Sline TDI 2006 Fuel pump issue - relay?

[Bingbloke]

Hi All,

Im being driven mad by an issue with my wifes A3 TDI sline 2006 - BKD engine.

Its been good as gold for years and now all of a sudden it conked out driving home.
(Literaly 10 Meters from home, so that was good a least )

So, it now wont start.. Turns over OK, but wont fire up!

I think it might be a fuel pump relay, but cant for the life of me figure out which one or where?
Guy at the Audi garage was not that helpful and handed me a slim relay with number 646..

Plugged OBDII reader in and says something like 'open circuit on fuel pump' - cant rmrmber the error code..
I checked fuse 27 on panel hidden to right of steering wheel, for fuel pump and its fine.
I cant hear the pump prime when i turn the ignition on?
I then took the feed fuel lines off the fuel filter and cranked it over - No Fuel pumping through.
Then i unplugged the connector from the fuel pump in the back and tested voltage to the +/- and nothing. (with ignition on).?
Continuity on +/- pump terminals OK.

I've googled the heck out of fuel pump relay for this car and cant find ANYTHING...! very odd..

So.. need some informed advice on what to do next please... Help!
Relay Number? Location? Or any other ideas please.

Cheers in advance

Steve

 

[aqibi2000]

Go to the pump and measure if you get the switched 12v on the powered side of the motor winding.

 

[Bingbloke]

Go to the pump and measure if you get the switched 12v on the powered side of the motor winding.

Hi!
Thanks for reply.
So take the fuel pump out and check it?
I checked the connection terminals with the pump still in the fuel tank.

The google image i see just shows the +/- wires going into the plastic housing?

Sorry for questions but im OK at mechanicals, but still learning on the electrics side.

So does this car have a fuel pump relay???? (dont shoot me).

Cheers
Steve

 

[aqibi2000]

Hi!
Thanks for reply.
So take the fuel pump out and check it?
I checked the connection terminals with the pump still in the fuel tank.

The google image i see just shows the +/- wires going into the plastic housing?

Sorry for questions but im OK at mechanicals, but still learning on the electrics side.

So does this car have a fuel pump relay???? (dont shoot me).

Cheers
Steve
View attachment 178708

Remove the fuel pump and leave the wires connected, connect the multimeter.


If you can measure the presence of the voltage when the ignition is first turned on then it will confirm the relay fuse and wiring is all fine... (it runs for about 5-6 seconds audibly) thus equating to an open circuit damaged pump motor...

 

[Bingbloke]

OK cool... ill try that tomorrow.
If there is no voltage?
like i say, i have no voltage to the plug with the ignition just switched on either.
ill see what happens with the motor out and check 1st.
thanks so far dude..

 

[aqibi2000]

OK cool... ill try that tomorrow.
If there is no voltage?
like i say, i have no voltage to the plug with the ignition just switched on either.
ill see what happens with the motor out and check 1st.
thanks so far dude..

If no voltage measured with the correct method then result back upstream to locate this relay.

Likewise you can jump 12v to the fuel pump to confirm activity which would rule this out to be faulty.

 

[ScottyP45]

From what I can find, it's behind the dash panel under the steering wheel, just above the pedals. You can see them behind the fuse box on the end of the dash.

The fuel lift pump relay is placed in the fuse box / relay plate fascia 2 for 2007 Audi A3 2.0 TDI. The fuse box / relay plate fascia 2 is placed above pedals behind a plastic cover. See pictures below:

The fuse box / relay plate fascia 2

The fuel lift pump relay

The fuel lift pump relay is placed in "2b" position in the above picture.

 

[Bingbloke]

Evening all..
So update.
Took pump out and tested with a battery externally. Pump fires up.
So pump works as far as I can figure.
Then checked out relays again and think the relay is number 373.. swapped it about and still not joy.

I’m running out of options

 

[Bingbloke]

 

[aqibi2000]

As before measure voltage at pump when ignition is turned on

 

[Bingbloke]

Hey
Ok.. I’ll do that tomorrow.
How come if the pump seems to work with a 12v supply that I still need to plug it in and test? I’m just keen to learn lol
I checked the pins on the plug that plugs into the pump and switched on the ignition.. no voltage..
I’ll still try what you suggest, just interested how it differs from what I’ve done so far?

 

[aqibi2000]

Hey
Ok.. I’ll do that tomorrow.
How come if the pump seems to work with a 12v supply that I still need to plug it in and test? I’m just keen to learn lol
I checked the pins on the plug that plugs into the pump and switched on the ignition.. no voltage..
I’ll still try what you suggest, just interested how it differs from what I’ve done so far?

No voltage at the pin with ignition on means it can be the wiring/relay/fuse upstream from the motor.

I’m not sure if this is high side switch, one side of the motor would be connected to ground

 

[Bingbloke]

Right... update 2 (don’t laugh)

Small win and small disaster.
Found one of the fuses under the bonnet was in the wrong slot.
Hold my hand up, I must have put it in the wrong place when trying to see if any had blown. Doh.. fuse 24 I think was in F23.
So pump now primes!
Made mistake of turning ignition on with fuel pipe still disconnected inside though, to then see a huge fountain of diesel.. inside the car!!!! ahhhhh.... doh!
So after cleaning up my mess.. I have what seems like a working pump but still not firing..
what a ****** mare lol
So do I still need to take pump out?
Continuity tested ALL fuses I could see.. nothing bad so far.

Seems like I added a second fault to the original.. so now just back to the original.
Do another obd test tomorrow.
Thanks for assistance so far !

 

[ScottyP45]

Could be the high pressure fuel pump isn't pressurising the rail, or the fuel pressure control valve or the sensor has gone bad. I'd want to know what the rail pressure is, if the lift pump now works. You'd need VCDS to read the rail pressure while cranking. Should be something like 250-300 bar at idle or while cranking over.

 

[aqibi2000]

Ensure ASV is open, starter motor is fast enough and battery isn’t crap.

Start with a battery reset

 

[Bingbloke]

Hi All,
So i have a mate popping over with VAGCOM tomorrow to help.
Anything i need to check specifically?
Ill post the OBD error codes tonight and see if any of you can help further?
Need to get this thing running

 

[ScottyP45]

Rail fuel pressure requested vs actual while cranking for a kick off mate