Mercruiser 5 ltr MPI Hard start.

[Tantrum09]

I have a year 2002 5 ltr mpi mercruiser with a bravo 2 leg that is giving me cold start problems.

Engine cranks and cranks and sometimes kicks into life when i release the key - but it can sound like it's running backwards.

Once the engine is fired up i can switch it of and fire it up again no problem, it will be fine for the rest of the day. Sometimes it will fire up fine the next day. Problem is worse if the boat has been left for a couple of weeks.

Brand new batteries
Cleaned distributor cap.
Cleaned grounding point at back of engine.
New plugs, fuel filter etc.

Just wondering if anyone has had any experience of this fault and could give me some pointers.

 

[Don S]

Re: Mercruiser 5 ltr MPI Hard start.

Got an engine SN? your boat may be a 2002, but the engine may not be. If it's a 2001, it's a different setup than a 2002.

 

[Tantrum09]

Re: Mercruiser 5 ltr MPI Hard start.

Thanks for the reply, i forget the complete serial number but it begins OM300.....

The 555 ecm is stamped as being 2002.

Had the engine running this morning after it being a little stubborn to get going and was fine for the rest of the day. I'm hoping tomorrow i'll get the same hard start condition.

Managed to get the diagnostics on the engine and no fault does were listed.
Tested the fuel pressure on the rail and had a reading of 42 psi so that can be ruled out.

 

[Don S]

Re: Mercruiser 5 ltr MPI Hard start.

For a start, you can go up to the Adults Only sticky at the top of this forum, and go to the Merc Service manual links. You need manuals #31 and 36 for your engine.
One thing I have found that causes lots of problems is slow cranking and using the wrong type of battery. You need a starting battery (NOT a deep cylcle) for starting an MPI engine. The deep cycle will show to much voltage drop and may not allow the engine to start. Second is the rpm of the engine cranking may not allow the engine to sense that it is trying to start.
You might get a carbed engine that is turning slow to start, but not an MPI engine.