Author Topic: Secondary Filter Change  (Read 4043 times)

Adam Hicklin

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Secondary Filter Change
« on: May 29, 2020, 08:37:35 AM »
Is the larger bolt head the one to crack open to purge air after a filter change?  After filter change, Would procedure be to Hit the air purge button on the racor filter control, crack the nut to bleed off air until fuel comes out, start the engine?  Thank you.

Mike Shumack

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Re: Secondary Filter Change
« Reply #1 on: May 29, 2020, 12:33:51 PM »
You don't need to purge the air out of the secondary filter. On a C12/C13, the engine's fuel pump is strong enough to prime the filter while cranking the engine.
In fact, CAT says do not pre-fill the new filter (they're concerned you will get dirt in the filter).

However, I usually fill it anyways. I plug the center hole in the filter and fill through the outer ring of holes. That's the way I was taught to do it (back before electronic injectors).

Either way, if your changing the primary and secondary filters at the same time, I would recommend you change the primary (Racor) first then start the engine to ensure that filter if full, then shut down and change the secondary filter. On the Racor style with the "purge button", there is a schrader valve at the top of the filter housing. You depress the schrader valve with a pocket screwdriver or such while holding the primer button until fuel flows out the schrader valve.

EDIT - add photo.
« Last Edit: May 29, 2020, 12:42:40 PM by Mike Shumack »

Adam Hicklin

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Re: Secondary Filter Change
« Reply #2 on: May 30, 2020, 06:55:42 AM »
Thanks Mike.  So where does all the air go?  I’ve heard horror stories of an air locked engine.  I also thought the air purge on the racor set up would prime the secondary also, hence bleeding the air off through the air purge nut. 

Mike Shumack

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Re: Secondary Filter Change
« Reply #3 on: May 30, 2020, 12:38:50 PM »
The air goes through the fuel return line back to tank.
Here's the page from the CAT Service manual.


Dave Atherton

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Re: Secondary Filter Change
« Reply #4 on: May 30, 2020, 02:41:17 PM »
Adam and Mike, loosing the larger hex head on filter housing is all that is required on air bleed with C-10 and up. The part that
Is misread is on the fuel manifold on engine after the remote secondary fuel filter has check valve in the the filter base that retains
Fuel pressure in the fuel manifold. This is the reason why the fuel transfer pump on front of engine has more volume than Cat C-9
and down. That aftermarket air bleed system in really not needed . Caterpillar bleed operation is very simple as Mike explained, loosen
The larger hex on  secondary filter base lay a grease towel over top of bleed plug start engine and shut off as soon as it starts tighten
Up hex plug and your done. If you do not lay grease towel over hex bleed plug while loose you will spray diesel fuel all over the place.
Dave Atherton Retired Cat Mechanic

Gerald Farris

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Re: Secondary Filter Change
« Reply #5 on: May 30, 2020, 02:46:47 PM »
Adam,
I am like you in that I do not want to induce any air into my fuel system that can be prevented, so, I change the primary filter and push the air purge button while holding the Schrader valve in the top of the primary filter housing open until I get liquid fuel. Then I change the secondary filter and loosen the air bleeder in the top of the filter housing, then push the air bleed button until I get liquid fuel, and tighten the bleeder. Then I crank the engine.

Gerald   

Adam Hicklin

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Re: Secondary Filter Change
« Reply #6 on: May 31, 2020, 06:10:22 AM »
Update-  I changed the filter.  Less fuel was lost than I expected. Spun the new filter on.  Primary filter was already full and purged of air.  Ran the Racor purge air device through 2 cycles with the air purge bolt cracked on the secondary filter.  Never got any fuel to come out of the air purge bolt on the secondary.  Decided to try to start it.  The C-12 started right up.  Didn’t sputter, smoke, or skip a beat.  Not sure exactly what happened, but it worked!  Thanks for the help and guidance. 

Dave Atherton

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Re: Secondary Filter Change
« Reply #7 on: May 31, 2020, 02:39:40 PM »
Adam, the reason why your engine started because of what is called a fuel manifold on engine the retains fuel in engine via of check
Valve at entry to manifold because your secondary fuel filter is located away from engine the filter base has the air bleed hex plug of
which loosen to bleed. I did indicate this the way engine was built and instructions in your caterpillar maintenance manual  bleed air system.
Which is very easy and simple. Than the mfg of motorhome for there own reason add on aftermarket attachment to the
fuel system on there own . This than bought many options as which is best builder of engine or builder of motorhome
and that up to you to decide what is best for you. Myself a caterpillar person not a fan of aftermarket add on attachments or aftermarket parts. Lack of understanding how different  engine each of us own is a big problem. Many
Owners have caterpillar C-9 and down engine which fuel system is different installed aftermarket attachment away
from builder of the engines , yes I can relate many repairs and problems in area called the fuel system being modified.
Dave Atherton Retired Caterpillar Mechanic

