92 Mercury 25 hp rebuilt - Now no fuel pressure??

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citadel1995

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May 2, 2010
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I got this motor from a friend, & it was locked up. pulled it apart and rebuilt. I have 120psi in both cylinders. I rebuilt carb & fuel pump as well. It fires up great but as soon as it runs all fuel out of carb bowl its dies. the only way to keep her running is by pumping the bulb. I've changed the lines and tank but nothing seems to help. I'm out of ideas except for getting another carb rebuild and rebuilding it again. Any ideas on what I should do or what else to check? Thanks for any advice!
 
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citadel1995

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Re: 92 Mercury 25 hp rebuilt - Now no fuel pressure??

Thanks, I did recheck pump. I pulled it apart and checked for junk blow it all off, pumped the bulb and gas shot out good, put it back together and the same thing, would only keep running if I continue to pump the fuel bulb. So I took it apart again and put the old diaphragm and gasket back on and now it'll continue to run if in gear, but if out of gear it will only keep running if I keep pumping the bulb. I did order a new set of gaskets and diaphragm and will put them on when they arrive. What else could I check? I rebuilt a Yamaha jet ski a while back and to test the carbs I ran a "pop-off" test with air to test the needle valve & spring weight but also to see if it held pressure for a few minutes and if it didn't hold pressure then the carbs needed to be rechecked for leaks around the gaskets and stuff. Is there anything similar that I can do to this carb and integrated fuel pump to test it? How could I check the vacuum or pressure that the fuel uses to pump the fuel? Thanks for any advice. I'm more confused now though since it runs when in gear but will run out of gas when in neutral.
 
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citadel1995

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Re: 92 Mercury 25 hp rebuilt - Now no fuel pressure??

OK so I'm a idiot for not paying attention when I reinstalled the Carb. The gasket that came with my rebuild kit did not have the hole punched for the engine to pressurize the fuel pump. I hole punched an opening reinstalled the carb & she runs great.
 
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oldman570

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Re: 92 Mercury 25 hp rebuilt - Now no fuel pressure??

The hole is located on the intake flange of the carb and should match up with one in the intake manifold. It is only about a 1/8" hole I believe. If the gasket between the carb and intake dose not have a hole, you can place the gasket on the intake and use a awl to punch/locate it on the gasket. then make a hole with smooth edges in the gasket. The gasket may have the needed hole already , and was not placed correctly when putting the carb back on. JMO
Oldman570
 
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Fun Times

Fun Times

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Re: 92 Mercury 25 hp rebuilt - Now no fuel pressure??

JEREMIE DAVIS said:
I'm having the same problem , can you tell me where you punched the hole ?
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Hi there JEREMIE DAVIS, Welcome to iboats.:) Please note that the chances will be very low that the OP (citadel1995) will be back online anytime soon to be able to help tell you where the hole needs to be punched since his last time online was back on March 9th, 2013 @12:01 PM.

If possible, before posting on an old thread, try checking on the last time the OP was online by clicking on his username then click on view profile to see if it's worth your time and effort to reply to someone that has not been online for some time. In this case you may want to try sending the OP a private message referencing this old thread before bringing it up out of the archives. Please see iboats announcement for more details. Announcements - Mercury & Mariner Outboards
Thanks you!
iboats Moderator team

As for locating where a hole might need to be punched out like the OP did, sounds like you'll need to remove the carb to inspect if there is an open hole someplace that is being covered by the gasket. That can be a common occurrence using aftermarket or sometimes OEM superseded part numbers. It's always best to watch for open usable holes being covered over when rebuilding carburetors.

Good luck.:)

Edit: Nice job oldman570.:)
 
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