Pump is activated after a while when the motor is not running

[okkimi]

I have a problem with this system. The car is Audi S4 biturbo.

When I put the ignition on, but not start the motor, the pump goes on after a while. If the motor is started right after the power is on, the pump works as it is supposed to be.

Somehow when the ignition is on and the motor is not running, the controller "thinks" that the injectors are 100% open because there is 12 V at the injector "-".

If I disconnect the green wire from the injector, the pump is not activated.

The system should be connected correctly as in the photo at the diagrams section shows. What could be the problem?

Can the injector signal be inverted?

[Richard L]

This sounded like the fuel injection(+) is turned off and make the HFS-03 thinks the injector is fully on. Not a good situation.

I suggest relocating the red wire of the grey harness to the fuel injector (+). When the ECU turn off the fuel injector, the system will automatically turned off and the pump will not come on again after a few second.

There is also a danger, it will also spray water into your inlet tract at 100%.

Please let me know.

[okkimi]

I measured the voltages, and when the motor is not running, there is ~9 V in the injector "+", not 12 V as it should be. That is very strange, since according to the wiring diagram there should be straight connection from the wire that I measured, and it has 12V! When the motor is running, injectors have 12V. There shouldn't be nothing between the ECU connector wire 3 and the injectors "+".

I have to look more the diagrams to find out the possible cause.

[Richard L]

Are the any inline resistor between the 12V and the injectors?

It is very strange to see a 9V anywhere these days from a digital device. It may be easier to find a 12V source "only" present when engine is running and not before.

[okkimi]

I don't know, there shouldn't be. But I measured the lines, and there is very big resistance from the injector to the ECU connector pin 3. It should be straight wire according to schematics. I also measured from the other S4, and it is the same. Very strange. I have to find out the correct year schematics to be sure about the connections.

I measured the voltages again, and it is 3.5 V measured against the ground (on both injector pins). Previously I did it against the "+", and that was the ~9 V.

So I guess that if I change the HFS-3 red wire to something that has 12 V, that doesn't change the situation since the injector "-" has that 3.5 V?

[okkimi]

I found out that the connection diagrams in ELSA and Bentley manual are different! The Bentley manuals are made for US cars, and the 2000 year car in the manual is different than ELSA year 2000. Damn.

The ECU pin 3 wire goes to the ignition coils, not to the injectors. That's why I can't see the 12 V in the injectors. The power comes through the fuel pump relay to the injectors. But it is still a mystery that why there is that 3.5 volts because the relay is open. Maybe the ECU isn't grounding the lines or something, but I guess that it doesn't matter.

I'm sure that when I change the HFS-3 red wire to the wire which connects to the fuel pump relay (yellow connector in the ECU box, wire green/yellow, pin 8) it works as supposed to be. I'll let you know when it's done.

[okkimi]

Yes, it works!

The connector is more orange than yellow, but anyway.

[Richard L]

Can you kindly scan the alterntaive ECU pin out for me and send it to me so I can made a wiirng drawing for others. Altrenatively, a pin number of the injectot (+) will help.


Richrad

[inzunzar]

Richard, I am having the same issue okkimi had, did he sent you a diagram, it is OK to connect red wire from ECU connector to pin #8?

[Richard L]

It is important that the red wire of the grey harness is connect to a +12V source with the following:

ignition key at "off" ................ no 12V
ignition key at "accessory" ............. no 12V
igntion key at "pre-crank" ................ 12V
ignition key at "cranking" ............. 12V
ignition key at "run" ............. 12V

You can use use a DMM on test pin 5 of the controller to confirm this.