Author Topic: Air purge  (Read 5470 times)

Adam Hicklin

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Air purge
« on: August 21, 2019, 04:15:33 PM »
Can someone explain the air purge process for this set up.  The fuel line from tank to primary filter was changed, along with the line from primary filter to fuel transfer pump. So there will be a lot of air in those lines.  I also want to change the secondary filter.  Should that be done now, and purge it all at once, or done after I have purged the air from the tank to transfer pump?  I’ve never changed the secondary myself. 

Thanks in advance. 

Mike Shumack

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Re: Air purge
« Reply #1 on: August 21, 2019, 04:56:58 PM »
That's a nice clean Service center.

Here's the instructions for priming the "Primary Fuel Filter".

I like to change one filter (fill/prime it with fuel) then start the engine, then shut it off and change the second filter, (and fill it with fuel) then restart. It's easier to stay out of trouble this way.


Adam Hicklin

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Re: Air purge
« Reply #2 on: August 21, 2019, 05:19:03 PM »
Mike, would that be the same process for the secondary filter?  Cracking the hex nut open to allow fuel to run out?

Mike Shumack

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Re: Air purge
« Reply #3 on: August 21, 2019, 05:57:15 PM »
No. That purge mechanism only works on the primary filter housing.
 
Do you have a manual hand pump on the secondary filter housing. If so, you can fill the filter with clean fuel then use the hand pump to finish filling it and pump fuel through the lines/head. EDIT - I now see in your photo that you do not have the hand pump.

Usually, if you fill the primary filter (before touching the secondary filter) then start the engine to get any remaining air out of the primary filter, you can then change the secondary filter (fill it as much as possible with clean fuel) then just install it and start the engine. There will be enough fuel in the head and lines to keep engine running while any remaining air in the filter is purged out.

Dave Atherton

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Re: Air purg
« Reply #4 on: August 21, 2019, 06:47:45 PM »
Mike, little suggestion on Caterpillar fuel systems. In fuel system with electronic engine
It is not recommended to prefill the secondary 2 micron fuel filter and the location of
hand pump on fuel filter base is on the secondary fuel filter. Reason for this reguardless
of thinking I have clean diesel fuel prefilling the fuel filter you are putting fuel fine in center
of fuel filter where unfiltered fuel is going directly into the engine fuel rail. Remember how
Caterpillar fuel system operates, fuel tank to primary fuel than to fuel transfer pump is
under suction after the fuel transfer pump diesel fuel is under pressure to secondary fuel
2 micron 1R-0751 ( C-9 and down and 1R-0749 Caterpillar C-10 and up. ). The reason the
hand primer pump location on the secondary fuel the entry of unfiltered fuel enters the fuel
filter on the outside ring of holes. The diesel fuel fines are than filtered from entry to fuel rail
on the engine. Last secondary 1R-0751 and 1R-0749 fuel filters installed new, sets up a 5 psi
back pressure and fuel filter reaches end of life at 10 psi your ECM fail safe will turn on lamp
on dash ( indicating change out fuel filter at 13 psi your engine will Derate itself down to
37 % in power until secondary fuel filter is replaced ). Many people choose to follow there own
Guide lines to the point of buying aftermarket fuel filters and prefill filters before install.
This practice is ok until the fuel fines mess up the fuel rail and system which will get very
costly. It is my intention to set correct operations as per Caterpillar operations for fuel systions.
Dave Atherton Retired Caterpillar Mechanic

Frank Bergamo

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Re: Air purge
« Reply #5 on: August 21, 2019, 06:55:16 PM »
Adam,
yes, the purge system will work on secondary filter if your purge pump is working. Loosen hex bolt on secondary assembly, exposing o-ring on bolt. Push purge button and let run until you get fuel pushing out. This allows installation of secondary filter without contaminating fuel going into fuel system. Filling secondary filter is not recommended unless your purge pump is not working. If purge pump is not working, best option is to install manual pump on secondary housing to purge air. Also, last option as Dave stated in above post, fill filter with fuel into outside ring of holes, with center hole plugged, being very careful not to introduce anything into center hole on filter.  Hope this helps.
« Last Edit: August 21, 2019, 09:17:54 PM by Frank Bergamo »
Frank & Paulette Bergamo
2019-       : 2007 Marquis Topaz IV  C-15 600 HP Allison 4000
2014-2019: 2002 Marquis Emerald C-12 505 HP Allison 4000
2004-2014: 1986 Executive Diplomat 3208 250 HP Allison MT-643
Grand Junction, CO.

