Air in primer pump bowl
03-10-2024, (Subject: Air in primer pump bowl ) 
Post: #1
Air in primer pump bowl
2012 prostar with maxxforce 13 is getting a lot of air bubbles in the primer pump bowl.
I ran a clear line from the davco filter to the primer pump and I see a lot of air bubbles in the line.
Does anyone have a fuel line schematic? I'm going to pick up some new fittings tommorow to make up a test line but I need to know what lines go where.
The davco filter has inlet on right outlet on left and what appears to be 2 return lines lower left.
03-11-2024, (Subject: Air in primer pump bowl ) 
Post: #2
RE: Air in primer pump bowl
Just some random guessing...

Davco or other fuel filter seals allowed to suck air?.

.. or maybe a bad fitting on the suction side lines?.

.. Or maybe cracked pick-up tube in the fuel tank?.

Sometimes someone has to resort to extreme measures to find suction side leaks when all other options have been exhausted, and no one can find it ....

-- Blocking off the one side bleeder hose .. and using the other bleeder circuit to pressurize the fuel tanks up to to 5 psi, regulated air pressure (BUT NO HIGHER), and letting it sit for a couple-three hours + wiggling lines around gently at their fittings to see if a pickup line drips, is one way to find suction side hose or filter housing leaks.

CAUTION !!!!!!!! .. NEVER, EVER, EVER, REMOVE THE FUEL TANK FILL CAPS WHILE THE TANKS ARE UNDER ANY KIND OF POSITIVE PRESSURE!!!>. It only takes about 1 or 2 psi pressure for there to be enough force built up behind them to break your wrist or put someone in the hospital for attempting to unscrew them. The pressure at the cap is amplified greatly by the volume of the tank itself.

After / Aside from leak testing the suction side piping and filters ...

-- Pressurizing the tanks like this and having the fuel line(s) going into the bottom of a bucket to see if there is air getting in them is also how to check if you have cracked pick-up tube(s) in a tank as well. A cracked pick-up tube at the top of a fuel tank can be otherwise difficult to find.

User's Signature: ->: What I post is just my own thoughts and Opinions! --- I AM Full Of S__T!.
 Thanks given by: hookliftpete
03-21-2024, (Subject: Air in primer pump bowl ) 
Post: #3
RE: Air in primer pump bowl
I ran a clear test line from davco input side to my fuel tank and there were no bubbles in that line but still hab bubbles from davco to primer pump. I replaced the davco 382. Made no difference. At this point I'm sure the lines running from the tanks to the davco are good. The 2 lines at the bottom of the davco have me stumped as I don't know what they are for. Does anybody have a fuel system schematic ?

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