Merc -5-7-efi-please-help-fuel-system-issue

[fotonews]

Can i test fuel system out of the engine? I took everything out, following service manual info, fuel cooler,pump,regulator,hoses from filter and hose going to carb. Its a 1998 5.7 efi, tbi. Changed a few damaged o-rings, pump energizes, regulator is dry, When i had system in the boat i disconnected fuel line going to carb. turn key to on position and no fuel came out of hose but i could hear pump energizing. is this right?

 

[alldodge]

Can i test fuel system out of the engine?

Yes, you need is 12V applied to the pump, connect a fuel line coming in and out. If you run it open the fuel should come out fast once fuel reaches the pump. Wear safety goggles and remember the high pressure pump produces at least 30 psi.

I took everything out, following service manual info, fuel cooler,pump,regulator,hoses from filter and hose going to carb. Its a 1998 5.7 efi, tbi. Changed a few damaged o-rings, pump energizes, regulator is dry, When i had system in the boat i disconnected fuel line going to carb. turn key to on position and no fuel came out of hose but i could hear pump energizing. is this right?

You should have 2 fuel pumps, a low pressure one which produces 3-7 psi and your high pressure one on the cool fuel. If you can not get fuel out the high pressure side check for a restriction in the line coming from the tank through the fuel filter.

Are both pumps turning on?

 

[thumpar]

The manual only shows one pump for this system. I know some of the earlier ones had 2 (like mine) but I don't think this one does. The manual for it is #24.

 

[fotonews]

Ok thanks guys, I got a new pump today. Tomorrow I will test old one again and if nothing will test new one and see if there is a difference. I only have one fuel pump according to manual...

 

[alldodge]

Sounds good, most times you just never can be sure without the engine serial number. Look forward to hearing results

 

[fotonews]

Well…yesterday i changed the fuel pump. Took boat for a spin and works fine. Today took boat out again, idled out the channel for about 15 min then stepped on the gas and same problem again, hesitation and i always hear an intermittent hisssssss sound like if pump is starving for fuel. Tomorrow i will order fuel pressure regulator, hopefully that will be the end of this issue.

 

[fotonews]

No Title

Hello everybody, after many months troubleshooting a fuel issue i have finally found the culprit: water in the gas tank. Yesterday i took the anti siphon valve and to my surprise i found it clogged to the max thus no gas was getting to the engine. I replaced the valve with a unrestricted barb and changed the fuel separator with one with a clear bowl and drainage. Im going to run like this until all water is out the tank. See the photos attached.
​Finally I'm enjoying my boat!!