Golf '95 Mk3 TDK @ 230000 km suddenly dies when idled and has lost power.

[sparkie]

On my car there is a clear fuel line from the filter to the injector, I am sure it's the original line, so if yours is original too, it'll be the same, and as stated above you can clearly see bubbles in the fuel line

[$hitblast]

Sorry about the late feedback, guys. I didn't realize we'd come to a page 2 already Well, I have clear, see-through fuel-lines. They were changed some three to four years ago. I saw a single, really small bubble, about a millimetre in diametre, when looking for sediments in the fuel lines from the filter onwards last week (without checking the connections). I have seen this before, when there were no problems.

I'm guessing the air may be trapped in a reservoir in the top portion of the pump, and after a time, there may be enough of it to mess with the pressures in the pump?

Like mentioned, I tried changing the filter, but it made no difference. The connections seemed fine, but I didn't look at them in detail. Also, the filter was filled to the brim when I disconnected it. I don't think there could be much air in it, but then, as opposed to the pump, the filter has its output at the very top. I guess it would just pass air on if it was coming from further back, instead of collecting it. Or does air not pass through the filter, and stay on the pre-filter side?

Edit: Also, there was no rubber washer beneath the plastic cylinder where the fuel return connects to the filter. Should there be? The plastic cylinder just sits on the filter with what looks like half a mickey-mouse holding it.

Edit 2: Which is easier; for fuel to leak out, or air to leak in? Which shows up first? I haven't seen any fuel leaks, but I remember the smell of hydrocarbon for a short while about two weeks before the problem started while out driving. The problem went away on its own, though.

Edit 3: I just remembered I also took a good look at the clear fuel lines while idling it after the current problem arose, to see if any air was passing through, but I couldn't see any then.

[$hitblast]

Update: I plucked out the fuel level meter and ran water through its lines to check for blockage or leaks. I coult not see any. The lines and rubber hose seem fine, and there seems to be no sludge inside them. The filter at the stem was clear, apart from slight brownish material in two of the several cells. On the inside of the bottom lid, there was a little bit of sludge, but seemingly not enough to block the intake. There is a crack at the bottom of the pipe housing for the fuel return, but the fuel intake is fine; see picture. I'm guessing the air leak is not related to the fuel meter.





Edit: I also took a gander into the tank. Although in rainy daylight, I couldn't see any sludge, and the fuel seemed clear.

[$hitblast]

Bubble-trouble. Seems you were right, Gldgti.

I put off the car-trouble for a week or so due to exams. Today I put the fuel metering unit back in. I checked the hoses to it before connecting, and they seemed fine, both inside and outside. I fired it back up, and it seemed to operate smoothly. No smoke. I popped the lid to check the fuel lines again. At first, there was nothing to see, but after a minute or so, small bubbles started trickling through, coming from the filter and entering the pump, then exiting by the fuel return. Over a five-minute period they got larger and larger, the engine coughing more and more until it abruptly died.

I'll try'n get hold of a large syringe, so that I can pressurize the intake line from the tank to the filter to check for leaks at the connections and suck to look for bubbles.

Edit: Creds to Gldgti

[$hitblast]

..and I can hear a wheeze at the top of the filter. Seems to be coming from the fuel-return-connection. The tee seems to be fine, but I guess the cause of a leak is easier to hear than to see. The filter is brand new, so perhaps the tee has altered its shape. Could be I could fit a thin, flat o-ring at the bottom of the tee-connection?

[gldgti]

..and I can hear a wheeze at the top of the filter. Seems to be coming from the fuel-return-connection. The tee seems to be fine, but I guess the cause of a leak is easier to hear than to see. The filter is brand new, so perhaps the tee has altered its shape. Could be I could fit a thin, flat o-ring at the bottom of the tee-connection?

can you take a photo of this filter. your description doesnt sound like what i remember from my mk3 aaz.

[$hitblast]

Certainly



Edit: Mine's an AAZ too, btw.

