[T3] B brain

Jim Adney jadney at vwtype3.org
Sat Jun 2 21:24:13 PDT 2018

On 2 Jun 2018 at 22:44, Jim Adney wrote:

> On 2 Jun 2018 at 13:36, Mark Reno wrote:
> > Cool. I do recall the voltage being low. The book says if terminal 18 on
> > the brain is not getting a ground than it should be replaced. What do you
> > think?
> Terminal 18 goes to the starter and is not a ground.
> You must mean terminal 19. Terminal 19 PROVIDES a ground for the fuel 
> pump relay. If the pump relay is not closing for ~1 sec when you turn the key 
> ON, there are a number of possible causes. A bad brain is only one 
> possibility.
> What are your symptoms? Do you hear the relay under the dash click when 
> you turn the key ON?

Here's a simple test you should do to see if a lot of the FI system 
is working properly:

Turn the key ON. As the key comes on you should hear a relay click. 
This is actually 2 relays, one under the back seat and one under the 
dash, coming on at the same time. Since they come on at the same 
time, you will hear what sounds like a single click.

About 1 second after you turn the key ON, you should hear a second 
click. That's the relay under the dash turning off because nothing 
happened after 1 second.

If you hear both clicks, you've checked a lot of the FI system. The 
brain is getting power and ground, and the fuel pump relay is being 
operated properly.

As a bonus, if you can hear the fuel pump buzz for that 1 second, you 
also know that the fuel pump wiring is good and that the pump motor 
is at least running. (This does NOT guarantee that it's actually 

You may need a second person to listen for the pump with an ear near 
the RF wheel.  

Do this test and let us know what you hear.

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

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