Retro fitting an EFI pre-filter

[h2oski]

Some time in the early 2000's, CC/PCM started installing a pre-filter between the fuel tank and the low pressure fuel pump (LPFP). I'm in the process of updating the fuel system in my 1999 AN (didn't come with a pre-filter) and so I thought what a great idea to protect the LPFP too. So I did some research, learned a lot, and OMG

CC/PCM also have two LPFP arrangements. The first is a completely separate pump that attaches to the engine block and feeds fuel to the FCC using a fuel line. The second is a pump attached directly to the side of the FCC and feeds fuel directly into the FCC. I upgraded my FCC to the latter for several reasons.

CC/PCM basically use three types of pre-filters...
1) A basic inline fuel filter with hose barbs.
2) A permanent manifold head with a replaceable spin on fuel filter.
3) A fuel filter/fitting assembly that attaches to the input side of the LPFP.

Each of the options offer protection for the LPFP. Over all size, serviceability, effectiveness, install location, filter surface area, filter restriction, flow, etc. vary and hence my confusion.

I wish I could go with option #2, but it's installed vertically and I don't have the depth in the bilge. #3 is interesting, but I've read the filter element is 150 microns and is more of a fuel screen than a fuel filter.

So for my boat, since the fuel lines run along the port side in the bilge, #1 is the best choice. I'm getting mixed information about what micron rating CC/PCM use. Even though my GT-40 didn't come with a pre-filter the fuel delivery system uses the same FCC side mounted LPFP as the newer boats. I started looking at the vendors that sell the pre-filters, one site says, 40 micron, another says 20 micron, another 22 micron, another 10 micron, and yet another 100 micron! When I called PCM, I could not get an exact answer on what micron rating the pre-filter should be.

To try and figure out what micron rating #1 should be, I looked at the other filter options. Maybe there is some consistent information for them. Looking at the micron rating on the other filter options, #3 is not an option IMO. The micron rating on #2 is 10 micron . Generally speaking, the smaller the micron rating the smaller the particle the filter traps. You have to be careful of how much surface area or how efficient a filter is too. If you have a 10 micron filter the size of a thimble the fuel flow will be very low and starve the FCC/engine. If you have a 10 micron filter like #2 above, the filter has a lot of surface area to maximize the fuel flowing through it. You want to minimize the restriction on the LPFP as it tries to draw fuel from the fuel tank.

The two more popular vendor sites that sell #1 specify 40 microns. Considering that and the size of the filter, that sounds about right for my application, I guess

The PCM part number for #1 is R080024A, I ordered one from each site (one is meant as a backup). When they arrived, more confusion, why is this so hard! One is a NAPA Gold brand and the other is a WIX brand. PCM doesn't make filters, I get it, but size does matter in this case. When I look up the part numbers they're each 13 microns not 40! Which brings me back to filter surface area and how much restriction they put on the LPFP.

I will use the 13 micron filters even though I wish they were bigger in size like #2. I'll just have to change it out with the FCC filter. Hopefully it doesn't clog up and fry my LPFP before then

-Scott

[shag]

Good research! Could you fabricate an aluminum bracket that would mount the #2 inside the engine compartment somewhere where you have more room?

[h2oski]

shag Thanks, yeah, I haven't given up on that thought yet; that's optimal to me. I'm still on the fence with #1 any way, so maybe I'll get creative The bilge depth increases as you move toward the bow of the bilge area. I thought about even mounting the filter head on the aluminum engine frame, between the two engine mounts, but it's tight right there. My boat has the factory ballast which includes two pumps along the port side, one is just in front of the engine and some plumbing right there. Maybe I could move the pump leaving a nice spot right there near/below/front of the FCC....

-Scott

[h2oski]

Intent on installing a pre fuel pump filter, I landed on option 2 (thanks to shag ), mainly because the newer models today use the same FCC system as my GT-40 (except I have a 5/16 high pressure fuel line). I want it to look as on purpose as possible. I can't imagine where else you can put this large filter.

In order to make room for the depth needed for the filter head and spin on cartridge, I had to rearrange a couple of things. I plan to replace the two factory aerator pumps with two impeller style pumps (fill/drain each factory tank). With that in the plan, I removed the factory aerator pumps, plumbing, and wiring from the through hull ball valve all the way back to the factory "Y" hose barb fitting under the fuel tank. I just left the brass through hull plumbing for now.

Now I have space close to the FCC and in front of the engine! Able to remove/replace the spin on fuel filter, plenty of depth for even the tallest filter cartridge, able to reach the center drain plug, the through hull ball valve and drop the FCC canister when it's time to change that filter. Granted, I don't have any ballast pumps now, but my fuel will be clean

With so many places to mount the filter head, where do I put it? Along the port side or along the front of the engine on the engine frame. I decided to mount it in front of the engine on the engine frame. The side would have been more "factory" maybe. The filter head certainly fit there, but after trial fitting the filter head and fuel hose fittings it didn't leave much room to remove the FCC canister.

I "manufactured" a bracket to mount to the engine frame and filter head assembly. It pushed the limits of my machining skills. CC wouldn't approve, I tried... It came out OK.



I positioned the filter head just to the port side of the through hull ball valve, so I have access to it and the center drain plug. I also wanted the fuel lines to continue and attach along the port side bilge wall for support then connect to the filter head fittings. You can see where I cut the factory ballast hose from the through hull plumbing. The ball valve is closed, but I will remove the handle and install a brass plug until I can tackle the ballast system changes later.




The black button screws are temporary until I can get stainless to blend with the aluminum. That section of the engine frame is thick too, like a 1/4".

Coming along..... next is running the new fuel supply line and connecting it all together.

-Scott

[srock]

Try to keep the option 2 filter from being too low in the bilge where the bottom may get constantly splashed with bilge water. Those filters rust on the bottom way too quickly, especially if you ever get them salty.

[h2oski]

Thanks srock . I was focused on keeping the filter on the same plane as the supply pump, tank, anti-siphon valve, etc. I didn't think about that. Hm..... I suppose I could use the shorter 10 micron filter (same efficiency as the PCM HP/HC fuel filter, less capacity) and put the bracket on top of the engine frame to get more of it out of the bilge. That would be a couple more inches out of the bilge.

Hm..... maybe I'm over thinking the filter being higher than the fuel supply pump..... make two standoffs to raise the bracket a couple of inches and bolt that assembly to the engine frame. I'll measure......

-Scott