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2010 Mercruiser 350 Mag MPI crank not start.

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briang0

Regular Contributor
HI,
It's been a minute since I have posted a Thread so please bare with me. I recently purchased a 1984 Grady White offshore. It has a 2010 Mercruiser 350 Mag MPI engine and a Bravo outdrive. I picked it up a week ago. Me being the happy idiot that I am, I purchased it with an engine issue. Crank no start. It's had a marina look at it but after 6 hrs the PO asked them to stop and he brought it home. Which is why it was for sale. The marina found a weak spark and fixed a low fuel pressure issue.
I started trouble shooting it today. I have had at least 6 different boats and have fixed all of them. This is the first fuel injected Marine engine I've worked on. I ran a fuel pressure test and found that when the engine cranks I have 40 psi on the rail. Once the engine stops cranking I have a pretty steady 35-36 PSI on the rail. I put an inline spark tester and I see a spark although it doesn't to be as steady as I have seen in other non EFI engines in the past. I removed the distributor cap and rotor and cleaned the contacts. I'm waiting for new merc parts to get delivered. I haven't run a compression test yet. The PO said that one was already done and the numbers were good. I have not reason not to believe him. Trust but verify.... I'm currently waiting for the rest of the Mercruiser service manuals to arrive.
I spent a few hours reading other thread and I have a few question.


Is the fuel pressure good enough to let the motor start? I did some research and I have found between 42 to 43 PSI running but I can't get there yet.
When I turn the key I hear the fuel pump turn on and run for a period of time and shut down. Similar to fuel injected automobiles.
Should I be hearing a beep when I turn the key?
Where does the beep come from the ECM?
What does the beep mean? (never had a marine engine in the past that was fuel injected or beeped.
Is there a pin on the ECM that I can monitor to see if it is in fact beeping and the sound source is not present?
The PO sent the ECM out to have it re-flashed. Is there any test I can do, like voltage test on a pin to verify that the ECU is starting up and ready? I don't have a Marine ECM tester.
How does the distributor tell the ECU when to fire the spark? I see a plug that is connected to the distributor but I didn't see anything actually under the rotor.

I feel confident I will be able to be victorious over this no start issue. I'll be retiring at the end of the year so I hopefully will have plenty of time to work on this project.

Thanks Brian
 
What is the motor serial number?

Fuel pressure gauges can be off a tad and 40 psi is enough to start, so it's not fuel pressure

The beep is turned off/on by the ECM. The beeper can be under the helm or on the motor, just depends where it was installed. The other issue with the beeper is it may have gone bad. If it is working but not heard then it's wiring or ECM.

To work on the motors you really need a scanner, either Techmate Pro or Rinda software. These can be found at www.Rinda.com

Where was the ECM re-flashed and is there a report of it? If no report than most likely it wasn't done or it may be bad. Some ECM can be repaired and other cannot, after getting the serial number we can find out more options
 
Thank you for the reply

The motor serial number is 0W675776 I would like to get a scanner I was hoping I might find a used one on eBay. Unfortunately I don't know where he sent the ECM to be re-flashed. I plan on pulling the spark plugs and doing a compression test this week. The cap and rotor which are Quicksliver are due to arrive today but the weather is not cooperating. I also plan on double checking that that the plug wires are in the correct spot. There has been several people with their hands on this so I want to make sure things are where they should be. I did not see any type of sound device/box on the engine the could possibly emit sound. I'll have to check under the dash.
Thanks again.
 
HI,
I took a picture of the ECM the other day I will post it. It does say ECM. I understood that the difference between a ECM and PCM is the PCM also monitors the transmission. My boat has a Bravo 1 stern drive. What is in there is an ECM. There are only 2 connectors that plug into it. This engine has been running for years before it just wouldn't start anymore.
 

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Have you tried opening the throttle body while cranking the engine over to sometimes help get added air to the engine should the idle air control valve be faulty...

The plug sticking out of the distributor housing is of a CAM shaft sensor that if searched online could be tested... You also have a Crank shaft sensor that would be mounted down low in the front timing cover under/behind the engine water circulation pump that should all voltages be good and nothing else wrong, basically starts the signal to get the spark going.

Often the cap and rotor can go very bad on this design and creates a weak spark under the cap as they cross arc more so often between coil lead and cylinder 6.

Yes 40 psi should be okey to get the engine started but now you need to find a way to ensure the fuel is getting out (spraying) of the fuel injectors as there are some known blockages that have occurred in these systems. Make sure the battery cold cranking amps are high say close to the 800CCA range with 12.6ish voltages. All battery and wiring connections are clean and tight....pull spark plugs and have a look, make sure no water, damage, etc. is in there.

IAC number 14, https://www.marineengine.com/parts/mercury_marine_parts/sn/0W675776/4442067US/12840_82

 
Is the only way to know if the ECM is working correctly is to try to interrogate it with a diagnostic computer. Can I pin it out to see if it's getting voltage and has a ground?
 
briang0 said:
Is the only way to know if the ECM is working correctly is to try to interrogate it with a diagnostic computer. Can I pin it out to see if it's getting voltage and has a ground?
Click to expand...
Yes, only way is with a scanner

You can do several checks to see if items are producing the correct voltage range to the ECM, but your unable to tell if the ECM is interpreting them correctly.

