Random fuel issue

[DeaconBlues]

1997 Larson 186lxi Volvo Penta 3.0 SX MLKD

So my newest problem has arrived. The boat will be running great all day and then without rhyme or reason, periodically my boat fails to start/stay running. The engine turns over good, plenty of fire, but its like its not getting fuel, or just gets a little sip only. I either get nothing but crank and spark, or I get one big Vroom and it dies immediately. Then again without ryhme or reason it seems to work itself out, and runs great again for the rest of the day or longer before it acts up.

Yesterday it ran awesome for instance all day. Plenty of starts and stops, different speeds, etc. Stopped at a place for a bite, came back out, and it did the above. 10 or 15 minutes of messing with it, and it just decides to run again, and no more issues the rest of the day?

I know you guys are going to tell me to go through the fuel system check I have read about here. Problem is, this is very random, and probably wont be happening when I test it. Also, i am supposed to be taking a bday group out today and would really like a problem free day.

Thanks in advance,
Joe

 

[ENSIGN]

Re: Random fuel issue

Start by checking all connections at the engine, key switch,battery and lanyard.start it up and do a wiggle test on all the connections.Check the gas and make sure there's no water in it.At this time everythings just a guess,you would be better off if it did'nt start.If you insist on taking it out tell someone where you're going.

 

[DeaconBlues]

Re: Random fuel issue

It's not electrical. Been there done that. That system has been repaired/replaced end to end. Its definitely fuel.

I've read a lot about vapor lock on here, and it sounds like that. I went in to eat, engine was hot, engine compartment was hot, 95 degrees, boat in the sun, come out and it won't start. Even the light pole thing back there was warm to the touch and its a cpl feet away from the motor. Leave the cover open for a bit, and what do you know, it works itself out.

 

[NHGuy]

Re: Random fuel issue

If you want to check for junk in your fuel. Run your fuel down to empty, maybe carry a little jug with enough fuel to splash for the ride home. Then when you get home disconnect the battery.

Remove the spin on fuel water separator and pour it's contents out into a clear glass jar. Cover & set aside (in shade). If it later separates into to distinct layers you have water in your fuel.
Remove the fuel sender, take a good flashlight and look in the tank for debris. Also remove the anti siphon valve and check for junk in it and in the pickup tube where it threads in. Make sure the anti siphon valve check ball moves smoothly and it's spring has some life.
If you see any debris in the tank, and I mean any, it's worth the effort to remove it. I'd be anal enough that I'd remove my tank and tip it over.

If you suspect vapor lock, why? Why now and not before? Has the boat gone to a different environment? You may be able to fight vapor lock with use of your blower and by opening your engine cover.

What about the carburetor inlet fuel screen? They need a line wrench to open correctly. A line wrench is a box wrench with one of it's 6 sides open to allow the wrench over the metal line. Sometimes you can open them with a quality open end wrench though. When you open the fixture have a rag there to catch the gas that drops out.

Another quick easy check is to the carburetor hold downs where it is attached to the intake. Put a socket or wrench on them and make sure they are snug. Don't smash em with torque, just check for looseness in a crossing pattern.

 

[DeaconBlues]

Re: Random fuel issue

Thanks for the tips. I checked the filter at the carb and its fine. THe other things you are suggesting are easier said than done. There is only a very small (maybe 12" by 6") opening to where the tank is. I can hardly get my head in front of it to see anything. I think I am going to go back out today and investigate vapor lock before I do anything else.

Yes, there are changing conditions that make me suspect vapor lock
1. Recently replaced thermostat and sender and the boats operating temperature is more like 175-180 these days, use to be about 160. Not certain why, but its hotter for sure.
2. The two times I have been out and had this issue, it was 95 degrees outside (well over 100 in the sun).
3. Both times I parked at a crowded dock in the sun with no breeze or anything.

I am going to try letting the boat Idle for a couple of minutes with the blower on and doghouse open before shutting it down today and see if I have any issues firing it back later.

 

[Rocky_Road]

Re: Random fuel issue

From an article:

ETHANOL AND VAPOR LOCK

Short description:
When the engine compartment becomes hot either by climate or idling, and you use ethanol-blend gasoline it can cause excessive vapors in your fuel line and starve the engine of fuel. The engine can run poorly or stop and will not run until the fuel condenses.

THE PROBLEMS

Vapor Lock

Fuel containing 10% ethanol is called E10. If you have ethanol in your gas, you run the risk of creating vapor lock because of excess vapors.

