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RE: [T3] FI fuel pump relay

On 5 Jul 2005 at 8:49, Matthew Jones wrote:

> The relay *was* buzzing. I can't recreate the fault now!

Don't you just hate intermittent problems!  ;-p

> There are only 2 single wire connectors on my engine : one for
> CHT (I assume - it goes down to the LH head area), and one
> at the back (towards front of car) which comes out of the FI loom
> and has a small white numbered wire going into it. The engine has
> been out recently, but this wouldn't have been disturbed as that
> part of the loom stays in the car.

The latter connection is the one that feeds the fuel pump relay. Make sure that 
the connector is actually mated properly. I've seen them where they were 
inserted without actually mating.

> Comparing the FI wiring diagram in my Bentley, our car is simpler
> as we don't have the emission control stuff. And the Haynes doesn't
> even have a wiring diagram of an FI car, so I don't actually have an
> accurate diagram at all!

If you just cross out the parts that were not provided in the UK, and the wires 
leading to them, then the Bentley diagram will be right for you.  

> Anyway, I tested the relay on the bench and it seems fine so I have
> put it back. I made a bypass switch just in case, which is also
> good for priming, and incidentally, for finding fuel line leaks without
> the engine running!
> I've written it up with a picture here: http://vw1600e.org.uk/fi/switch/

I recommend a much simpler setup which uses a momentary SPST pushbutton that 
bypasses the relay entirely. Yes, it's good for priming. For testing, I use a 
separate set of clip leads as a jumper.

There's a hazard in using a switch like yours: You're likely to forget and 
leave it on sometime, and regret it later.

> I had to replace a fuel line so I ran the pump for a good 10 - 20 secs.
> The pressure regulator started whistling. At first it seemed to be
> resonating with the pump, but then the pitch rose. It got quieter and
> faded out at something like 1 KHz. Wierd.

This noise and pattern is common. I THINK it is just due to small bubbles 
making their way out past the regulator. It's not just a sign of old worn 
parts; my '68 did this when new.  

Jim Adney
Madison, WI 53711-3054

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