2004 250 hpdi loss of power above 4400 rpm

have 04 hpdi 250 has loss of power above 4400rpm back off throttle to 4400 runs fine.give it gas above 4400 and just constant hesitation once in while it will catch run fine for few seconds then wanna die till i back off the throttle to 4400 then ia runs great.I put in new plugs and water seperator and fuel ball could it be the filter in the can or carbon build up or anything else any ideas greatly appreciated

Re: 2004 250 hpdi loss of power above 4400 rpm

HPDIs need the proper fuel pressure all through the system to run properly.
Have you checked to see if they are in spec while problem is occurring?
There is the low pressure and a high pressure so monitor both to make sure which is the problem.
If they are in spec then look at the screens in injectors

Re: 2004 250 hpdi loss of power above 4400 rpm

dont those motors have a vst chamber with a fuel pump in it similar to my 03 F115? if so I would clean the VST chamber and the screen on the bottom of the fuel pump...like 99 said you need to hook up a fuel pressure gauge and run it till it acts up and see what you got.

Re: 2004 250 hpdi loss of power above 4400 rpm

HPDIs have very high pressure on the rail( 600-700psi I think), so you may need a computer with software to monitoring what it is doing.
Maybe there are special pressure gauges for hooking up to it

Re: 2004 250 hpdi loss of power above 4400 rpm

Best not to continue running motor as it is, since a lean fuel mixture in one cylinder can overheat and fry that piston!...Good Luck!

Re: 2004 250 hpdi loss of power above 4400 rpm

99, do those motors even have a place to connect a fuel pressure gauge on the rail?

Re: 2004 250 hpdi loss of power above 4400 rpm

if it does, it is a different type off connector so no one would hook up a normal gauge is my thoughts,
but A/C gauges run up into hundreds of psi and they are just screw on with shrader valves, so I do not know for sure.
You definitely do not want high pressure fuel spraying all over the place, so a lap top would be the best

Re: 2004 250 hpdi loss of power above 4400 rpm

99yam40 said:

HPDIs need the proper fuel pressure all through the system to run properly.
Have you checked to see if they are in spec while problem is occurring?
There is the low pressure and a high pressure so monitor both to make sure which is the problem.
If they are in spec then look at the screens in injectors

Click to expand...

last week the problem happened when i went over 5000 now its happening at 4400 doesnt sound like a pump cause once and a while itll go.would low battery voltage cause it these motors are very sensitive to low voltage or the 100 dollar can filter in vst tank please help

Re: 2004 250 hpdi loss of power above 4400 rpm

unless you have the right equipment to test your motor ..there is probably not much we can do to help. you will either have to get a program and cable to hook your laptop up to it or carry it to a dealer. just the way it is with these EFI motors. almost done away with the shade tree mechanic.

Re: 2004 250 hpdi loss of power above 4400 rpm

If there is a restriction in the fuel system(screens/filters) the pressure test should show it. Except the injector screens will not show up in those tests
Low voltage is easy enough to measure with a meter.
But like Robert said if the problem is causing a lean condition it will cause major damage to the motor if you keep running it

Re: 2004 250 hpdi loss of power above 4400 rpm

it never hurts to send your injectors off for a good cleaning and flow test. if it were me I would do that first.

Re: 2004 250 hpdi loss of power above 4400 rpm

unless you have the right tools to diagnose this and know what youre looking for take it to a yamaha dealer. that being said what you are describing is a loss of fuel press. since it runs at 4400 rpm lift pumps are fine. next there is a screen in the bottom of the vst if its dirty- no wot. after that is a med pressure filter on top of the vst feeding the hp pump-if its dirty no wot. next is the hp pump itself there are screens inside it which are NOT serviceable without removing the pump and sending to flagship marine. there are no guages you can connect to the pump for testing only ydis diagnostics program. next in line are the injectors each one has a screen in it and should be sent for service with the hp pump where they will flow test before and after cleaning. other another issue could be failing injector driver though unlikely. I would start with the vst and med press filters and go from there.

Re: 2004 250 hpdi loss of power above 4400 rpm

Let's go simple first.....HPDI's are great, but very thirsty at WOT...they are designed to sip fuel in mid range at expense of gulping at WOT....I would FIRST hook up a cheap(15-20 dollar) vacuum gauge just in front of engine mounted filter. Run the boat with cowling off....you should have 2 inches of vac. at idle(or less) and NEVER more than 4.5 to 4.75 inches at WOT....if the vacuum goes over this, you will have problems....use a clear piece of vinyl and nipples and tee to connect vac gauge inline to you can see if bubbles appear. At high vac. you get bubbles as effect. Have had more than a few new boats from factory with HPDI's and vacuum problems. If the high pressure pumps can't be fed by the primary fuel pump cause it's fighting vacuum on p/u side then.....

Re: 2004 250 hpdi loss of power above 4400 rpm

Start by replacing all 4 filters, Outside fuel water separator filter, low pressure filter in the engine port side,its inside a clear plastic cartridge. VST pump filter its inside metal canister on front port side of engine, inline filter medium pressure just above VST.

This should solve your problems, dont keep running it as all your doing is leaning out the engine and possibly hurt a piston, the problem will not go away by trying to run it hard over and over. Once it starts hesitating like that the only cure is filter change, it would not hurt to install new plugs.