600 sci fuel pressure too high
 

At start-up, when powered ignition got a code on smartcraft, e-lock for high fuel pressure. Powered off, cycled on and fine for several legs of a poker run.
Coming into lunch stop, burned an IAC motor. Replaced that, everything fine for couple more legs of run.
Fired up for last run of day and motor idled lower rpms than normal, shut-down and found it had blown gasket out of water/fuel seperator and has blown out the dampeners in the ends of fuel rails. This done with no high pressure warning from smartcraft.
Fuel pressure regulator is clean, looks fine.
Will swap fuel pressure sensor and replace dampeners, then check pressures.

Any thoughts/experiences. Know IAC motors burn often on these, is fuel issue related ?

TTT.

Any 600/700 owners or techs with any thoughts ?

Tested yesterday on hose, everything seems normal, no alarms or codes on display.

if the return line is plugged or restricted, the fuel pressure will spike. and you wouldn't have gotten alarms because once it blew up all the seals the pressure was back to being low or normal... they acted as relief valves and regulators. and just because the regulator looks good doesn't mean it is...

Good thoughts.

Any direct experiences out there with fuel pressure issues in 600/700 sci ?

Kelly,
I don't but have you called Mercury racing about it and see what they have to say? Just a thought, good luck and let us know what you find out.
Dean

Dean, I did talk to Merc, they said there have been issues similar caused by mechanical fuel pump (one driven by seawater pump) becoming heat-soaked and building pressure while sitting, symptoms exactly like my result. This is a real possibility for my cause. A change has been made to a pump which has a bleed-off incorporated, part number 889275T. I will see about updating my pumps.

I am having the same issue with my port motor, a 525. What is the status of your repair?

John

John,

Replaced both my mechanical fuel pumps, per Mercury tech's suggestion. Also replaced both fuel pressure regulators. Fuel pumps were leaking fuel into seawater oump drive cavity, so think they were culprit.

Cured my issue.

Whats Wrong With That Damn IAC!
 

Just as a followup here. On the newer efi engines from Mercury with both supercharging and naturally aspirated versions if there is a fuel delivery or fuel pressure volume or pressure issues such as this case, the idle is the first thing that is affected the greatest because most boats spend a lot more time idling than they think. When the fuel delivery becomes an issue, the IAC (Ford type) IAC on these newer Merc offerings, the IAC is a stepper motor valve that is trying to hold the idle steady even though the fuel delivery issue is trying to do the opposite, so that little IAC motor is running counts from 0 to 100 so many times over a short period that it gets to hot and usally may heat up and possibly burn out ,first the electrical connector and then the IAC itself. When you are having any fuel delivery issues from bad pumps, pinched fuel lines, undersized fuel lines, clogged fuel water seperators, bad regulators or faulty injectors, the quick back and forth loads on the IAC will eventually smoke this little guy if the fuel issues are not remedied quickly.
Just a word to the wise. When you start having idle, alarm code, fuel delivery and pressure issues on an EFI engine, take corrective action as soon as possible and do not expect the "Magic Fairy" to correct the situation for you. Lean burning any of these efi engines is usually very damaging and sometimes disasterous and the wear and tear on other items such as injectors, dampers, regulators and IAC's is expensive, troublesome and avoidable.

"If its Broken - Fix it!"

Best Regards,
Ray @ Raylar