[T3] On my 73 square

[William Jahn]

Jim I agree I too feel it's running lean mainly because as you said the
unplugged TS1 does make it more rich .

 ON the runners . Yes I cleaned the head to gasket surface 5 times each and
made certain there was not one bit of old crud anywhere to could come close
to falling onto the surface . Used a wooden pick to get the loose stuff off
and a shop vac to pick it all up then used carb cleaner spray several times
so it looked like new . I also used a brass wire brush to clean the runner
to head and checked they were flat I even used a wire brush to clean every
bit of rust out of the the bores where the injector seals seat as well and
cleaned the entire runner everywhere all around up to where the two runner
pipes are fixed to the mounting and I even drove it till hot and re torqued
the two runner nuts. I wanted to be certain . I even used carb cleaner on
the runners and compressed air even used compressed air plus the shop vac
on the head area at least 5 times each side. Made certain the intake studs
were clean and the holes in the runners . The old gaskets still looked good
and I left them in place before I cleaned most of the crud around them the
shop vac into each head port just to make sure nothing fell into the
cylinders , May have been  over kill I wanted it clean.

 I plan of checking all the connections from the ECU connector to each
component still connected as well as disconnected just to rule out any
possible fault.

 I realize the Bosch tester offers an advantage yet I can get pretty
creative with jumper leads and alligator clips from a DVOM so I can use two
hands . Last time I had the ECU connector off I cleaned the ECU contacts
and the connector and I closed each gap on the connector so it would make
good contact you know what they look like , I even made certain the leads
were crimped well in the connector on each terminal. I also used electronic
contact cleaner.

 I don't have another MPS other than the one ending in a D instead of an E
all the other numbers were the same .

 Check this link
http://www.bosch-classic.com/media/bosch_classic/teile_1/nachfertigungen/motor_2/druckfuehler/Mini-Katalog_
Scroll all the way to the bottom just above the last box where it ends  on
the left shows the D model just above the 3 E model MPS , that's the one I
was using and it did work fine yet the 116 I put on a year ago worked just
a tad better nothing that really stood out unless you really A/B'd them.
They all look  identical all have the exact same nose ,if not for the
number you would be hard pressed to find any difference at all.  I imagine
it's just the calibration that would differ.

 On another site which I shall not name I am constantly  told to adjust the
MPS which is not something I care to do , I feel it will just make things
worse. It might be a last resort if everything was proven to be in spec  if
one had a sniffer. The issue I have was not gradual or a long term change
it was more or less sudden.

On Sat, Sep 14, 2019 at 9:35 AM Jim Adney <jadney at vwtype3.org> wrote:

> On 13 Sep 2019 at 16:11, William Jahn wrote:
>
> > I will check the voltage at the ECU from the power relay , to be
> > honest after I fixed the relay plugging in the air temp it seems to run
> > even worse and the same with it unplugged.
>
> Fixing the supply voltage should have made it run leaner, which normally
> would have made things better. Your observation that it's worse now, makes
> it seem even more likely that it's running excessively lean, which is
> consistent with removing the air temp sensor, which richens it up a bit.
>
> This is also consistent with the problem starting as the engine and head
> sensor warm up and lean out the mixture.
>
> Things that will make it run lean:
>
> Vacuum leaks at the air runner to head connections. (I'm pretty sure you
> have fixed those, but did you get both surfaces nice and clean and flat
> before you installed the new gaskets? You could also check with some
> propane there.)
>
> Low fuel pressure (measure while driving)
>
> Bad connections in the injector circuits (Measure the resistance from the
> ECU injector pin to the separate ground pin on the same connector, should
> be ~2.5 Ohms. Also make sure the brain connector fingers are close enough
> that they will make good contact with the brain circuit board. I have some
> little bits of brain edge connector that you could use to test the
> tightness of
> each conector pin.)
>
> Leaky aneroid in the pressure sensor (try a different, late (116) E
> pressure
> sensor) This is rare, but it happens.
>
> That's all I can think of at the moment, but there may be more.
>
> > I don't have a problem spending the extra time checking wires with a
> > DVOM.
>
> The Bosch tester essentially gives you 1 or 2 extra hands. You can set the
> tester to look at a particular resistance path, while you watch the needle
> as
> you wiggle wires to look for intermittent/weak connections. It takes 2
> people
> to do this with a DVM.
>
> If you don't have the Bosch tester, get a friend to help.
>
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
>
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