How to change the fuel water separator? Tips please!

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SargeW

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Dec 12, 2008
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Where ever we park it!
Well I am changing the fuel filter and fuel water separator on the MH.  Saw rust chips in the sight glass on the separator, and knew it was time.  The fuel filter was easy, used a pair of  fuel line clamps and lost minimal fuel during the change.  Now I tried to drain the fuel water separator and I just keep getting a steady stream of fuel. 

So how do you stem the flow long enough to make the change? 

The engine is a 2010 Cummins ISB, 6.7   

Any advice guys?
 

Harry B

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Jan 9, 2009
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342
Location
Central Florida
Get the back of the coach where your filters are up higher . Or lower the level of the diesel in your tank. I had the same thing happened to me as well when I had full tank.  Got to be messy to swap the old filter with a new one.  Learned not to do this with a full tank anymore.
 

Kim (skyking4ar2) Bertram

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Jun 16, 2010
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Wish I had this question three days ago when I was in the Freightliner shop for my first service. Had a really great tech who was showing me where everything was and answering a lot of questions since I had previously owned a Cat, not a Cummins.

I will be anxious to hear the solution.
 

SargeW

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Well, I tackled it and figured out a solution. And since others have or will be doing the same thing, I decided to make a "how to" post with a few pics.  When looking around the web I had found a few similar questions, but they all had a similar answer.  Just like Gary's solution, which isn't a bad idea wasn't going to work for me.  The reason is that I had planned on using the same sight glass at the bottom of the old filter.  It is just a heavy plastic see through part of the filter at the bottom.  It has a thumb screw drain and a "water in fuel sensor" attached.  The new filter came with two new gaskets, one thick one for the top of the new filter, and one thin that fit down inside the lip of the sight glass section. 

So the "quick change" wasn't going to work for me.  I needed not only to re-use the old sight glass, I needed to take some time and clean out the inside.  It had crud and rust debris from my Canadian fueling for a few months, and was in dire need of scrubbing out. 

So after opening the petcock at the bottom of the Water/Fuel separator, I soon figured out that this technique was not going to empty just the filter.  I finally settled on removing the line from the fuel tank that connects to the top of the filter housing. It looked to be a compression fitting, but I wasn't sure yet.  The correct line to remove was fairly easy to determine as one line headed for the tank, and the other for the fuel pump.

The nut on the top of the housing was fairly easy to get to, and even had enough room to get a wrench on the nut without too much effort.  My open end 3/4 wrench was too small for the nut, so I opted for a medium sized Crescent wrench.  The fuel line appeared to be movable, as I jiggled it around before starting to loosen the nut.  The line itself did not lend itself to using a compression pliers on it to squeeze it off, as the line was a fairly rigid tube.  I didn't want to risk crushing the line and causing more problems.

I put the wrench on the nut and twisted a bit, and was surprised at how little effort it took to start to loosen the nut (I was happy about this, as it more than likely was not a high pressure line.)  A few turns with the wrench and I could finish backing the nut off by hand.  With the nut slid back I could see that the fitting was indeed a compression fitting.  A brass ferule around the fuel line is fits into the fitting on top of the filter housing. The brass nut snugs against the ferule and seals it tight.  Another small bushing fits inside the fuel line to keep the end from getting crushed when tightening the brass nut.  A little tugging and wiggling of the line freed it from the fitting on the filter housing.

I still figured that the fuel line would pour fuel out as soon as the line was removed, which it did.  As a solution, I used a rubber "air tubing cap" that I had in the tool box. I had bought a pack a while back when the air line on my air conditioner actuator failed on my previous motorhome.  The caps were various sizes, and resembled a rubber bullet, with the center drilled out.  I selected one of the caps that fit inside the line and as soon as I pulled the line off, slid a rubber cap into the inside of the fuel line.  Success!  The fuel line was plugged and I lost about a teaspoon of fuel. 

I removed the sight glass and cleaned it out good.  It took a bit of effort to scrub out clean, but it turned out like new.  The filter itself was a different story.  It is fatter around than the other fuel filter was, and my oil filter wrench was too small.  After a while tugging and turning and not being able to get it to break loose, I went "cave man" on it.  I selected a long thin blade screwdriver from the tool box, and using a rubber mallet, drove the screwdriver through the center of the filter.  Using the screwdriver as a lever, it now loosened up easily and I unscrewed the old filter. 

Putting the new one on was easy, and soon had the new filter on and hooked up.  I pulled out the rubber "plug" out of the fuel line and re-attached it to the filter housing.  Being careful to seat the brass ferule well into the fitting, I snugged down the nut on the fuel line.  Again, I only lost a few drops of fuel out of the line. 

I had to go through the on/off cycle on ignition about 4-5 times to fill both filters via the fuel pump on the rig.  In my research prior I found different opinions on weather you should pre-fill the filters.  So I opted to let the fuel pump do it, and then I was sure that all fuel to the motor had been run through both new filters first.  So after cycling the key and filling the filters, we cranked the key about 3 separate times until the motor started (I had the DW turning the key while I laid under the rig and checked for leaks from the filters).  I am sure that I had to work out a few air bubbles in the fuel line before the motor would start. 

Once it started, it ran smooth and purred like a kitten.  I let it run for about 5 minutes and revved the throttle a few times.  Shut it down, waited a few minutes and restarted. It fired right up.  I took a few pics to clarify the process. 

I hope this helps someone on their adventure to change a fuel/water separator. 

 

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DITTO

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Joined
Jul 27, 2009
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112
Location
Cape Cod
Tip I learned from mike at camp freightliner....remove the fuel fill cap...depressure the fuel system...helps limit the flow!
 
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