B4 fuel line question

The other day I slid out dodging a deer and went sideways into a reflector pole. I ended up with minimal damage, just a small dent in the passenger rear door and a flat spot on the right front tire, but the pole cut both the hard fuel lines in half under the car.
So, my question is, Has anyone ever replaced the fuel lines from the fuel tank to the filter? I tried to splice them together with rubber fuel hose but that didn't work. And I have had zero luck with the Bentley manual and searching online as for how to fix this problem. I'm thinking about just ordering a couple lengths of rubber fuel line but I'm not sure how long or what size I'd need, or if it would even work.
Any ideas here?

Curious why splicing didn’t work.... I did this decades ago with metal lines, and never had an issue. Was it because of the OD?

I see no reason why running full lengths of rubber wouldn’t work.... isn’t one 1/4” and the other 5/16”?

-Todd

I'm not sure why the splicing didn't work either. I clamped pieces of rubber fuel line to both lines, and then filled the fuel filter back up with diesel, the engine would start after a few cranks, run a bit and then die. When I looked under the car with the engine running, the splice on the larger black(supply?) line was looking good, but the smaller blue line would just start erupting fuel through both ends of the splice, right past the hose clamps. I opened up the access panel to the sending unit today and it appears that I should be able to run rubber line from the tank to the filter. But I'm just wondering if anyone else has tried this, and what issues they ran into. Also what size fuel line and how long I need to get?

Sounds like it was the OD... I’d try some compression fittings from HD.

-Todd

Compression fittings are the way to go, just make sure you use the metal inserts, otherwise the plastic line won't hold.

I got some compression fittings from Ace, 1/4" for the blue line and 5/16" for the black line. Used a pump to prime the black line and fill the fuel filter and started the engine, no change. It ran for about a minute and then died, and fuel was leaking out the compression fitting on the blue line. Is there a way that the blue line could have gotten plugged? Or maybe some check valve somewhere that is stuck?

Did you use the metal inserts to put inside the plastic lines before installing the compression fitting? If not, the line will deform and not seal.

What he said about the insert sleeve. Was the ferrule a good fit or was it sloppy? Metric to SAE doesn’t always work out.

You may be able to get clear vinyl to stretch over the blue, if heated. Vinyl isn’t D2 rated, but it’ll work for a while.

-Todd

I went and got the insert sleeves and re-did the fitting and its still leaking. And its doesn't seem to be a constant leak. While the engine is running for the few seconds that it does, there is no leak. But then when the engine dies, the clear lines going between filter and pump foam up and then the fitting underneath starts leaking.

Here’s a thought....

Disconnect the blue line and place the engine side into a container. Start the car and see if it shuts off.

If the blue is the return to tank, then perhaps there is a restriction at the sender, but that doesn’t really explain why you’re sucking air, on the supply side.

-Todd

Blue is supply, black is return.

I wasn't going to get into this thread but I seriously think you should consider finding a replacement fuel line.

It's available, the feed line that is, from VW Classic parts for about 27 euro plus I'm sure there's a shipping fee. This is for the sedan pipe, the variant feed pipe is slightly cheaper.

There's also used ones but finding one of those is trouble right now, the cars are getting kind of thin in the JY's and not a lot of parts people are dealing in B3/4 cars.

You could try running rubber hose that distance but I that's a long ways and you have to fish it through part of the undercarriage structure.

I'm not really sure of a good solution beside wholesale replacement.

Steve

On my car, the smaller blue line is the return, checked at the filter and the sending unit. And I'm pretty sure that fishing a rubber hose through the body from the sending unit to the filter is gonna be easier than trying to push a hard plastic line through. What I'm trying to figure out, is 1) Why is there so much pressure on that line that its blowing fuel through a compression fitting and killing the engine? And 2) If I have to replace the entire line, What size do I need to order?

I just checked and you were right, the blue is return (the smaller) line. I don't know why I thought the opposite.

You will recall that there are one way check valves at the tank for both these fuel lines, not sure if those are damaged or not. Can't explain why you have burst compression fitting on the supply, it doesn't make sense.

