Engine Won't Idle Under Load

[Chief Engineer]

I have seen filters get sucked in. Maybe some pieces of foam lodged in the valves.

Or melted and fouled the injector tips.

[Northeaster]

re: the weeping fuel leaks. Be careful not to tighten the fuel banjo bolts and copper washers too much, or you may strip expensive parts like the manual fuel pump ( which the bolts thread into and may be made from easily stripped aluminum!!).

Certainly, don't do as I did and try to tighten the bolts without replacing the washers with new ones, or annealing (heating/cooling) the old ones, so they are ready to be crushed again.

[meyermm]

Is there anything else you failed to mention? second engine dying and water in fuel of number one was not mentioned originally. I think the $170 for fuel filters will be minor by the time these engines are running correctly.

[SkiprJohn]

Are the vents to the fuel tanks clear? Sounds like a fuel starvation problem to me but it could be any of the other problems listed too.
regards,

[osirissail]

On the alternator theme, although there are also plenty of other valid reasons for stalling at idle - the better alternator regulators come with a "delayed on" function that does not allow the alternator to engage until "x"minutes after starting and will drop the alternator "off" below a certain rpm level.

[Chief Engineer]

If there is an obstruction in the fuel line prior to the lift pump....you can suck air in thru the gaskets on a racor or any of the hose clamped joints.

Another, although rare occurrence, is that the pickup tube inside the tank has a crack or pinhole in it....when the fuel gets below that air gets in.....in a similar vein, some pickup tubes have a fine screen on the bottom which clogs and the resulting vacuum can cause air to get in anywhere on the suction side.

[Tiki 38']

An update on these engines. Firstly, thanks to everyone who took an interest. It was great having total strangers pitch in and help me out. Lately I have read Nigel Calder's book on small diesel engines in boats. I wish I had read this before I had left the wharf! Truly helpful and interesting. Chief, Nigels book showed me what a properly designed fuel tank is supposed to look like! Hmmm, so many things in my boat were not quite right. The engine that will not idle under load, still will not. Strangely, it will idle in gear while it is cold, but after it has fully warmed up, it dies at idle in gear, or using the electric capstan. Nigel's book is pointing towards poor fuel injection. I'm leaning towards an air leak in the fuel line. Mabee both... However, I have discovered that it runs much better with the engine cover removed. It was staving for air at normal operating speeds. The other engine, I have done serious damage to. I ran it up to full power with a dirty air filter element. Bad idea! It sucked so hard, the filter disintergrated and all the dirt it had trapped ended up going thru anyway, and then some. Result, rings shot, and no compression. Thanks to the book, I can get it to run badly on two of the three cylinders! Now thats a huge improvement in my mechanical skills! :-)

[anjou]

So many answers, here is one more.
If its a recent development, check the Fuel filters, Air filter and no load idling revs.