[T3] (Fwd) 1969 Fastback Fuel pump

[Jim Adney]

On 22 Jun 2020 at 6:32, Tim Schiller wrote:

> I may have declared victory a little too soon. Fuel relay appears to work
> with the 2-click and the appropriate voltage to each terminal. Car also
> starts with no apparent problem. However, the fuel relay oeclicks
> almost continuously.
> 
> If a grounding problem, can I remove the 19 ground wire from fuel relay
> and ground the fuel relay directly to body to see if clicking stops?

I'd start by trying to determine if the main power relay is also clicking almost 
continuously. That would narrow down the possible causes. Do this by 
putting your hand on that relay so you can feel it click.

If the main power relay is NOT clicking. the problem must be in the wire #19 
wiring, the brain, or the in the relay itself. Start by finding the wire 19 
connection on the wall just to the left of the IAD. Make sure that connection 
is secure. Make sure all the push-on connectors on both relays are tight.

Providing your own ground for the fuel pump relay coil ground, as you 
suggested, would be a way to test that relay alone, but it would be somewhat 
difficult to do, since that connector is in a plastic housing. I've never seen a 
relay fail in this way, but it's possible. I have good used relays if you need 
one.

You could ground the wire running forward from the left of the IAD. If that 
stops the continuous clicking, that clears the relay and the wiring from there 
forward, leaving the FI harness and the brain itself as suspects.

If the main power relay IS clicking, check the wiring from the ignition switch 
to that relay, and the ground wire for the brain, which should be somewhere 
near the middle of the engine case. Also find and check the 2 connectors 
that bring power to the FI harness at the far left front corner of the engine 
compartment.

If it comes down to the brain, there's a single transistor in there that controls 
wire 19. Sometimes the leads on that transistor rust away on cars that have 
seen a lot of moisture. I can replace that transistor or sell you a good B 
brain; the cost is about the same either way. So far, however, I've only seen 
this problem on D brains, where Bosch used a different fiber spacer under 
that transistor. That spacer tended to hold moisture against the leads.

-- 
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA
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