Im running a 265 with twin 200 hpdi motors and when i bring her up over 4700 the port engine starts to fall on its face... it drops back to 42-43 but the starboard pops right up to 5200. Does this sound like a typical VST filter issue? or should i be looking into the 02 sensor? At the beginning of the season I changed both VST filters, racor filters, and fuel strainers. the only fuel filters I didnt replace were the metal in line filters before the VST tank. Any feedback would be great. I think im going to order a new vst filter and swap it out.
HPDI QUESTION
- Thread starter Rosstafari
- Start date
It does sound like fuel starvation. I don't think O2 would produce that symptom.
It could be lift pumps too. It could be that small screen filter on the VST pressure regulator too.
You also need to check that the primer bulb is not starting to collapse when at speed and the engine sputters. That would indicate a blockage in the fuel pickup. Even a blocked vent can produce those symptoms. Running with the fuel cap open will eliminate a clogged vent issue
You can check the VST filter when it is removed, by looking into the pickup tube hole through the filter screen. It you can't make out the shape of your hand on the other side ( the screen appears opaque), the filter is clogged.
It should look like a fine screen that allows you to make out shapes when looking through it.
It could be lift pumps too. It could be that small screen filter on the VST pressure regulator too.
You also need to check that the primer bulb is not starting to collapse when at speed and the engine sputters. That would indicate a blockage in the fuel pickup. Even a blocked vent can produce those symptoms. Running with the fuel cap open will eliminate a clogged vent issue
You can check the VST filter when it is removed, by looking into the pickup tube hole through the filter screen. It you can't make out the shape of your hand on the other side ( the screen appears opaque), the filter is clogged.
It should look like a fine screen that allows you to make out shapes when looking through it.
thanks for the feedback guys, im going to start by changing the vst filter. a friend of mine brought up a good point, earlier in the season on my second run out i acidentally ran the aux. tank out of fuel due to not having the valves in the right direction so there is a possoblity that i could have sucked up some shit from the bottom of that tank. The only thing that i question about that theory is that i have put about 10 hours on the boat since then and have pushed about 130 gallons through the motors with no issue up untill two nights ago.
Think you need to get on THT and search HPDI Mystery Filters. I'd change the 10-micron Yam fuel/water sep to a 2-micron Racor. Good money is on a clogged up fuel system; but your 02 sensor needs to be serviced every year.
To rule out a low pressure pump, have someone squeeze the primer bulb and see if the power comes back.
My experience is that this doesn't always detect a bad pump. I think that if a pump has a bad check valve or a bad interior diaphragm, the pumping of the bulb will help but if the outer (rear diaphragm) is leaking, I think that the pumping just pushes fuel into the crankcase and does not increase pressure to the high pressure pump.Grog said:
I suppose a bad injector could be a factor but a bad O2 sensor(blocked or clogged) most often results in a too rich mixture and that won't explain the loss of revs at speed. More likely that results in excess black smoke and/or plug fouling.
Like the previous poster said - go on THT and search for "mystery filters". I just went thru this in the past 7 days with a 2001 150 HPDI and it turned out to be one of the filters in the HP pump. Yamaha says replace the $1300 pump - BS! Good stuff for sure and saved me lots!
highfive28 said:
Yep, there's even a post over there complete with pics showing the guy removing the screens from the pump with a sheet metal screw. Not sure if it's the mystery filter thread or not. You got your new Racor fuel filters coming right?
well I ordered a new vst filter that should be in tomorrow. I took the boat out again over the weekend and managed to pull a few more hundred rmps out of that motor but performance was still not what it should be. Now I am also experiencing engine stalling at idle speeds. as soon as you pop the rpm up just a touch she runs all day long. I was planning on fishing offshore this weekend so I hope I will have the boat dialed in by saturday. FINGERS CROSSED.
