Removing plastic fuel lines - remove clip? - PeachParts Mercedes-Benz Forum

m1tch · #1 07-05-2015, 05:13 AM

Hi all,

After taking my inlet manifold off I think I must have knocked a few of the plastic lines so I might have to take off some of the lines and replace the O rings.

It seems that there is air getting into the line between the large fuel filter and the lift pump. As well as between the large fuel filter and the shut off valve - I am guessing that there will be just 1 of the O rings that have gone as those lines are all connected?

I can see that there are white clips on the top of each of the lines - do I simply need to remove these and then the line will come out (for me to then replace the O rings). Are these the same as the lines on the back of the large fuel filter etc or indeed the the line entering the fuel pre filter. I did remove the pre filter to check the finger screen and it was 100% clean. The lines are clear and seems like they have been replaced fairly recently as they are still flexible.

jay_bob · #2 07-05-2015, 07:22 AM

Those clips are counter intuitive.

The way to release the line is to push the bottom of the "U" towards the center while pulling the fitting out. Under the black cap the "U" presses against two tabs. These tabs release the internal latches in the fitting.

The "U" should be free floating in the middle of its travel when you plug the hose back in.

m1tch · #3 07-05-2015, 03:21 PM

Quote:

Originally Posted by jay_bob

Those clips are counter intuitive.

The way to release the line is to push the bottom of the "U" towards the center while pulling the fitting out. Under the black cap the "U" presses against two tabs. These tabs release the internal latches in the fitting.

The "U" should be free floating in the middle of its travel when you plug the hose back in.

Thanks for that, I wasn't sure which way they were removed - rather not break anything! I will check to see if the U clips are free floating etc, are there U shape clips on the lines on the back of the fuel filter etc?

jay_bob · #4 07-05-2015, 04:09 PM

The majority of the fuel lines on this car are the plug in type with a few notable exceptions.

The steel lines from the tank (supply and return) emerge in the engine bay on the left side.
(Well at least they do on my LHD car.)
They transition to black rubber hoses for the leap over to the engine.
The supply hose terminates on the fuel preheater.
The return nose terminates at the fuel filter bleed port.
These rubber hoses are secured on my car with worm screw clamps. You may have Oetiker (Clic-R) band clamps instead.

The remainder of the supply side lines are all the plug in type. It goes from the preheater to the pre filter to the shutoff to the lift pump to the main filter back through the shutoff and into the injection pump. This last connection is a direct connection using a nipple on the back side of the shutoff valve that goes right into the body of the IP. There is an o-ring at this junction that is forgotten and is notorious for leaking. P/n 021-997-75-48

The return side consists of three hoses that join together at the fuel filter.
The injector returns are jumped together with small gauge rubber hose that pushes onto the injector barbs. There is a barbed fitting at the filter bleed port for the end of the injector return hose. The opposite end at cylinder #6 has a stub of hose with a plug stuffed in it.

The pump return line is on the back side of the IP. This connection is a traditional banjo fitting with 2 crush washers and an o-ring. If you order a new hose the crush washers and o-ring are not included with the hose. The other end of this hose plugs into the bleed port on the primary filter and has 2 extra nipples, one is for the injector return hose and the other is for the tank return hose.

m1tch · #5 07-06-2015, 02:45 AM

Quote:

Originally Posted by jay_bob

The majority of the fuel lines on this car are the plug in type with a few notable exceptions.

The steel lines from the tank (supply and return) emerge in the engine bay on the left side.
(Well at least they do on my LHD car.)
They transition to black rubber hoses for the leap over to the engine.
The supply hose terminates on the fuel preheater.
The return nose terminates at the fuel filter bleed port.
These rubber hoses are secured on my car with worm screw clamps. You may have Oetiker (Clic-R) band clamps instead.

The remainder of the supply side lines are all the plug in type. It goes from the preheater to the pre filter to the shutoff to the lift pump to the main filter back through the shutoff and into the injection pump. This last connection is a direct connection using a nipple on the back side of the shutoff valve that goes right into the body of the IP. There is an o-ring at this junction that is forgotten and is notorious for leaking. P/n 021-997-75-48

The return side consists of three hoses that join together at the fuel filter.
The injector returns are jumped together with small gauge rubber hose that pushes onto the injector barbs. There is a barbed fitting at the filter bleed port for the end of the injector return hose. The opposite end at cylinder #6 has a stub of hose with a plug stuffed in it.

The pump return line is on the back side of the IP. This connection is a traditional banjo fitting with 2 crush washers and an o-ring. If you order a new hose the crush washers and o-ring are not included with the hose. The other end of this hose plugs into the bleed port on the primary filter and has 2 extra nipples, one is for the injector return hose and the other is for the tank return hose.

Thank you so much for your help, I know that the injector return lines and banjo bolt on the back of the injection pump are fine, I think the air leak will be somewhere between the fuel filters. I am also tempted to change the O rings over on the back of the shutoff valve next time the inlet manifold is off, they seem fine and I didn't have any air in the system before I knocked them when taking the manifold off typically!

jay_bob · #6 07-06-2015, 07:17 AM

You can change the SOV o-ring without removing the IM. The washer bottle can be drained and moved out of the way which allows access to the SOV. The washer bottle heat exchanger can be removed without breaking the coolant lines.

I would follow the fuel path as described above and see where you are getting air. Note there are two independent paths in the fuel filter housing, the pre-filter and main filter flows do not mix. The o-ring on top of the pre-filter is another known leak point. Also the clamp that holds down the inlet hose to the pre-filter gets tired and does not provide enough pressure to keep the o-ring seated. They really should have put 2 bolts on that clamp.

Remember the lift pump pulls some serious vacuum (enough to collapse the tank if the relief vent is plugged). In fact the pressure on the discharge side of the fuel pump is still below atmospheric. This means if you have a leak it will admit air instead of leaking fuel.

m1tch · #7 07-07-2015, 04:27 PM

Just gone out and had a check around, I have replaced the O ring on the pre filter body although I noticed that when the engine turns off, this starts to fill with air - I am guessing that the O ring on the line going into the top of the pre filter is leaking? Although if its the pre filter then wouldn't that mean its connected to the main filter as well?

I have also removed the top bracket from the larger fuel filter to get access to the other lines - I can see that 2 of the 3 are well sealed, its the line from the lift pump to the main filter which seems to be loose - will get another O ring for that and see if that sorts it.

m1tch · #8 07-10-2015, 06:23 AM

Seems that the air leaks are now sorted, I believe there were 2 leaks on my car, the main one was on the pre filter - I removed this to check it when I was doing other engine work. I would suggest checking and replacing this large O ring as a good starter as its easy to get to and will also mean that you can check the pre filter.

The other one was on the furthest right line on the larger filter - this has no clip or anything apart from a bracket holding it in. I removed the top bracket and found that this line didn't have much force needed to twist it slightly. I removed the end from the filter, cleaned inside where the O ring seated, cleaned everything up and checked the O ring. I also also added some high temp silicone seal (the black stuff) to the mating surfaces to give a better seal, the bracket was then tightened back on.

The car now fires up straight away as it should do even when sat overnight, before I had any other issues I did notice that there were a few tiny tiny bubbles when revving the engine in the right most line. With these 2 fixes there are no bubbles at all in any of the lines.