Engine Dies...

[drh1965]

I've got a new problem... I have an idea what it might be but wanted to get some expert insight.

I can run the engine for around 15 minutes or so, when suddenly, the RPM drops and it dies seconds later. Usually, it'll start right back up in a few seconds. Sometimes I go through a fuel system bleed and then it starts.

Is this caused by air getting in to the fuel system? That seems like the obvious problem.

Thanks!

[Pblais]

Air in the lines is a good bet. You can get bubbles of air that get trapped in the line too. Water in the lines does the same thing but not so easy to get in there and it's usually not possible to restart. A loose clamp on a hose fitting is a good thing to check that is easy to do so check all of them.

[SkiprJohn]

Aloha Darrell,
Could be air through just a small bit of a leak in your fuel line or it could be a clog in your line which does not let enough fuel through to your injector pump. In trouble shooting it is always best to check the easiest simplist things first. Tighten all the clamps on your fuel lines and check the pickup tube in your tanks. You can change filters too if you haven't done that in awhile.
Good luck,
JohnL

[AnchorageGuy]

Sounds like an air leak but also change your fuel filters if you have not and if you have in inspection plate in the tank, check the bottom of the fuel pick up tube.

[Boracay]

We could give a more accurate guess if we had more information.

What is the engine model?
How old is the engine?
How many hours?
What is the general condition of the engine?

What recent work has been done?
When was the engine/fuel system last serviced?

What is your fuel system setup?
i.e. What is the vertical distance from the fuel level to the lift pump?
What is(are) the location(s) and type(s) of your fuel filter(s)/water separator(s)?

Is there an electric boost pump?

What type of hoses/hose clamps do you use and what is their general condition?

Do you have a vacumn gauge on the filter? It's a very handy piece of gear for troubleshooting, sometime even the silliest problems--like closed valves.

Your engine is behaving exactly as mine does if I forget to open the fuel valve, (except for the restart) so in addition to the suction air leaks, look for a clog.

[never monday]

It sounds like he's picking up a clot int the tank. When the engine dies it looses vacuum and drops the clot. Then allowing a restart.
Been sailing in rough seas lately?

[David M]

You never mentioned, have you changed the fuel filter recently? Always try the simplest things first.

[hellosailor]

If you do bleed the fuel lines, and some of those fittings use paper-thin copper "crush washers", be aware those crush washers are supposed to be replaced EVERY time you bleed the connection. They distort and CRUSH to fill and seal the imperfect joint.

Cheap by the dozen since the trip, or the shipping, usually costs more than they do. But they'll plague you and create leaks if you don't treat them like dental floss: Use once and replace!

[drh1965]

Thanks for all the replies... some interesting ideas. I'll be doing some experimenting tomorrow. I had already done all the simple things so I might try getting a section of fuel line and drawing the fuel out of a bucket. I'm leaning towards some kind of fuel tank issue (clot, pin hole in pickup, etc).

BTW, would an old fuel tank sender under-ring have any chance of being sucked up against the pickup? I would think it would be too heavy??? But, it could explain the symptoms. The problem is... I have no clue how I would get it out. I can't find it either.

Thanks!

[hellosailor]

"old fuel tank sender under-ring"
Even if it wasn't past my bedtime that would puzzle me, what do you mean? There's sometimes a gasket under the "ring" where the sender locks into the fuel tank, but that shouldn't make any difference.

I don't think nayone has outright said it, but sometimes there is a "sock" on the bottom of the fuel intake hose, down in the tank. Usually made of stiff nylon mesh. When theose get old, they can collapse and clog from crud in the tank--so the system works just great, until after some minutes the sock clogs and the fuel supply is cut off and the engine quits. IF there is a "sock" on your fuel intake, this is the time to order a new one and change it. Whatever the new one costs--you still have to get in there and pull the old one to check it, the labor is usually worth more than the part will cost you. And, if there's crud in the bottom of the tank--that's what can clog the sock, don't put a new sock in old crud.

Diesels ARE wonderfully reliable. If and only if, you understand and maintain the entire system to a very high spec.

[hugosalt]

Darrel, For what it's worth...
I had some similar problems with my fuel system that plagued me for a while.
(Yanmar 3GM 22 hp basic fuel system with Racor filter.) Motor would run no problem with boat flat. When I sailed with substanial heel (either side) Problem... Coming in at the end of the day I would start motor... would run 10-15 minutes then quit.
Had to bleed it to get it running again. Seemed like air infultrated somewhere, something loose or moved? Trouble shot the system, tightening, changing, checking, cleaning...feeling confident a thorough delibrate check out of the fuel system would trace the problem... No Luck! (Aux. tank with its own filters and fuel line into motor would run in all conditions no problem.) After I came up empty, 2 mechanics over a course of a year where brought to there knees ...alongside me! It wasn't until I changed every component of the system, except the tank(that would have been next) That it was fixed. We still don't know what the culprit was. But I have an entire
suspect fuel system as a spare!
In addition to the very good points indicated in the previous posts :
Check your vent line, sometimes little flying critters like to make nests blocking vent.
Check if screen inside P.U. tube, if you have screen check if clean. Older systems
may have had screens, newer ones I THINK??? do not. I removed mine.
Remove P.U. tube and check for hairline cracks (use magnifing glass) at upper connection caused by fuel sloshing about tank, especially if no baffles in tank.
Was told to run unused fuel return line to bottom of tank by fuel tank manufacturer,
(I didn't get why, but they thought it may make a difference!)
Hope your difficultees are not as ellusive as mine were! Good Luck!

[hugosalt]

Oh! benefits from problem...
Lots of spares...some may even be good!
Aux fuel tank installed.
Can bleed motor in the dark!

[drh1965]

Originally Posted by hellosailor

"old fuel tank sender under-ring"
Even if it wasn't past my bedtime that would puzzle me, what do you mean? There's sometimes a gasket under the "ring" where the sender locks into the fuel tank, but that shouldn't make any difference.

The under-ring is fitted inside the tank so that the screws that go through the sender have something to screw in to. The PO dropped the ring in the tank and just screwed over-sized sheet metal screws in to the plastic. I repaired that leaking mess but can't get the old ring out (can't find it).

Originally Posted by hellosailor

Diesels ARE wonderfully reliable. If and only if, you understand and maintain the entire system to a very high spec.

If you amend that statement with "you and all previous owners" I'd agree completely

[drh1965]

Originally Posted by hugosalt

Oh! benefits from problem...
Lots of spares...some may even be good!
Aux fuel tank installed.
Can bleed motor in the dark!

Ah... I'm starting to understand how you feel. Seems that's a virtue of buying an older boat

I think I've got the problem licked now... I cleaned the pickup with a wire and bled the system again. The engine ran for an hour after that. Hopefully, it was something stuck in the pickup.