To much fuel pressure ?

[elpaso]

1989 twin Merc 230 HP IOs<br /><br />Port engine ran good but carb. leaked. Rebuilt,<br />replaced fuel separator-filter. Clean, no water.<br />Installed carb. runs good still leaked.<br /><br />Switched carbs. same problem on Port.<br />Neither carb. leaks on SB. <br />Both carbs. leak on Port.<br /><br />Can an old 1989 mechanical fuel punp have<br />to much pressure ?

 

[WillyBWright]

Re: To much fuel pressure ?

I wouldn't think so. Could the overflow gas be coming out of the fuel pump? Marine mechanical fuel pumps have a hose leading from a small fitting on the pump shell to the throat of the carb. That's just in case the diaphragm springs a leak. That way the leaked gas goes into the motor and not into the bilge. That hose should be greenish-yellow in color. It should always be empty.

 

[elpaso]

Re: To much fuel pressure ?

I have the overflow tube from the fuel pump off.<br />and stiking in a plastic bottle. I see nothing.<br /><br />Thank you for an idea. I have no idea whats<br />going on. I would buy a pressure tester,<br />but do not really know what I need. Or just change the pump and cross my fingers.

 

[BRIAN03]

Re: To much fuel pressure ?

I've seen it befor. Does it have an electric low pressure fuel pump? If it does the problem is in the electric fuel pump. You can switch fuel pumps to verify. It seems the pressure regulator in the fuel pump doesnt work.

 

[elpaso]

Re: To much fuel pressure ?

The engines are 350 Chevys with mechinacial<br />fuel pumps no electric pumps involved.<br /><br />Original pumps with 740 hours.<br />Question is can an old pump increase pressure-<br />not decress with age as you would expect.

 

[BRIAN03]

Re: To much fuel pressure ?

I've never heard of that on a mechanical fuel pump. I think you need to install a fuel pressure guage in the fuel line. If you do have fuel pressure higher than 6 psi there is a problem.

 

[Squirterguy]

Re: To much fuel pressure ?

Mechanical Fuel pumps are spring driven, thus is why they loose pressure after a time. Buy an inexpensive vaccumme / fuel pressure gauge and tee it into the fuel line. You should get around 8PSI, much more is bad on float seats. The problem being engine specific though IS weird. Does your fuel pump have 3 connections?? (from tank, to carb, to tank (return)) If so, there COULD be a by-pass valve sticking and overpressuring the float needle seal. Hope this helped. I'm out of ideas.

 

[BRIAN03]

Re: To much fuel pressure ?

I have never seen any marine mechanical fuel pump more than 6 psi. I have check many pumps over the years. You can buy a male/female t with a schrader valve built in to check fuel pressure.

 

[Bondo]

Re: To much fuel pressure ?

I Agree with BRIAN03, 6psi is the Upper Limit of Ideal......<br />Unless you're running a Fire Breathing Monster like JetAaron..... <br />But,Even Then, at Idle I think 8psi Could Be a Problem.... <br />My Merc. Manual lists the window as 3 to 7psi......

 

[Squirterguy]

Re: To much fuel pressure ?

Thx for the compliment bondo. hahaha<br />If I recall correctly, my running window is 5 to 7 psi, due primarally to my N2O system, circa 1979. Sure don't want THAT to suddenly lean out at full scream. Holed pistons suk. I just had to replace my fuel pump last summer due to insufficient flow at WOT, simple starvation, no Nitrous. I still can't think of any flood/leak reasons though that haven't been explored. Good info guys.

 

[akriverrat]

Re: To much fuel pressure ?

o.k.-no one else will ask so i must...just where are the carbs leaking?