[T3] car died on way home

Bryon Garvin spinningrooves at gmail.com
Fri Apr 13 19:16:12 PDT 2012

Here's the latest:

My friend 1 hour away mailed me a known good FI relay (under dash).  Before
replacing, I tried to start car.  This time, ONLY 1 CLICK.  Relay under
dash not working.  Tried multiple times.  Priming pump did work, but FI
system wouldn't run pump.

Replaced the relay with known good relay.  Same problem.  1 click only,
from under back seat.

So this is my question....now that the relay under the dash won't click,
the only thing I have done differently is remove the brain and inspect it
like Jim said to do.  I re-installed the brain and then did my tests which
I described above.  Do you think there's a chance that the transistor I was
checking under the heat sink was marginal and I've disrupted it permanently
by wiggling the heat sink?

I think I might be at the point where I need to try a new ECU.



 - Bryon, 71 Fastback FI/MT

On Sat, Apr 7, 2012 at 8:40 PM, Jim Adney <jadney at vwtype3.org> wrote:

> On 7 Apr 2012 at 16:53, Bryon Garvin wrote:
> > Testing blue/white wire in plastic connector (back-probing method):  Got
> > 12v with key turned, jumped to 14v when engine ran, back to 12v when
> engine
> > died.
> Okay, the 12 V supply side of the relay is fine. That means that it's
> getting its supply from the main power relay as it should.
> > Testing white wire in plastic connector:  Got 12v when key turned, then
> > this:
> >
> > 1st time: stayed at 12v while engine ran, when engine died, still showed
> 12v
> > 2nd time: dropped to 5v while engine ran, when engine died, back up to
> 12v
> > 3rd time: same as first
> This side of the relay is not getting grounded properly, so the relay
> is probably fine. That wire is grounded by a transistor in the brain,
> but this will only work if the connection all the way back to the
> brain is intact. The problem could be the connection at the engine
> firewall, just to left of center, where the FI harness wire connects
> to the other end of that white wire, it could be a problem in the FI
> harness, or it could be the transistor inside the brain that is
> responsible for grounding this wire.
> Check the firewall connection first. This is a 1 to 1 connector. Make
> sure the male plug is actually inserted INSIDE the female connector,
> not just alongside it.
> If that connection is good, remove the connector from the brain and
> look in the opening. Turn the box so that the PC board is on the
> bottom with the connector slot facing you. On the right side, about 2-
> 3" in, there will be a metal case transistor with a heat sink on it.
> Push gently on the heat sink to see if the transistor will move
> easily sideways in any direction. Just gently. It will feel stiff in
> all directions if all 3 legs are intact.
> It could also be a problem internal to the transistor, but there's no
> easy way for you to check that. I would have to send you another
> brain to try to see if that fixes it.
> My first bet is on the firewall connection. I've seen a transistor
> with a leg rusted off, but that was in a very humid environment.
> > Hand on fuel relay under back seat confirms that it clicks off only when
> > the key is turned off.
> Good, that's as it should be.
> --
> *******************************
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
> *******************************
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