[T3] Fuel pump isn't working.

[Jim Adney]

On 2 Nov 2021 at 23:18, Jeff Palmer wrote:

> When I turn the key to the ~onTM position I did not hear a click from
> under the dash.  When I turn it to TMstartTM and crank the motor, the
> relay under the dash clicks rapidly.  Multiple times per second.  I
> didnTMt hear anything at the relay under the back seat (maybe it is
> silent?) but I will check the grounds next spring.

This sounds like there's a loose connection somewhere that gets shaken by 
the vibration of the starter. Things to check:

The larger relay under the back seat is your FI main power relay. It supplies 
power to the FI brain when the key is in ON or START. Check that all its 
wires are on there securely.

Find the FI main power relay under the back seat and make SURE it's 
ground wire is secure under the relay mounting screw.

Check the red hot wire that runs from the battery + terminal to the main 
power relay. Make sure it is connected at both ends.

Under the dash, mounted to the firewall, up and left from the steering 
column, is the fuel pump relay. The FI brain turns it on, but will turn it off ~1 
second later unless the engine is turning over. So when you turn the key ON 
both relays will close (but you will hear this as a single click) and ~1 second 
later, if you don't try to start the car, the fuel pump relay will drop out, 
producing the second click. Just turning the key from OFF to ON and 
listening for those two clicks will tell you a LOT about the condition of the FI 
system. If you do not get the two clicks, then there's a problem that's likely to 
be fairly simple that you need to fix before trying to start the car.

There's a single white ground wire from the FI harness to the top of the 
engine case. Make sure it's well connected.

There's a connection in the engine compartment that often gets undone and 
then redone poorly. It is an inline connector between the FI harness and the 
main body harness, located against the "firewall" at the front of the engine, 
just to the left of center. (By "front" I mean toward the front of the car.)

Also in the engine compartment, in the FAR front left corner, there are two 
inline connectors that connect two white wires from the FI harness to two 
wires coming out of the main body wiring harness. Check those connections, 
too.

If all those things are good, you should get the two clicks. If you still don't, 
get back to us.

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