Mercruiser 5.0 MPI Starter crank time?

[stevek2020]

I have a Cobalt 200, (2007 first time on the water is this year) with a Mercruiser 5.0 MPI motor.
I turn the key and wait 4 seconds after start warning beep.
I engage the starter and it takes 3 to 4 seconds before the engine is running.
It doesn't make any difference whether the engine is cold or hot.

This week end, I drove a Volva Penta.
Time to start is a half second, cold or hot. Simply unbelievable.

Is it normal from a MPI Mercuiser to crank this long?
All the cars and trucks I have start in less than 2 seconds.

 

[Fireman431]

Re: Mercruiser 5.0 MPI Starter crank time?

I have a 2001 MPI (7.4L) and if the engine haven't been run for a week or two, it will take about 3 seconds for them to fire.

If they're warm or just started a few days earlier, maybe 1 second to fire.

I wonder if you're loosing fuel prime in the system, such as the fuel filter allowing a little air to seep in. Noticed any fuel leaks? Is there a anti-backflow valve in your system? Can you actually hear your fuel pump hum/buzz when you first turn the key?

Just tossing some things out there. I may be way off base.

 

[stevek2020]

Re: Mercruiser 5.0 MPI Starter crank time?

Thanks. The boat is a 2007, first time on the water is 2010. The dealer says this is normal.

I was hoping that I didn't get a junker and that I needed to go out and buy a Volvo Penta.

Its nice to know you have good start times.

 

[c03camson]

Re: Mercruiser 5.0 MPI Starter crank time?

I have a 2003 same motor and mine takes about 3 to 4 seconds to start as well. I always thought the reason was that I have a deep cycle marine battery instead of a starter battery. I was told that an actual starter battery would help it start quicker. maybe somebody will chime in and say if that is actually true or not.

 

[Aloysius]

Re: Mercruiser 5.0 MPI Starter crank time?

There's either an oil pressure sensor, or a program that allows oil pressure to build up before firing. ALL digitally controlled engines do this.

 

[rodbolt]

Re: Mercruiser 5.0 MPI Starter crank time?

nothing on that mercruiser,or volvo, that does anything with oil pressure at key on.
at key on the ECU powers up and cycles the high presure pump to build rail pressure in anticipation of a crank signal.
as far as the volvo starting faster it simply depends on which volvo model you listen to.
the 8.1L can start in as little as 45* of crankshaft rotation.

 

[JustJason]

Re: Mercruiser 5.0 MPI Starter crank time?

If your using a small battery, deep cycle, undersized cables, bad connections etc starting time will be longer.
3-4 seconds isn't that bad though, and nothing I would worry about unless it goes from a consistant 3-4 seconds to longer.

 

[JustJason]

Re: Mercruiser 5.0 MPI Starter crank time?

There's either an oil pressure sensor, or a program that allows oil pressure to build up before firing. ALL digitally controlled engines do this.

That's not how it works.

 

[msojjo]

Re: Mercruiser 5.0 MPI Starter crank time?

The motor i have now 350 mpi, starts at a flip of the switch, under a second. The carbed motors i've had started in less than 3-4 seconds. That's a long time, if that's accurate, to be cranking on the starter, somethings not right.

 

[Aloysius]

Re: Mercruiser 5.0 MPI Starter crank time?

The long crank time allows the oil pressure to build. True, there is no measuring of it. Some older engines power the electronics through an oil pressure sensor. Some older brains also react quicker, since there's fewer inputs to check. New engines, the ECU also checks crank sensor and other sensor inputs before triggering spark/fuel pulse.

Long crank/no start can result from low voltage. If the brain doesn't see 10 volts or so, it won't work. High current draw can easily drop the cranking voltage to an unacceptable level. This also applies to Pertronix units.

With key on, the fuel pump is energized momentarily to build rest pressure. It won't reactivate until it sees a certain pulse count from the crank sensor. If you have a rest pressure problem, cycling the key a few times will allow the pump to build adequate pressure.

 

[stevek2020]

Re: Mercruiser 5.0 MPI Starter crank time?

This is great information.
Since the boat sat in the dealer's showroom from 2007 through may 2010, I think I should check the battery, battery cables, fuel lines for cracking, fuel lines for proper tightness.

What do you thinK?