Confounding Diesel Problem - Looking for Ideas

[SoonerSailor]

I have a Westerbeke 44B with 280 hours on it in my Valiant 40. Since we purchased the boat, shortly after the re-power, we have had problems with the engine starving for fuel and often shutting down completely after 1 to 3 hours of operation - but not always. Sometimes I can throttle back to 1200 rpm and it will run happily there, but trying to push past that and the engine may stumble and die. After sitting for an hour or so, she starts back up and runs fine for another 1 to 3 hours. Switching between fuel tanks and between the dual Racor 500 filters makes no difference. Opening the fuel fills in case of faulty venting makes no difference. Tank fill makes no difference. Initially it was though to be biomass in the fuel, but that too has been eliminated and the secondary fuel filter on the engine remains clean. Four different diesel mechanics have not identified the real problem yet. Naturally, it never does this when the mechanic is on board.

The 44B has a self bleeding fuel system, and the engine mounted pump seems to be operating normally. We have two fuel tanks connected to a common vent. Each tank has a 3/8" fuel line going to a tank selector T valve. From there the fuel line goes to a pair of Racor 500 2 micron filters, individually selectable, thence to the engine fuel pump. Fuel return line from engine goes to a T valve to choose tank to return to.

Next step is probably replacing the fuel lines after the Racors.

So, any good ideas here? Why does it happen only after the engine has been running a while? We're baffled.

Chip

[sabray]

Pick up tubes in the Tank blocked. Fuel intake line sucking air. Check fuel returns for restriction do the fuel line sizes meet the specs for the install. Maybe they left some old stuff in place that was good for the old engine no good for the new. Old tanks and yuchey pick up tubes with a screen very possible.

[Starbuck]

Chip,

I had a problem with exactly these symptoms. I changed all the filters, or so I thought. I replaced fuel, scrubbed down my fuel tank, and was stumped. I was trying to "start with the easy stuff," like my dad had taught me, and I thought I had, but I'd overlooked the real beginning of the fuel delivery system.

There was a small screen attached to the end of the pick-up tube in my fuel tank that was the culprit: the only "filter" that hadn't been changed in 20 years. It was a 2" square of metal mesh: same material from a screen door, wrapped around and taped to the opening of that pick-up tube. It was 95% clogged. I tore it off, replaced the tube, and she's been running fine ever since.

Before you make yourself crazy chasing air leaks and then wonder if you should have your injectors serviced and begin pulling parts off the engine, inspect the end of this tube. Not all manufacturers used a screen here, but if you have one, it hasn't seen the light of day since the factory. I got to mine by removing the sender unit (the circular cover where my fuel lines exit and return, your config. may be different) from my fuel tank: the tube is attached to this assembly.

Good Luck,
Jeff

[Lancerbye]

Once was involved in troubleshooting a similar problem on a 3 cyl. Volvo diesel. It started up after a refit. The end result was that the third cyl. downstream on the fuel rail was starving because of undersized or unbalanced fuel supply. Ran good until the unit had to work. I am not familiar with the Westerbekes. If it is a common fuel supply pump this should not happen. In the case of the Volvo, it used a common line and individual cyl. pumps. By making a Tee at the middle cyl. and supplying both ways the problem was eliminated. I have also seen fuel lines delaminate causing a shut down when the suction increased. Acted like a joker valve. Just some more ideas to provide fuel for the fire. Good luck.

[sabray]

Hey. I Said that. But your right. It would explain why it's all joy dockside. Start sloshing around and tank yuck sticks up the tube. I can't do thumbs up for your comments but you get the idea.

[delmarrey]

Originally Posted by Lancerbye

I have also seen fuel lines delaminate causing a shut down when the suction increased. Acted like a joker valve. Just some more ideas to provide fuel for the fire. Good luck.

And that goes for the exhaust hoses as well. If one is delaminating the back pressure could be chocking the motor. How old are the exhaust hoses?

