View Full Version : 496 HO Fuel Pump

06-29-2009, 10:11 AM
Anyone have eny problems with the fuel pump on a 496 HO? I was out yesterday and the engine died on me almost like it ran out of gas, but I had 1/4 tank. I figured maybe it sucked up some stuff off the bottom of the tank or something so I changed the fuel filter. Still wouldn't restart after the filter change. I pulled the filter back out after cranking it for a bit and the fuel bowl barely had any fuel in it. Ended up getting towed in seeing that it was getting late.

Knot 4 Me
06-29-2009, 10:24 AM
Do you have an in-line filter (automotive metal canister type) between the tank and booster pump? If so, it could be clogged. I removed mine. Do you hear both pumps energizing when you turn the key on? Edit: Nevermind on the in-line filter...you have the newer fuel system setup.

06-29-2009, 10:39 AM
Replace the inline canister filter too. I destroyed 2 f/w separators, 2 inline filters, and 2 fuel pumps with crappy gas a couple years ago.

06-29-2009, 11:11 AM
It just so happens that I did have some fuel pump issues with my (departed) 496's. And I have a new fuel pump with the cooler assembly for sale., as well as a HP pump (new ) with no cooler part.
Some time back I had some fuel issues and I got stuck with the new pumps. It was my LP pump that had some dirt in it.

07-04-2009, 04:35 PM
The Mercruiser CoolFuel 3 type pump and cooler/filter assys. used on 2004 and new Merc engines require that you refill the fuel filter canister resivior area with fuel before restarting. the empty chamber will not allow the primary pump to prime and so it cannot pick up prime from the tank/line supply.
Also all boaters who have this CoolFuel 3 system remember to check the filter and water seperator filter disk (White plastic)underneath for debris and contamination. If they are clogged or have water fouling they tend to turn
a dark gray or black and should be replaced or the lean out of fuel flow can drop fuel pressure and severly damage the engine.

I liked the old spin on better only because they were obvious and got changed more often.

If you are in a bind for a replacement filter or water seperator disk from Merc, you can use a carb cleaner or spray alcohol cleaner and clean these from the inside out and usually remove enough dirt and clogging material to get you back home or to finish your weekend, but be careful not to run the engine hard and burn a bunch of pistons.

Raylar just had two 496's in the shop that suffered catistrophic piston and engine failure from a lean burn caused by lack of filter replacement and service!! The resulting fuel pressure loss can destroy and engine quickly!!

Best Regards,
Ray @ Raylar

07-05-2009, 12:29 PM
On my boat (Formula fastech) when the fuel tank gets to around 1/4 tank it will starve for fuel on plane or getting on plane. When the fuel gets to the wrong side of the tank pick up it will get air in the line. Then it will take forever to get restarted . Kind of like a vapor lock. I no longer let it get less than 1/2 tank of gas before a fill up. Just a thought...Jeff Wurl