Hello All, I have a 2005 200HP HPDI and have had recent surging issues while underway. It will start seemingly fine, get up on plane, hold a constant load (3500-4000 RPM) for some period of time (5-10 minutes but varies) and then starts to surge. Through YDS, I watch high pressure fuel pressures drop from within spec (750psi-800psi) to almost nothing during a surge before it rebounds back to spec when I cut throttle/come off plane. Sometimes it won’t rebound though. I suspected fuel/filter/restriction issues.
Engine has about 695 Hours on it and I know the previous Owner did limited PM work on the fuel system components (therefore I didn't feel too bad about throwing some parts at it, see below).
Things I have learned from these forums and have already done to try and remedy:
It did throw a 26 code for Injector #1 during the latest surging episode but I suspect that this is a symptom, not the cause because they have all been tested and I can’t imagine a faulty injector would drop the fuel pressure to this level? Injector #1 passes the diagnostic test in YDS for whatever that is worth.
I am sort of leaning towards maybe the Medium Pressure Pump (but why would an electric pump fail intermittently?) or something in the VST starving the HP Pump. The HP pump seems to be outputting fine initially so I have a hard time believing it is shot. Again, the engine will come up to speed and might stay there for 5-10 minutes at the same RPM before sputtering/surging. The belt on the HP pump looks fine but could this be a slipping/bad belt? Only other thing I was thinking was fuel hoses in the engine but I can’t see any sign of pinholes/etc…
Anyone have any thoughts on this issue? Been stumped. Love this engine but I am at a loss with this one. Thanks in advance, this forum has been great in getting me this far at least!
Engine has about 695 Hours on it and I know the previous Owner did limited PM work on the fuel system components (therefore I didn't feel too bad about throwing some parts at it, see below).
Things I have learned from these forums and have already done to try and remedy:
- Obviously checked fuel quality by running it off a standalone 6 gallon tank of brand new gas. Same issues persist.
- Replaced both Low Pressure Fuel Pumps.
- Removed and cleaned O2 sensor.
- Had all injectors professionally cleaned (InjectorRx). Replaced all mystery filters at injectors. All tested good.
- Replaced low-pressure fuel filter.
- Replaced VST filter and clean VST tank.
- Replaced medium pressure “can” filter (between VST and HP Fuel pump inlet).
- Replaced both “mystery” filters in the HP Fuel Pump.
- Replaced all spark plugs.
- Checked all system grounds, battery connections, voltages, etc.
- Measured medium pressure fuel pressure and it falls within spec during startup. I have yet to do this on the water, underway.
- Checked Neutral switch both visibly and in YDS. Appears to be functioning correctly. In a surge, the cylinders affected by the switch still say they are active (not off like when in neutral).
It did throw a 26 code for Injector #1 during the latest surging episode but I suspect that this is a symptom, not the cause because they have all been tested and I can’t imagine a faulty injector would drop the fuel pressure to this level? Injector #1 passes the diagnostic test in YDS for whatever that is worth.
I am sort of leaning towards maybe the Medium Pressure Pump (but why would an electric pump fail intermittently?) or something in the VST starving the HP Pump. The HP pump seems to be outputting fine initially so I have a hard time believing it is shot. Again, the engine will come up to speed and might stay there for 5-10 minutes at the same RPM before sputtering/surging. The belt on the HP pump looks fine but could this be a slipping/bad belt? Only other thing I was thinking was fuel hoses in the engine but I can’t see any sign of pinholes/etc…
Anyone have any thoughts on this issue? Been stumped. Love this engine but I am at a loss with this one. Thanks in advance, this forum has been great in getting me this far at least!