Keith Moffett

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Re: Secondary Filter Change
« Reply #8 on: June 03, 2020, 05:32:23 AM »
Just a heads up for future readers.
I changed the Secondary filter (I use CAT filters) on our C13.  While I always prefill filters, I didnt this time. 
No start.  I bled the line at the filter base and retired with no success.  I watched videos on my error and reread this thread.  I called Gerald and talked his ear off (thanks Gerald).  I pulled the new filter off and prefilled it being sure to plug the center hole.  I re bleed the line and tried again.  No start! 
I spoke to a local fellow (truck mechanic) who asked why I hadn't refilled the primary filter.  My answer was you only do one at a time.  He laughed and said pull it and replace and prefill the primary filter and before turning the engine pull the secondary filter again and prefill it again.  Then hook a battery charger to the chassis batteries to help the engine turn faster. 
After all this the engine turned maybe 20 seconds and fired up.  Loped a bit and ran better than before.
Perhaps bad fuel had plugged the primary filter?  Or possibly the full fuel tank was lower than the filter.  Beyond that I have no explanation.  I know CAT says this shouldn't have happened.

My thanks to Dave and Gerald and Mike as well !
2007 Patriot Thunder
45' C-13
2006 Explorer Ltd.
DW is Carol
Safe travels and
May God bless!

Lee Welbanks

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Re: Secondary Filter Change
« Reply #9 on: June 03, 2020, 02:52:11 PM »
Keith, Did you also replace the primary filter and not fill it either? The lift pump will not pump air, if you have a air leak in the primary your motor may not start. According to Cat the lift pump will fill the secondary filter under cranking, I've read a few write ups stating that you can damage injectors if air gets into the system.
Since day one we've filled the filters and not had a problem with a motor starting. I had Cat here in Phx service my coach once, never again, the not so sharp mech didn't install the primary correctly and it sucked air into the system and we had a hard time getting the C13 to start.
Take the time, plug the center and fill the filters with good clean fuel, make sure your filter seal surfaces are clean and you will not have a problem starting the motor.


Keith Moffett

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Re: Secondary Filter Change
« Reply #10 on: June 03, 2020, 09:31:42 PM »
Yeah, been kicking myself! 
There is a 'lift pump's?  On a C13?  Didnt know that.
2007 Patriot Thunder
45' C-13
2006 Explorer Ltd.
DW is Carol
Safe travels and
May God bless!

Lee Welbanks

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Re: Secondary Filter Change
« Reply #11 on: June 04, 2020, 02:39:15 PM »
Yeah, been kicking myself! 
There is a 'lift pump's?  On a C13?  Didnt know that.
Yes there is a lift/transfer pump, from your primary/water filter follow the fuel line to the front of the C13, at the bottom right corner as you are looking at it you will find the lift pump. A steel line goes from the lift/transfer pump to the secondary filter housing.

https://www.youtube.com/watch?v=KE-UOGhoYsg
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Keith Moffett

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Re: Secondary Filter Change
« Reply #12 on: June 05, 2020, 07:07:50 AM »
Lee
Our engine starts quickly.  I will say it could use more power on hills.  I lose a gear or two even on minor hills.
Very informative video.
Hope Dave chimes in for an opinion.
Thanks
2007 Patriot Thunder
45' C-13
2006 Explorer Ltd.
DW is Carol
Safe travels and
May God bless!

Lee Welbanks

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Re: Secondary Filter Change
« Reply #13 on: June 05, 2020, 09:53:18 PM »
Keith, What are you showing for boost pressure at around 13 or 14 hundred rpm's you should be around 45+psi, my C13 will hit 49 psi full on at about 1300 rpm's.
Low power could be a few things or a combo, low fuel pressure, transfer pump, transfer pump sucking air in the fuel line,  fuel pressure regulator, air leaks in your turbo to head piping, aftercooler leaking. I wouldn't think it would be a injector as you don't have that many miles on the motor.
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Dave Atherton

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Re: Secondary Filter Change
« Reply #14 on: June 06, 2020, 07:28:34 AM »
Lee and Keith, tomorrow I will pull up the fuel system on Cat C13 on my cat sis technical program and pass along
Few ideas. For Keith your low power could be within the twin turbochargers. Dave Atherton Retired Cat Mechanic
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