Return fuel line is leaking with bad pressure ?

A few weeks ago I noticed the fuel lines in between the injectors were leaking so I replaced them and they started leaking right away again. So as the car was running I pulled the small return line off the injector pump and fuel was coming backwards out of that pump with a stream. Talked to Frank Irving about this problem and he thought it was a bad pressure issue. I replaced the T going into the fuel filter and I checked to make sure the fuel line going into the tank was not clogged. It is still doing it. As the car was running I pulled the return line off after the injector line and before the filter and it was coming out properly so I pulled the little fuel line coming before the pump and the fuel was still coming backwards out of the pump. The funny thing is the car still runs for the most part fine but just lacks power.

So you had both the small and the bigger line off of the fitting on the pump and you still had fuel coming out of the small fitting? Can you hold back the pressure with your finger?

That fitting there is a pressure regulator but I think that it should have a check valve in it.

What you could do is call the folks at Diesel Fuel Injection services in Portland, Oregon and and talk to them about it.

Please keep us posted.

whitedog said:

So you had both the small and the bigger line off of the fitting on the pump and you still had fuel coming out of the small fitting? Can you hold back the pressure with your finger?

That fitting there is a pressure regulator but I think that it should have a check valve in it.

What you could do is call the folks at Diesel Fuel Injection services in Portland, Oregon and and talk to them about it.

Please keep us posted.

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yeah you can hold your finger on the small hose coming out of the inlet side of the pump but the outlet side towards the filter has too much pressure.

I'm confused again. Don't worry, it happens often.

Which hose is it that you have excessive fuel coming from? Is it the Purple one? The light Blue one or the cloth covered one withthe white dots that goes to the same area as the Purple one?

whitedog said:

I'm confused again. Don't worry, it happens often.

Which hose is it that you have excessive fuel coming from? Is it the Purple one? The light Blue one or the cloth covered one withthe white dots that goes to the same area as the Purple one?

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I'm sorry it is kind of confusing. I am probably not explaining it right. The red, yellow, green and blue arrows are the low pressure return lines--correct? that goes into the pump and we will call that the inlet. The purple one is the outlet comes from the pump, into the T that goes into the filter.


The low pressure return line when it goes into the pump, when you pull that line off the pump the fuel is coming backwards out of it, steady stream so it is not letting the car return any fuel out of the injectors. When I pulled the fuel line off the outlet before the filter thinking it might be a back pressure issue, the fuel was still coming backwards on the inlet side.

sorry guys if it still confusing, it is still confusing to me too trying to explain it better but I don't know the names of these lines. thanks.

both the return side of the pump AND the return lines from the injectors are under positive pressure.

What did you use to replace the return lines from the injectors to the IP? Hose even a tiny bit oversize will not seal tight enough.

Yes, you will always get fuel if you remove the return lines from the barb at the large return line.

DPM said:

both the return side of the pump AND the return lines from the injectors are under positive pressure.

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Yes they are both under positive pressure.

paramedick said:

What did you use to replace the return lines from the injectors to the IP? Hose even a tiny bit oversize will not seal tight enough.

Yes, you will always get fuel if you remove the return lines from the barb at the large return line.

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I used the factory return line from TDIparts.com and yes I know you are always going to get quite a bit of pressure from the large line going to the filter but there shouldn't be pressure going back towards the injectors.

slow02tdi said:

I used the factory return line from TDIparts.com and yes I know you are always going to get quite a bit of pressure from the large line going to the filter but there shouldn't be pressure going back towards the injectors.

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There is ALWAYS pressure coming from the barb fitting where the return line connects to the IP. Now whether it is excessive is another point.

paramedick said:

There is ALWAYS pressure coming from the barb fitting where the return line connects to the IP. Now whether it is excessive is another point.

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Bruce, what about where the injector return line tee's to the IP? Is there pressure from the pump there? I seem to recall that there is some flow there but I don't have my Beetle with me to check.

Yes, a bit. That excess fuel has to go somewhere. Makes an awful mess if you forget to hook it up. Don't ask me how I know.......

red,yellow,green, blue are the metal high pressure lines to the injectors themselves. The black hose with the white spots are the low pressure return lines.

weedeater said:

red,yellow,green, blue are the metal high pressure lines to the injectors themselves. The black hose with the white spots are the low pressure return lines.

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Yeah. I let it pass though. I know that my photo skills aren't.

