[T3] car died on way home
spinningrooves at gmail.com
Fri Apr 13 19:32:51 PDT 2012
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.
> - 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
>> > 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
>> > 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
>> VWType3.Org mailing list - type3 at vwtype3.org
>> Contact gregm at vwtype3.org if you need help with the list.
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