Changing Fuel Filter, Water Separator on CAT engine

[jmgrigsby]

I have a 2004 Coachmen 38-foot motorhome with a Caterpillar 3126 engine. Could someone please explain how to change the Fuel filter/Water Separator? And do I have another fuel filter? if so, where?

Thanks for your help.

Jim

[wolfe10]

Jim,

Welcome to the FMCA Forum.

Your chassis maker, not Caterpillar makes the decision on what fuel filtration to fit. Caterpillar only provides the filtration specs (2 micron for your engine).

Call your chassis maker with your VIN and ask them. Here are the choices in order from best to worse:

Best: Primary fuel filter/water separator with clear bowl (so you can see contaminants without having to open the drain with 10 or 30 micron filter element, AND a Caterpillar secondary fuel filter (2 micron) WITH manual primer pump.

Next best: Same, but no clear bowl (now you have to open the drain to check for contaminants).

Next best: Same, but no manual primer pump (no easy way to prime the fuel system).

Worst: Single fuel filter/water separator with 2 micron filter element and no primer pump.

AFTER you find out what you have, I can walk you through the change process (I present the Caterpillar Maintenance Seminars at the FMCA Conventions and am moderator of the Cat RV Club (an FMCA Chapter) Technical Website: http://autos.groups.yahoo.com/group/CATRVClub/

Brett

[jmgrigsby]

Brett,

Thanks for the quick reply. I have not called Freightliner but I think I only have one fuel filter-- the Fuel filter/water separator. It doesn't have a primer nor does it have a clear bowl - it is a black bowl with a drain ****.

I just purchased a new Cat fuel filter/water sep and they said to reuse my bowl.

So could you please give me the steps to replace this fuel filter/water sep? (And I will call Freightliner to see if I have a second fuel filter.)

Thanks,

Jim

[wolfe10]

Jim,

I responded to your PM.

It is critical that you KNOW whether you have a one or two filter system.

If one filter, the filter element HAS to be 2 micron. If you fit the 10 or 30 micron element which is the proper element for a two filter system, you would allow "rocks" to pass through the filter and get to the injectors.

If you have a two filter system and fit the 2 micron element as a primary, it would clog quickly and the 2 micron secondary filter would catch nothing.

And how you prime the system is very different depending on whether you have a manual primer pump or not.

As I told you in reply to your PM, if it is important that you change the filter(s) this weekend (before you can contact Freightliner) let me know and I can talk you through it.

Brett

[Jon796]

You can also just follow the fuel line from tank to engine and find out how many filters you have.

[wolfe10]

You can also just follow the fuel line from tank to engine and find out how many filters you have.

Jon,

Absolutely correct -- theoretically.

BUT, tracing fuel lines in the bundles of hoses and wires in most RV chassis today, particularly if you don't have a strong technical background can be both frustrating and there is a reasonable chance that you will miss one.

Brett

[Jon796]

Brett,

Those filters are very large. If someone can not follow the lines to find those filters, he should be doing the filter change!!! LOL

[Jon796]

Looks like Wolfe answered this question in another forum look at the 4th post down on this link.

http://forums.woodalls.com/Index.cfm/fusea...60.cfm#23235960

[wolfe10]

Jon, et al;

The problem is that Freightliner made both single and two fuel filter chassis.

Determining which he has is important.

And sure, once we know what set up he has, there is no problem coming up with the correct procedure.

But, unless one is stuck on the side of the road, I am very hesitant to guess or recommend guessing by others.

Both part numbers and procedures vary according to number of filters and whether there is/is not a manual primer pump.

Brett

[wolfe10]

I am posting this PM I received from Jim so we can continue this important subject:

Group: Members

Posts: 2

Member No.: 15,810

Joined: 5-November 10

____________________

Brett,

This is a follow-up to our emails from 2 weeks ago.

We went to Branson last week - and on the way back I noticed a "loss of power" - when going up gentle hills with pedal to the floor, it would only go about 40 mph - it would slowly get up to 60-70 mph on flat land.

I did not get to call Freightliner before I left (wish I had now). I called this morning - and I have only 1 fuel filter on my CAT 3126. It is the "fuel filter/water sep". I do not have a primer on it. It does not have a clear bowl either - the bottom of the unit is solid black plastic with a drain ****. I have already purchased a new filter from CAT - but they said to reuse the black plastic bottom. Could you please tell me how to replace this "fuel filter/water sep"?

I really appreciate your help - I'm new at having a diesel engine.

