Mercruiser 350 MPI (2007) Hard starting

[harleyd558@gmail.com]

I have a 2007 mercruiser 350 MPI. Last year I changed to plugs, wires, and IAC valve which went bad on me. Everything so far has been working good until yesterday. We took the boat for lunch, and it started right up. We stayed about 3 hours or so, and then when we went to leave, the engine would just crank, crank, and crank, but would not start. I then tried fully opening the throttle, and it started up withing about 5-8 seconds, and I backed the throttled down. She idled fine, and ran fine going back. Once re-docked, I let it idle for about 10 seconds before I shut it off. I waited about 10 minutes, and wanted to try starting it again to see if would happen again. Well, it did the same thing, crank, crank, crank, but would not start until I opened the throttle; as before, it started right up within 5-8 seconds, I backed it off, and it ran O.K. any suggestions?

 

[alldodge]

tried fully opening the throttle

You might have injectors leaking. If you go to WOT this shuts off the injectors, and is used for a flooded motor. Check your fuel pressure at the rail to be sure the regulator is keeping it at 43 psi at 1800 rpm

 

[harleyd558@gmail.com]

Not familiar with injectors. How would one know if they were leaking? leak on the outside? Or are you saying if the pressure doesn't maintain 43 psi replace the fuel regulator? If WOT shuts off the injectors then what you're saying is the pressure would be high? As you would need fuel pressure to start correct?

Also, odd thing, is I sent the same message to mercruiser themselves, and they replied possible bad IAC valve. When I did replace it, it was aftermarket. $50 vs $120 for OEM.

 

[alldodge]

When I did replace it, it was aftermarket.

OK, you replaced the IAC, and did it fix your issue?

 

[harleyd558@gmail.com]

I had to go back a read what I wrote. Yes, I did write, it was LAST year I replaced my IAC valve, plugs, and wires. I also wrote since then, up until Sunday my engine has been runny fine. It wasn't until I returned Sunday afternoon when I started to have a problem. The engine would crank but not start. I tried, and tried and tried. I then disengaged the drive and opened the throttle wide open. After about 5-8 seconds it started right up and ran ok all the way back to my dock. I waited about 10 seconds at idle before I shut it off then waited about 10 minutes to see if it would start up again. It did the same thing, just crank, and crank until I disengaged the drive, and opened the throttle wide open, it started right up again in about 5 seconds.

 

[greno]

Sounds like bad IAC valve.

 

[alldodge]

The normal failure of the IAC is the motor will die at idle. You can start it by giving it more throttle but when its brought back to idle it dies.

With your not starting unless giving it full throttle, the IAC might be sticking, but could be other things. You can remove the IAC and clean it with soap and water, NO carb cleaner. Can even use some WD40 or other light weight oil, but do clean it with soap and water afterwards.

While cleaning, also clean the place where it is installed