Mk 5 Golf 1.4 Petrol starts and idles fine then dies. PLEASE HELP

[itstrevreally92]

Hi All,

So, here i go. I've owned my 05 mk5 golf for over a year. About 2 months ago i was driving home from work and pulled up to collect a takeaway. When i returned to the car to start it she would start up and die as if there was no fuel. I got the car towed home and i tried to start it again. since that very day the same sequence happens;

-turn key in ignition all lights on dash come up fine
- turn the ignition and the car starts without issue
- the car idles then for between 5 and 10 seconds before choking and slowly shuddering until it cuts out
- i can successfully start the car each time but the length of time of idling changes. if i 'pump' the fuel manually by turning the key on and off for a while she tends to get more time idling
- if i put my foot on the accelerator and push down to the ground the revs will fly up and everything sounds fine but she immediatley cuts and dies.
- if i gently apply acceleration she can rev continously for maybe 4 or 5 seconds before cutting out

I used the OBD reader and got fault code 'P0685' which i assume is the main PCM/ECU relay but i dont know which one this nor where it is ha.

I changed the fuel pump and the fuel filter. i bought a brand new 167 relay from VW thinking that was the culprit but no.

I have had to begin cycling my pedal bike to work as ive put alot of money into fixing and or diagnosing the problem. Any suggestions or ideas would be greatly appreciated. its awfully cold out this time of year a bike just wont cut it haha.

Thanks Guys

[Crasher]

That suggests the 458 relay in the engine fuse box is not being triggered, jump the 1/30 and 2/87 sockets and see if it runs and a new relay does not cure it, I have seen it where water gets into the harness under the ebox and rots the "welded" connection in the harness that provides the ECU and ECU main relay with permanent live so check for constant battery voltage, from fuse 26 in the ebox to socket 3/86 of the 458 relay. The relay is earth triggered from the ECU upon ignition line 15 power.