Offshoreonly.com - WOT problem

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Have a Volvo Penta 420DPXa 2002 190 hrs. Boat runs good at idle and just cruising at 3-3.5krpms. WOT problem happens will run 4800 rpms for about 3-5 secs. then starts to surge. drops down to 4-3.5krpm somtimes 3krpms. bring back to idle for few minutes and try again same thing. No backfire or anything like that just kind of stutters. I just change the fuel filter. Check the raw water cooling lines cooling the fuel pump--getting water from heat exchanger and passing through pump. This engine is multi port injected with coil packs per cylinder. I am thinking fuel pump maybe.

a little history before purchasing this boat-- took for a test drive two weeks before buying. Weekend before purchase previous owner ran the tank out of gas three times. Maybe burned up fuel pump?

I see a little air valve steam like a tire on the fuel pump assy and another on the fuel rail over the top of motor. Is this the spot to check for fuel pressure. if so what should it be?

Maybe I am not on a good path here any input is appreciated.

Motor starts quick, not like it is starving for fuel there.

Sounds very much like fuel starvation. As you say, check fuel pressure at WOT to confirm. Dont know how to do it on a Volvo 420 though. Likelt causes, fuel pump, fuel filter, anti siphon valve, injectors, etc

Today had Palmer Power out of Houston sea run test my rig. After diagnostics found a Faulty TPS sensor and a week of waiting for parts that was replaced it was determined to ensure everything ok that a sea run be performed. They report 20psi of fuel at WOT which is causing my problem. The are ordering the HIGH pressure side of fuel pump assy and hopefully will be sea worthy.

Quote:

Originally Posted by dualprop

they should of cked the fuel pressure while checking it out the frist time :( but thats the norm in the Marine biz,.Like mats said it could be more than the pump.may be a restriction ,anti siphon valve,but the pump should fix it ,just make sur e you have good press at wfo

I Think I Saw You Boat At Palmer Power A Few Weeks Back. Does It Have Teal And Green In It. Looked At It And Could Not Figure Out What Kind It Was. Looked Nice Though.

Quote:

Originally Posted by Strip Poker 388

Can mechanics check WOT fuel pressure being out of water?? I was thinking that they had to be in the water running to check this?

Let me know if you know of a better way so I can know in the future without having to waste time going to a from lake.

Thanks.

Quote:

Originally Posted by BY U BOY

I Think I Saw You Boat At Palmer Power A Few Weeks Back. Does It Have Teal And Green In It. Looked At It And Could Not Figure Out What Kind It Was. Looked Nice Though.

http://images.photo.walgreens.com/34...3453%3A5ot1lsi

http://images.photo.walgreens.com/34...344%3B97ot1lsi

http://images.photo.walgreens.com/34...3453%3B3ot1lsi

it is a 2001 26' commander signature. Thanks for the compliment.

You can check static and possibly idle fuel pressure with the boat out of the water. However, many of the fuel pressure related problems will not show up until you are under load. As you say in your starting post you have the problem under load at some 3000 rpm. What you want to do is to check fuel pressure exactly when you have the problems.