[gldgti]

yep, looks like your o-ring could be leaking. vagcat says it should be 15.4 x 1.8mm o-ring, and it has vw part number N 90426402. you can see it there on the metal spigot - from the last photo it kind of looks like it might be damaged a bit, but hard to tell. You should be able to remove the o-ring from that groove in the spigot and check it out, but it shouldnt be hard to replace it anyway.

you also want to make sure all the hose connections are not leaking - its not uncommon for the hose to permanently deform over a long time and as such the hose clamp ends up being loose. the best thing to do is to replace the hose or if there is enough slack, shorten it by about 1/2" and use a new good quality hose clamp aswell (if the old hose clamps are good quality then its probably fine to re-use, but I've seen lots of cheap hose clamps fail in the past).

you might also find the leak by having it running, and watching for bubbles as you smear petroleum jelly around the fittings. this tends to make a mess though. often its easy enough to find the leak just by wiggling the hoses and connections and watching for any corresponding change in the bubble flow.

how old is the fuel filter? a blocked filter will usually exacerbate an air leak problem, because even more air will get sucked into the system due to the higher negative pressure in the feed line (if the leak is between the filter outlet and the pump anyway).

you should also carefully inspect the plastic fitting that clips over the o-ring for cracks.

[jets]

you should also carefully inspect the plastic fitting that clips over the o-ring for cracks.

The T4 uses the same system & are of similar age to the Mk3. Going from the T4 Forum, this part is often needing replacement.

[$hitblast]

The filter is brand new. No-name, though. I changed it when the problem first started. Changing the filter made no difference at all. The pictures are a little grainy. I took som new ones with a real camera. In real life, there seems to be no damage to the o-ring. The T-connection fits snugly onto it, and I can hear a slight suction sound as I put in on.

I don't have any jelly, but I tried jerking the connections about. It didn't seem to make much difference, but the flow is already so bubbly, it's hard to notice any difference. I tried putting extra pressure on the T-connection, but I don't think it made any difference. Still, would the cleary discernable wheezing from the T-connection-area be a give-away?

I can't hear any wheezing with the engine running, as the engine-sound is perhaps too deafening, but when it gets too much air and stops (within a minute or so), fuel rushes towards the filter in both the supply and return line for a period of ten to fifteen seconds, indicating lower pressure in the filter, and it wheezes for this duration. Perhaps I could put a little grease at the bottom of the T-connection to shore it up a little.

[gldgti]

Have you tried sucking fuel through the feed line? I guess I dont really advocate doing this with your mouth (i have done it more than once, but i guess I wouldnt recommend it) - but basically if everything is OK on the feed side, it shouldnt take any more suction than you can provide to get fuel up.

seems like maybe theres a blockage in the feed line somewhere, and its causing the car to run out of fuel by sucking air instead - i.e. the pump is pumping way more volume than the fuel line is able to supply.

you could try and test this by running a long fuel line all the way from the tank to the inlet of the filter. if the car starts and idles OK and its not sucking any bubbles through, then you can be sure that there is a problem in the fuel line between the tank and the filter.

I would try this with some clear pvc hose - you could even just drop the end of the hose into the tank (remove the pickup or even just go down the filler tube) and run it all the way round to the engine bay and plug it onto the inlet of the filter. Ofcourse you cant drive it but you can start it and idle it and rev it.

it might be tricky to prime it but it should run just fine once primed.

[Ryeman]

Hose delaminating and blocking ?
just a thought.

[$hitblast]

I disconnected the feed to the filter and tried sucking out some diesel. It didn't come right at once, as I suppose it had to be sucked all the way from the tank, but then worked fine and didn't taste too bad either. I got a mouthful in a three or four seconds. There was a bubble in the first mouthful, but none in the second. I sucked out two or three desi-liters, all in all. Seems it killed the plaque on my teeth as well

I cut off half an inch of the cables to and from the filter, and started the car after each, but it didn't make any difference. I tried to do the cables connecting to the T-connection as well, but I didn't manage to put that type of clamp back together.

[gldgti]

I think you would have to try with a substitute fuel line to be really sure.

to make it easier, you could just put some diesel in a small bottle and run short fuel lines from the filter inlet to the bottle. To isolate the fuel line is the only way to be certain thats where the problem is.

When you make these changes to the system (like removing a fuel line and putting it back again) are you priming just by cranking hte engine over? Does it prime fairly quickly?

[$hitblast]

I'll give that a try. Try'n hitch a ride to the parts store and get some hose.

I don't do anything but turn it over to prime it. I churn it for about twelve seconds x 3-4, and that will usually start it. It then ODs on too much air after about a minute or so.