Fishing the line through the existing cavity just means attaching the new line to the existing line and pulling it through when you extract the old one, will work for the supply and return line too, in fact you might be better off to do them together at the same time.

Steve

I'd have to agree with Steve as well, replacing the line is really the best way to go. Even if you can splice it together successfully you'll still have at least 2 additional modes of failure going forward to think about and to look after. If you can find these lines, make sure they are from a TDI as the VR6 ones are different in that the black line stops short of the tank for a filter assembly where as the TDI supply line comes right off the sender with a short hose using Oetiker clamps and does not end until the hoses going into the shock tower filter. The blue return line iirc is the same TDI or VR6.

I've changed these before, it's an easy job, they pull out from the back after the hoses up forward have been removed, also using Oetiker clamps. There are grey/black? foam bits that get stuffed around both hoses at each end of the body entrance/exit that are important for chaffing and put in place only after both lines are run.

You really can't connect them end to end to run the other, too many formed bends on the tank end of each line. Tying a string to the old ones before they come out is the trick, then tape the new ones together and cover the ends and pull them in the body going towards the engine. It can be a little tricky getting them to exit up forward so that is where the string will serve you well.

Steve, I read somewhere that there might be check valves but wasn't sure. Is there a way to check those, or in my case unstick them? as that could explain why the return line is over-pressurizing. And I do plan on replacing the lines, but for now, I just need to get it running. The weather here is changing and I need to get the snow tires put on it and at least be able to drive it around the driveway and into the garage once I can get new fuel lines.

Steve, I read somewhere that there might be check valves but wasn't sure. Is there a way to check those, or in my case unstick them? as that could explain why the return line is over-pressurizing. And I do plan on replacing the lines, but for now, I just need to get it running. The weather here is changing and I need to get the snow tires put on it and at least be able to drive it around the driveway and into the garage once I can get new fuel lines.

Check valves are accessed through the round trunk cover the sender comes out of. The are both between the plastic body lines and the sender right on top of the tank.

TDIDaveNH, Thanks. I'll give them a look when it quits raining outside. Hopefully its just a stuck check valve and I get it it running and into the garage.

Thanks for the help everyone. It was a stuck check valve on the supply side. I took the bad check valve out and hooked the hose to the sending unit, and started the engine, it ran for half an hour until I shut it off. Compression fittings are both leaking under the car though. So, I'll be ordering new check valves and a couple rolls of fuel line. And re-doing them all.

3A5-201-215-A is the part number for the plastic sedan fuel lines. They were available 10 years ago when done on the B4. As I recall it's both lines as a pair and you just have to work them around obstacles under the car. Wasn't that hard. May be discontinued.

I got a roll of AC Delco 5/16" and a roll of 1/4" fuel line and 2 new aluminum check valves off Amazon and replaced it all from the sending unit to the filter. Was easier than I thought it would be and total cost was about $65. When I pulled the old lines out, I noticed that in the past, the supply line had somehow gotten crushed inside the tunnel going up to the filter. The car is running a lot better now than it was before the lines got cut. Thanks again to everyone for the advice, especially about the check valves.

Glad you've got it taken care of. When you say fuel line did you do it with rubber fuel line or nylon like the OE stuff?

That's an odd place to find a section that got crushed. I have to wonder how on earth it got that way hidden inside that box structure?

Steve

I just bought 2 25ft rolls of bulk rubber fuel line, at around $20 per roll, I couldn't justify trying to find the OE lines. They don't fit in the plastic clips like the plastic lines, but I just turned the plastic clips 90° and zip-tied the lines to them. I used new fuel injection clamps from O-Reilly to tighten all the connections except for 1, the 1/4 line was a bit loose on the sending unit, but a brand new worm style clamp got it tight.

As for the crushed section inside the body, it actually looked more like it might have been twisted into a kink. I'm guessing from the other evidence on that fuel line, it was replaced before I got the car and they might have had trouble feeding it through the body, causing the bad spot.

Sounds like a winner all around then. Just glad that it's back in operating condition.

I can understand why you wouldn't want to waste time trying to find the OE lines, there probably aren't too many of those things floating around out there anymore.

Steve