350 MPI suddenly Cut Out at 3700 rpm.

cfd95 said:
SeaAyeOwe said:
I get a spark at the coil, just in case I have swapped coils - no change.

When you say ignition module, what is that? This is the HT unit I changed over from other engine.

View attachment 41452[/QU
https://www.mercruiserparts.com/Sho...=40&bdesc=Distributor+and+Ignition+Components
Number 6 in the picture.
You said the motor just shut down which sounds like an ignition problem.
If it was a fuel problem motor would have spit and sputtered before it shut down.
Click to expand...

I am not sure that would be true - if you lose fuel pressure suddenly the engine will bog down. To be honest I was on plane at 3800 when the engine cut out so I have no idea if it spluttered or not. In the three second it took for me to realize what had happened and then bring the boat to a rest it may well have spluttered.
Click to expand...
 
cfd95 said:
SeaAyeOwe said:
I get a spark at the coil, just in case I have swapped coils - no change.

When you say ignition module, what is that? This is the HT unit I changed over from other engine.

View attachment 41452[/QU
https://www.mercruiserparts.com/Sho...=40&bdesc=Distributor+and+Ignition+Components
Number 6 in the picture.
You said the motor just shut down which sounds like an ignition problem.
If it was a fuel problem motor would have spit and sputtered before it shut down.
Click to expand...

Thanks but if the cam sensor was faulty I would not get life on the rpm needle gauge when I crank her and I see 70-100 rpm on th gauge so that seems to suggest the cam sensor is ok.
Click to expand...
 
Maybe your CF3 has water in it from a corrosion breach in the inner wall. Did you check your injectors with a noid light?
 
scoflaw said:
Maybe your CF3 has water in it from a corrosion breach in the inner wall. Did you check your injectors with a noid light?
Click to expand...
I do not have a Noid light but I should find some way of checking injectors I agree, maybe I will buy one.
 
OK - an update. $400 CAD high pressure pump kit.
Fitted today ........ And Voila !!!!!! ............ Nothing !!!!!!!
Nothing - still the same $&?:#%*^++ problem. No change at all. I am exasperated with this.
How goddam hard can it be ... Fuel, spark, air compression.........

I have a new mechanic in the morning for an hour or two max, he is booked two weeks out but a friend nudged him to come take a look - fingers crossed.

I need to sleep and stretch out my bones - I have been down in that bilge twisted around like nobody at 6ft 1 and 240 lbs should be for too many hours.

Stay tuned.
 
I can imagine the frustration ; stay with it, at least you are learning along the way? I am following this and looking forward to the fix
 
I am no expert in this area, but I have the same motor and had basically the same problem. Turned out to be an ignition sensor that is located inside the distributor cap. It is only like an $80 part that I think I spent about $800 on mechanics to finally find.


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harrisc said:
I am no expert in this area, but I have the same motor and had basically the same problem. Turned out to be an ignition sensor that is located inside the distributor cap. It is only like an $80 part that I think I spent about $800 on mechanics to finally find.


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Click to expand...

Thanks - I think my distributor is the newer type without that sensor. Like to hear other views on that though.
 
OK - bought and used a Noid light. No pulse at the injectors - starting to feel like it may be an ECM issue.
New plugs to be fitted today given the amount of wet cranking these ones have had.
I am going to source an ECM to swap out and see if that helps.
 
SeaAyeOwe said:
OK - bought and used a Noid light. No pulse at the injectors - starting to feel like it may be an ECM issue.
New plugs to be fitted today given the amount of wet cranking these ones have had.
I am going to source an ECM to swap out and see if that helps.
Click to expand...

Why don't you just swap ECM's with other motor?
 
sfergson727 said:
PM sent in response to yours.... I don't know if the ECM's on the 350 are the same as I have on the 8.1, but I have two near new ECM's as spares, I might be willing part with one of them.
Click to expand...

Thanks for the PM asking the q on ECM failure, Given I am in Canada and post is crappy let me see if I can get one locally first Scott - really want to try to salvage some of the holiday weekend.
 
sdleo26 said:
Why don't you just swap ECM's with other motor?
Click to expand...

I am going to try that next, does anyone know if the ECM is good that it will run on ten other engine? I know that the gauges etc will be screwed up on the smartcraft but not sure if it would run (assuming it is not a bad ECM).
 
Swapped the ECM from the port bad engine to the starboard good one - starboard started without hesitation, ECM is not the problem. Also tried the starboard ECM in the port engine, it would not start still.

New plugs, new hp fuel pump, new fuel filters all in line, fuel at 43psi, fuel verified getting to the plugs, spark on plugs verified, swapped ECM, swapped fuses, swapped relays, swapped iac, looked in distributor cap, Noid light showing no pulse on injectors ........ I am stumped .......... Two seperate mechanics both also stumped.

Time for a boat change :smt013
 
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I suggest you call the Mercruiser tech line at this point and see if they can help. They won't be available until Monday though.
 
prob need to connect diag computer / read codes. should have a port like the OBDii port in most newer cars a certified Mercuriser mechanic will have one. on your motor they can tell you how many minutes you spent at idle at wide open etc Any Who... My guess is probably crank shaft sensor But the Right mechanic with proper equip should be able to diagnose
 
Bad wire, connector? Start tracing power supply
How are you getting fuel to the plugs without power to the injectors?
 
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Two seperate mechanics with diagnostic units - no codes present from now or since the failure - other than those codes from me swapping parts. Crank shaft sensor had no faults plus I can see the rpm needle move to 100 rpm when cranking and usually when tehsnsor is gone you can tell as the needl will not move.

The plugs were wet, but the injectors were not pulsing on the Noid light. We had poured fuel into the throttle body so may have been from that. Anyways I changed the plugs.

I should also have said I have also tried a start on the crossover to eliminate the battery - no luck. I think I am just going to wait until the Mercruiser mechanic is available and try to enjoy what is left of the weekend.

Any more ideas - keep them coming, I will update once I get it resolved.
 
Not sure about Merc for certain but most injectors work on a ground pulse from the ecm. The other wire going to the injector has a constant 12v supply. So checking the power at the injector would be real easy.
 
Yes one of my mechanics used the voltage method and said that there was no pulse at the injectors.

The issue seems to be between the ECM and injectors - but who knows, I am exhausted with the whole thing right now and just need some clear space between me and ten problem to stat thinking clearly again.

I have swapped, changed, tested so many things I am losing track. Meanwhile working and trying to keep the admiral happy on a holiday weekend means I have to take a break from tracking it down :grin:
 
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