Primer Bulb Woes on my 9.9 Merc.

[Sock Puppet]

OK, so this is a bit strange. 2009 Mercury 4-stroke 9.9. Bought the motor used last year, and this is the first time out. Motor is seriously like new. I changed the engine and lower unit oil, cleaned the plugs, and gave it a good inspection. I've had it running a total of at least an hour before taking it out. Brand new Attwood 6 gallon tank. Brand new fuel line. New fuel connector at motor. Tank sits in the aft locker on a shelf. Fuel line runs up about 10", 3' horizontally (including the bulb), through a barbed bulkhead fitting, 16" downward to the motor.

Had to motor for about an hour on Friday, and it ran perfectly. Started and stopped about 4 times when needed without issue.

Saturday we had to motor for about 45 minutes or so, and she would try to die every few minutes. Would give the bulb a few slow squeezes and off she would go.

Same story on Sunday during 30 minutes or so of motoring.

Inspection of the hose/fittings netted no visible issues. All hose clamps are tight, connectors were solid with no leaks. Plenty of fuel in the tank, and the line inside the tank appears to be fine.

Were the installation at fault, I would think problems would have popped up on Friday.

Input is appreciated.

 

[Joe]

did you open the vent on the tank?

 

[Ron20324]

did you open the vent on the tank?

And is the vent itself clogged up?

 

[kloudie1]

Air leak (very small) into the barbed bulkhead fitting? Air leak at the tank end quick disconnect fitting either hose or sealing ring inside fitting. ?

 

[Sock Puppet]

I used this tank, which has no manual vent: http://www.iboats.com/6-Gallon-Portable-Fuel-Tank-with-o-Gauge-Attwood/dm/view_id.1084061

I will recheck all hose fittings and the connectors to see if I can find any issues. Thank you for the suggestions!

 

[Stan Breaux]

Maybe you should manually vent the tank

I wonder if their ventless design is as good as they think it is.

Maybe you could try loosening the filler cap and see if it keeps running.

Just a thought.

 

[Sock Puppet]

I wonder if their ventless design is as good as they think it is.

Maybe you could try loosening the filler cap and see if it keeps running.

Just a thought.

This crossed my mind, but I'm thrown off by the lack of problems on day 1. I did not have the tank full, only put 3 gallons in. Maybe there is an issue with the pick-up tube inside the tank that I can't see, and the lower fuel level after day 1 exposed it.

 

[John T1594]

Primer bulb

This may be a long shot but I had a similar problem with a primer bulb. I had installed an outboard style primer bulb on the fuel line feeding the primary filter on my Yanmar 2QM15 diesel engine (1980 H30). It simplified filling and bleeding the fuel filter. After a few years of service, the engine started to experience the problems you described - it would start and run just fine for various amounts of time and then just quit. A few squeezes on the bulb and off we would go again - until next time. I got stuck out on the water one time and noted that I could not get fuel to flow when I squeezed the bulb. I removed and bypassed the bulb and the problem went away. It turns out that the little one-way valve inside of the primer bulb came loose and would float around, eventually blocking the fuel flow. When I squeezed the bulb the blockage would be removed until it happed again.

 

[RichH]

The vent on many of the newer remote tanks are once-way 'mitral valve' types which easily stick and do not allow proper venting (to atmosphere). Since this valve is a one way valve when the tank becomes HOT it also will easily overpressurize the tank and screw up the fuel mixture and/plus readily deform the the needle control valve inside the carb bowl (the constant deformation of the deformable float valve needle tip lowers the float and that changes the fuel mix ratio !!!!).

Rx: Either remove this stupid valve or loosen the cap when running the OB. The valve is probably a 'CARB' requirement ... the same dangerous stupidity you find on most portable gasoline containers these days.

 

[markwbird]

Ethanol

Sounds very similar to issues that I have had all due to ethanol in the fuel. The ethanol very quickly dissolves the rubber in the fuel line and clogs up the carb. Engine runs about an hour and quits. Disassemble and clean carb, runs another hour. So, finally I did another carb cleaning and, this time, installed an inline filter just before the connection to the engine. Now I can get a whole season between carb cleanings. Also, very important to run engine dry at the end of the day as ethanol attracts water which, when left in the carb, will corrode.

 

[thinwater]

^^ Additives will stop the corrosion issue (Biobor EB, Stabil Ethanol, Sea Foam).

Adding a filter is always good. It doesn't take much, whether from the can or the system. Cheap and easy to change. I seem to clog one ~ every other season on the dingy. I use cheap lawn mower filters from Advance Auto. They are more than big enough for the tender.

As for running the carb out of gas, that is urban legend. The manual is talking about storage, not regular operation. Since the carb will not be completely MT, that only promises that whatever remains will dry. I have not done that in 20 years, and my motors are old (twins on the boat and a dingy). I DO use anti-corrosion additives, keep the tank full, and close the vent religiously where applicable. If I can't close the vent, there is a vent drier.

No problems after starting this program.

 

[Sock Puppet]

Gents, thanks again for all of the great advice. I haven't had time to work on it yet, and probably won't get out this weekend, but will take all of this into consideration. I really appreciate the help!

 

[Brian D]

I have often had similar problems in the past. But I read that if one keeps the bulb vertical with the arrow pointed up there shouldn't be any problems. Since I have started doing that, I have had zero issues.

I guess by keeping it pointed up the weight of the fuel in the bulb keeps the one-way valve closed to prevent fuel from heading back in the the tank. That is just a guess as I really don't know, but I can say that I do keep the bulb vertical with the arrow pointing up.