Thanks a million,

Jim

[wolfe10]

Jim,

First step is to VERIFY that the filter element you have is a 2 micron filter element-- CRITICAL to your injection system. Remember, if you had two filters, the primary filter can have a 10 or 30 micron element, as the secondary filter will have a 2 micron element. With only a single filter, it MUST have a 2 micron element.

Since you don't have a primer pump, you will need to fill the new filter with fuel prior to installation. I would suggest you purchase a new bottom bowl, so the removal/installation goes quickly (and you have a spare if the bowl ever cracks).

The small outer holes are the INLETS, the center large hole the OUTLET. So, slowly pour clean diesel into the outer holes so the fuel will be filtered before going to the engine.

To minimize air entering the fuel system, make sure the fuel tank is full, and perhaps even park with the nose uphill. It is better to have a little fuel run out the filter housing when the old filter is removed than to have that 30' of fuel in the line from filter housing to tank drain back to the tank leaving you with 30' of air to purge!

After installing the new filter, start the engine. If it doesn't fire right up, don't run the starter for more than 20 seconds at a time without letting it cool for 2 minutes. With the starter running, the fuel pump is running and purging any remaining air from the system.

Long range, consider adding a secondary filter with primer pump.

Brett

[jmgrigsby]

Brett,

Are you saying that the new filter which I purchased from a CAT Dealer(part # 198-6378, same # as the one currently on it) may not be a 2 micron filter element?

If it is not a 2 micron element, where would I buy a 2 micron filter that will fit?

And how often do you recommend that I should replace this filter?

Thanks,

Jim

[wolfe10]

Jim,

YES, that is the correct filter: http://www.holtrv.com/pdf/mi-range.pdf for your SINGLE FUEL FILTER chassis:

Primary Fuel Filter w/Water Separator 198-6378 (single filter system) found on the right side of Page 2.

But, often the parts guy doesn't ask if you have one or two filters, and the filters are very different for the single vs two filter set up (in terms of micron rating).

Ask for it by part number and you are "good to go".

How frequently should you replace the fuel filter-- a more difficult question. There is really no "average life" for a fuel filter. If all you "feed it" is clean diesel, it could go a million miles. Feed it one tank of contaminated fuel and it could clog several sets of filters.

So, change it:

When you open the drain and get more than a tablespoon of water or dirt out of it. Again, if you fit a clear bowl, you could SEE the contamination without having to open the drain.

A symptom of a clogged filter is that you will start to loose power under high load conditions (when maximum fuel flow is demanded by the engine). Changing fuel filter(s) is an inexpensive first "go to" procedure if you experience loss of power under high demand conditions. This is particularly true of the single filter set ups, where one fine filter (2 microns) does all the work vs a two filter set up where the primary filter removes the water and larger particles and then the secondary filter (2 microns) only has to remove the small ones.

Most just routinely change the fuel filters at every oil change (once a year).

Brett

[jmgrigsby]

Brett,

I purchased a new "clear" bottom bowl for the new fuel filter.

I noticed that there is a big screw head on the bottom of the bowl - with "PUR" next to it.

What's that for?

jim

[wolfe10]

Jim,

Some bowls have a drain, some have a hole into which a water in fuel sensor is threaded. Some have both.

Here is a link to Parker Racor that has a picture of a bowl with just drain, but shows part numbers for the other options:

http://www.parker.com/literature/Racor/788...rial_Change.pdf

As far as the PUR is concerned, here is their answer found on the document above: "Additionally, the plastics recycle identifier code (PUR) will also be found on the bottom outside surface."

Brett

[jmgrigsby]

Brett,

My new bowl and a drain also - thought that "PUR" might stand for purge.

Anyway, I will put my new filter and new bowl on probably tomorrow.

Thanks for your help.

jim

[jmgrigsby]

Brett,

Today I replaced the fuel filter/water separator - but it won't start.

Here's what I did - I extended the front jacks so that I have the front end a little higher than the back end.

I removed the old filter - only a little fuel ran out from the fuel line(top).

Then I put the new clear bowl on the new filter and filled the outer holes. Looked like the center was filling up so I opened the drain and let some fuel out of the bowl.

Then put it on.

I cranked it and it ran about 30 seconds.

I cranked it for 20 seconds and let starter cool for 2 minutes.

I did thid 5 times.

What did I do wrong?

Jim

[wolfe10]

Jim,

With the single fuel filter and no manual primer pump (IMO 2 filters and manual primer pump is the "proper" setup) it is easy to get air into the fuel system when changing filters. About the only thing in your description that I see that you did "wrong" was to not completely fill the filter (so fuel was right at the top of the center of the filter). And even a little air in the lines can cause a problem.

