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RE: [T3] Dead Injectors Puzzler

On 8 Jan 2001, at 12:19, Fuhriman, Mark wrote:

> > -----Original Message-----
> > From: Jim Adney [mailto:jadney@vwtype3.org]

> > Try checking the TIMING of the spark for all 4 next time. 1 & 3
> > should look alike, timed to the timing marks, while 2 & 4 should
> > light up the wide molded spot on the pulley that is 180 deg from the
> I did that, and there is no cross firing.  Everything is "spot on".

Okay, good.

> The distributor contacts *do* fire the #1 and #3 together and
> #2/#4 together, right??

No, that's the problem here. More on this below.

> > Do all 4 of your injectors LOOK alike?
> Yes, they are all the same yellow color.

And do they all look alike. The Bosch ones have nice rounded corners, 
but there are some rather cheap knockoffs with squared-off yellow 
plastic that I don't trust.

> Maybe I can measure the voltages in turn at each injector connector
> and see if there are any differences... hmm..  Anyone know what
> voltage I should measure?  Should be the same voltage at all 4, right?

It will just be a pulse, so it's hard to say what you will measure. 
Still it should be pretty much the same on each injector.

> > Hmmm.... Yes, puzzling. Check the 10 digit Bosch number on the
> > brains; are they the same? Sometimes more than 1 OE number
> Same Bosch part numbers.  And they both have stickers on them
> indicating that they are Bosch-rebuilt units.  Maybe the brain swap
> just introduced another variable that I don't want.

Okay. I think it's possible that when Bosch rebuilt THIS brain they 
changed something that allowed the engine to continue to run, even 
though one of the trigger points was not working right. I've never 
seen this, but it's possible that they finally saw this as enough of 
a problem that they thought it deserved a fix.

The problem with this theory is that the 1&4 injectors and the 2&3 
injectors fire together, not 1&3. This would only be true, however, 
if the injectors are wired up correctly, so my guess is that the 
injector wiring is swapped on one side of the engine.

The boots on the injector wires were originally color coded. The 2 
front injectors have black boots (the same color as the rest of the 
FI connectors) while the rear injectors have grey boots. Since at 
least SOME of your boots are probably gone, here's the wiring list so 
you can trace it down. For each injector I list the cylinder #, wire 
# from the brain, and the ground wire #. I believe these numbers are 
the same for all years, except possibly for the grounds. The wire 
numbers are printed in small black letters near each end of the white 
wire and the first 25 numbers are the position of the connector that 
these connect to the brain. So in the worst case you can figure these 
out by tracing from the brain connector with a VOM.

These are the 69 numbers:

cyl 1	3	26
cyl 2	5	27
cyl 3	6	28
cyl 4	4	29

If you find that you have a pair swapped, then unswapping should get 
an appropriate pair to fail together, and it seems like that is going 
to point to the trigger points. Getting the plugs on the right 
injectors should also smooth out the cold idle.

If the wires are correct at the injectors then I would also check 
them at the brain, as they can rather easily fall out of the backside 
of the connector if you remove the handle, and it would be easy to 
put some back in the wrong slots. The numbers on the brain end are 
always easy to read and they should just be in order, 1-25.


Jim Adney, jadney@vwtype3.org
Madison, Wisconsin, USA

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