350 Mag MPI hard starting

[Yellow Yota]

Sometimes my engine is a little tough to start. I'll have to give it a little throttle to start up, and it usually cranks over for a couple of seconds before it fires. I turn the key to the "on" position and wait for the fuel pump to get pressured up before attempting to start. Also, I sometimes smell gas right after it starts. Like it's running rich.
Any thoughts? Every EFI engine I've ever owned has not required throttle input to start. Once it starts, it's just fine. Runs smooth like a top.
This is a 2004 model with 145 hours. I just got it a couple months ago, and have only put 10 hours on it so far. I'm just wondering if I need to be concerned.

Thanks,
Chad

 

[Bondo]

Re: 350 Mag MPI hard starting

Ayuh,.. Probably due for a Full,+ Complete Tune Up...

 

[Fun Times]

Re: 350 Mag MPI hard starting

Ayuh,.. Probably due for a Full,+ Complete Tune Up...

That and it also sounds like it's time for a throttle body cleaning along with cleaning or replacing the idle air control, (IAC).
This could be why you need to advance the throttle at start up.

If your also getting a fuel smell then you will want to check your spark plugs to see if they look somewhat rich.

If the plugs are rich looking then you will want to check to see what the engine temperature goes up to, On average It should reach a minimum of 154 degrees within 8 minutes at idle speed and then average around 163 degrees when warm.

If the temp is low or slow to rise up, Then more than likely it's time for a new thermostat kit for your engine.

Also don't forget to change the distributor cap and rotor.

Hope this helps good luck.

 

[havasuboatman]

Re: 350 Mag MPI hard starting

I couldn't agree more. Especially about the IAC valve.

 

[Yellow Yota]

Re: 350 Mag MPI hard starting

OK. It makes about that long to warm up. Never timed it, but I will next time. Runs right around 160* according to the thermostat.

What and where is the IAC? How will I know if it needs cleaned as compared to replaced? What to clean it with?

Clean TB with carb cleaner, I assume?

I will check and just go ahead and replace the plugs. Recommended plugs?

Are these parts (T-stat and IAC) things specific to my boat motor? Or a Chevy part available from NAPA?

Thanks for the help everyone!

 

[Fun Times]

Re: 350 Mag MPI hard starting

What and where is the IAC? How will I know if it needs cleaned as compared to replaced? What to clean it with?

(1) Depending on your engine serial number that you have, The (IAC) could be either mounted to the throttle body it's self or it could be off set to the side of the throttle body hooked up by some hoses,ect.
The IAC is kind of like a moving choke to help maintain the idle speed as needed.
After you clean the throttle body and (IAC) with Throttle body cleaner that you can buy at any auto store, You will know if you need to install a new (IAC) if you still need to advace the throttle a little bit at start up to give the engine some extra air, Because the (IAC) might not be able to keep up and do it's job fast enough. The (IAC) is a part that moves in and out by way of a little stepper motor, They do go out kind of often sometimes.

Clean TB with carb cleaner, I assume? (2) Throttle body cleaner is what you want to use.

I will check and just go ahead and replace the plugs. Recommended plugs?

(3) You should only use the spark plugs that would come stock in that engine. (AC Delco) You should be able to find the part number of the spark plugs on top of the engine flame arrestor cover, There should be a sticker with this information on it, If not I would need your engine serial number to play it safe for me to Quote your part number.

Are these parts (T-stat and IAC) things specific to my boat motor? Or a Chevy part available from NAPA?

(4) The only place you should buy your T-stat and IAC is from a Mercruiser dealer either online or walk in to a dealer with your engine serial number.
The spark plugs can be very expensive if you just by them from a Mercruiser dealer, But if you do your home work online with your part numbers you can find them/Everything you need here at a more reasonable price. Good luck
Also check out my recent back history post about spark plugs for your style EFI engines and gapping procedures, It may be of some help to you.
Here they are. http://forums.iboats.com/showthread.php?t=386391
http://forums.iboats.com/showthread.php?t=386927


Also here is only an example of what a (IAC) is, See number 16 in this link below. Remember you can only find your parts by using your engine serial number.
http://www.mercruiserparts.com/Show...359.png&inbr=7585&bnbr=80&bdesc=Throttle+Body

 

[Yellow Yota]

Re: 350 Mag MPI hard starting

Thank you for the info! I will get on checking into the situation ASAP!

So, is the IAC spendy? I'm going to replace the plugs, cap, and rotor. Change the engine oil and out-drive oil. Clean the throttle body and IAC. Hopefully that takes care of the problem.......

Thanks again,
Chad