Ethanol ?boils? at 87?F (at normal atmospheric pressure) and turns from a liquid to a gaseous state. By comparison, most automobiles have their fuel pump in the gas tank, so the whole system remains under pressure unlike boats whose fuel tanks are vented. In a closed system, the higher pressure raises the flash point of the ethanol reducing the amount of vapor that is produced. In addition, most automobile fuel lines are outside of the vehicle allowing them to stay cooler.

Since most boat fuel lines are in the enclosed space (sometimes even insulated) of the engine compartment, normal ventilation will not cool the fuel significantly enough to avoid the potential problems of vapor lock. Furthermore, since the fuel pump in a boat is mounted on the engine (versus a car where the pump resides in the tank) the action of the pump can reduce pressure in the tank to below atmospheric pressure and further reduce the flash point.

Boat engineers are aware of this problem and are reducing the likelihood of this occurring by reducing the suction required by the fuel pump, minimizing hose fittings and bends, and including a quality anti-siphon valve. In existing boats, fuel lines and filters should be kept as low in the boat as possible and tank vents should be cleaned and open.

Heat Soak

Most boats have ?forced? ventilation. Air moves through the engine compartment when the boat moves forward. Heat soak happens after you have been at high RPM and then stop or drift on idle for a while. Because of heat soak the engine compartment will rise to a point where the ethanol will boil

THE CURE

To prevent vapor lock (i.e. boiling ethanol):

1. Make sure the engine compartment has adequate ventilation.
2. Relocate fuel lines to be low in the bilge. (The bilge is cooler because it is in direct contact with the water.)
3. Monitor the engine compartment temperature.
4. Add (or turn on) engine room blowers.
5. Keep the tank vent clean and unobstructed.

I have read other places that using a higher octane rating can be of some help...I use 97 (instead of regular) and Marine Sta-Bil (1 ounce/ 10 gallons) and my restarting has improved. Living in Florida, heat-soak is always an issue.

Happy boating!

 

[DeaconBlues]

Re: Random fuel issue

Great Info and Thank You!!!

I had the issue again today. Ran good at idle and WOT for over an hour. Stopped and anchored at a sandbar. Stayed about an hour and no start. Waited it out with the blower on and doghouse open for about 30 minutes. Sprayed a bit of starter stuff in the carb and it fired and ran fine the rest of the day???

Still thinking vapor lock, however my girlfriend had a wise observation... smelling a lot of gas back there when it happened. If it were flooded it would also get better after a bit of time and start with some starting spray right?? So what would cause it to flood after shutting it off....

HELP PLEASE.. this boat has been a 5k nightmare so far. Problem after problem... I feel like if I sort this out, I am gtg..

 

[Rocky_Road]

Re: Random fuel issue

Great Info and Thank You!!!

I had the issue again today. Ran good at idle and WOT for over an hour. Stopped and anchored at a sandbar. Stayed about an hour and no start. Waited it out with the blower on and doghouse open for about 30 minutes. Sprayed a bit of starter stuff in the carb and it fired and ran fine the rest of the day???

Still thinking vapor lock, however my girlfriend had a wise observation... smelling a lot of gas back there when it happened. If it were flooded it would also get better after a bit of time and start with some starting spray right?? So what would cause it to flood after shutting it off....

HELP PLEASE.. this boat has been a 5k nightmare so far. Problem after problem... I feel like if I sort this out, I am gtg..

You might want to try your next restart without any throttle pumping whatsoever...you may be flooding a warm engine.

Keep us informed!

 

[DeaconBlues]

Re: Random fuel issue

No throttle pumping at all today, I considered that. If its flooded, then it was flooded before I even reached for the key.

 

[NHGuy]

Re: Random fuel issue

Some carb gurus will be along in a while. You may be on to something. Such as stuck float or such. I haven't enough carb repair skills to comment.

 

[Alpheus]

Re: Random fuel issue

What kind of carb are you runnin'? If excessive fuel smell is present it very well could be a carb issue ie floats,well plugs,etc., or vapor lock. Gas/ethanol in a vaporous form smells just like...gas.

 

[DeaconBlues]

Re: Random fuel issue

Holly 2 Barrell.

Good point, so I guess I would smell gas either way. Well I figure I have two plans of attack here and really should probably just do both and cover my bases.

1. Rebuild the carb.
2. Figure out how to get my eyes and hands around the tank and check the filter and anti-psyphon valve, etc.

Its just such close quarters down there, I'm not certain how to do that and the boat is probably half full of fuel right now too.