From another topic about the HydroHot, Rick LaLand asked a question about fuel filters on his Cummins. Rick is a new member, new to diesel motorhomes and is the new owner of the Monterey BJ and I enjoyed so much for a dozen years.
Rick wrote, ".....Bill since I have your eyes how often did you replace the fuel/water separator filters..I noticed you changed them 7/2014 at 114k miles I have read a bunch of forums and reviews but I'd like to keep up your service regiment if possible. I will be getting the trans. serviced this july as you said that was next on your list. Thanks Bill and to all who chime in
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When it was new and I was new, it was serviced in professional shops about once a year or around 15,000 miles. My favorite was the Cummins Coach Care shop in Coberg. Gradually, with the help of BAC members (especially Marty) I learned how to do it myself. The last three annual lube, oil and filter changes were done by me! I did the last Onan lube, oil and filter myself too.
Fuel filters were included. Twice I had to change them between service intervals.
Unlike gasoline, diesel can get stuff in it. It might come from the pump but it can come from the tank too. The filters obviously prevent whatever it is from getting into the engine. When I did the service myself, I emptied the filters to see how well they worked and was surprised to see how much stuff they caught, especially the primary filter.
The first, or "primary" filter is the one with the plastic bowl on the bottom. The bowl allows your to look for water from condensation in the tank. I never saw any water, but if you do, use the drain knob to let it out.
The primary filter is probably good enough and in many motorhomes there is only a primary filter. Beaver put in a backup or "secondary" filter that catches the smallest of stuff if it gets past the primary. When I changed the filters, I never saw anything drain out of that one.
Rick, you Monterey can be very good at telling you need a filter! If they are beginning to "plug", there is a reduced fuel flow to the engine. The engine can't produce full power. The first time I noticed it was while driving up a slight grade and the motorhome did a slight lurch. It got gradually worse. The lurch was caused by the engine computer saying it was not getting enough fuel and it "derated". As soon as it derated, it saw enough fuel and returned to full power. After awhile it was (sort of) chugging along. The Aladdin engine monitor showed I could not get above 45% torque. A really odd thing was that every time it "chugged" the ATC light on the dash flashed briefly. That lead to hours of (expensive) trouble shooting until and experienced mechanic suggested a filter change and "see what happens". Lesson learned.
A few years later I saw the ATC light flash once. I checked the Alladin. With the peddle to the floor board, it showed 97% torque. I changed the filters at the next stop and it returned to 100%.
The reason the ATC light flashed had nothing to do with the engine. When the engine "derated" and "rerated", a pause in consistent power to the drive wheels caused the Automatic Traction Control to sense a change and trigger the light.
Having a spare set of filters and being able to change them is a good idea. It can prevent a bad day. It can be a little messy. Grabage bags are a good idea. A common "strap wrench" helps a lot. The two filters unscrew. If the fuel tank is full, some fuel may want to siphon out, so it is a good idea to be ready to quickly screw on the new filters. The normal routine is to reuse the plastic bowl, so not only do you need to unscrew the filter, but the bowl has to come of first.
There are theories about needing to "prime" the new filters by filling them with fresh, filtered diesel. That is hard to find if you are doing this yourself. In the Cummins book you have, it says to put them on dry. Then you turn on key, but not to start. If you run from the front to the back, you will hear the electric "lift pump" run for 20 or 30 seconds. Do that 4 times and the filters should will be "purged" and full. Then you can start the engine. For me, it always died after the first half minute. Then I could re-start and it would continue running.
Another theory is that you may only have to change the primary filter when your "need to". Certainly if you only drive a few thousand miles a year, you may be able to change the fuel filters every second year.
Hope this answers your questions Rick!
