Mercruiser fuel pump problems
 

I have a 45' wellcraft excalibur fited with 2007 mercruiser 496 ho efi's, the starboard engine is running at a fuel pressure of 80+psi, have checked the pressure regulator that is working fine, checked the vacuum and it is the same on both engines, can anyone suggest what else to try before replacing the fuel pump

How can the pressure regulator be working fine if its not regulating the pressure????

There are 2 fuel pumps. One is a low pressure pump and one is a high pressure pump. The low pressure pump may be bad.

Yeah my 525s at idle are supposed to be regulated to around 39 psi and when you pull the vacuum hose to simulate WOT they bump to 43. 80 sounds like reg is not acting like a regulator

there is screen before regulator,sets into cooler, can clog with trash blocking return. return hose could be twisted, kinked restricting regulator function.

I swopped the regulators over and they both work on the other engine

Since you're fuel pressure is as high as 80 + psi, you may be experiencing a paint delamination issue within the inside of the mercruiser gen 3 cool fuel module & top cover where the paint peels off the castings and could clog the fuel passages, high and low pressure fuel pumps, fuel regulator, and in extreme cases, the paint gets in the fuel rail and clogs the fuel injectors.

On the gen 3 modules, high fuel pressure is typically a blockage on the fuel outlet side of the top cover/regulator. On Gen 2's, it's typically on the fuel return side of the regulator, or more importantly a blockage under the regulator on both systems.

Googling (Paint inside mercruiser gen 3 cool fuel module housing and cover) will result in more info to consider.

http://clubsearay.com/showthread.php...-Module-Issue*

P.S, since you have the gen 3 cool fuel system, you do not have a screen before the fuel regulator or a fuel return hose to restrict regulator function.

Good luck with it.

Thanks for that at least it is something else to look at. The engine will idle for a while and then just run out of fuel but the tank is half full

Could be the paint peeling inside of the cell as mention above. Mercruiser had some issue's with that and IMO some fuel treatments & stabilizers could be one of the many factors making the paint peel. Some fuel additives are BS inwhich contain alcohol in some form.

You have a round 10 micron filter disc below the pull out basket make sure it is not clogged with debrie. It sits below the basket in the bottom of the fuel cool cell. It is a very important filter in the Gen III cool fuel cell. It is very easy for that filter to cause a restriction. How bad or well does this engine run ?

The engine runs ok on throttle but is a little rich, when on idle it runs for a while and then stalls and will not restart and shows no pressure at the fuel rail it is almost as if it has ran out of fuel.

I'm sure you're probably aware of this already, But just in case, i'll throw it out there. When you get your fuel pressure back to normal, you'll want to install new spark plugs.:ernaehrung004: