High EFI fuel pressure problem

[Intercoastal]

I have a 2007 Mercury 90ELPT 4S
Serial # 1B522264

It's very hard to start, takes 8 to 10 tries. Sometimes runs ok afterwards and starts normally after warmup. I checked to following:

Battery load test: very good
Checked all fuel lines and filters: all good.
Replaced anti-siphon valve just in case.
Replaced both fuel filters-no debris in filters.
Opened and checked the FSM. Both pumps work, bowl switch works properly. Screens clean and fuel pressure regulator hose as new.
Key on lift pump fills housing and high pressure pump runs fuel pressure is between 40-50 PSI.
Once started, fuel pressure stays 40 to 50 and creeps upward to about 70 at idle and high idle. I get a critical alarm shortly afterwards.
The fuel pressure seems high (even giving the accuracy of the gauge kit some leeway) and I am stumped as to why.

I don't have the diagnostic software and am trying to work through this myself, as I have decent mechanical skills. Anyone have any ideas to further narrow this down? Mercury parts are expensive and I am trying to avoid buying parts that aren't the trouble.

Suggestions very much appreciated.

Tim

[EuropeanAM]

Welcome to BBC!

Need more data to determine if the fuel pressure is CORRECT (though I do agree that it MIGHT possibly be climbing too high from your description).

If the manifold reference hose properly attached, and providing manifold pressure (vacuum) reference correctly?

Also would be a good idea to elaborate on "hard to start, takes 8 to 10 tries". Any details you can provide on that statement may be helpful.

Also- any maintenance history?

[Intercoastal]

Thanks for the response. The manifold reference hose is properly attached and is is good condition. I have not checked the vacuum reading. What reading should I be seeing on my vacuum gauge?

As to the hard start, when it is a cold engine, I turn the key on and wait for the fuel pump to stop running, then choke it for a few seconds and try to start. The starter spins quickly but no start after about 8 seconds. I repeat the process 2-3 times and occasionally get a try to start. I'm not smelling fuel like it's flooded and the fuel pressure is around 50psi where it stays the entire time I'm trying to start it up. Several more tries with choke and fast idle with mixed results. Eventually it starts and seems to idle normally. Air temperature here is about 45. Once it does start, fuel pressure increases up to 70 PSI and does not go down when I use the fast idle lever.

Hope this provides some clues.

Tim

[EuropeanAM]

When you say you "choke it" please describe the action you are physically taking. There is no "choke" on your EFI Fourstroke....

Control should be in NEUTRAL, no throttle applied. Turn key on. Turn to start. It should start.

I suspect your fuel pressure regulator is bad, inside the FSM.

[Intercoastal]

I'm highly suspecting the regulator as well. Control was in neutral. I used the fast idle lever. Seemed to help. I'm going to replace the regulator and report back. Thanks for your input Don.

[Intercoastal]

So I replaced the fuel pressure regulator and my fuel pressure is normal now. But. a few seconds after throttling up, I get 6 beeps and loss of power( Guardian Mode I suspect) Fuel pressure remains 40 to 50. I have checked all connectors and hoses. If I cycle the key off and restart, It's fine again until I throttle up and the same thing happens again. Any words of guidance?

[EuropeanAM]

Are you possibly trying to accelerate in NEUTRAL? If so, you are inducing a fault (never accelerate unless you're in gear, in the water, going somewhere).

[Intercoastal]

I was in gear in a large tank.

[EuropeanAM]

You will need to get it on the G3-CDS system for printouts of the Run History and Freeze Frame (Fault) History.