Botched a Simple Fuel Filter Change

[Chotu]

Ok, there is nothing simple about the fuel system but I was trying to do a simple Racor prefilter change.

I haven’t done this in at least 10 years. I have Outboard’s on my catamaran.

Here’s what I did.


1) Figure out which of 3 Racor units goes to the engine and is currently in use filtering. Surprise surprise it was the very dirty one.

2) Drain scum out of bowl and filter housing. I drained to completely empty because there is an electric fuel pump. Figured I’d refill with that.

3) change filter and close up Racor with new seals,etc. left it dry

4) figured I’d bleed Racor air from the secondary filters on the engine using the manual bleed pump. . Nope. They spurt out tons of diesel instead of filling Racor.

5) used the electric pump to try to fill the Racor. Literally nothing. Just makes noise and does not fill Racor.

6) dumped the scum back into the Racor I drained out to at least get things working. Nope. Not enough to fill the Racor to the top. About 1/2” or 1cm of airspace at the top of the Racor.

My concern at this point is I’ve screwed up bad

How do I get the air out? I don’t want to just run the engine and bleed. It’ll spray diesel everywhere. We have to live in here and my lungs can’t handle that level of irritant.

I don’t remember having all this trouble on my old yanmars. But they didn’t have a fuel polishing system and I didn’t drain out the Racor completely I don’t think.


I’m VERY rusty. What do I do next?

[OloteleMtn]

Hire a mechanic to show you how to do it properly....best thing i can say.....good luck.

[Marathon1150]

What model Racor do you have and how is the electric pump plumbed into it?

[a64pilot]

You have Diesel outboards?
Yanmars?
Anyway you should have a secondary filter on the engine, that should have a bleed screw. Yes you will get quite a bit of fuel out before you get the air out, that is from the length of fuel line between the two filters, so the fuel in the lines has to be bled before you get to the air. So have a hand full of paper towels. Remove the pond scum you dumped in and I’d replace the filter too.
Consider placing the two filters closer together.
Second thing you can do is remove the secondary filter, place a coffee can or something under it to catch the fuel, rum pump until Racor is full and you get solid flow of fuel into the can, replace secondary filter, bleed at screw.

On edit, we are talking about a different boat? Catamaran has nothing to do with it?

The fuel pump can’t fill the filter because there is air in there, all it can do is compress air.
If electric pump is before Racor, leave lid loose, run pump and shut off just as filter fills up. Tighten lid, turn on pump and slowly open bleed screw and catch the little fuel spillage in a rag, then when it becomes just fuel, close screw, turn pump off, start engine and go to high idle, engine may stumble for a sec but should pick back up.

If pump is after Racor you will have to loosen bleed screw and catch any fuel spill. Pump should hopefully suck air and pull fuel into the Racor, but fuel pumps do a better job if pumping fuel than sucking air, so it may or may not go fast.

I’m either case you have to let the air out, to let the fuel in.

[Chotu]

Originally Posted by Marathon1150

What model Racor do you have and how is the electric pump plumbed into it?

Standard Racor fuel/water separator with 30 micron filter. It’s the primary filter. Like on all marine diesels.

Pic attached. There are 3 of these. One for the generator, two for the main engine and a whole lot of plumbing and valves that are actually very hard to see.

I guess the questions are:

1) can you leave air at the top of the Racor?

2) How can I bleed this system without getting diesel all over the place? It’s got to be several cups/pints/a liter of fuel in the lines and secondary filters to pump through before I get fuel with no air.

[Chotu]

Originally Posted by OloteleMtn

Hire a mechanic to show you how to do it properly....best thing i can say.....good luck.

This isn’t good advice. I have done this many times on my old boats and also on land.

THIS particular setup is crazy because there are valves everywhere and I can’t see all the hoses at once.

Basically I have a partially filled Racor primary filter and may or may not have diesel in the line to the secondary filter.

Just trying to understand my next steps because I’m rusty. It’s been over a decade.

[OloteleMtn]

1. No, it must be full and no air present
2. Not enough info to advise.......more complete photos might help

[Chotu]

Thank you! That’s clear.

I am in the monohull right now up north steering clear of Covid for a while.

I’ll try this.

Originally Posted by a64pilot

You have Diesel outboards?
Yanmars?
Anyway you should have a secondary filter on the engine, that should have a bleed screw. Yes you will get quite a bit of fuel out before you get the air out, that is from the length of fuel line between the two filters, so the fuel in the lines has to be bled before you get to the air. So have a hand full of paper towels. Remove the pond scum you dumped in and I’d replace the filter too.
Consider placing the two filters closer together.
Second thing you can do is remove the secondary filter, place a coffee can or something under it to catch the fuel, rum pump until Racor is full and you get solid flow of fuel into the can, replace secondary filter, bleed at screw.

