Mercru 350 mag mpi ski

[hondon]

This unit came to me for a winterize from a regular customer that purchased it at our store.It has been out of service for only a month or so ,but did get at least partially trailer sunk,up to the stringers as they tell me.When we try to start this unit it will fire off as usual while cranking then nothing after the key is released.Isolated the boat harness and switches by jumping everything at the engine harness plug and cranking with a remote button.No change.Walked through troubleshooting in manual 36 Mercru ECM 555 with the Rinka scan tool as I do not have the harness to use the DDT.No applicable codes recorded.Merc tech has given me some direction but so far no luck.What am I missing?

 

[hondon]

Re: Mercru 350 mag mpi ski

Sorry , I should also add that fuel rail pressure is to spec at 45 psi.

 

[newport dave]

Re: Mercru 350 mag mpi ski

When the key is on, is there power across the main power relay? Do you hear the fuel pump come on?<br /><br />Dave

 

[hondon]

Re: Mercru 350 mag mpi ski

Yes and there is b+ power to the coil at the correct pin at the coil.I have spark at the plugs confirmed by at least a timing light however they come out of a troubleshooting session wet with fuel from all the cranking and monitoring.I,m thinking faulty CPS.Will a DDT scan tell me this if I get the proper harness?The Rinka will not.

 

[newport dave]

Re: Mercru 350 mag mpi ski

I don't use the DDT, I use the Rinda software on my laptop computer. I have yet to see a failed CPS, however I did see a failed CMPS with similar symptoms. <br /><br />When the boat took on water, was any part of the engine wiring harness or harness connectors submerged?<br /><br />Dave

 

[muc]

Re: Mercru 350 mag mpi ski

You don’t list a serial #. But a failed crank sensor= no spark. DDT will not tell you.<br />Cam sensor can only cause a slow start. If you think it might be a cam sensor just disconnect it (it is not needed to run motor) you will get a trouble code with it disconnected.<br />Sounds like you got a tether cord issue or a wet spark switch (distributor).<br />Also have you checked for water in the fuel?

 

[hondon]

Re: Mercru 350 mag mpi ski

Serial # is OM311322 .Cap has been off and examined for moisture and dried a few times out of frustration. Tether was isolated out of the loop when the boat harness was unplugged and I jumped the 5 and 6 pins on the engine harness,heard the fuel pumps running just like turning on the key.This person says this unit was full of water up to just below the deck which means that some engine harness would be submerged. Fuel cool pump plug and boost pump plug surely,also this thing came along way over winding mountainous roads with that water in the bilge.Who knows what got dunked. I'll try the cam sensor.Merc wants the readout from the DDT because they say they can glean a little more info off of it and I will be able to test my coil drivers with it.Not nessesarily a load of crap but hey ,we have the tool,I guess we should have all the crap that goes with it.Thanks guys and sorry for the novel.

 

[Don S]

Re: Mercru 350 mag mpi ski

Cap has been off and examined for moisture and dried a few times out of frustration.

Dried of what? was there moisture in the cap each time???<br />Get ahold of Mercruiser service bulletin 2003-06 and have a look at it. I think you may have found your problem in the wet cap.

 

[hondon]

Re: Mercru 350 mag mpi ski

I,m familiar with that bulletin and that was the first place I went when this problem cropped up . No moisture or white residue under the cap,in fact this thing looked cleaner than most I have inspected because it gets used alot.Plus I am getting spark to the plugs.No water in the fuel as evidenced by my fuel sample when the water separator was changed.When installing a new filter I always fill it with fuel and in a winterize I give it a shot of stabilizer to shortcut the run in time to the rails. Thank you though, and keep those ideas coming.Merc techs are scratching their collective heads.They are not out there in the field like we are.Thanks for any insight or advice.

 

[Don S]

Re: Mercru 350 mag mpi ski

When the engine starts, is should run at about 12 to 1500 rpm for a few seconds then slow to the 600rpm range. Is it running ok at the higher rpm, then dieing when it drops to normal?

 

[newport dave]

Re: Mercru 350 mag mpi ski

You say that you are getting spark to the plugs. I assume that is while you are cranking (since it doesn't run), and you said that the engine fires while cranking. <br /><br />The fact that it fires while cranking tells you that your secondary ignition components are not the problem, and that it is not a fuel delivery problem. It sounds like you are losing your primary ignition when the key is released. I don't have a manual for that engine (very few ski boats here), is it a Delco EST dist?<br /><br />Dave

 

[Don S]

Re: Mercru 350 mag mpi ski

Hi Dave, the distributor isn't the EST, it's the new Chevy composite distributor with the flat cap.<br />Also, the engine is known as a 350 Mag MPI Ski, and it doesn't have to be in a ski boat either. Matter of fact the engine hondon is asking about is in a 27' CrisCraft with twin engines and inboard drive systems.

 

[newport dave]

Re: Mercru 350 mag mpi ski

Don,<br /><br />Thanks for the diagram! I looked it over and have a few questions.<br /><br />Is "Item # 56 Coil Driver" the connection to the distributor?<br />Is there an igntion module in the distributor?<br />Does it switch modes (dist module mode to run mode) as the engines starts like the Delco EST unit does?<br /><br />Thanks,<br />Dave

 

[Don S]

Re: Mercru 350 mag mpi ski

Is "Item # 56 Coil Driver" the connection to the distributor?<br />

No, it does not hook to the distributor. The coil driver hooks directly to the ECM. The distributor only distributes the pulses from the coil to the proper spark plug. The ECM also controls the timing.<br />

Is there an igntion module in the distributor?

There is a module in the distributor, but it is not used in this particular engine.

 

[Richard Petersen]

Re: Mercru 350 mag mpi ski

Now I am sure I did the right thing when I ordered the 5.0 L with a carb and plane old distributor. I carry a spare dist. module rotor/cap coil. I can limp home if needed. NO WAY / computer/ tow/ cell phone /USCG.

 

[hondon]

Re: Mercru 350 mag mpi ski

So there lays the rub.Since that ECM controls so much of what happens with this unit and we all hold it in such confidence and we really ca'nt "swap out" troubleshoot these units,it is left to the tech.I will probably have to convince the person that owns this unit to buy a new ECM for his 2 year old boat.Not a conversation I am looking forward to.

 

[Don S]

Re: Mercru 350 mag mpi ski

Why don't you swap out the ECM from the other engine? That would tell you where the problem is if the problem switched sides.

 

[newport dave]

Re: Mercru 350 mag mpi ski

What about just swapping out the crank and/or cam sensor?<br />Dave

 

[hondon]

Re: Mercru 350 mag mpi ski

From what? Where did we get the idea I was working with twins here?

 

[Don S]

Re: Mercru 350 mag mpi ski

From the serial number of the engine that you posted. I ran it through MercNet and it shows it was in a 27' ChrisCraft with twin engines.