So this is a walk-through of how i diagnosed a fuel leak and then bled the fuel lines on my 2002 VW POLO 1.9 SDI. (9N model). I couldn't find much info on the internet and thought it might help someone else.
So the other day i experienced difficulty starting my VW polo 1.9 sdi 2002, (9N engine model). It normally starts immediately, but this time it turnt over for a good 30 seconds before finally stuttering, then eventually firing on all cylinders. Once started, it ran perfectly.
However, on driving for a few minutes i started to notice the smell of diesel. I pulled over, lifted the bonnet and there was diesel all over the engine, pooling below the injectors. Anyway, i had to get it home, so an hour later, i decided to start it again, (it was a bitch to start again), and got it back to my house.
I discovered there was a large hole in one of the scavenger/return pipes coming off the third injector back to the diesel pump. I took the pipe off and went and got a replacement. My lack of knowledge meant that i left it for about a hour without the pipe connected. This obviously let loads of air in the fuel lines....
I replaced all the scavenger pipes on the car and attempted to start it. No luck at all. Not even firing on one cylinder. This was because i let a lot of air into the fuel lines, an it needed to be bled.
Some diesel cars have a fuel pump in the fuel tank which can be used to get fuel back to the filter/engine bay fuel pump when the lines need to be bled. But on the SDI polo it only has one fuel pump in the engine bay. Therefore it needs to suck the fuel all the way from the tank, through the filter and into the pump, then push it out through the injectors into the engine. I had let so much air in that there wasn't any air within the filter, so a long way for the fuel to go before it was going to start! Basically i thought the only way to get it to start was to just crank it over and eventually it would pull the fuel through the lines.
I managed to flatten the battery trying to get it to start, but without any luck at all, not even a flicker of life. I then got the local car part shop to charge up the battery and attempt to start it again. I stopped after the battery began to die again.
3rd attempt: Pre-filling fuel filter and bleeding the fuel lines via the injectors.
I read about pre-filling the fuel filter on this forum page: How To: SDI/TDI Fuel Filter Change - Car Care, Maintenance and Mechanical - Club Lupo
I pre-filled it using this info by pouring some diesel in the top of the filter after removing the T connector on the top.
I then got my friends car and connected the batteries using jump cables (this was because my battery was pretty much flat again, and i was too embarrassed to go back and get the shop to charge it up again...) I started her car and got her to give it some revs to give my battery some extra power.
I then 'cracked' off the far right (when looking at the engine) injector and got a friend to crank the engine for 10 second intervals (to give the starter some rest), every time the engine was switched off i tightened the injector again to prevent any air getting back in (not sure if this is essential). After quite a while, maybe 5 mins of on and off cranking, some diesel began to come out. But it wasn't spurts, it was more of a trickle. However, the engine wasn't even slightly firing up. I then for some reason decided to crack the far left injector nut instead, (tightened the far right one, so only one injector was cracked). I began the process again with my friend cranking the engine over for 10 seconds, followed by some rest. After the second attempt fuel began to come out in a trickle and the engine began to fire on one or two cylinders. On the third attempt it fired up completely. I tightened the injector nut, disconnected the jump leads and the car was back to life!
Anyway, the reason i'm posting this was because i couldn't find much information about bleeding the VW POLO 1.9 SDI 9N (2002- not sure what year) diesel fuel lines. I read a lot about using VAGCOM (or whatever its called) to plug into certain cars to electronically start the fuel pumps in the tank and engine to prime them. But obviously on the POLO SDI 2002, there is no fuel tank pump, so this wasn't possible.
So hopefully if anyone else wants to save some money and do this themselves, all they need is a spanner for the injectors, a mate turn the car over and probably a battery charger or jump leads.