Adam Hicklin

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Re: Air purge
« Reply #6 on: August 22, 2019, 03:52:56 AM »
Semi success!!!  Fuel line is routed, secured and connected.  Racor purge pump IS working.  Was able to bring fuel to the filter and purge the air.  Started right up with no signs of air in the sight glass. Ran at idle and 1000 rpm.  All seems well. 

Now the secondary filter.  Consensus is that the Racor purge system will purge the secondary filter by cracking the hex nut until fuel comes out.  And it will do this without pre-filling the filter,  Do I have that right?  Or, it seems the other option is to carefully fill the filter while plugging the center hole. I realize this is risky.  I’d rather not try it if I do t have to. 

Looking down the road for when the Racor gives up or starts sucking air, there is no way I could easily put a manual pump on my secondary filter.  It’s too close to the hydraulic reservoir.  Other options?

Steve Huber Co-Admin

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Re: Air purge
« Reply #7 on: August 22, 2019, 04:19:53 AM »
Adam,
If you want to stay with a Racor system, they have a replacement system. See the Racor or Cat article in Common Problems (Members Only).
Steve
Steve
Coachless
2015- 6/24  07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp

Mike Shumack

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Re: Air purge
« Reply #8 on: August 22, 2019, 10:54:08 AM »

Now the secondary filter.  Consensus is that the Racor purge system will purge the secondary filter by cracking the hex nut until fuel comes out.  And it will do this without pre-filling the filter,  Do I have that right?  Or, it seems the other option is to carefully fill the filter while plugging the center hole. I realize this is risky.  I’d rather not try it if I do t have to. 


Dave is correct, CAT does not recommenced filling the secondary fuel filter (they want you to install dry). CAT is concerned you will get dirt in the filter.

However if you still want to, you should fill it through the outside holes in the filter then if any dirt got in it will be caught be the filter media. The video below if from a CAT mechanic he explains how to change the fuel filter and whether or not he fills them before installing. This not to say don't listen to Dave - it's just another perspective on the question.

https://www.youtube.com/watch?v=P6MLDH0zTpw

Steve Huber Co-Admin

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Re: Air purge
« Reply #9 on: August 22, 2019, 03:19:42 PM »
Mike,
Both CAT and Dave Ahterton recommend not prefilling the secondary filter. Why would any of us choose to follow the instructions to the contrary from a non-CAT endorsed source? These "internet experts" have NO skin in the game. If one causes damage to their ~$35K+ engine trying to follow these internet instructions, they have no recourse. One of the reasons the BAC Forum is well thought of and respected in the RV community is because the information on Forum is, in the main, accurate. In the future, please refrain from posting links to these types of utube videos.

All,
Obviously you are free to use any source of information you choose in caring for your coach. It's your coach and your $. I just want to try to keep the info on the Forum accurate.
Steve
Steve
Coachless
2015- 6/24  07 Contessa Bayshore C9,  400 hp
2013-2015: 00 Marquis Tourmaline, C12, 425 hp
2005-2013: 01 Contessa Naples, 3126B, 330 hp
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Dave Atherton

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Re: Air purge
« Reply #10 on: August 23, 2019, 03:50:33 PM »
Gentleman, think everyone needs to understand what Caterpillar engine you have in your motorhome.
Reason changing fuel filters and bleeding of air within the fuel system doing engine service. I do
believe on Ask Dave Technical section think I explained the difference in air bleeding fuel filters on
Caterpillar C-10 and up and Caterpillar C-9 and down. Both engine groups are different and fuel
transfer pumps are different.starting with the Caterpillar C-9 and down the fuel transfer pump is
a gear pump and the width of the gears are .250 and struggles to maintain correct fuel pressure
and fuel flow ( reason for install of the electric Caterpillar fuel pump into the fuel system ) bleeding
of air within this system the install of hand pump on secondary is very important to fill secondary
fuel filter. Next on to the Caterpillar C-10 and up the fuel system is different because fuel system
maintains a fuel manifold under pressure. The fuel transfer pump in located on lower right corner
These engines. Why are the two systems are different the fuel transfer pump are both gear type
Except the C-10 and up gear width are .500. Which will pump more volume and pressure with out
the aid of install electric fuel pump. In addition the secondary fuel filter base has two check valves
and a hex bleed plug to maintain fuel in the fuel manifold at all times at 90 psi. Last in install
secondary fuel filter ( dry ) just loosing the hex bleed plug engine will start and fill secondary fuel
Within 3 to 5 seconds shut engine down tighten hex plug your done. Reason for all this the fuel
transfer pump in made for volume and pressure and will meet pulling fuel 35 to 40 feet away with
no problems. The Caterpillar C-9 and down was not rated to pull fuel beyond 16 feet and does not
have a fuel manifold to maintain fuel pressure within the system. Dave Atherton Retired Cat Mechanic
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