On edit, we are talking about a different boat? Catamaran has nothing to do with it?

The fuel pump can’t fill the filter because there is air in there, all it can do is compress air.
If electric pump is before Racor, leave lid loose, run pump and shut off just as filter fills up. Tighten lid, turn on pump and slowly open bleed screw and catch the little fuel spillage in a rag, then when it becomes just fuel, close screw, turn pump off, start engine and go to high idle, engine may stumble for a sec but should pick back up.

Of pump is after Racor you will have to loosen bleed screw and catch any fuel spill. Pump should hopefully suck air and pull fuel into the Racor, but fuel pumps do a better job if pumping fuel than sucking air, so it may or may not go fast.

[Marathon1150]

Anyway you should have a secondary filter on the engine, that should have a bleed screw. Yes you will get quite a bit of fuel out before you get the air out, that is from the length of fuel line between the two filters, so the fuel in the lines has to be bled before you get to the air. So have a hand full of paper towels. Remove the pond scum you dumped in and I’d replace the filter too.
Consider placing the two filters closer together.
Second thing you can do is remove the secondary filter, place a coffee can or something under it to catch the fuel, rum pump until Racor is full and you get solid flow of fuel into the can, replace secondary filter, bleed at screw.

The fuel pump can’t fill the filter because there is air in there, all it can do is compress air.
If electric pump is before Racor, leave lid loose, run pump and shut off just as filter fills up. Tighten lid, turn on pump and slowly open bleed screw and catch the little fuel spillage in a rag, then when it becomes just fuel, close screw, turn pump off, start engine and go to high idle, engine may stumble for a sec but should pick back up.

If pump is after Racor you will have to loosen bleed screw and catch any fuel spill. Pump should hopefully suck air and pull fuel into the Racor, but fuel pumps do a better job if pumping fuel than sucking air, so it may or may not go fast.

I’m either case you have to let the air out, to let the fuel in.[/QUOTE]

I have the same filter as in your photo (looks like a Racor 500). The above advice from A64 is also what I would do. Our electric pump is between the tank and this primary filter so we use the pump to fill the filter canister after putting the new filter in. The valve between this filter and the next filter is closed when I open the canister, replace the filter and refill it. Then open the downstream valve. Usually, the engine (Perkins 4.108) will start without bleeding after this process. Sometimes, I have to open the bleed screw on the secondary filter, particularly if the engine stalled because of a plugged filter (see photo - paper towel remnants from mechanic who cleaned the tank prior to leaving Mexico for the South Pacific). And sometimes, I have to open the bleed screws on the high pressure pump, downstream from the secondary filter. I use the electric pump to do this rather than the manual pump on the side of the secondary filter because it is easier to use.

[chris mac]

Fill a small bottle with clean diesel. Use it to top off the racor filter housing before putting the lid on.then use the manual pump to the inline filter to bleed any air bubbles.

[Chotu]

Thanks for the real time advice.

It was one of those cases where you have a piece of toast for breakfast and are doing so many things you don’t get to eat until late in the day.

More an issue that I couldn’t see straight so I was unable to understand the complex routing of the fuel polishing system and 3 primary filters. Moved on to the oil changes for the main and generator and doing impellers and a belt.

Today I’ll replace the secondary filters and bleed the system after cleaning out the Racor again and draining the scum back out of it.

Thanks and I’m sure I’m all set now. After over a decade it became fuzzy. But after reading A64 and Marathon1150’s summary of the procedure (and having food) it was clear again.

[downunder]

Originally Posted by chris mac

Fill a small bottle with clean diesel. Use it to top off the racor filter housing before putting the lid on.then use the manual pump to the inline filter to bleed any air bubbles.

[zstine]

Dump the scum out of the raycor. Fill it with fresh fuel as far as possible to still be able to screw back on.. place towels under to catch minor spills. There shouldn't be that much air... I don't blead the air out, just run the engine with revs 1500 to 2000. Rpms will drop as air goes through and maybe stall, but I was able to get the air out by running the engine. No bleeding. Done this several times... if not, the air will at least be at the engine and will require less pumping fuel out to get out the air.

[Cheechako]

Many things possible but... FYI, when using the electric pump to fill the Racor, leave the top off until it's full. Then tighten it up. You are trying to push air in the system. If you fill it like this you likely wont have to bleed the engine at all.

[Thumbs Up]

Chotu, this is what I do. I pull the tank vent tube loose from the vent fitting on the hull. Blow into that tube then quickly plug it with a bolt. Now your fuel tank is pressurized. Open the bleed screw on the filter until you get clean fuel running out