Hello,

I have an 2003 donzi with a 496 ho giving me some trouble. Idle rpms are fluctuating as the IAC sounds like it is contantly opening and closing (loud hiss). Fuel Pressure at the Schrader valve with key off is only 24 pounds, motor off. When I turn key to on, fuel psi spikes to 30 and drops to 24 where it generally remains, even when I start engine and romp on it. When I give it a little gas to around 1800 rpms in neutral, the engine will surge to 1800 then it will drop to around 1400 and flucuate between 1400 and 1550 rpms. At WOT I've only been able to achieve 4400 rpm when I typically get around 4900. Any ideas?

-NO alarms, no scanner codes triggered, no bad history reported on scanner. I used carb spray to search for vacuum leaks and found none. (mechanic verified this, but he also "said" fuel pressure was in spec and it clearly is not @ 24 pounds). Spark Plugs are fresh. Crank position sensor changed.

This is a 2003 engine, so fuel cooler is gen. II. I've replaced the water separator/filter, but not the inline filter before the boost pump, which I plan to do this weekend. Could a clogged in line filter (before low pressure boost pump) be the culprit or is it more likely something with the high pressure boost pump? Spec fuel pressure should be 43 psi. While I'm getting only 24psi, I'm still able to get 4300 rpms. Could problem be something else? Boat has about 200 hours on it.


posting videos of problems below.

Any help would be appreciated.

Thanks



http://www.youtube.com/watch?v=43Q104u2EJw
http://www.youtube.com/watch?v=mlkpe9TzBko
http://www.youtube.com/watch?v=07NJ8JV3kmY

Mine had the same symptoms and it was the fuel pressure regulator. Mine was a 2005 Mag HO.

Press down on the IAC see if sound goes away.I had to change mine on the water this weekend.Did not have new gasket and its leaking at gasket.May not be problem but an IAC should not make that much noise.

Pachanga,

Do you recall, which fuel pressure regulator it was? there is one on the fuel rail and I believe there is one on top of the high pressure fuel pump where the fuel cooler is located (by port engine mount)?

I just pulled my ticket. They also replaced the knock sensor. It should throw codes...but no alarm.

The Regulator kit part # is 861126A1
Knock Sensor 878187

Looks like that regulator is the one on the bottom side of the engine. I will also try that this weekend.