engine does not start again when hot !

[boayan]

sorry for my english
thank you for your time any ideas about this problem ?
engine starts and works as usual for, let say half hour, then we stop to sail, after a while engine starts but stop after one minute like with a fuel problem or like if air in system, of course we checked for leaks, changed all filters and reprime the system, but when hot it does not want to work . next day, starting without problem and so on . any ideas ? thank you

[Chief Engineer]

Need to know what type of engine gas or diesel

if diesel does it have glow plugs

[boayan]

thanks for your interest
diesel engine, very old yanmar 40 HP(3LM), no glow plug

[Chesapeake]

Have you checked to see that the fuel tank venting is working properly ? If not you could build up a vacuum that will restrict fuel flow to the engine. Over time the vacuum will subside and the engine will run again for a while. Just something else to look into. Seems that engines have more problems than sails ;-)

[NCboatrx]

I agree with Chesapeake. Check the tank vent system first. If that is not at fault, you may have any one of the following,
1) a partially blocked fuel pick up in the tank
2) valves (tappets) may be adjusted too tight which can cause lower compression when the engine is hot
3) a weak fuel lift pump.
Please let us know how you get on.
Stan

[DeepFrz]

Running for a minute means, to me, that the motor started just fine but then died. Is this assumption correct? If so then I feel that there is some sort of fuel blockage and Chesapeake's suggestion that the vent may be blocked is certainly a good possibility.

Something else to check is your fuel pickup tube. Make sure that there is no screen on the end that is at the bottom of the tank. If there is a screen, remove it and throw it away.

Check that the fuel line is clear. With the pickup tube out of the tank and the line disconnected at the filter make sure that you can pass a wire through the tubing and that it comes out clean.

Check that the bottom of your tank is clean with no buildup of sludge.

I once had a situation where the motor would start but would not run more than about 15 to 30 seconds. Turned out to be a clump of sludge lodged in the fuel line.

[The Mons]

I had a generator that did this.

One of the linkages associated with the fuel cut off solenoid was a bit tight. When it got heated and expanded from the engine running, it would freeze the the linkage so that the engine could not start. When the engine cooled sufficiently, the linkage was once again loose enough to operate correctly.

You might have an analagous situation.

[Chief Engineer]

The most common cause I have seen that cause this is water backflow into the exhaust line while under sail. This causes backpressure when you try to start the engine....Normal cranking of the engine will not expel this water. Next time it happens, try draining the muffler

[jrd22]

Sounds like an air leak to me that shows up when things get warmed up (mechanical fuel pump maybe?). It starts and runs OK for half an hour when cold, but then starts and only runs for about one minute later. Does it start again after it stops the second time?Either that or an electric stop solenoid having problems when warm if it is equipped with one.

[Chief Engineer]

I looked at a picture of your vessel from another post.

If this has been a recurring problem, I would look at the "run" the exhaust line makes from the engine to the outlet.

I have seen many a sailboat, that has some age on it, and when exhaust hoses were replaced, the "loop" was left out. This was done for unknown reasons. "Thought the loop was extra hose and previous owner didn't want to cut it...who knows.

On the other post there was talk of the stern squatting. Could the exhaust outlet be under water at a certain point of sail and allow the water in?

[anathema]

I'm assuming you've checked the obvious gauges such as the temp gauge? I had a similar problem on my old 17 footer (gas)..I had a coolant leak and did not know it..engine would run for about 15 mins then stall from heat..float around for a while and it would run again..then stall after about a minute or two..same symptoms?