THIS is the one you would need and is the cheapest to get into, but $50 more you can get Diacom software and use your laptop. Diacom isn't as portable but it provides more input being displayed at on time.

There is a guy on ebay selling an older Techmate version with more fittings but they would do you no good
 
Depending on your location you might be able to rent a scanner type option, https://www.ebay.com/itm/225583715490?_skw=rinda+tech+rentals&itmmeta=01KPKQ0Y065WVBCHZSJAPB49W7&hash=item3485d654a2:g:V0UAAOSwPjBn8CDr&itmprp=enc:AQALAAAA0GfYFPkwiKCW4ZNSs2u11xCtJnj1RDtZZpOEHeeQ5rsklr1sRpX4LS/N9IXouTIP7hysZLkqXV+QRzCIuEE0KUBfCeUYir8EWOXwV9tZraiT5s03pDGyFvy8gFJqyvDG0C801l21Y0TDkjxKMmKjPR6P8h5Kqn8elvqoOmRoW3eFFQO3PqwOR6Qybe/cPh7IaiVqlgQkbtdLwCPX+K7EiscHOpLBLc8nbZ69sMIqsqoRz7eWw2U9Boxzo/3eElXhkbCFJ84GZcv+Xo/EhTHsNlw=|tkp:Bk9SR5bgg_e0Zw
^
^With that you out to be able to send an output signal to the warning horn system to see if it sounds...Or should the stern drive oil reservoir go empty and things working correctly, it should sound the warning horn too...Beep-Beep.

Do you see the RPM gauge moving while trying to start the engine?
 
The trouble shooting continues.... I put a new distributor cap and rotor Quicksilver brand. I figured while I was there I replaced the Cam shaft position sensor. No Joy Still cranking away but not firing. I checked for spark and it still has spark I'm not 100% if its hot enough. The spark tester I have has a neon light in it. I can see it firing.

I cleaned all the battery contacts and ohmed the ground connections. Found one that was corroded so I went around and cleaned up the ground connections and the connections on the battery. Did not change anything. I also added a couple of cans of dry gas to help remove any water in the tank.

Tomorrow if the weather holds and my parts arrive. I plan on removing the spark plugs and will do a compression test on the cylinders. My plug wires will not arrive until the end of the coming week so I will use the existing wires for now.

Last question, looking at where the plugs are and their accessibility is, should I consider removing the exhaust manifolds when doing the plugs? I will be doing most if the removal blind I will not be able to see the plugs and I will be doing most of the removal by touch. I'm not worried about removing the existing plugs but putting the new gapped plugs back in is going to be difficult at best. I don't know if I will be able to get the spark plug socket between the exhaust manifold and the water hoses coming out of the bottom of the manifold. I do have a nice spark plug socket that is used to remove sparks plugs from Mercedes which will hopefully help a little.

Depending on the results of the plug removal I may be investing in some Diacom Software next week.
 
You need a adjustable spark gap tester, one you can open it up about 3/8 inch to see if it will jump
https://shop.advanceautoparts.com/p...P?product_channel=local&store=8520&adtype=pla

Similar to one like the above but there are several brands

Unable to say if you can do the job with or without the exhaust mans. Doing by feel takes some doing but so long as very light touch is used there should be no issue. That said your also going to do compression test and with mans removed will make it much easier

If you do remove, get some 3/8 - 16 threaded rod. You want 2 pieces about 5 to 6 inch long. Remove the bolts on each end of Man, screw in threaded rod. Remove remaining bolts than slide the Man away from the motor and lift up. Keeps you from holding all the weight
 
Well I believe that I found the issue. I pulled the plugs the morning and did a compression test. Unfortunately 7 of the 8 cylinders had pressure readings between 30 and 60 one cylinder was good at 120 PSI. In a Hail Mary attempt I am soaking the 7 low cylinders in Marvels Mystery oil. I’ll give them a few days to soak then I’ll rock the crank back and forth and see what happens. In the meantime I’ll be doing some research on buying a used engine and talking to some local shops about the possibility of a reman or long or short block. I think the boats too old for a new engine.
 
briang0 said:
Well I believe that I found the issue. I pulled the plugs the morning and did a compression test. Unfortunately 7 of the 8 cylinders had pressure readings between 30 and 60 one cylinder was good at 120 PSI. In a Hail Mary attempt I am soaking the 7 low cylinders in Marvels Mystery oil. I’ll give them a few days to soak then I’ll rock the crank back and forth and see what happens. In the meantime I’ll be doing some research on buying a used engine and talking to some local shops about the possibility of a reman or long or short block. I think the boats too old for a new engine.
Click to expand...
try michigan motorz for a reman long block $3800 or new base engine $5500.

Might be worth a leakdown test may get away with a valve job.

Sounds like despite what the seller told you he knew the engine was roached. You seem handy swapping long blocks is not that much work. Cheapest option could get a used truck engine and marinize it
 
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