[T3] Re/ Mystery Fix...

[Jim Adney]

On 27 Jan 2013 at 18:49, Daniel Nohejl wrote:

> Jim, 
> 
> What do you mean when you say: 
> 
> > No, grounding #19 still uses the relay, but it bypasses the safety 
> > cutout in the brain. It's useful for testing, but dangerous to run 
> > this way for long.
> 
> In what way is it dangerous? I'm curious because over the summer, my
> wife and I wound up having to jump the relay under the dash to ground
> to get the fuel pump to work on our '69 Squareback. 

If you're actually jumping one terminal to ground, that would mean 
that you no longer have the white plastic plug that surrounds the 2 
coil terminals on the relay.

> Funny thing was, when we got the car, it had a "D" ECU with all "B" FI
> parts and the pump did it's 2-3 second prime thing. Once we changed
> the ECU over to a "B", the pump wouldn't prime. We tried three
> different "B" ECU's and no change. Meaning either we had three ECU's
> which happened to "break" in the exact same way or wire #19 went bad
> somewhere. We tested it for continuity from the engine to the dash and
> the wire checked out fine. Strange. 

It certainly sounds strange, but all the brains work in exactly the 
same way, so you either had 3 bad brains, or there was some problem 
with the wiring between the brains and the relay. The latter is quite 
possible.

The delay is ~1 second and it's only there to allow the pump to work 
long enough to get the engine started. Once the engine is turning 
over, the brain keeps the pump running.

> I guess all of this is a long way of asking if we should be looking to
> remedy this jump to ground situation in the near future because it
> presents a danger of some sort? 

Part of the brain's function is to shut off the pump if the engine 
stops for any reason. Imagine that you're in an accident that severs 
a gas line. The engine stops for lack of gas, but your bypassed relay 
continues to pump gas out onto the accident scene. Even though you 
survived the crash, you might still die in the fire. It's not a 
pretty thought.

It's a feature well worth preserving.

I had one friend who died in a car fire. It wasn't a VW and I don't 
think it was this sort of problem, but I don't want that to ever 
happen to any of you.

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