Faulty Filter Fix

Here is a photo of the offending beast. You will need to refer to this photo in my narrative to see what the problem is.

Faulty Part

I am negative about this system for several reasons, and recommend it be removed from boats:

  1. Messy to change and actually introduces a potential contamination problem. Due to the size of the filter, it should be filled before installing. This is a 2 man operation, with one person holding the thing, and the other dumping diesel into the filter. Most people will simply pour the fuel into the center hole of the filter. This is actually where the fuel goes out to the engine, so any crap in your filling bypasses the filter and goes directly to the filter on the engine. To fill these properly, that center hole should be blocked and the filter filled through the smaller holes in a circle.
  2. The selector lever allows left, right, and both. If you have contamination and block a filter, there is no way to isolate it and run only on a clean filter. With the selector lever vertical, you are pulling from both elements.
  3. Filter cannot be changed with engine running. In an emergency this may not be something you want to do.
  4. No easy way to add a vacuum gauge.

There are better options than this, but like everything, it costs money!

If you look at the top of the filter housing, you will see a series of connections. There are 2 nuts on the top of the stack and these are the fuel inlet and discharge to the engine. Underneath the nuts are adapters that convert it from a ⅞ x 14 JIC thread to a UNF or UNC thread in the housing. (The “F” and the “C” just refer to coarse or fine thread). This is a non sealing thread and Racor uses this because any thread that seals by changing pitch would put stress on this aluminum casting and crack it. This screws into the filter housing casting.

Now, in order to create a seal, there are 2 connections where this has to be air (or vacuum) tight. As we all know, any air into the system and the engine will not run. The seal between the UNC/UNF side of the adapter is created by an o-ring, compressed into place and prevented by distortion by a flat washer. If you look at the photo, underneath the flats on the adapter you will see what look like a thin black shadow. This is actually the edge of the o-ring you are looking at, being squeezed out of position. What is missing from this set-up is the large flat washer that will compress the o-ring so it will seal on the inside and outside surfaces. It took me a while, but I finally got the engineering drawings from Racor and the washer is clearly shown. As the boat ages, this o-ring becomes less flexible and loses it’s sealing qualities, especially when it is missing the compression washer. That washer also prevents the o-ring from being twisted out of position as the fitting is tightened.

Where did it go on my boat? Don’t know. Maybe the adapter fittings were never there when that system was sold to Nordic and somebody went to the hardware store and made the connections up from parts used for a propane service? In any case, it will leak slightly, and the lift pump on the engine will lose its prime. Ironically, once the engine starts it will accommodate this small leak and keep running, but the problem will only worsen over time. In the mean time, you are mixing air and fuel in the injection pump. Most pumps will tolerate a certain amount of this, but not all. Cummins says their engines only consume about 30% of the fuel supplied forward, and the rest is returned to the tank. Nobody knows the real numbers on this because the engine manufacturers will not supply the data. This excess fuel does serve a critical purpose, however. It cools the pump and lubricates all the pump parts in the low pressure chambers. Without this lubrication you will burn up a pump fairly quickly.

In my case, the problem was compounded by somebody else chasing this problem before we owned the boat. This is the second sealing surface. I mentioned nut on the top part of this adapter was a JIC fitting, and this refers to the taper on the flare that is used as a seal. JIC uses a 37 degree taper, and the more common SAE fittings use a 45 degree taper. Both are industry standards, but SAE is more common. To make things easier in the industry, somebody came up with a “universal” nut that would seal on both types of flares. This has a stamp on the nut that says “JIC/SAE” and rather than sealing flat against flat, it seals with a small contact surface defined by a circle. This is not an ideal situation and I would not want it on a hydraulic fitting holding pressure, but should work fine for the small amount of vacuum this system holds. In my case, somebody adopted the “let’s tighten everything even more” repair philosophy and pulled down on these 2 nuts and distorted them. This also caused a vacuum leak.

These adapters that go between the filter head and the lines are available from Racor, but I tossed the part number. I think they are about $7 each. If someone continues to use this filter set-up, I would inspect the system and see if the washer is present. It should be obvious. If not, buy new adapters and put them it. It does not address the situation where somebody may have over-tightened the nuts on top, but it is a start. Frankly, I would toss the whole mess! It will leave you with a repair that you will have to use barb fittings and hose clamps, but this is not the end of the world. You can write to Racor and ask for this part on a 75/B32009 filter setup. I’m sure they have it at their finger tips by now because I drove them crazy getting the details on these components. Please refer to my comments in part #1 and the photo.

My final comment will be on hose clamps. Not shown in the photo, but cutting into my fuel line were the hose clamps with slots in them. These should be illegal, and I call them “fire-starters”. They will distort and cut any fuel line over time, and only add to your misery. The proper clamps are the ones that do not have slots cut in them, and are available from Defender for around $2.50 each. The proper size for a ⅜ fuel line is a 7/16 to 11/16 clamp. Or you can go to West Marine and pay $4.99 for exactly the same clamp. I should also add that the hose fittings that have a yellow collar on them are self-sealing and do not require hose clamps. That collar is to show you the hose is fully placed on the fitting. Put a small amount of WD-40 on the inside of the hose and push it on. Try not to get it on your hands or they will slip. Put the fitting up against something solid and push hard. A hose clamp will actually distort this seal.

I hope all this makes sense. As Dave from Nordic tug told me, in 2001/2002 “anything was possible” and I hope my situation was an isolated one. This was a nasty problem to find and I have to take my hat off to Cummins Northeast  for their guidance in eliminating an injection pump problem, and especially to Bob that owns Casco Bay Diesel for talking me through some of the things that had been incorrectly repaired on my injection pump. Bob generously gave me a lot of time over the phone and he is a true gentleman and a rare breed today! Those repairs are a story for another day, and not for the faint-of-heart. I have training on some pumps, but this was unfamiliar territory for me.

Let me know if there is anything here that needs clarification. Good luck.

As that old C&W song says……..And that’s my story and I’m sticking to it!

One thought on “Faulty Filter Fix

  1. Barry says:

    What size Nordic Tug, and what year please. Also the center lever goes port, center both in, starboard and no fuel…4 positions. If your tanks were full when you changed the filter gravity should fill the filter when you select each filter. Captain Chris Yacht Services on Facebook has an excellent post about this.

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