HPDI Vmax problems

[all wet]

Dang engine problems are keeping me off this water a lot lately.  Here's the issue, 250 Vmax HPDI under 200 hours, was running WOT on way back from fishing and a couple minutes into the run it starts sputtering, back it on down to idle, still really rough running, check engine light on.  Seemed like a fuel issue but the on-board filter is brand new, engine canister filter good, VST filter all clean, no junk at bottom of VST tank.  Put on a new Yamaha fuel primer bulb, anti-syphon valve at the tank is clear, blew out the fuel pick-up line to the tank to make sure nothing had blocked it.

Next, check compression, all good.  Got a mechanic to hook up a diagnostic program, and get a zero fuel pressure reading while the engine is running, error reading for the throttle position sensor, error for fuel pressure sensor, low voltage at the sensors.  OK so maybe the ECM?  He had a parts motor there same as mine, so we put that ECM on my engine.  All the same readings as before, so not the ECM.  

One of the wiring harnesses has already been replaced too.

So it's not a fuel issue, not the ECM, sounds like it has to be some sort of electrical problem.  I wouldn't think all the sensors crapped out at the same time.

Any of you guys had any similar problems, solution suggestions?

 

 

 

 

[smilemaker]

As I stated in an earlier post DO NOT BELIEVE  THE COMPUTER. It only tells you what the ecu is sending out. For ignition it will tell you that a signal was sent to each coil but it does not tell you if the coil fired and sent a charge to the  spark plug.  There is also a box controlling the signal to the injectors some engines have 2 one for each side. The computer will tell you if it sent a signal to the injector but will not tell you if the injector worked properly.

A good mechanic will understand this and let the computer  help him but must rely on his knowledge of the motor.

[smilemaker]

After all my troubles with my 200 hpdi I would start with a pressure gauge on the Schrader valve after the vst tank. If it has 50 lbs than if it is fuel problem most likely high pressure  pump. Fortunately not often. If pressure is below 50 check  low pressure pumps. Cheap parts 80 bucks.  From there  look at medium pressure pump in the vst.

For electrical get an old fashioned timing light. With engine running hook the sensor over each plug wire after the coil to see if the coil is actually firing. If not replace coil. I am assuming that  you already checked plugs. If problems only come with engine hot check coils with TL  while on the water.  Mine only cut out under load but tested ok for resistance in the driveway.

Hope this gives some understanding of the system.

[ififish]

Will just give you symptoms and fixes for my vz 250 in the past year.

running on 4 cyl only-very rough-throttle position sensor malfunction- never shows on yds

electrical issue to tps- change wifing harness. -very common issue and doesnt show on yds either

Oil tank not filling from reserve tank- immediate alarm and limp mode. Wiring issue inside reserve tank near float

trim motor corrosion and quit- replace and rebuild

ran terribly rough- fouled plugs from long idling- changed spark plugs

 

I highly recommend Tim and Derrick at Marine Supply in Winter Haven. They worked diligently to take care of any issues and looked past Yamahas recommendations of ecu replacement which it was not. The wiring issues had to be traced and probed for hours. 

My boat ran great this past weekend and feel confident for the future.

[all wet]

Thanks for your input guys.  I have the boat back over at the shop where it was worked on last time for the same issue.  It was fixed for a while (8 hours of run time) before it's happening all over again.  The previous fix was to replace one of the wiring harnesses, and clean up the main ground on the boat.

Obviously the diagnostic computer reading of zero fuel pressure is wrong, since the engine does run.

I'm thinking it's an electrical ground or short somewhere.

 

[smilemaker]

Have him look at the coils while running.

Mine were sporadic and had to run awhile before cutting out. Use timing light to check them at the plug wire after the coil.

[all wet]

Just an update on the problem and the solution found.  It was the speed sensor, which connects to the water pitot tube in the lower unit and converts to an electrical signal into the wiring harness.  I had noticed the speedo wasn't working on the gauge and just figured something had clogged up the intake hole.

Turns out the speed sensor had a very small hole in it and was allowing water into the connector to the wiring harness and creating a short.  Thus all the other sensors on the harness were giving error codes.

I could have just unplugged the sensor connector and used the GPS for speed indication, but liking things to work the way they are supposed to, I had the speed sensor replaced.  Time to get back on the water now and catch some fish.