Engine runs 10 minutes then stops

[eje]

Yanmar 3GM30F
I replaced both fuel filters & bled the system. The engine will run well for about 10 min then stops. I have to refill the filter and bleed the line between the filter & HP fuel pump, then it will start and run again for about 10 min.
I don't see any fuel leaks. I assume I have an air leak but can't find it.
Any suggestions on where to look?

[Searles]

First check the fuel tank breather ,find it a b check it has an uninterrupted air flow, then check all o rings in the fuel filters ,check the fuel lift pump isn’t leaking .⛵️⚓️

[chris mac]

I have the same engine, 2 of them . One of the weak points is a tiny fuel supply hose. Mine is 3/8. That means any elbow or fitting is likely 1/4" or less. These get plugged quite easily. Usually the first one coming from the tank, or even the pickup tube in the tank.
Once it blocks you only have the fuel in the filter, which on my racor is roughly 10 minutes of run time.
I would recommend polishing your fuel, and checking that the fuel line has good flow. If it's plugged I would start at the fitting on top of the tank and work towards the engine.
Good luck

[Greg4cocokai]

Also, check that there’s not a plugged screen on the pick up inside the tank. I’ve been on two boats where that was an issue.

[Starbuck]

Experienced a similar mysterious fuel starvation syndrome. It was the end of the pickup tube that had a 1 square inch piece of metal mesh, like in old screen doors, wrapped around the end of the tube at the bottom of the tank and glued. Pulled it off & no more problem.

[Bill O]

All good suggestions so far. Do you have a vacuum gauge on your racor? These are helpful for troubleshooting and letting you know your filter is getting clogged before the motor shuts down. Added an automotive vac. gauge between the racor and pump that is mounted outside the engine room. This made it much easier to view the gauge (rather than looking in the engine bay) to detect any problems.

As suggested by Chris and Greg, would start at the tank checking to see if the vent is clogged or a clogged pick up tube. Usually blowing air into them clears them out if there is a simple blockage. If the blockage is in the pickup, probably need to polish/clean your fuel and tank (did you have a lot of sediment/water in your racor when you changed it?).
Only reason I added "probably" to the statement above because we had this similar issue w/a tank pickup that clogged often. It turned out that tank had a fine screen in the end of the pickup tube and would clog with the smallest amount of stuff. Took much time to determine this issue and was very frustrating!

[marcjsmith]

If it was running fine before you did a filter change, and you didn’t touch anything else but the filter and that’s when it started running bad...

Filter gaskets, o rings, etc would be my first go to. Pull filters, check the gaskets orings, surfaces etc, ensure they are clean. Button it back up and try bleeding again.

[gonesail]

also when you are tightening up fuel filters .. it helps to dab a bit of silicon grease on the gaskets.

[eje]

Again, the issue is- after filling the filter bowl & bleeding the line to the HP pump the engine starts & runs for @ 7 min, then stops. The filter bowl will be empty.
I refill the bowl & bleed the line to the HP filter and it runs well agsin for @ 7 min.

I've eliminated, or think I've eliminated several things-

Not the vent. I opened the cap- no change. If it was the vent, I'd expect it to start again after it stops. But the filter has to be re-filled & the line bled after it stops.

I replaced the nylon gasket on the filter bleed screw- no change. Lost the new gasket, tried an o-ring- no change

I disconnected the Raycor and put a line into a fuel can running directly to the uplift pump- no change. This tells me the problem is likely downstream of the Raycor filter.

I removed the filter, checked everyhing. Reassembled- no change.

I replaced the uplift pump. It ran for 20 min then stopped

I put the old nylon gasket back on the filter bleed screw- ran for @ 7 min.

I still suspect an air leak on or around the filter, but cant seem to find it

[Bill O]

Chasing down these problems can be very frustrating.



To be clear, which "filter bowl" are you saying is draining the Raycor or the filter on the motor?



I'll assume it's the Raycor.


So how about putting a fuel line to the Raycor from a fuel can (w/clean fuel). This will tell you if the filter is leaking. If the filter drains then an air leak in the filter. Replace all seals and gaskets. If the motor runs w/o draining the filter, then we move back to the main fuel tank.

Check for a clogged pick up tube in the main tank. Remove the intake fuel line from the Raycor (to the main fuel tank) and blow some air into it. You should hear it bubble a little. Hook up the fuel line again to the Raycor and start up the motor. If it runs longer than 7 min then you had a clog and you'll need to clean your tank/polish your fuel.

[eje]

Originally Posted by Bill O

To be clear, which "filter bowl" are you saying is draining the Raycor or the filter on the motor?
I'll assume it's the Raycor.

The filter I'm referring to is the main filter mounted on the engine. When it runs out of fuel the engine stops.
I ruled out the Raycor & the fuel tank when I fed fuel from a can directly to the uplift pump and it still stopped at @ 7 min.
I figure I must have an air leak I'm missing downstream of the Raycor between the uplift pump & the HP pump.

I removed all the lines downstream of the Raycor, checked engine filter and the banjo bolts for damage.

[Bill O]

OK thanks for clarifying.

[Pauls]

You have an air leak either at the filter which you are refilling or between it and the tank. A very helpful way to find the source of the leak is to temporarily install a section of transparent tubing in the supply line. Air bubbles in the fuel will be easily visible. Relocating the transparent line to different locations can allow you to pinpoint the leak.

[s/v Jedi]

For this situation I have a Walbro fuel pump that I use for bleeding but also boost fuel function. It simply pressurizes the fuel feed system incl. the Racor filters to 7psi, which not only keeps the engine running, but also shows where the leak is because now that it is positive pressure, fuel will leak out.

Search this forum or use Google to search for “s/v Jedi fuel system” and you will find diagrams etc.

[hugosalt]

Eje, Would seem you have isolated problem to your "secondary filter" (filter mounted on your motor).
I do not have my service manual for my 3 GM in front of me as it is on the boat, however
I consider myself somewhat familiar with said fuel filter and don't remember a "nylon"
gasket on the bleed screw that you refer to in post #9.
I do believe that there are or should be what I call "copper crush washers" in several spots and they should be considered consumables. Thinking ?? that your nylon gasket
may be in place of a copper crush washer.
Again I don't have my manual in front of me but likely a diagram is on line.
A quick search turned up Yanmar parts #s
23414 08 0000 or
23414 12 0000 (or both think there are several different sizes on filter)
In any case changing out any of these copper washers on your filter will be cheap and easy next step in troubleshooting problem.
Hope this helps.