[David M]

You could also run the engine from a bucket of Diesel. What this would do is to isolate the problem to your engine or your fuel delivery system.

[noelex 77]

A blocked fuel tank vent line would give the symptoms you describe.

[Boracay]

Fuel return: have you checked that it is returning fuel?

[Laidback]

Originally Posted by SoonerSailor

I have a Westerbeke 44B with 280 hours on it in my Valiant 40. Since we purchased the boat, shortly after the re-power, we have had problems with the engine starving for fuel and often shutting down completely after 1 to 3 hours of operation - but not always. Sometimes I can throttle back to 1200 rpm and it will run happily there, but trying to push past that and the engine may stumble and die. After sitting for an hour or so, she starts back up and runs fine for another 1 to 3 hours. Switching between fuel tanks and between the dual Racor 500 filters makes no difference. Opening the fuel fills in case of faulty venting makes no difference. Tank fill makes no difference. Initially it was though to be biomass in the fuel, but that too has been eliminated and the secondary fuel filter on the engine remains clean. Four different diesel mechanics have not identified the real problem yet. Naturally, it never does this when the mechanic is on board.

The 44B has a self bleeding fuel system, and the engine mounted pump seems to be operating normally. We have two fuel tanks connected to a common vent. Each tank has a 3/8" fuel line going to a tank selector T valve. From there the fuel line goes to a pair of Racor 500 2 micron filters, individually selectable, thence to the engine fuel pump. Fuel return line from engine goes to a T valve to choose tank to return to.

Next step is probably replacing the fuel lines after the Racors.

So, any good ideas here? Why does it happen only after the engine has been running a while? We're baffled.

Chip

Without going into great detail, a common fuel fault is a very small leak in between the tank and the low pressure pump --- At low RPM sufficient fuel makes its way to the engine -- increase the RPM and the system will suck air (not much) and the engine will falter.
So suggest go over all connections - change olives, gaskets, washers etc...
The leak will be an air leak under suction - no fuel will leak.

[CSY Man]

Had the same problem on previous boat and as a result ended up using the motor less and less: sailed through the reef in Salt River and sailed to and from the dock as I could not trust the engine any more.

Found the problem after a while and it was just like described above:

There was a small screen attached to the end of the pick-up tube in my fuel tank that was the culprit:

Easy to fix: Just ripped off the screen and let the filters do their job...

[Hud3]

I had a similar problem--the engine would run, but I couldn't get it to rev over 2200 rpm. Turned out to be little spiral shavings of aluminum left over from when the tank was fabricated. They had partially plugged the pickup tube. I ran a length of electrical wire through the tube to clear it out, and the problem never came back

[mbianka]

I recently looked into my boats fuel tank (which had been empty for three years since I converted to electric propulsion). I was shocked to find a tar like substance coating the bottom of the tank. You can see some photo's here:
THE BIANKA LOG BLOG: IN THE TANK: Part One, Scene of the grime!
Embedded in this grime was some sand grains from 20 years of fuel fills. It does not surprise me that fuel lines or pickup tubes can get clogged with this stuff.

[smurphny]

A couple of years ago,I had a small hairline crack in the crappy plastic elbow, leading from the fuel tank. The one on top of the vertical feed tube that goes to the bottom of the tank. Drove me nuts. David's suggestion above will narrow it down, may also give you a place to attach a emergency fuel supply.

[SoonerSailor]

If it was a fuel pickup or vent problem, it would be reflected in the Racor filter vacuum gauge, which is referenced to atmosphere, but we aren't seeing that. Switching tanks should also make a difference in that instance, but it doesn't.
I'm convinced the problem comes after the Racor filter block. I don't know if the fuel lines were replaced with the repower, though they don't look old. There may be a delamination or crud in the line from the filters to the engine fuel pump - or perhaps a problem with the fuel return. Thanks for the ideas so far.