Check my (newbie) thinking on fuel

[djousset]

I have been gifted an unscheduled lesson on fuel issues.

Here's what I know:

Plenty of fuel in the tank. I filled it to 7/8 last fall when hauled out, stabilizer added.
Commissioned the engine and the start on the hard went fine (although only about 2 minutes).
I changed out both fuel filters. Also changed oil and replaced oil/air filters.
I installed new exhaust elbow. Fuel shut off is open.

The on-the-water test, engine started beautifully, and ran beautifully…... until it didn’t. It just stopped after a couple of minutes. Logic tells me either no fuel, or air in the system? I’ve checked all the obvious (to me) items and would like some advice on next steps.

I started by trying to bleed any air out of the system. I worked the lift pump for awhile and with the bleed screw opened on the secondary filter saw no diesel coming through. I opened the filter and the vessel was empty. The Racor pre-filter has diesel in it. So maybe a blockage of some kind between the racor and the lift pump, or between the lift pump and the secondary filter? The engine did run for a short bit so I assume it used the diesel that was in the secondary filter (I had filled the housing and bled it when I changed it out)

My inclination is to start at the tank and remove and check the fuel hoses one at a time to see which have fuel in them: tank to racor, racor to lift pump, lift pump to secondary filter. Then maybe remove the lift pump or replace the shut off valve depending on what I find? Is there anything I should be doing instead of, or before that step? Is there a more likely culprit?

[Tellie]

I would agree with a fuel delivery issue as well. The engine ran well until it ran out of fuel. Certainly check to see if there are any blockages starting from the fuel tank to the fuel pump.

[Deep Blue Water]

Diane,
what are the fuel lines, rubber or metal? If rubber, what's their age? Sometimes on old rubber fuel lines the 'inner liner' can collapse and restrict fuel flow.

[Compass790]

Almost certainly air in the system from your filter change. Cant remember what sort of Yammer you have but the lift pumps are ridiculous to pump using the little lever. You cant actually do it if the engine stops with the pump cam lobe at the highest point. Try rotating the engine a bit.

It's much better to install a squeeze bulb ( there will be screams here from other posters ) or a cheap inline 12v fuel pump to prime the system.
Follow steps in manual to bleed air.

[skipmac]

Had similar problems recommissioning my Pearson a few years ago. After much trial and tribulation I confirmed first, that it was a fuel problem and second, it was due to an air leak in the system.

In my case I was finally able to isolate the air leak at the old Racor primary filter. It was the original 1984 filter and Racor had since made a slight modification to the design. The old parts I needed were available but I ended up replacing it with a dual Racor setup which I love.

If there is fuel in the Racor but not in the secondary filter on the block then leak should be in the Racor somewhere or in the line between the Racor and the secondary.

[jooa]

The manual lift pumps on Yanmars are absolutely hopeless and in my opinion a major safety problem. Imagine having your fuel system sucking in air due to rough weather, engine stops, and you are quickly blowing towards the rocks... install an electric lift pump, it could save more than just your boat and you can bleed your system in about 90 seconds (personal experience).

Also check the pick up tube that goes into the fuel tank, they often have a wire mesh screen on the end which can clog. The common wisdom is to remove the wire screen.

[mvmojo]

If the on engine secondary filter canister was empty, it is highly likely that you have an air leak in the fuel line somewhere between the off engine Racor and the on engine filter. The engine is sucking fuel out of the on engine filter and that fuel is being replaced by air being sucked in through the air leak. Check all the fittings between the Racor and the secondary filter.

I also second the suggestion to get some sort of pump to bleed the engine. A squeeze bulb is the cheapest and easiest to install. Put it before the off engine Racor (between the tank and the Racor) and you can use it to fill the racor as well. Alternately, you can install a small 12v fuel pump and just flip a switch to fill the Racor, bleed the engine, etc.

[skipmac]

Originally Posted by mvmojo

I also second the suggestion to get some sort of pump to bleed the engine. A squeeze bulb is the cheapest and easiest to install. Put it before the off engine Racor (between the tank and the Racor) and you can use it to fill the racor as well. Alternately, you can install a small 12v fuel pump and just flip a switch to fill the Racor, bleed the engine, etc.

I will third that suggestion. I purchased a small electric pump that serves as a backup in case the lift pump on the engine fails and it also works to prime the system if needed and to transfer fuel between my two tanks.

Very handy spare to have.

[SSAsailor]

You said that you worked the lift pump for a while and nothing is getting to the secondary filter - are you sure the lift pump is pumping? Did you try rotating the engine slightly? If the cam is in a certain position, you won't be able to operate the lift pump manually.

On the yanmars I have owned, you can feel if the pump is pumping because if it isn't the stroke on the pump lever is shorter.

[Anchorage Frank]

I would suggest that you replace the o-ring on the tank filler cap and possibly replace the racor as well.

[Squanderbucks]

My vote is with the suggestion about installing some sort of pump between the Racor and the on-engine fuel filter ( referred to as "last chance Filter"). Can be a simple as a squeeze bulb or an electric pump with a switch in an easy to reach spot when doing the bleeding. A Basic system can have one or two squeeze bulbs or one electric pump in the position of bulb near the tank.

My boat has an electric pump that serves this purpose and does second duty as a fuel polisher if some additional valves are put in to bypass the engine.

This is not a one time issue. You can end up with air in your lines for a number of reasons and all go back to having to pump fuel back into the lines somehow. I suggest while it has cropped up as an issue now and is a PITA it can also happen when you are in a much more hurried situation and having a setup that quickly solves the problem is a great relief.

[Mike Banks]

Was there any water coming out of the exhaust outlet? Is there plenty of coolant in the heat exchanger? Did you prime the raw water impeller? Were the inlet raw water sea cocks open?

[Ramona]

Start with the Racor filter. Either replace it or replace the top o rings. They are notorious for air leaks.

[crashley]

Check what you last worked on
IE if you changed a filter check the o rings etc on that
If you changed a fuel line check the connections on that line
Problems like that are usually linked to the last maintenance

[wingssail]

A quick way to see of there is a blockage is to disconnect the vent line and pressurize the tank it by blowing into it. It is easy to make fuel flow this way.

This is how I fill my pre filters after changing them. You can easily make the fuel flow all they way to the final filter and the bleed screw (unless there is a blockage).

Be careful when you let the pressure out, you may get a face full of diesel.