Merc 350 Mag fuel problem

[Timcoulter]

My mechanic replaced the fuel module in my 2009 Merc 350 Mag engine after it failed and only allowed me to idle into port. Since the fuel module replacement I have had erratic starting and occassional engine stuttering early on in my cruises. Once underway it will cruise for two hours with no problem. After shutting down the engine I will generally experience a hard start and will need to let it sit for five minutes to restart the engine. Also from a cold start the engine at low RPM will stop after 10 minutes and need five minutes before it will catch and restart. My mechanic has checked the fuel pick up tube, which is OK, and has taken out the shut off solenoid system between the tank and fuel module. My mechanic is stumped. Any ideas on how to fix the problem.

 

[alldodge]

S/N for others is 1A335113

Is it a Bravo drive and open cooling or closed?
Also mechanical throttle or digital?

If distributor cap and rotor has not been changed do change it. The caps have been know to look great and be bad. Its best to keep a spare in the boat at all times

Has the motor been scanned for codes and if so are there any?

 

[Timcoulter]

S/N for others is 1A335113

Is it a Bravo drive and open cooling or closed?
Also mechanical throttle or digital?

If distributor cap and rotor has not been changed do change it. The caps have been know to look great and be bad. Its best to keep a spare in the boat at all times

Has the motor been scanned for codes and if so are there any?

It is a Bravo drive with an after market closed cooling system that was added two years ago. I think it is a simple mechanical throttle. My mechanic is an authorized Merc dealer and has the computer to check codes but has indicated he needs to have the event happen to check the code.

 

[alldodge]

When motor won't stat right away, have you ever tried to give it just a little throttle (throttle only mode)?

 

[Timcoulter]

It is a Bravo drive with an after market closed cooling system that was added two years ago. I think it is a simple mechanical throttle. The Manuel indicates it is a 4000 MPC Gen 2 Pistol Grip Remote. My mechanic is an authorized Merc dealer and has the computer to check codes but has indicated he needs to have the event happen while on the boat to pick up the code.

 

[Timcoulter]

I have pumped the throttle a couple of times with no response.

 

[alldodge]

I have pumped the throttle a couple of times with no response.

Isn't what I asked
Only a carb motor "may" benifit if the throttle is pumped, you do not have a carb motor.

Since there is an issue with the restart then it may be the IAC (Idle Air Control) valve. Put throttle in "throttle only mode", and move it forward only about an inh or so. Do not move it more then that. Then see if it starts easier

 

[Timcoulter]

I understand what you are saying and will give this a try on the throttle. Also will replace the distributor cap and rotor and ask my mechanic to check the codes again. I welcome any other ideas. What are your thoughts on a bad relay causing the problem? Seems fuel related to me. Thanks for your help!

 

[alldodge]

If the fuel pump is shutting OFF then yes this will stop the motor. Fuel pressure should be 43psi. Place a gauge on the rail and see what happens

 

[Timcoulter]

I replaced the distributor cap and rotor today and noticed it ran a little smother. Also replaced a circular filter below the fuel water separator. It was black but didn't appear plugged up. I have asked my mechanic to check the codes and will also ask that they check the fuel pressure again this winter. Will reserve a mechanic now for next spring for up to eight hours of trouble shooting. In the Seattle area two month out for any service help. Send some mechanics our way.

 

[alldodge]

Go to the local auto parts place that rent tools. Get a fuel pressure gauge and connect it to the fuel rail. There is a Schrader valve under a cap same as bicycle tire. Use the button on the side to bleed the air out of the gauge until gas comes out of clear tube. Tune the key to ON and OFF a few times to bleed.

Need a rag and safety glasses

 

[Timcoulter]

Is it safe/feasible to do this test while cruising on plane? It is good to know that I can spend the time necessary to try and duplicate the problem. I think I can replicate the problem during the first ten minutes of idle given enough attempts from a cold start. The problem is very erratic!

 

[alldodge]

Yes, once the air is bleed out of the gauge, it can stay on it until your done. Days even

 

[Timcoulter]

You can purchase a decent fuel gauge on Amazon for $30. I am going to create a bracket to hold the gauge and an old iphone or GoPro and record the pressure as it would be difficult to watch the gauge under power with the engine cover up. Any thoughts on this idea.

 

[alldodge]

Should work fine