Like I said I am having problems with the soft black line with the white dots on it. The pressure is not coming from the injectors to the pump--it is coming from the pump to the injectors which is backwards. I might have to get video of it so you guys can see how bad the problem is as it is hard to explain.

Leaking return lines with back pressure video inside

Hey guys I have this weird issue with my car. Watch the video and see what you guys think about the fuel coming backwards on the return line. Thanks--Daniel.

http://s395.photobucket.com/albums/pp36/slow02tdi/?action=view&current=HDV_0175.flv

Does the car run Weird ..

No the car runs actually pretty good just runs sluggish.

Then don't mess with it .. Funny thats the first time I've seen someone pull a fuel line while the cars running .. I'll check thread in morning goin to sleep Rich ..

fixumrich said:

Then don't mess with it .. Funny thats the first time I've seen someone pull a fuel line while the cars running .. I'll check thread in morning goin to sleep Rich ..

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Me too. I don't like the idea of Diesel pouring all over the front of my motor...

BUMP.

Looks to me like that's return fuel bypassing out of the injection pump. That point is a junction for the return from the injectors and
the return from the pump to head down the return to the tank.

When you take the hose off, the pump return just spews out instead of
going into the return hose.

^^^yup^^^

What issue are you trying to diagnose? If any?

Or did you just decide to start disconnecting stuff while the engine was running?

The fuel flow you are getting from that fitting is probably normal. Your original problem was leaking from the return lines, correct? Make sure you have the correct size line or else it will continue to leak.

I just don't see how you guys think this is normal. Those lines are made to return whatever fuel the injectors don't use and it can't do that right now because of the back pressure. It has nothing to do with the hoses. I have replaced them 2 times within the last month with factory hose. I even used little hose clamps on them once. So you guys are just saying I shouldn't mess with it--out of sight out of mind? With it not returning the fuel it causes the lines inbetween the injectors to be constantly leaking out to the block. Anybody can help me I would greatly appreciate it. Thanks--Daniel

I will talk to Kyle at Diesel fuel injection service this morning .. And report back later .. As for the lines. We use Mercedes benz fuel return line . Better fit and made for fuel .. All those lines are for is what ever fuel is not injected is sent back to the system .. My first guess would be the check-valve on the Quanity adjuster .. I've been told that little valve is about a 100 bucks . Crazy for one part. Rich !!

http://forums.tdiclub.com/showthread.php?p=2391452

So to summarize:
- You are experiencing leaking/wet injector return lines and lack of power.
- You have replaced the lines twice and tried clamps as well.
- Return line to filter has been checked and the thermostatic tee has been replaced.

You are still experiencing the same problems. You pulled off the return line that goes to the injection pump and have a steady stream of fuel at idle. It is normal for fuel to come out as you are seeing, but for some reason it appears to possibly be too much, possibly causing the leaking return lines.

But before going down that road, you need to make sure where the leak is stemming from. Have you checked the caps on the two unused injector return barbs? Have you checked the flare nuts on the metal injector lines? Have you changed your fuel filter lately?

In a quick search of this problem, I've never seen an instance of anything wrong with the IP causing this. Leaking return lines are always solved by replacing them.

I only have a real basic grasp on these fuel systems so I know I'm not a huge help. You might try contacting Franko6 again, or user drivbiwire.

Good luck.

Any timing-related fault codes? Case pressure-control valve and the orifice in the return banjo work together to pressurise the pump for timing purposes. Any chance the outlet/return banjo bolt has been replaced with a standard one (no orifice) which would mean fuel spewing from the pump and a lack of timing advance?

Well talked to Kyle at DFIS and he set me straight. The flow you see is normal . That Case pressure valve is appx. 100 bucks as stated before. What you don't want to see is no fuel coming out of their. BAD ! They see it a lot on veggie cars.. Also the pressure in the case is appx 2 to 3 bar .. And a pump can recirulate appx 36 litres in one hour . Hope this helps .
As for the other drivability problems you have start with the basics . Fuel filter intake clean ? vacum lines sano .. Vnt not sticky . n75 functioning properly .. and so on .. Get your house in order .. Then get the thing chiptunes and have fun .. Merry X-mas Rich 1

Thanks guys for the help. I guess if you guys say it's normal then I am going to go with that and replace the lines one more time and hope for the best. Just doesn't make sense to me how it can return with backward pressure but oh well I'm not a TDI mechanic. Where do you guys recommend me getting the return hose from? I have been getting it from TDIparts.com lately and it appears it is not working. Apparently the lack of power could be coming from somewhere else. Everybody have a happy Christmas!