Fuel problem on 370. I have a...

[Into_the_Mystic]

Fuel problem on 370.  I have a 2010 370 with 496 B-3's with Axius.  I had a fuel problem about a week ago when starboard engine just shut off.  Limped back to dock and tried to figure out what was happening.  Played with fuel solenoids, turn knob to bypass and eventually got it running.  Then port engine did exact same thing.  The next day, I put an ohm meter on all three solenoids - all where within range (2 were at 15, one at 16).  Checked voltage at the solenoids (disconnected plug) and all were good.  Thinking it was a fluke, put solenoid back to normal from bypass.  Then yesterday, went for cruise and everything was running great.  Just as I was pulling into dock at end of day, lost an engine and then the second one quit.  After I tied up, played with bypass again, and after many tries (15-20 attempts), they both finally started.  I can here both fuel pumps run and build pressure.  I don't think it's a fuel filter issue (they run smooth and not coughing or sputtering).  Is this an issue with heat in engine compartment causing solenoid to act up?  Both times it happened, it was after an extended slow cruise (no wake back to dock).  Is the slow speed allowing heat to build up and cause issues?  Should I leave solenoids on bypass?  I get no errors on vesselview.  Any insight would be appreciated. Thanks, Pete

[wingless]

Welcome to the forum.

It sounds almost like heat induced vapor lock, except the thermal mass is so large that restoration to normal should take a very long time.

A good first step is to use a fuel pressure gauge before and during the problem.

There is an expensive Mercruiser solution that adds a series low pressure pump before the existing high pressure pump to push the vapor through, back into the fuel tanks.

On my boat I designed and installed a custom thermostatically controlled heat exhaust that maintains the engine room temperature low enough to prevent vapor lock. This was implemented prior to Mercruiser releasing their system.

[Into_the_Mystic]

Would running blower help reduce heat while running at slow speed. I thought the idea of cool fuel was to prevent vapor lock?

[wingless]

The blower is required to suck air from the lowest point of the engine compartment.

Heat rises.

In my case those required blowers had zero effect on vapor lock.

No direct experience on those engines, but the 454 MAG MPI Horizon engines on my 2000 380DA also had fuel and fuel pump cooling and they would still suffer heat soak vapor lock.

Measuring fuel pressure is a very good first step. A fuel pressure gauge is an essential tool.

[Into_the_Mystic]

Thanks. What psi am I looking for fuel pressure? As far as I can see, it should be around 43? If vapor locked, what would pressure be?

[wingless]

The full pressure should be 34-38 or 41-45 PSI, per FSM tests. A gauge can be inaccurate, showing low or high when the boat is okay. I have seen old school gauge calibration w/ a fluid piston compressed by a free weight.

Use the gauge and get a reading during normal operation.

Repeat during problematic conditions.

If vapor lock, then the pressure should be near zero, or bouncing around, because the high pressure fuel pump won't compress / pump air.

The service manual also defines restricted output tests to verify pressure can reach 60 PSI, plus 10" vacuum applied to port and engine idle tests. The measured fuel pressure should drop when vacuum is applied to the fuel pressure regulator. It should rise to at or near maximum when atmospheric pressure is applied to port.

[wai_phung]

I had a similar problem, searay painted the inside of the fuel module and the ethanol in the fuel broke down the paint. The paint flakes flowed down and clogged up the fuel rail and some of the injectors. I ended up complaining to mercruiser and they had a technical bulletin to cover parts and labor for both motors

[Into_the_Mystic]

Thanks. I’m praying it’s not cool fuel 3 paint issue. What were your symptoms? My fuel pressure is right around 40 both ruining and when key is turned on. I changed both fuel filters (they were pretty clean) and treated fuel. Haven’t had a chance to get back out to see if vapor lock or not. Let me know what you had happening to lead to CF3 issue. Thanks

[FIG]

Had the same issue (2007 310 Sundancer, 350 MAGs Horizon) on both engines with identical symptoms. Both times Gen3 Cool Fuel. Replace them now before your injectors get clogged. Had to remove fuel rail, and injectors and cleaned all of them.