[T3] Two Tests

William Jahn willjahn975 at gmail.com
Tue Sep 17 10:33:07 PDT 2019

I miss read it, thought you had the rich one in and after testing put it
back in, I was focused on the 3 year frame. I can't quote each line on
gmail with firefox like you can used to, something to do with windows email
program that won.t work now.

 I got that info on the 72 co adjust on clymer . I read about the trigger
advance on a link on Samba forget the added manual name they made it sound
like it was different trigger points which made no sense think it was
enfrink now i see it was the cam being advanced.

 I looked at the pedal that is fine as are the tube from the tunnel to the
engine tin that's all as it should be. I found cable replacement on a link
here http://www.vwtype3.org/literature/clymer/service/Clymer.1972.07.pdf.
plus you mentioned it on the TPS adjustment sheet you sent me. To have
someone press the pedal to see if the throttle returned . All I can say is
mine does have a slight bind sort of a tight spot when first pressing down
on the pedal that to me feels like a bind . I need to cycle the gas pedal
and see if the throttle actually closes each time I feel lubing the cable
would not hurt and might explain why the idle changes in RPM. It may not be
related to the cable yet if it does bind and throttle does not close fully
then adjusting the idle bleed and the throttle in not closed then something
is not right.

 I do find quite a bit of varied info when reading different D-jet sites.

 All I can do right now is see if the cable is an issue that would clear up
if the RPM variable in the cable binding or the FI system. It did this
before I fixed all the vacuum leaks it's just worse now. Then I need to
check the wires from the ECU to each component just to make certain TS1's 2
leads are not crossed or grounded with any one of the other leads and the
voltage from the power relay at the ECU . I just have the Bentley to go by
and FI page 19 has the diagram all I need.

 I do know in the Bentley it does warn not to ground wires with the key on
at the ECU or rather allow hot leads to touch a ground which can cause
issues in the ECU , I've never screwed up like that.

 I just know my car does act lean and all I can do is make sure the wiring
is sound and voltage is proper and if it's an ECU internal fault, well just
go from there. I looked inside the 72 ECU yet as you know you can't see
much without removing the one lid.It looks like resisters and capacitors ,
transistors and maybe small transformers all RC and time based . It seems
to me since TS1 is resistance to ground and pin 1 on the ECU and it sees
resistance then a short to ground shouldn't harm the ECU internals. Yet
since the one you have runs rich it may not have anything to do with TS1 or
TS2 internal ECU it could be any of the circuits and there seem to be quite
a few and all of it is just controls how long the injectors stay open
based on temp correction , engine speed and most of all manifold pressure
based on load and altitude what the ECU does with the MPS signal.

 I wanted to ask. I know you removed the EGR and plugged the ports, did you
remove the EGR relay? I did because it would do nothing and since on the
TPS #14 & #17 are in series from the relay to the ECU and pin #14 is used
that pin has to be a ground since on the 72's without the EGR TPS #14 is
ground . I wish I knew how that worked , if pin 14 in the ECU is always a
ground or only when the engine is running . You can check the TPS unplugged
to adjust it and test it yet it's not connected to the ECU . I ask because
the Bosch tester does not seem to look at that circuit.

On Tue, Sep 17, 2019 at 6:35 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 16 Sep 2019 at 16:58, William Jahn wrote:
> >  Since you tested these 048 ECU's and the one in your car makes it rich
> > perhaps that's why yours works well with TS1 .
> I removed the brain that ran rich 3 years ago. Yesterday, when I ran that
> batch test, I included the "rich" one, just to see if it still gave the
> same
> impression. It did. I could smell MUCH more gas when that one ran.
> > If you ever find what goes wrong in this version that can make it run
> > rich/lean let me know. I'm still confused what the real difference is
> > between the 028 and 048. All I could find was the 028 worked with the
> > 72 dual vacuum can yet both 72
> We'll never know, because Bosch has never released data on their ECUs.
> All we know is that they figured out a way to get around the complicated
> tuneup proceedure that the dual vac can required, which was a really good
> thing, if only because those cans have a much higher failure rate and they
> are VERY expensive.
> > and 73 distributors had the trigger point cam advanced.
> As did the '72 distributors.
> I don't think this is related to any of the other changes. You can swap
> '68
> and '73 distributors into either year car and not notice much of a change.
> What I've read, and believed, is that the change was made so that the gas
> would sit behind the intake valve for a bit of time for all 4 cylinders.
> Earlier
> cars, up thru '71, gas got sprayed behind closed intake valves on 2
> cylinders
> and behind open intake valves on the other 2. They thought that making
> both "the same" might even out the idle. At speed, where the times are
> much
> smaller, I don't see this as having any effect.
> Once the engine is hot, there's no longer any question of how quickly gas
> will get vaporized, so the timing of the injection pulse no longer matters.
> We don't know if Type 4s ever got this change.
> > I also read that on the 72 they had the adjustment pot for the CO Mine
> > does not.
> No, Type 3s never got the adjustment pot. That was strictly Type 4s, 914s,
> and Volvos, perhaps others.
> > For all I know since the tag is missing both ECU's I have could be 048.
> Without the tag, I don't know how to tell the difference. It's possible
> that you
> could see something different inside, but you'd have to have them side by
> side to look closely.
> > if I see 1000 RPM idle and push the pedal down it will raise up to 1200
> > so I think my cable is sticking .
> By far, the most common cause of the pedal sticking is that the "ramp" on
> the
> back of the pedal is catching on the carpet. This is easy to see, once you
> get
> down there and look, and feel. Do this with the engine off. It's easy to
> fix, by
> just readjusting the carpet position: Slide it upwards a fraction of an
> inch.
> If that's not it, check that the throttle cable is not "bare" between the
> body
> and the engine. There should be a flexible housing there, and that housing
> should slip into a pocket in the breast plate of the engine. Careless
> engine
> installation often leaves that housing misaligned and not dropped into its
> pocket. That can make things stick, and the misrouted cable will slowly
> saw
> thru the sheet metal of the breast plate and pocket.
> That housing also has a sort of sleeve fitting at its front end, which
> must
> slide over the cable tube where it exits the body. Make sure that
> connection
> is also properly done.
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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