Yanmar 2GM20F Fuel Lines, High or Low pressure?

[SirMichael]

Every year I try to go through some of the maintenance on our 88 Hunter 28.5 & the 2GM20F engine.

This year, I drained out all the diesel fuel in the tank and cleaned it out (brush on a long flexible rod, & vacuumed out the inside). I also used a USB portable camera with LED lights, to inspect it.

I'm going to change the fuel filters (again, I did it a number of years ago) but I would like to also change the fuel lines from the tank to the filters and the return line. I'm also going to add a small hand pump to be able to bleed the system when I change the fuel filters.

The question is, do I need HIGH pressure 1/4" lines, or will LOW pressure hose work OK?

ALSO, I saw on some previous posts where some had gone from a 1/4" line to a 5/16" line, should I make that change as well when I order the fuel line?

Sir Michael

 

[Hollyberry]

The line from the tank to the first pump (whether mechanical or electric) is under suction.. no need for high pressure. By the time you're at high pressure you should be into metal tubing in the injector system. i don't believe the return line is under any significant pressure either as it is open ended...
If you haven't had any fuel supply issues I see no advantage in upsizing the line - and you'd need new fittings as well...

 

[dlochner]

The question isn't high or low pressure, it doesn't matter if you use USCG approved fuel lines. Don't use cheaper fuel lines for cars. Only use USCG Type A fuel lines.

 

[dlochner]

The question isn't high or low pressure, it doesn't matter if you use USCG approved fuel lines. Don't use cheaper fuel lines for cars. Only use USCG Type A fuel lines.

Let me clarify. The "high" pressure lines on a diesel are those lines after the injection pump. These lines are typically metal, I'm guessing copper or some alloy. The "low pressure" lines are the return lines to the fuel tank.

The really important issue is permeation of the hoses and that is what the USCG Type A addresses. Hoses that are not approved can have fuel permeate the hose and leak, creating both a fire hazard and a pollution hazard.

 

[SirMichael]

Thanks guys, I've found some Marine grade (USCG approved) line. I'll just go with the 1/4".

Sir Michael

 

[Ralph Johnstone]

The question is, do I need HIGH pressure 1/4" lines, or will LOW pressure hose work OK?

Certified marine fuel line hose only comes as low pressure hose. If you're not using certified marine fuel hose, not good, not good at all.

Just completed replacing all the fuel hoses for the 2GM20F this winter. The 24 YO hoses were as good as new outside the motor housing but a little hard inside the housing. Only ran as much new hose as needed until it hit a filter or pump outside the housing and then kept the old hoses.

I'm also going to add a small hand pump to be able to bleed the system when I change the fuel filters.

Please don't do that because, well, (see picture above). If it's an OB hand pump :

...........the rubber of the bulb is soft and thin and easily punctured. The real problem with these is that they're likely hidden somewhere where they can leak to their heat's content without being seen.

There's really no worry about purging air from your primary filter if has a local inlet valve as shown :

After changing the filter element, the casing is full of air. Crack open the inlet valve, open the air vent and fuel will slowly fill the body while forcing the air out. Close the vent when all of the air is gone. Maybe best to change the element when your fuel tank is full to ensure you've got a head above the filter body.

Same goes for the secondary filter.

It's a good location to accumulate and periodically vent air.

When you you renew your hoses which are full of air, remove the air at the two filters. The one place which will cause you some problems is the short vertical hose from the secondary fuel filter outlet to the high pressure pump :

No where to get rid of the air so pull the upper fitting apart and dribble fuel from the filter outlet into the vertical line. When the line is full, jam the hose onto the upper filter while it's still dribbling and you've got an air free fuel line.

 

[Claude L.-Auger]

To add my 2 cents I'd say that people who want to add the OB type hand pump want to do so because they think using the little lever on the fuel lift pump does not work good ! It does if you realize that the fuel lift pump is actuated by the camshaft, which is lobed. so if you're not getting fuel when using the actuator on the lift pump, just rotate the flywheel until you feel some pressure on the actuator. And when you do you'll get plenty of fuel. I generally crack open the screw on the Yanmar filter and it does not take more than a few shots on the actuator to get good clean fuel coming out of the air hole in the screw. Unless the fuel lines are totally empty in which case it will be longer. But you can cheat if you're in a hurry. Decompress the cylinders, and hit the starter button. You'll get fuel coming out of that air hole super fast. Please note that I'm note recommending this, I'm just saying it can be done.

 

[Ralph Johnstone]

To add my 2 cents I'd say that people who want to add the OB type hand pump want to do so because they think using the little lever on the fuel lift pump does not work good !

You're exactly right. Used to use that method very succesfuly before I installed an electric fuel pump.

 

[Dalliance]

If the pump you want to add is one of those squeeze bulb types, don’t do it. They’re notorious leakers.

One thing I learned about the manual lift pump on my Yanmar 2GM, after much frustration, is that it does nothing until the bottom 1/4 of each stroke where you start to feel resistance. I was stopping where I felt resistance, so the pump was doing nothing. Make sure you’re actually pushing that lever all the way down.

I second Ralph Johnstone’s suggestion to add an isolation valve, an in-line shutoff, at the primary filter inlet. It minimizes how much air you have to bleed from your lines. I added one when I moved my primary filter to a more accessible location in front of the engine. I still kept the fuel shut off at the tank in case I ever need it. Both the added valve and the more accessible filter location make things a lot easier.

Instead of adding another pump to the system, I had a eureka moment recently when I realized that the small suction tube on my little West Marine vacuum oil extractor fits into the bleed screw hole (Or maybe it was the adjacent air vent screw hole.) on top of the secondary Yanmar fuel filter. It provides a fast way to pull air out of the fuel line & filters without adding the risk of a leaky squeeze bulb or the cost and complexity of an electric pump. Suction first and then just minimal strokes of the manual lift pump afterward to confirm no air bubbles. I always change both the engine oil and the fuel filters at the same time in the fall before winter lay up, so the oil extractor is there anyway and can do double duty. A little diesel fuel oil in the dirty engine oil that’s going to the oil recycle barrel doesn’t matter.

 

[Hollyberry]

The squeeze bulbs can also be an insidious source of air in the fuel lines - since mostly under vacuum, leaks don't always show up as wet...