Merc 5.0 MPI won't start

[RichRab]

I have a 2002 Merc I/O 5.0 MPI motor. Before I found out at the end of last season that I should not fog the motor I did as I have for the past 10 yrs. I took boat out of stoarage and it fired right up. I have used the boat a few times with no problems. Two weeks ago I filled the 50 gal. tank with about 35 gal. Drove boat about 4 hrs with no problems. Boat sat two weeks and cranks fine but will not start. I checked in dist cap and it is dry. The gas dock said they are not having problem with gas. I have what I think is good spark going to plug wires. I pushed schrader valve in fuel line and gas sprays but I do not think it is strong. Could a sensor be damaged from fogging and be stopping motor from starting? Thank you, RR

 

[RichRab]

Re: Merc 5.0 MPI won't start

Update..went to boat today. Changed fuel filter and checked pressure. 40 psi which I am told is good. Spark looks weak. Tried another coil and still no start. Going to change plugs tomorrow. Will update.

 

[alldodge]

Re: Merc 5.0 MPI won't start

Do you have a kill switch and is it in the run position?

 

[RichRab]

Re: Merc 5.0 MPI won't start

I do have a kill switch and when it is off the fuel pump does not run. Thank you. RR

 

[alldodge]

Re: Merc 5.0 MPI won't start

Well guess I'm going to need your serial number to look up your engine. But a few checks are:
With the key to run find a solid purple wire and see if there is 12V present.
Are you getting spark

 

[Don S]

Re: Merc 5.0 MPI won't start

When you changed the fuel filter, did you check to see if there was any water in the old filter? It's not going to run if there is a lot of water in the fuel system that got past the filter. The filters only hold so much water, then it goes into the fuel system.

Should be able to bleed some fuel out of the system through the schrader valve on the fuel rail to see if there is water in it.

 

[RichRab]

Re: Merc 5.0 MPI won't start

When I changed fuel filter I drained the old filter and gas looked good. A mechanic removed and cleaned injectors and said they were dirty and rusted as if they had water in them at some time. Boat runs and I will be using it Sunday and hopefully all will be fine. Thank you, RR

 

[RichRab]

Re: Merc 5.0 MPI won't start

Went to boat on Sunday and Monday and it ran fine. Mechanic thinks that when I wash boat water goes down seat and sits on top of motor causing a rust problem. The oil pressure gauge is not working and the depth gauge kept flashing .05 and after a couple of hours flashed 17. I think we might have knocked off a wire somewhere. More diagnosing needed. Thank you, RR

 

[RichRab]

Re: Merc 5.0 MPI won't start

I found that the big plug on the top rear of motor was not pushed in and the clamp was loose. Tightened it up and all was well. Thank you. RR