Air in Fuel Lines: Should I change fuel lines?

[Mike Davis]

Recently, I have to bleed my fuel lines frequently. I am bleeding from the fuel pump. The engine is a Universal M25. The manual says to bleed from the top of the filter first. On my boat, a CD31, the top of the fuel filter housing is almost impossible to get to, nonetheless, to bleed. Does anyone know any tricks to get to the nut on top of the filter?The fuel lines look to be original and probably should be changed. Before I do this, can anyone tell me what sizes the fuel lines are? There are two different lines, 2 different diameters. Has anyone done the job before? Any insights?
Mike Davis

[Steve Laume]

Mike, I would not rely on anyone to determine what sized lines you need for your boat. Take a sharpie and label the feed and return fittings on your fuel tank and make sure you know which is the inlet and out let of your filter or label that as well. Put a tab of duct tape on each line labeled feed and return then remove the hoses and take them with you when you go to buy new ones. It is hard to mess up the size and length when you have the originals in hand.

Not being able to bleed the fuel filter is a bit of a problem. If it is the original Fram, I would take it out and use it for a dinghy anchor. The Racor filters are very nice and elements are available everywhere. If you have a decent filter and still can't get at the bleeding screw I would move it when you replace the hoses.

One more thing to consider, is adding a vacuum gauge on the intake side of the fuel filter. This will tell you when the filter needs replacement and could help with some other trouble shooting.

Why yes, one thing does lead to another, Steve.

[Ken Cave]

If your fuel lines are pre-2000, they need to be changed pronto, as the "new" diesel fuel
has been doing nasty things to the hoses.

A friend of mine was caught with this problem, and when he finally replaced them he found that
the insides were flaking off and gumming up his filters.

And you thought that our new gas with ethanol is the only problem!!

Ken Cave
Dragon Tale

[Sea Hunt Video]

I just read an article in BoatUS magazine that says the US Gov (EPA) approved the distribution of Ethanol 15 back in 2010

Apparently, there is now some type of Congressional action to try to limit, reduce or eliminate Ethanol 15 because it can't be used in a lot of vehicles, boats engines, etc. According to NMMA, there is not one single marine engine on the market today that is warranted to use E15 fuel

Everyone says that Ethanol 15 cannot be used in trucks mfg. before 2001. My mpg went down substantially once I started having to use E10. My faithful 1994 Chevy Tahoe with almost 300,000 miles may be on her last breath - no fuel. Sad, sad, very sad.

So far, I can get clean, unadulterated diesel at the marina next to our sailing club. Sadly, this marina is on the "chopping block" and will probably be gone, sold and demolished within 12-18 months.

On a brighter note, Dolphins v. Falcons, 1600 hrs start time. GO DOLPHINS

[Maine_Buzzard]

That you need to bleed the lines at all is troubling. The root cause is usually a failed fitting at the tank or filter. certainly upstream of the mechanical lift pump on the engine.

Hard to troubleshoot, because it's a tiny hole and might not weep when the engine is off. Starting with the tank, take the fuel line off and follow those earlier instructions about marking and measuring... Check the fittings to be certain they are snug- my tendency is to use two or three fingers to tighten the brass fittings. Any brass to aluminum connections? These are worth a whole thread on by themselves...

Eventually you will find a fitting or a hose connection where it's not secure.

While you are at it, absolutely relocate the fuel filter and install a Racor one if you can. some have the plunger right on the top, and make for easier filling. All I need to do is a few pumps to get the siphon started and then close the bleeder screw on the filter top.

For a Universal M25, it should be 5/16 or 3/8" fuel line. If the ends are cracked and swelled, it's certainly time to replace.

[mcos]

My cd27 had what turned out to be several very small fuel leaks. This manifested in trouble starting and surging. After tightening everything and replacing filters and fuel pump I put in an electric diesel fuel pump - installed in the line coming out of the fuel tank. I left the mechanical pump in also. When the electric pump was turned on I quickly found the weeping fittings that had been allowing air to be sucked in. The engine runs fine now and I only use the electric pump to prime the system before lighting off the engine. The pump was about $40 from an auto parts store. Wired to a toggle switch installed next to the starting station. Bonus is that if your mechanical pump fails, you have a built in 'spare'.

[JWSutcliffe]

I think the fuel filter that Mike is referring to is the "last chance" filter with spin-on element located on the side of the engine below the injector pump. On the CD31 it is essentially impossible to access this location, either from the front or back of the engine. I am planning a filter element/fuel line replacement project for the spring and intend to cut an access hole through the wall of the slide-out trash bin compartment adjacent to the starboard side of the engine.

[tjr818]

Installing a new Racor filter is in the plans as part of my spring upgrades. Where in the world can you put a Racor on a CD27? I'd like it be below the tank so that it will fill by itself, but I don't think that is possible. There is a wood cross member above the engine that has room, but then I'd never be able to get to the stuffing box by going over the top of the engine again. I'd have to do that through the port cockpit locker. Any ideas?

[tjr818]

...his manifested in trouble starting and surging. After tightening everything and replacing filters and fuel pump I put in an electric diesel fuel pump - installed in the line coming out of the fuel tank. I left the mechanical pump in also. When the electric pump was turned on I quickly found the weeping fittings that had been allowing air to be sucked in. The engine runs fine now and I only use the electric pump to prime the system before lighting off the engine. The pump was about $40 from an auto parts store. Wired to a toggle switch installed next to the starting station. Bonus is that if your mechanical pump fails, you have a built in 'spare'.

This seems to be the way to go. Can you tell me what electric pump you installed? Which autoparts store did you use? Thanks.

[tjr818]

...One more thing to consider, is adding a vacuum gauge on the intake side of the fuel filter. This will tell you when the filter needs replacement and could help with some other trouble shooting....

Steve, Help me with this. Intake side? I have the gauge and I am planning my fuel system rebuild right now. I was going to put the gauge between the filter and the engine, figuring that when the engine driven pump had to suck a little harder the vacuum gauge would show an increase in suction. Am I wrong on that?

[Steve Laume]

Yikes, sorry about that. You are right, there wouldn't be any vacuum on the inlet side if the filter clogged.

I did this a long time ago, Steve.

[gates_cliff]

TJR, I've been considering adding a Racor filter also, and had the same thoughts about locating it. Please post pics once you do get it installed.

On the other hand, I'm not all the big but I can't really reach the stuffing box from over the engine. I have a drip from my stuffing box and I was trying to take some once and dropped my cell phone into some water that had accumulate. Of course ruined the phone.

[tjr818]

TJR, I've been considering adding a Racor filter also, and had the same thoughts about locating it. Please post pics once you do get it installed.

On the other hand, I'm not all the big but I can't really reach the stuffing box from over the engine. I have a drip from my stuffing box and I was trying to take some once and dropped my cell phone into some water that had accumulate. Of course ruined the phone.

I will post some pictures once I get it installed. I am planning on mounting the Racor in the Port lazarette on the hull behind the fuel tank.

I am not a skinny guy, but I can put an old seat cushion on top of the engine, squat down in front of the engine and then plop myself on to the cushion. With my stomach on the cushion I can reach the stuffing box and adjust it as required. I find it FAR easier than entombing myself in the lazarette and trying to reach the stuffing box. I could post o picture of that procedure, but it wouldn't be pretty. I might get banned by the obscenity board.

[tjr818]

Good day to work on the boat today, 70 degrees! Here are two pictures of how I access the stuffing box:

IMG_1629.JPG

IMG_1630.JPG

Also I did find an alternate spot for the Racor. On the starboard side behind the drawer, mounted onto the side of the icebox.
It is a bit harder to get to, but it is lower and it would save a few feet of fuel line. I can't decide.