Oops - changed fuel filter, ended up on the hard shoulder..

[molgrips]

I was seeing a lot of bubbles in the fuel line - looked like it was coming from near the fuel filter.  Someone else on another thread mentioned that changing the fuel filter and rubber hoses cured their bubbles, so I thought I'd change the filter and hoses myself just to see.

Well, it seemed to go okay until I tried to drive it.  Hardly any power, could barely drive and completely stalled a couple of times within a 4 mile trip.

I connected the thick rubber hose up with jubilee clips - maybe I did this wrong, and I should've used some other kind of clip?  I'm not sure how I can work out where the air leak is... :x

[mk2diesel]

fill the IP   , then disconnect all the line to the tank and blow air thru them ( cleans the blockages ) make sure they're free .... then reconnect and start the engine ( will run on the full pump till it reprimes itself)   use hose clamps ( or gear clamps)  on all the hoses ...  pay attention to the fuel flow direction on the filter  ....

watch for the O ring on the fuel filter return valve ( if it has one) if it's missing, the filter will suck air instead of fuel...

[Smokey Eddy]

pay attention to the fuel flow direction on the filter

x2
should be little arrows engraved in the top

[Dakotakid]

You must be dealing with a Mk. I, right???
You need to replace those copper washers on the input line to the filter holder from time to time. I used to buy washers with plastic on them many years ago when I ran A1's. I always purchased them in bulk and didn't whimper when I pitched the old ones.

[molgrips]

This is on a 1994 B4 style Passat 1.9 TD with the AAZ engine.

After I'd calmed down from almost needing to be towed home, I went back and tried to work out if I'd wired up the filter wrongly.  I concluded that the larger diameter fuel line coming from the tank was the fuel line, and the narrower blue coloured one was the return.  So I think I got it right...  I tested all the bits of the fuel system as best I could.  I sucked and blowed on the fuel line - no obstructions.  I sucked and blowed on the filter - fine.  I disconnected the fuel line and stuck the end in a bottle of fuel and noticed that it was hardly sucking anything up, and there was very little sucking pressure at the end of the hose when I put my finger on it.  There was a little more when I stuck the end of the line direct to the fuel pump in the fuel.

In any case, I reassembled it all, and checked all the joints, and it's now okay but there's still loads of bubbles in the fuel line....

Something else I noticed - when I stop the engine, there seems to be quite a vacuum sucking fuel back FROM the ip into the filter.. what's that all about?  It could be pressure blowing out of the IP I supose but doesn't seem like it.

[Smokey Eddy]

Oooooooooooooooooo
maybe the IP is leaking air into it?  

[burn_your_money]

Take your fuel cap off and see what happens. Your fuel tank might be getting a vacuum lock

[molgrips]

Right, well it seems to be ok now.  No bubbles when I got to work this morning, even when revving the engine.

I will check to see if there's still sucking back into the fuel filter from the tank.  Is there supposed to be some kind of breather in the fuel filler cap?  I guess I can try opening the cap, closing it, starting the engine and then opening the cap again to see if there's an inrush of air.

Without the bubbles, the engine's a bit smoother perhaps, but there's still a bit of vibration and noise at speed.  What's better though is the performance through the rev range.  There used to be a flat spot in the power about 2.5krpm, then above that there'd be vibrations and resonances coming and going.  Now it is consistent and easy all the way through the rev range.

[8v-of-fury]

I sucked and blowed

 :lol:

[molgrips]

I sucked and blowed

I normally charge for that, so count yourselves lucky.

[8v-of-fury]

I normally charge for that, so count yourselves lucky.

hahahahahhahahahah!!!!!! :lol: