Changing Fuel Filters

[rchrsty1]

hello,

I have a 1996 Safari Serengeti diesel pusher (Cat 3126 engine) and wanted to know the protocol for changing the Fuel filters.

Its a two fuel filter setup, with the clear collector cup on the bottom of the Racor filter and a primer at the top of the Racor as well.

Please advise, I know to put oil on the new gaskets, but have been told to put fuel in the filters as well and then prime? I was thinking it would be better to just prime that way the fuel gets filtered... I am just worried about getting the system air bound when I change them.

Thank you

Ron

[wolfe10]

Ron,

Welcome to the FMCA Forum.

First issue is what is the fuel level in tank compared to the primary fuel filter head. If the level in the tank is higher (full tank or nose of coach higher than back or combination), fuel will run out when you remove the primary filter. So, you will want a catch bucket under it. An old square 1 gallon milk jug cut off works well. Having a little run out is better than if the tank is lower in which case when you remove the primary filter, the fuel will all drain back to the tank leaving you with 20' of air in the fuel line. Best long-term answer is to install a ball valve at the inlet to the primary filter.

Do you have a spare clear bowl? That makes the change a lot quicker, as you can remove the old one and immediately install the new one. I like to carry a spare anyway, as plastic can crack.

If fuel level in the tank is higher, as you install the new filter, leave it slightly unseated from the gasket-- it will fill with fuel. When fuel is running out of the top, tighten it all the way.

I have no problem in you filling the primary filter with fuel if you choose-- the secondary filter would catch anything that may be in the "clean" fuel you use.

Now, remove the secondary filter (hopefully a Caterpillar 2 micron filter) and snug up.

Push the primer pump until it goes from EASY to really hard to push. Easy is because of air in the system. Fuel, being non-compressible, it will become HARD when the air is removed. It should go from easy to hard all of a sudden. The number of strokes can vary, based on amount of fuel vs air in each of the filters as well as line from tank.

BTW, what suspension are you on?

[rchrsty1]

Hello,

Thank you for your help!

The primary filter is lower than the gas tank, so I will get a pan ready, and get the new filter ready as well.

I will get a spare clear bowl too.

The suspension is the velvet ride.

Thank you again

Ron

[wolfe10]

With the Velvet Ride suspension (aka B.F. Goodrich Torsilastic), ride height is important and adjustable.

From center of wheel (mark center of hub cap) to bottom of belt line molding should be 25" +/- 1/4". Measure on level ground. Then count the number of the 1/4" thick shims at each wheel position. Post what you find and we can walk you through the process or perhaps suggest who in your area can do it if you don't want to tackle it yourself.

[roymeyer]

Hi Brett,

I started to drain the water separator filter as instructed on the filter on my C7 engine but it seems to syphon as I have drained the equivalent of the filter with no slowing of the diesel stream.

Am I not doing something to start?

Thanks,

Roy

[wolfe10]

Roy,

Do you have a clear bowl primary fuel filter or metal bottom filter?

The purpose of opening the drain is ONLY to see if there is any contamination in the fuel-- both dirt and water are heavier than diesel and would settle to the bottom of the filter. So, you only need to drain enough to verify that no dirt or water are in the fuel. So, on most cases, only drain 1-2 ounces.

Fuel SHOULD continue to run out the filter if the level of the filter drain is below the level of fuel in the tank-- just straight physics.

Now, if you are changing the fuel filter, let us know and we can give directions. If this is the issue, do let us know if you have a Caterpillar secondary fuel filter with MANUAL PRIMER PUMP. That makes a difference in how it is done.

[roymeyer]

Brett,

Thank you very much for the quick response, I am changing the filters and the directions on the filter say to drain the filter first then unscrew the filter then remove the clear bowl.

If the flow continues as is I will have quite a bit of fuel leaked out by the time I can put the new filter on.

No primer is visible nor can I feel anything on the mounting bracket where the 2 lines come to the filter. Where would this primer be if not there?

[wolfe10]

OK, let's go step by step:

You need to find the secondary fuel filter (if you have one!). If you do, the primary filter will have between a 10 and 30 micron element. Then, the secondary filter will be a 2 micron element (per Caterpillar specs). If no secondary fuel filter, then the primary fuel filter will need to have a 2 micron element-- BIG difference.

The reason you need to locate it, or verify that you do not have one is that the filter change procedure is different if you do/do not have the manual primer pump that would be on the filter housing for the secondary fuel filter.

Also, post the part number for the filter you are using-- that will tell us what micron rating it is.

Telling us what coach/chassis you have may also help identify what fuel system you have (fit by chassis maker, NOT engine maker).

[roymeyer]

Yes I do have a secondary filter that is a bear to get to. It looks like I either have to remove the bedroom floor or somehow stretch my reach from under. Sounds like I have to figure that out to accomplish my task.

[wolfe10]

Yup, go back to my last post and let us know exactly what you have-- Will send you a PM.

[roymeyer]

Alliance ABP/N122-S32FRT04

Cat 1R-0751

These are the new filters I got from Cat with my Vin

[wolfe10]

Good. Your primary fuel filter is 12 micron, a good choice.

And the secondary is the proper 2 micron Cat one.

When you look at the secondary filter, is there a manual primer pump on the housing? That will dictate the procedure for changing the filters.

[roymeyer]

I cannot see the housing from under the motor home, I'll have to pull the floor up to see it. Could you tell me both procedures so when I do pull the floor I will be able to change the filters?

Also you said the fuel will continue to flow while the primary filter is off because of the vertical location with regard to the full fuel tank.

I would have thought a simple in line valve would have been engineered into the design. Guess I'll have to work fast.

[wolfe10]

Yes, an diesel-compatible ball valve on the inlet to the primary fuel filter is a VERY good idea. If fuel level in tank is higher than the primary fuel filter base, fuel will run out. If level in the tank is lower, VERY BAD things happen-- fuel siphons back to the tank leaving you with 25'+ of air in the fuel line! So, better for a little fuel to run out.

If you have a manual primer pump on the secondary fuel filter housing, you install both filters dry (just put oil or diesel on the seals before installing them). Then unscrew (counter-clockwise) the kurl nut which is the handle for the pump and pump in and out. It will go from easy (air) to hard in just a couple of strokes-- may take over 50 strokes of easy before it starts to get hard to pump. When hard (fuel is not compressible) push in the kurl nut to its "full in" position and tighten in place (clockwise).

If no primer pump, both filters need to be installed FULL of diesel. A lot messier and still can have some air in the system.

[roymeyer]

Thanks Brett, I'm slowly figuring out that there is NO comparison to working on my car's.

I appreciate all your help, have fun in Perry.

Roy

[lmsooter]

Roy,

I have a spare clear bowl that I install on my new primary filter, then I place it in a small plastic wash basin and place that on the frame under the old filter. As soon as I get the old filter off I, quickly as possible, replace it with the new filter assembly. After replacing the secondary filter, I use the primer pump to remove the air. At one time, I filled the new filters with clean diesel before installing but I quickly decided a primer pump would be nice so I visited my CAT dealer and got one to install. Remove 2 bolts put the primer pump in place and torque 2 bolts and done.

[wolfe10]

Yup, if you have a Caterpillar secondary fuel filter base, you will have either a manual primer pump, or if the chassis maker's bean counters made the decision, a block-off plate. A Caterpillar manual primer pump can easily (two bolts) replace the block-off plate if that is what you have.

A VERY good idea.

[roymeyer]

Thanks Leary and Brett, I now have ideas to put into play.