[T3] car died on way home

[Bryon Garvin]

Sorry, I forgot to add:  Is there a way I can test the brain to see if that
transistor is bad?  A continuity check or something that would point out
whether that transistor is ok or not?

On Fri, Apr 13, 2012 at 7:16 PM, Bryon Garvin <spinningrooves at gmail.com>wrote:

> 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.
>
> Thoughts?
>
> Thanks,
>
>  - 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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>
>
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