Motor starts - runs but won't restart after shutting off except when one tank is used

[studioq]

I've had this issue now with 3 different fuel tanks. 1998 Johnson 50 SPL carbed - running on mix gas only.

With the old metal, 6-gallon OMC fuel tank - the motor can be started, stopped and restarted without any issue. It has yet to cause any trouble.
When I switch to my reserve tank - a 6-gallon plastic OMC tank and run for a while and then shut off the motor - it is very hard to restart - almost as if the motor has lost prime and can't be primed even if the fuel bulb is pumped. Strange thing is - raw oil is discharged into the water after consecutive attempts to restart. After a while of cranking and pumping the bulb - cranking some more - the engine comes to life once the old metal tank has been put back on.

So I went and bought a new 12 gallon tank that is the new style of EPA approved, vent-less blah, blah, blah - and it comes with its own special hose with a pressure regulator to prevent engine flooding when the new vent-less tank becomes pressurized by heat, etc.

I put this tank on - the hose is a little difficult to prime (get the bulb to firm up) - but then the motor starts and runs for hours without issue. Once you shut the motor off it becomes impossible to get the bulb to prime again and you have to crank forever and it won't start until you put the old metal tank on again. And it does discharge oil during the cranking process - but not after the motor kicks over and begins to burn.

Kind of at a loss with this one..

 

[sutor623]

Sounds frustrating, to say the least. You say ventless, but all modern fuel tanks need vents to function. The old pressure style tanks didn't have vents, you had to pop the cap to vent them.

Honestly, it sounds to me like you are flooding the engine out. But more importantly, I think you are fouling out your spark plugs on long runs. Does your motor still have the thermostat installed? Does the primer bulb get hard when priming? If not then you could have an issue with the carb needles seating, allowing more fuel than necessary to go onto the carb.

 

[sutor623]

also, how old is your primer bulb?

 

[oldboat1]

could be the new connectors. Try substituting the connector from the metal tank.

 

[studioq]

Sounds frustrating, to say the least. You say ventless, but all modern fuel tanks need vents to function. The old pressure style tanks didn't have vents, you had to pop the cap to vent them.

Vent-less in the sense that it doesn't vent raw gas fumes out into the atmosphere - but does allow air in. The tanks are designed to expand and swell up under pressure..

Honestly, it sounds to me like you are flooding the engine out.

Me too - otherwise - why would there be all of the excess raw oil floating in the water after multiple crank attempts?

But more importantly, I think you are fouling out your spark plugs on long runs.

I have yet to witness this.. Old plugs looked great and I just put new ones in - but I can certainly give it a look. The motor is very responsive to the throttle and doesn't indicate any fouled conditions.

Does your motor still have the thermostat installed?

If it's on the rear of the powerhead and has a single wire coming from it - then yes..

Does the primer bulb get hard when priming?

Only when initially starting the motor cold. Once the motor has been run it becomes harder to prime. This condition only exists on the two plastic tanks - not on the old metal one..

If not then you could have an issue with the carb needles seating, allowing more fuel than necessary to go onto the carb.

Entirely possible.. I have noticed on a few outing with the metal tank attached that I have forgotten to open the cap - so a good amount of back pressure has developed - possibly sucking the fuel back in once the motor is stopped.. That could be why it doesn't happen on that tank.. I know I haven't always done this..

But what I do know is that with the one metal tank - I can start and stop the motor at will without any issue..

 

[racerone]

The old metal tanks had 2 wee pins.-----When the hose is attached these 2 pins are pushed in.----One is a valve to let gas out.---The other is a valve to let air in.-----No hose attached and cap tight the tank is sealed.

 

[OldLRRP]

The new EPA tanks swell and force fuel into the engine causing the engine to flood. The fuel pump is designed to suck fuel from the tank not have it forced from the tank. I purchased one of these: http://www.attwoodmarine.com/prevent...l-demand-valve
This works but it takes a couple or more pulls to get it started. This is how I determine the state of tune for my outboard. I will replace the hose and remove the valve. I will just leave the fill cap, on my tank, loose so it will vent.
Before purchasing the new tank my engine would start on the first pull if the engine was still warm.

 

[studioq]

The old metal tanks had 2 wee pins.-----When the hose is attached these 2 pins are pushed in.----One is a valve to let gas out.---The other is a valve to let air in.-----No hose attached and cap tight the tank is sealed.

Yes - and the other two tanks do not have those pins... Another head scratcher...

 

[oldboat1]

I've had similar problems -- find that releasing pressure between the bulb and the engine connector allows normal operation with reconnection. It's neither environmentally nor user friendly, but push the valve in with a small screwdriver or similar, releasing fuel into a container (won't be a lot, but released with some force -- keep it away from your face). Additionally, the new O-rings in the connectors can be tight, so sometimes hard to seat fully into place.

Edit: Thinking about it, will stand by that temporary "fix" as it seems to work -- but not sure it's relieving pressure or maybe an air lock(?). I'll just suggest it has worked for me, for whatever reasons.

 

[studioq]

I purchased one of these: http://www.attwoodmarine.com/prevent...l-demand-valve
This works but it takes a couple or more pulls to get it started. .

I bought one with the new tank as well and thus far I'm having issues getting it to prime..

 

[studioq]

I returned the new hose and got another just like it.. I still found it difficult to prime - as in getting the bulb to firm up - and the engine had to crank over a few times to get a steady idle.. But once it was up and idling it ran for the rest of the day without issue. I did not however turn off the motor in the middle of my run as we put 30 miles on her that day. Later on during wash-down I turned the key to start the motor on muffs and it fired up instantly. I had at that point vented the 12 gallon tank wanting to see how much fuel remained after such a long day.(about 1.2 gallons).

It's going to take some experimentation to figure out if the new hose is making the difference. Right now it's fishing season and I have little desire to spend my day in the bay stopping and starting the motor to try to figure out what's going on.. I'll report back here if I figure anything out..

 

[studioq]

Went out all day for another 30+ miles.. Motor stopped and started all day without issue.. The new hose primes - but doesn't seem to firm up like the old style bulbs.That being said - I did install a new inline fuel filter in the motor. Not sure if it made any difference.. But it seems that the flooding issue has been corrected by replacing the two items. The good news is I was able to go all that distance and only use about 10 gallons. - averaging about 20 mph (GPS) during the long runs..