Your "I cranked it for 20 seconds and let starter cool for 2 minutes" IS the proper purge technique and will work unless the line from fuel tank to filter is filled with air.

If fuel drained back to the tank (i.e. filter housing above level of fuel in the tank) you may have to open the inlet to the fuel filter housing and pressurize the fuel tank (just hold an air nozzle with your hand covering most of the diesel fill. It does not take much PSI to force fuel through the line.

Brett

[jmgrigsby]

Brett,

I started over - filled the filter full.(it may not have been full the first time)

Tried to start it again - nothing after 5 tries.

To pressurieze the fuel tank - unscrew the fuel filter a few turns?

Then add air to tank?

Jim

[wolfe10]

Brett,

I started over - filled the filter full.(it may not have been full the first time)

Tried to start it again - nothing after 5 tries.

To pressurize the fuel tank - unscrew the fuel filter a few turns?

Then add air to tank?

Jim

Jim,

This works better with two people. Start by slightly pressurizing the tank as I outlined.

Have someone else either open the line from fuel tank at the filter housing (better) or unscrewing the filter most of the way.

Keep the tank pressurized until fuel with no bubbles comes out at the filter. Tighten line/filter.

The reason opening the line is better than just doing the filter is that the air in the line can be forced into the filter, rendering it full of air.

Again, long term, consider a secondary fuel filter with manual primer pump. That is what Freightliner started with and returned to after lots of exactly this same complaint on the single filter/no primer pump set up.

And as you did, raise the nose of the coach/do this with full fuel tank to minimize fuel siphoning back to the tank.

Brett

[jmgrigsby]

Brett,

How many crank tries should it take to start it?

I think my battery is getting slower.

Jim

[wolfe10]

You may need to plug in and recharge your chassis battery (assuming your chassis battery is charged by your converter or charger.

If is is not, use a separate charger or the boost switch.

Brett

[jmgrigsby]

Brett,

I will need to talk more about adding a primer.

Jim

[wolfe10]

This file is from the Cat RV Club Files section and dates back to 2006, so the part numbers will need to be verified:

To add an OE Caterpillar secondary fuel filter WITH PRIMER PUMP to a

3126 engine installation that came from a chassis builder with a

single filter and no primer pump the following parts are required.

The prices listed are over the counter retail-- local prices may

vary.

The primary filter (the one you already have) should be installed

between the fuel tank and transfer pump. The secondary filter (the

one you are adding) should be installed between the transfer pump

and the engine head (pressure side of fuel system).

Fuel hoses will need to be made, but most hydraulic shops have fuel

hose with the appropriate fittings or your Cat dealer can have them

made. This filter/primer can be mounted anywhere you want for easy

access to servicing.

This will allow the installation of both the primary and secondary

fuel filters DRY. Any diesel you pour in a filter is NOT filtered

and could contain particles larger than the 2 microns which can not

be seen by the eye, but could affect the injection system. And with

the primer pump, all you do is hand pump it until it becomes firm.

You have removed all the air from the fuel system so the engine will

start right up.

My recommendation would then be for a 10 micron primary filter/water

separator element along with the Caterpillar 2 micron secondary fuel

filter that you are adding. You will experience less filter clogs,

as the filtering duty is shared by two filters with the first

removing water and larger particles and the new one the small ones.

# 1 Fuel Filter 1R-0751 $10.28

#3 Fuel Filter Base 141-5138 $39.56

#3A Insert Fuel Filter 112-6523 $19.64

#10 Plug 9S-4182 $4.59

#5 O-ring for #10 6V-5048 $1.92

Primer Pump 105-2508 $65.87

Primer pump gasket 1P-0436 $0.85

Bolts for primer pump

Quantity 1 8C-6561 $0.22

Quantity 1 7X-2501 $0.12

Washers for primer pump

Quantity 1 8T-4205 $0.11

Quantity 1 8T-4224 $0.11

Note: The Cat RV Club is an FMCA Chapter.

The Cat RV Club Website is: http://catrvclub.org/

The Cat RV Club Technical Website (a Yahoo group) is: http://autos.groups.yahoo.com/group/CATRVCLUB/

Brett

[jmgrigsby]

Brett,

This web site is amazing.

I am getting your reply very fast.

I'm not good with computers as you can see.

Thanks for your help.

I am plugged in to shore power.

I going to try to bleed the fuel line now - I'll let you know if that works.

Thanks,

Jim