Logo
FULL SITE MENU

Mercruiser EFI cold start

S

shankos

New member
I have a 5.7 lt mercruiser 350

I have a 5.7 lt mercruiser 350 mag mpi motor. It is EFI.

To start it you turn the ignition key to accessory and it pumps fuel as you can hear it doing so. You then wait a couple secs and crank it.

When the engine is cold (ie first start for the day) it is a real pain to start. It will crank the motor every time but then it will stall.

The idle when cold seems a little rough.

You have to rev it to stop it stalling.

Once it gets up to running temp it starts up perfectly and runs/idles perfectly.

Anyone got any ideas to look for.
 
Change the spark plugs. Use T

Change the spark plugs. Use THROTTLE BODY cleaner and clean the TB bore and plates.
 
spark plugs are fairly new &#4

spark plugs are fairly new (less then a year) and they are long life ones.

I will try cleaning the throttle plate and bore. I wiped it out but have not pulled it off and fully cleaned it with spray.

I have heard about an idle air intake valve. Thought maybe this might be causing problems. I however was not sure where it is located. I would guess the throttle body bore somewhere.
 
the idle air control bypasses

the idle air control bypasses the throttle plate in the throttle body. It is how the ECU controls idle RPM
 
"[b]"spark plugs are fairl

""spark plugs are fairly new (less then a year) and they are long life ones."

Ayuh,... When was the last Full,+ Complete Tune Up,..??

Just changing the sparkplugs don't count..."
 
No idea when the last complete

No idea when the last complete tune up was.

I was not looking to take it to mechanic at this point for a tune up. It only has an issue with cold start and idle. So was looking for things to check myself that could be causing the problem.

I am thinking that maybe there is an issue with with the ICU. I will check it out for blockages/cleanliness.

I have not had an EFI before. My last boat motor was 350 chev with carby which i was quite familiar with but I am not so familiar with electronic system.
 
Dan

Cold starting and idle

Dan

Cold starting and idle issues with EFI can be several things. Me I am no expert on EFI so I do not offer answers.

The best thing to do in my opinion is to bring it to someone who does have answers. Someone who has the break out box (scanner tools) to check for codes and inturprit what they mean.

Without direct knowledge or understanding you could end up spending more than it would cost to have a proffesional check it out.

My opinion
 
"kghost I 100% Agree with you,

"kghost I 100% Agree with you, Good post as usual.
happy.gif


It could be anything from batteries to sensors and without the right tools and the right guy using the tools that understands how everything works together you could be in for a long battle.

If you do decide to go to a service shop you should look for a MerCruiser premier service dealer in your area, They should be the better bet at finding the starting problem.

http://direct.where2getit.com/cwc/apps/w2gi.php?&client=mercurymarine&template=s earch

If you do decide to find it your self you will need a service manual for your engine, You will also be needing a Rinda scan tool to start with.
http://www.rinda.com/marine/marine.htm

This is just my opinion also. Good luck to you with what ever way you decide to go with this problem.
happy.gif
"
 
I was really looking at trying

I was really looking at trying to determine a few things to check / try before having taking to take to a mechanic.

If I could try some common issues out first to eliminate anything obvious or common. If i failed then i could resort to marine mechanic however they are usually expensive for even a simple task.

I already have a service manual for the engine. I do not have and of the ECM scan tools. I think i can get any error codes out using a simple LED setup (well i have done it on a car dunno if mercruiser the same)

There may be no error codes showing up tho. Then i would have to probably resort to other methods.

Again i dont know how fancy the computer application is. I just know there is normally engine sensor error codes that show up when there are issues.
 
"if you have the manual, read

"if you have the manual, read it. Then read it again. It covers a lot of material.

MPI's are MUCH TOUGHER to diagnosis w/o the scan tool. If you want to learn about your engine, invest in a Rinda tool or their software. If you get it right, that scanner will pay for itself time and time again, in the future."
 
"[b]"No idea when the last

""No idea when the last complete tune up was."

Ayuh,... All the electronic controls in the world are Useless,...
If the mechanical hard parts are Neglected...

It could be a Simple as water in the fuel filters..."
 
Back
Top