[T3] Fuel Pump Relay - 69 Fastback
willjahn975 at gmail.com
Sun Jul 11 11:21:17 PDT 2021
Correct me if I'm wrong. Yes the battery is low and may be shot. When
checking for a voltage drop in one wire to the power relay one the pump
relay times out the only draw on the power relay is the ECU . The take the
ECU draw out test the wire from Batt to power relay with it disconnected
at the power relay, I don't know what the ECU draws but doubt it's much..
Sometimes the pump works and the engine runs and most times it does not ,
Why? Once the battery issue is addressed whatever is causing this issue
will still exist . Isn't it possible the ign switch run circuit does have
high resistance most of the time and when it does start and run just luck
it makes a good connection. That switch only has the start/run and run
circuit once the key is released.
When running the starter this is the largest draw the battery will see and
even with a good battery fully charged, the voltage 12.6 it can drop down
to 9.5 volts at the battery.
On Sat, Jul 10, 2021 at 10:43 PM Jim Adney <jadney at vwtype3.org> wrote:
> On 10 Jul 2021 at 15:51, Tim Schiller wrote:
> > Voltage at battery 11.84, voltage at power relay 11.84
> Sounds pretty low.
> > Turn key on and voltage at power relay drops to 11.67 Is this enough of a
> > drop to make a difference?
> Regardless of where it started, it's normal for the voltage to drop when
> start drawing current.
> > Voltage at fuel pump relay (87 pin to fuel pump)when cranking engine is 9
> > to 9.8
> Sounds very low.
> If the battery voltage isn't above 13 V when charging, it's possible that
> battery has a shorted cell, so you now have a 10 V battery instead of a 12
> battery. Almost any amount of charging should bring the resting voltage
> above 12 V if all 6 cells are working.
> If charging seems to be making a difference, do what you can to reduce the
> charging current to less than 1/2 A, then keep it up for a week and watch
> voltage. It should rise somewhat steadily to nearly 14 V. Don't let it go
> 14.5 V.
> Jim Adney, jadney at vwtype3.org
> Madison, Wisconsin, USA
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