Diesel dying after running at 2k RPM few hours.

[phorvati]

I am looking for a good way to troubleshoot this.

I have a westerbeake 4-108. Rebuilt in 2012. Over the last two summers, I am noticing that if i run at 2k RPM, engine is more susceptible to dying. Symptoms are definitely air in fuel line. Engine starts sputtering, and dies within a minute. If i throttle back when i first hear it , sputtering stops and I can get away without engine dying. It happened 3 times in the last 2 years. And each time if i bleed it, it starts right up.
Twice it happen on bouncy seas, and fuel tank about 1/4 - 1/2 full. I have a small 20gal rectangular tank. I wonder if it could have sucked air that way?
Some more info...
Primary fuel filter is Racor R20S, and secondary is the wix 33166.
My return goes back to a tee at the vent fitting.
The first time it happened, i found that mesh strainer at the intake tube was completely clogged. Since then i cut off the mesh, so my tube is a bout 1/2" shorter. When it happened the second time, tube was free and primary filter did not appear to have too much crud in it.

I am wondering if at higher RPMs the line after the primary filter lets air in somehow. Maybe its not big enough to supply adequate fuel flow.

As long as I motor at no more then 1800RPM, engine runs fine. In fact it never died. I don't have an hour meter on it but I put about 100 hours per year. Exhaust is clean. No fuel in the water, and I have the usual startup smoke, some condensation on cold days, but under normal load, and when warmed up, exhaust is always clean. Engine runs at about 180F.

Thanks for any feedback.

[senormechanico]

Could be fuel pump dying and/or air getting into fuel line before lift pump.

[model 10]

Same kind of problem and it was a build up of crud down inside the pick-up tube. The tube was 5/16"od and was down to about 1/8"id for about 2".

[sailorchic34]

Sure sounds like a bad fuel pump. Might try adding an electric pump to the system and see if that makes the problem go away. Curd in the pickup line or a clogged return line might do it too.

[Mainebristol]

Another remotely possible source of trouble is a clogged secondary fuel filter. Should be immediately evident if you open it to see, and a quick fix if this is the problem. Easy to check, anyway.

[Nicholson58]

Originally Posted by sailorchic34

Sure sounds like a bad fuel pump. Might try adding an electric pump to the system and see if that makes the problem go away. Curd in the pickup line or a clogged return line might do it too.

If you are sure that air is getting in then look for faulty fittings, hose, or gaskets. The other possibility is a leaky diaphragm in the lift pump. If you have crud in the tank I highly recommend you clean it out. Rebuilding that HP pump is not cheap.

[k. michael marquardt]

First thin change the fuel filter.
Micro goo can clog it without showing much.
Your fuel line had a dirty mesh filter. That's an indication.

[Chuck Hawley]

Originally Posted by phorvati

I am looking for a good way to troubleshoot this.

The first time it happened, i found that mesh strainer at the intake tube was completely clogged. Since then i cut off the mesh, so my tube is about 1/2" shorter. When it happened the second time, tube was free and primary filter did not appear to have too much crud in it.

OK, I had EXACTLY this problem on a custom 67' race boat with a single 40 gallon tank and a Perkins 4-236. However, when I removed the pre-pre-pre filter, I allowed fuel and grit to go into the electric fuel pump which was intended to help prime/bleed the system. The fuel pump had an internal filter (wire mesh) to protect IT, so I had only moved the problem downstream.

I think you've got a "collection" problem where something small happens over a long period of time. Is there any way to know if you have low pressure on the suction line, like a blockage or a kink?

Or, when you break apart the fuel line, do you sense you're relieving pressure?

Can you feed the engine from a foolproof source (5 gallon jug located above the engine) to see if the problem persists?

Chuck Hawley
Alerion Express 38 Yawl "Surprise"

[W3GAC]

Don't know if you have any brass compression fitting on fuel hardline, but a frequent issue with your symptoms is a very very hard to see crack that that can mysteriously develop (usually in the female compression nut) for no reason at all other than temperature cycling/ metal fatigue on older/ original installations. Less us all know what you eventually find. Helps build a valuable data base.


Sent from my iPhone using Cruisers Sailing Forum

[HopCar]

A mostly blocked vent line on the fuel tank might cause those problems. As you run fuel leaves the tank faster than air can come in. A vacuum builds in the tank over time until the fuel pump can't draw fuel. The engine shuts down.

I had the exact problem you had with the pickup screen. I hate those things. Let the dirt come through to the filter where it's easy to deal with.

[Russ]

Wrap EVERY fitting with small piece of Paper towel and run engine for a bit and look for pink staining of diesel on paper. To do it right you should run a fuel pump BACKWARDS in the system since the system is made to draw (vacuum pressure) fuel and placing the fuel under a Forward head of pressure will show any air leak better. Run pump for at least and hour or more. Don't ask why I know this but battled with this prob for months fores one one passed on this trick. Russ

[phorvati]

thank you for all your recommendations.
during re-build, Injection pump got rebuilt, and injectors as well.
But i didn't really do anything with the lift pump. So lift pump was just removed and replaced after the engine got back from the shop. I have the service kit for it, and i think that might be the first thing to try. Maybe i get the electric one instead.

[HopCar]

Before you go to the trouble of rebuilding the pump, try running with the fill cap loose. That will tell you if you have a blocked tank vent and it doesn't cost anything to try.

[Mikado]

[QUOTE=phorvati;2148438]I am looking for a good way to troubleshoot this.

I have a westerbeake 4-108. Rebuilt in 2012. Over the last two summers, I am noticing that if i run at 2k RPM, engine is more susceptible to dying. Symptoms are definitely air in fuel line. Engine starts sputtering, and dies within a minute. If i throttle back when i first hear it , sputtering stops and I can get away without engine dying. It happened 3 times in the last 2 years. And each time if i bleed it, it starts right up.

The fact that after you bleed the system it starts right back up tells me it is an air in fuel problem and nothing to do with gunk buildup in lines or filters.

I had the exact same problem on a Perkins diesel several years ago. I inspected, cleaned, and re-tightened every fuel line connection between the tank and injectors and the problem went away.

[shakey doug]

Remove lift pump lid and clean filter screen.