[T3] Fuel Pump Relay - 69 Fastback

Jim Adney jadney at vwtype3.org
Fri Jul 9 10:35:02 PDT 2021


86 should get 12 V from the main relay as long as the key is ON.

85 gets grounded by the ECU for ~1 seconds unless the engine is turning 
over. If the engine is turning over (or running) the ECU keeps this terminal 

85 & 86 are the connections to the relay coil, so the relay should close and 
send 12 V to terminal 87 for ~1 second after the key is turned ON or as long 
as the engine is turning over or running.

Check the fuel pump fuse carefully. Sometimes the fusable link can break 
but still look good.

87 is the power source for the fuel pump. It should have 12 V on it as long as 
there is 12 V from 85 to 86. Follow that red wire to the firewall and find a 
brown wire that comes along with the red wire from the pump. The brown 
wire is the fuel pump ground.

It can be helpful to get someone to listen down by the RF tire, to see if they 
hear the fuel pump buzz. It should always buzz for that first ~1 second.

On 68-70 cars that brown wire goes to ground via a rather torturous route. I 
make a very simple $10 kit to greatly improve the reliability of that ground, 
but I need your VIN to get you the right kit.

If you're not getting full voltage from the pump relay, try a small jumper wire 
from a reliable 12 V source to the red wire to the pump.

There are lots of possibilities for why your car won't start. Check to see if the 
pump is running. If it's not, continue checking out its power source, both 12 V 
and ground. If those are okay, the problem could still be in the pump. I 
rebuild them, but that starts to cost real money.

Stick with this and keep us in the loop. We all want to see you get this 
running nicely.


On 8 Jul 2021 at 22:07, Tim Schiller wrote:

> Car had been running well until it would not start. It initially started but sputtered, then nothing. I did not try to start again for about 4 month´s. I tried again, it started, I washed, waxed and went to fill up before a show. After waiting 3 1/2 hours for a tow at the gas station, it hasn´t started since. I tell this story only for background leading up to my question.
> Tested Fuel Pump Relay and no power to the 87 pin for the 1-1 1/2 seconds when key is turned. The 86 pin has 12V when key turned and 12V to power relay under back seat.
> I tested fuel pump directly and it appears to work fine when it has 12V
> Replaced Furl Pump Relay and I get power to the 87 pin for the 1 - 1 1/2 seconds. Car still doesn´t start. Check voltage to 87 pin again and I´m only getting about 5V for the 1-1 1/2 seconds. Should I be getting 12V? If I should have 12V, suggestions on why I not and what I should check next?
> Any help is appreciated 
> Tim
> Sent from my iPhone
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Jim Adney, jadney at vwtype3.org
Madison, Wisconsin, USA

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