Re: filthy rich

["Melissa & Jim" <jadney@vwtype3.org>]

On 21 Oct 97, Greg Merritt wrote:

>  my '71 has started running incredibly rich--dumping out smoke.  It
> runs rough at idle & cruise, and just *flies* with oodles of power
> when accelerating hard.

I can think of about three things to look for:

1)  Make sure the voltage regulator is regulating at the proper 
voltage.  The system voltage should start out at around 12.5-13 V at 
idle and rise with increasing RPM to 14.1-14.4 V as measured at the 
battery.  If it is too low the D-Jetronix system will run rich.  the 
fix is to replace the voltage regulator.  Buy a genuine Bosch 
replacement.

2)  There is a vacuum leak that is fooling the FI into thinking that 
more fuel is needed.  Make sure the Pressure Sensor hose is connected 
to the right point on each end and make sure the pressure sensor 
itself does not have a major leak in it (put a clean hose on it and 
suck with your mouth.)  Do not worry about any other hoses or small 
leaks--they will just add to the idle bypass air and, at worse, make 
the idle a bit high.

3)  Check your fuel presure to make sure that nothing has gone wrong 
with the return side of the fuel loop.  A kinked or flattened line 
here could drive the fuel pressure way up and make the mixture too 
rich.

4) (Okay, I lied.)  Make sure that it is not the cold start jet by 
removing the electrical connection from the jet..  On late 71-72 
cars, if you reverse the two wires that go from the starter 
solenoid toward the rear of the car the cold start jet will run 
whenever the engine is running.  Another check for this is to note 
that when you turn the key ON you normally hear TWO(!) relay clicks 
separated by about 1 second and when you turn the key OFF you hear 
only one click.  If you don't hear the second click after the one 
second delay those wires are reversed.  Have you done any starter 
work recently?

If none of this pans out I would suggest you look around for another 
"D" brain to try.  That's a long shot, however.

Jim
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       Melissa Kepner                                    Jim Adney
                             Laura Kepner-Adney
                         jadney@vwtype3.org      
                             Madison, Wisconsin
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