Flat primer bulb with df115 cutting out

[aboard whatever]

Hello all! Hope someone can give me some other ideas to look at! I am scratching my head!!!

Problem: 2007 df115hp with low hours on an old deck boat. Pump bulb goes flat after sitting app** 18 hrs. Requires priming the fuel tank to initiate a vacuum...then running the boat while "cutting out" for app** 2 miles to bleed air from engine.

I have : Replaced the high pressure fuel filter, low pressure fuel filter, the fuel/water separator filter and the primer bulb

Question: Does blowing back toward the fuel tank test the "one-way valve" in tank?

Can you have an air leak in the motor without a fuel leak?

None of the alarms are activated. It seems to be air leakage with subsequent loss of vacuum.

Any ideas??? Would like to go fishin'!

[artdf175]

How does your fuel tank vent?
Usually when the fuel bulb goes flat there is a restriction that blocks the air vent
In the situation you describe try opening the cap on the fill tube and see if you don't hear a big sucking sound
Art

[Moonlighter]

I had a similar problem a while ago on my DF115 and it was simply a dirty lot of fuel that had clogged the water separating filter. Easy fix. New element and done. Plus, it saved me the considerable time and expense of having to replace the engine-mounted filters and getting the VSR cleaned out.

It does sound more like air getting into the lines somewhere, or as Art said, the breather lines partially blocked or kinked. So check that. Blow thru the breather line back to the tank, (fuel cap off) and it should flow freely.

I heard once of a tank where the pickup tube in the tank developed a split and was sucking air once the fuel level dropped a way. Only way to check this is to pull the pickup out of the tank and inspect it.

Or possibly, as you indicate, a faulty anti-syphon valve on the tank. They can work one minute and not the next. Rather than fool around trying to test it, I would get rid of it. Not required on outboard powered boats anyway.

I'd remove that valve, they are only a PITA, you can usually unscrew the fitting from the tank, take it to the workbench and punch out the ball, spring and seat inside it and then reinstall the empty barb. Seal threads with gasket goo.

Good luck, let us know how you go.

[artdf175]

I may have misread your first request
the primer bulb is basically a one way valve
to go flat just sitting idle is a new one..
Do you have it mounted in a vertical position? top end going to the engine?
cannot believe that gravity would create enough pull (fuel pulling back to fuel tank) to collapse the bulb.
I still suspect you have a air vent situation with the fuel tank

Hello all! Hope someone can give me some other ideas to look at! I am scratching my head!!!

Problem: 2007 df115hp with low hours on an old deck boat.

Pump bulb goes flat after sitting app** 18 hrs.
**** this is hard to explain unless sucking fuel out of the tank is creating a vacuum, thereby partially collapsing the tank...****

Requires priming the fuel tank to initiate a vacuum...
****explain this one again.. there should never be a vacuum.. the fuel tank requires an open air vent so fuel flows freely****

then running the boat while "cutting out" for app** 2 miles to bleed air from engine.
***this is confusing.. there is no "bleeding air" I have ever heard of.. basically when you pump the fuel bulb you are filling up the system from the bulb all the way to the high pressure pump, that should then vent any excess air.. at that point there should be no air in the system..

**


I have : Replaced the high pressure fuel filter, low pressure fuel filter, the fuel/water separator filter and the primer bulb

Question: Does blowing back toward the fuel tank test the "one-way valve" in tank?

Can you have an air leak in the motor without a fuel leak?

None of the alarms are activated. It seems to be air leakage with subsequent loss of vacuum.

Any ideas??? Would like to go fishin'!

[aboard whatever]

artdf115..no it is not mounted vertically...

moonlighter have replaced the filter on fuel/water separator as mentioned in original post..

will pursue options mentioned by you both...its driving me crazy!!!

[artdf175]

I think you will find that the primer bulb is reccomended to be installed vertically
however, you say it flattens out after X number of hours
what procedure do you use to then get it full/back to normal shape?
and not sure what you are referring to when you say: priming the fuel tank to initiate a vacuum... explain further

[aboard whatever]

artdf175..the primer bulb is mounted vertically between the built in fuel tank and the fuel/water separator. When I can't get the bulb to prime, I take the fuel hose off the end of the bulb that feeds to the fuel/water filter and place my thumb over the end with a little gap and prime the bulb till it gets hard and replace the hose...that is what I mean when I say I have to re-prime

[aboard whatever]

artdf175..the primer bulb is mounted vertically between the built in fuel tank and the fuel/water separator. When I can't get the bulb to prime, I take the fuel hose off the end of the bulb that feeds to the fuel/water filter and place my thumb over the end with a little gap and prime the bulb till it gets hard and replace the hose...that is what I mean when I say I have to re-prime

would it make a difference if the primer bulb was mounted after the fuel/water filter? Its been set up this way since we purchased in 2011 with no issues like this

[artdf175]

you keep confusing the situation..
first ..
artdf115..no it is not mounted vertically...
then you say:
artdf175..the primer bulb is mounted vertically between the built in fuel tank and the fuel/water separator.

I believe the primer bulb, in most instances, is mounted after the filter so it pumps fuel directly to the engine..
however, in your case it probably should not make a difference.
your comment just rules out the water/fuel separator
have you checked the air vent for the fuel tank?
IF the bulb goes flat.. there is a problem in the system before fuel gets to the primer bulb. something is plugged up or being hindered by a check valve.

check the fuel tank venting and let me know what you find..
Art

[Solarman]

Do you see an arrow on the fuel bulb? Is that arrow pointing to the fuel tank, or to the separator? The arrow on the bulb should point towards the motor, the direction the fuel will flow. If bulb is flat after sitting for some hours, open the full tank fill cap and see if it sucks air?

Post us back.

[noelm007]

Don't over think this, the bulb going flat is a restriction between the bulb and the tank vent, whether that is a kinked hose, a blocked air vent, a blocked pickup inside the tank, fuel lines deteriorated internally or the bulb itself is faulty is up to you to find.

[aquamort]

I think we need some clarification here. When you say the bulb goes flat do you mean its all "sucked up" flat or do you mean like a flat tyre where you then have to pump the bulb up again to make it feel firm? This will make a huge difference in advice that you will receive.

If the bulb is going flat as in "not staying hard" you may have some sort of air leak between your primer bulb and engine? (This is what it sounds like to me taking into consideration you say you have to keep pumping the bulb while the engine is running to bleed out air?) If so check basic connections first.