the
> 88 ur-Q.

Again, no such device fitted.

> The engine needs to be warmed up "before" you check and or adjust this basic 
> mixture using the 3mm allen in the fuel distributor. 

Yup.  Always done hot.

> When I worked at VW as a technician we would set the basic mixture to be 1.2% upstream
> of the cat (spec is 0.6 to 1.2%) with the O2 disconnected as outlined above. When the 
> O2 sensor is reconnected of course this mixture percentage comes down dramatically. You
> can't check the mixture at the tail pipe when doing this adjustment.

Again - no cat.  I use the tailpipe.

> Of course all the injector O-Rings should be good or replaced and also the screw in injector
> inserts/O-rings that go into the head should be replaced if they have not been done. 

All done.  Cracked O-rings caused a previous power ceiling problem.

> Regarding the crank oil seal causing a vacuum leak, 
> My 89 200TQ actually made the  squeeling noise one time after I started the car cold
> and it went away when I pulled the dipstick out. I am starting to wonder if my crankseal
> is leaking enough to distort the mixture on my car. I will check it out and let you know
> what I find.

> After you do the basic idle mixture  adjustment and reconnect the crankcase hoses 
> (but don't connect the O2 sensor yet) see if the upstream CO% goes much lower 
> with the crankcase hoses connected.

Yes, I'll try that.  I'm _really_ starting to suspect massive air bleeding into 
the system via the breathers.

> These CIS cars seem to suffer from Vapor lock in the injector fuel lines at 
> times which  can cause difficult starting and initial rough running after a 
> warm restart.

The car has a separate injector cooling fan.  On the 1988 MBs (and possibly 
some earlier cars) the nozzle/shroud has a 1 1/4" hole strategically placed to 
direct forced cooling air across the fuel lines.  It works very well - I've 
never seen vapour lock problems.

> Hope all this rambling helps

It does.  Thanks.

 Phil Payne
 phil@sievers.com
 Phone: +44 385302803     Fax: +44 1536723021     CIS: 100012,1660

 (c) Copyright Phil Payne/Sievers Consulting 1996