Re: [T3] Distributor In, can get it to run (defending the devirginized sensor)

["Leon Martinez B." <martinezl@icanet.com.mx>]

I (LEON)was the one that adjusted Mark's pressure 
sensor. The pressure sensor had a broken seal
and was previously adjusted. I have units 
that I have adjusted myself and what this 
does is change the length of injection spray
time. I have a "virgin" new one that I installed
for a little while , while I had new injectors,
new pump, 29 lbs fuel pressure, new points,
newly refurbished wiring and rebuilt engine 
with stock 1600 displacement.  The engine ran 
quite lean with the new pressure sensor, it
even shook slightly (little perceptable,I listen 
for perfection). 

>From the information an old VW dealer mechanic
retired in Mexico: 
I don't beleive that Bosch assumes
that gasoline is the same all over the world
and every system built will work exactly the 
same, even with different gas formulations 
(good and bad) and different engine wear
 that changes compression and also assumes that 
no engine will ever be modified in any aspect.
The seal was placed not because the Germans 
felt that perfect preadjustment was acheived 
but because emission standards in different 
parts of the world were requiring it, to prevent 
the backyard mechanic setting it "wrong".
The original pressure sensor in 1968 with part
number ending in 001 (still available but with 
epoxy glue on the screw)had no seal because
emission standards were not enforced and 
requirements were very loose. I have one
of these original ones.

In the 70's this "seal" requirement was 
enforced and many American cars with 
carburators had sealed mixture
screws with caps that limited adjustment. 
The computers in our cars had a modefication 
done on them to have a limited mixture 
adjustment in order to pass emissions. Other 
components like the temp sensors and their 
accompaning metal washers were added with
different part numbers in order to adapt 
the engine to pass emission tuneup requirements.
If engine wear took it's toll or different gas
 was placed in gas tank the engine's fuel 
requirements would change thus requiring 
adjustment. On newer carburated car the emissions
test often fail on slightly worn engines or 
engines that are running "perfectly"
with it's carburator adjusted by the owner. 
These cars pass when the technician sets 
the mixture "correctly" and places the seal
 back on the mixture screw the engine runs 
really crappy after that, misses, heats
up, loses power etc... Until the owner places the 
adjustment back to the better working position. 
Between my brothers and my Dad we have 20 cars and
have gone through this many times.

My Dodge truck with Carburated engine must
have adjustments changed when I go deep into 
Mexico because the exhaust would have black 
smoke out of it's pipe. Why do you 
think our stock carb setups have idle mixture
adjustments and a variety of jets to purchase 
or modify.

The newer type of injection system including
the continous K-jetronic has oxigen sesor to
act as it's "automatic" mixture adjustment 
when it directly detects fuel inbalances 
due to wear of compression, load, different
gasoline, injector wear or the infamous 
oxigenated gasoline that made many cars
run like crap.

When I removed my virgen pressure sensor
and placed a "newly devirginized " unit 
in it's place the engine did run like crap
 at first but when I adjusted mine
(this one had fine adjustment , some 
seem to have rough adjustment because of 
the center screw stuck in the outer screw) 
the engine smoothed out like glass , much
better than my sealed unit and accelerated 
gorgeously, Mark Healey can attest to that, 
he test drove my car and he even did not 
zoom it at all and he felt how
a stock EFI type 3 should feel. 

When I first did this a year ago or more
with the non virgin one I had 75 pounds 
of compression on my newly rebuilt engine 
(after 5000 miles ,too many shims
worked very well with an adjustable unit)
shortly after I installed the virgin 
pressure sensor and the engine engine ran 
weak and like crap so I determined 
that my engine's compression was too low 
for the factory adjusted sensor and needed
 either to be adjusted richer or 
increasing the compression was warranted. 
You have seen my past posts on my low compression
with good power but this was with my adjustable 
sensor. The same week I tried my new sealed 
sensor I increased engine compression (removed 
thick shims) I now had 100 to 105 pounds of 
compression (and still have). The new sensor
did not perform as I thought it would but 
it was better, the engine was still not as 
smooth as glass. So I installed a non vigen 
unit that I put together (I have several doner 
units) and after a quick adjustment by ear 
(Yes some people think it is bad)the engine was
 as smooth as glass and accelerated beautifully 
even with a 100 pounds of compression. I was 
able to vary the adjustment 2 turns one way 
and 2 turns the other way just like a carburator,
 it would rough up as soon one went too far 
either way. Too lean it would knock and loose
power, too rich it would smoke black and 
actually "flood" at stop signs but when 
adjusted slighty richer than perfectly
centered it would run beautiful. Some units
cannot adjust this easily because the 
adjusting screw is stuck inside the 
larger rough threaded insert that is turning
causing impossible adjustments which frustrates 
the non experimentor. Sealed one needs higher
compression or better gas.

To use my "vigin" sensor
I must either raise my compression or 
increase my fuel pressure , I do not wish to 
increse my linear fuel pressure as to compensate 
for my dynamic pressure sensor. I think increasing 
fuel pressure works best for bigger engine 
displacements but I still don't like to increase
 pump, hose and regulator stress as well as 
injector winding stress since they were designed 
for a certain pressure. Increasing my compression 
for my good sensor adjustment will not be practical 
so guess what ? I adjust my sensor. Originally 
these sensors had a completely exposed adjusting 
screw. The D-Jetronic Porsche and Jaguar experts 
on the internet explain how to "devirgenize"
these sensors. If it is good enough for these cars......

So Mark and other people who have inherited
devirginized pressure sensors, do not feel 
hopeless about this, your worn engines and 
worn lean injectors need this compensation
adjustment just like a carburation adjustment
and when your engine and injectors are tip 
top bone stock working conditionyou can "FActory" 
set it again with an oxigen sensor you purchase
for your dash or go to a emissions shop that can
do this easily. I did this once , I had them 
adjust it just above 14 to 1 ratio, a little richer
 to get some more perfomance; this setting is 
always done to rally cars. 

Mark, if your stuck and need help on your 
ingition, just e-mail me and I will check
it out at your house . The adjustment
to your predevirginized pressure sensor was
warranted because, boy did your engine shake
at first when started, seemed very lean 
probably caused by dirty or worn original
injectors.  I was just trying to compensate
for a badly running engine. The pressure sensor 
is my carburator. 

If we get togther 
I will check all of your injectors this time
to see if they are spraying well, with this 
malfunctioning you will never get a good tune 
out of your engine, I went through this
before (frustrating!!).

LEON MARTINEZ

1969 SQUAREBACK EFI/AUTO
SAN DIEGO AND TIJUANA






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