[T3] '73 Idle Test

Wed Aug 28 10:26:10 PDT 2019

 Jim :

 I am just going by the Brown Bentley for wiring. So far it's been right as
far as the wiring diagram and FI wiring go. Other than for an auto trans
such as mine they have the added page since the starter goes through the
switch in the shifter base as well as the back up lights.

 I don't have the cold start valve thermal switch or it's bracket on the
car at all , I never needed it. From the way it's wired stock all the
thermal/temp switch does is complete the ground the cold start valve or
rather complete the circuit so once the temp switch reaches it's set point
and the CSV is connected one side of the CSV has voltage only when the
starter is engaged and the temp switch at a low temp supplies the ground
since it's one wire on the temp switch and the temp switch through it's
mounting bracket is to engine case ground . I think all I really need to
check is the wire at the CSV two wire connector  that has voltage with the
starter engaged, It gets this voltage . I going off the Bentley page 19
fuel injection section. #12 thermo switch #13 CSV page 18 shows it better
power to CSV comes from #50 starter energized starter engaged only and also
from#50 to #18 on ECU . the other wires you mentioned are in double wire
connector #20 which begin at the power relay #9 the power is off term #87
power supplied off battery positive #30/51. The two wires off #87 then sent
voltage to the ECU #16 and #24 so these could have high resistance causing
low voltage on either #16 or #24 or both at the ECU similar affect to
having low system voltage. I want to see if the power relay has any voltage
drop between 30/51 and 87 since this is where all the ECU power begins. If
I see a voltage drop there the power relay contacts have high resistance
and either I need to remove the cover and check and possibly clean the
contacts as one would do with voltage regulator. Then move on to connector
#20 and check both wire #16 and #24 to see if there is high resistance in
either one or both which will lower the ECU voltage. Any one of these could
be what's causing the issue I have which is what you pointed out one post
back. I'm hoping this is where the issue is and could be I never looked at
connector #20 and after over 40 years the 1/4" terminals inside this now
black plastic once clear connector/insulator may not have broken wire
strands yet the brass terminals inside exposed to the weather might be in
real sorry shape and have high resistance.

 Jim Let me know what you think .

William

On Wed, Aug 28, 2019 at 9:02 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 27 Aug 2019 at 11:01, William Jahn wrote:
>
> > I removed the temp or thermal switch from the cold start long ago. At one
> > time when I still had the cold start valve plug connected I ran a wire to
> > a switch on the dash so I could ground the cold start so I could use it
> at
> > will yet it caused a rich cold start. I keep the cold start valve
> > unplugged just the fuel line on it
>
> Okay, so to do the check I suggested, you would have to plug the CSV back
> in and then check the voltage on the wire that used to go to the temp
> switch.
>
> Once you've done that, I'd suggest that you reconnect the wire to the temp
> switch and unplug the CSV. I just hate to see uninsulated wires left
> dangling,
> and there's no point in disconnecting both plugs.
>
> FYI, on my '73 both plugs are connected. That still leaves the CSV
> disabled
> down to about 14 F, which is probably lower than your car will ever see.
>
> >  I'll check to see if the other wire believe it's #18 on the ECU is hot
> > when not cranking it also ends up in the test connector there is a +
> there
> > and it is hot off the battery and #50 . I do know at the test plug + is
> > hot all the time. If 50  is hot all the time then that's the problem
>
> Yes, wire #18 is the one. I don't think it goes to the test connector in
> '73,
> although it did in late '71 and all of '72. (I suspect that VW eliminated
> those
> connections when they realized that running iginiton and starter wires to
> the
> test connector made hot wiring those cars easy!)
>
> Wire #18 gave the only source of extra enrichment in '68-9, unless M229,
> cold start valve, was installed. I believe that wire still gives extra
> enrichment
> in the later cars in the temp range down to where the temp switch enables
> the CSV.
>
>
> > On the temp sensors.
> > Yesterday working it the garage in over 100 degrees I removed TS2 and
> > found it was a VW # 022 906 041 Bosch # 0 280 180 012 that was used for
> > buses and T-4 . from what I could find a T-3 should have a bosch 0 280
> 130
> > 003
>
> 003 was the part for '68-9. 012 is correct for all later years. As far as
> I can
> tell, the only difference is the length of the wire, since that wire had
> to be
> much longer in '68-9, when the sensor was mounted under the #4 exhaust
> port.
>
> My impression is that ALL those temp sensors have the same resistance vs.
> temp characteristics. It's interesting that the 012 was sometimes labeled
> as a
> 311 part and later also sold as an 022 part. I didn't know that.
>
> My Bosch book calls out the 012 as correct for all aircooleds from '70-on,
> plus '80-3 Vanagons (were those still aircooled?) It calls out the 003 for
> '68-9.
>
> You can interchange those, but you'll have excess wire one way and have to
> make a wire extension the other way. Most of the early FI engines have
> been
> rebuilt by this time and had a replacement head installed that allowed
> installation of the temp sensor on top, which is a MUCH better way to do
> it.
> Clearly, VW and Bosch were learning how to do this in the first 2 years.
> What's amazing is how well it worked, even then. I'd love to hear the
> story of
> their pre-release testing program. They must have had FI cars driving
> around Germany for a year or so, just to work out the alpha and beta bugs.
> We can find photos of TPSs with 3 terminals in some of the literature.
> Those
> were never used in production, so they must have been prototypes, used on
> some of the test cars.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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