robmon
25.05.2021 8:56:13
You say you've spark, but where have you measured that? here
See full version: Mercruise 5. 0 non start
You say you've spark, but where have you measured that? here
Case in point: I too lost spark at the end of last season.. I pulled the boot off the coil and measured, and thought "well, that's good".. It still wouldn't start/run.. after a few minutes I checked spark again, but this time by pulling the boot off the dizzy tower.. one look explained it- it was straight up broken filliment.. swapped cables and it fired right up and didn't miss a beat. here
I have a 2003 Rinker 312 with 2 Mercruiser 5.0 MPI engines. I have had an ongoing problem with the port engine for some time now, on occasions I will go to start the engine and it just cranks over but will not fire up, the engine will turn and expels air/fuel mixture from the air filer when I stop cranking, there is fuel to the engine, I have a spark and the fuel regulator pressure is correct. There seems to be a timing problem and I have tried changing the coil, crankshaft sensor and fuel regulator with the other engine to no positive results. The strangest thing about this is that I will try to start the engine again after some time (from 1 day to several weeks) and it will then fire up like there was never a problem. This has happened to me on at least 4 or 5 occasions since the summer and although it corrects itself over time there is a problem that I would like to resolve, I never know when this will happen and it does not seem to be consistent with hot, cold or damp weather. I am leaning towards the issue being electrical with a breakdown in a sensor or module that seems to correct itself at times. I have not been able to get a computer plugged into the engine while this problem exists and when the engine fires up again no faults are showing. I also wondered if this could be a distributor issue? It is a mystery to me and if anyone has any ideas on what this could be I would appreciate the input.
Thanks in advance for any help
The coil firing is one thing. The fire getting to the tower and then distributed out to cylinders is another.. even if you had one or two wires bad (from the dizzy) the other cylinders would fire, making a rough running engine, but coughing as in running all the same.. this kinda indicates a central problem. [links]
Answer: There are 3 basic fundamentals with the operation of an internal combustion engine here
As illustrated in the short video below it is very easy to verify if the engine is in fact getting the required spark at the distributor, and subsequently each cylinder. We like to use a standard engine timing light while connecting it to the main coil wire lead in between the coil and distributor cap. Once you have the timing light connected you can crank the engine over and visually verify if spark is being supplied from the coil to the distributor. In the event that you do have spark we typically go ahead and verify that each individual cylinder is also getting spark. This basically eliminates the distributor cap as a potential problem item as well. here
Question: My Mercruiser 3.0L Marine Engine will crank over but won’t start. Is there an easy place to start when trying to diagnose this problem?
If you do not see that the coil is providing spark to the distributor cap it can either be the coil itself or possibly the engine control module. At this point you can either test or in some cases the coils are relatively cheap and its easier to just take your chances and replace the coil.
[links]
What info I have
The vessel was purchased back in 2003
Alpha 260hp / 330hrs
Serial # OM601083
Hi, Not sure on the year of make.
I have inherited the vessel from my late father more
Well unfortunately it could be a whole big list of things that could keep it from starting, but just know your engine model is not affected by the oil pressure switch by way of keeping the fuel pump turned off during starting. The ECM controls the fuel pump.
Hi there, welcome to iboats! What year engine do you have? Is this an alpha or bravo stern drive?
Also have you tried advancing the throttle only to about 1/4 throttle to see if the engine will start? This will allow more air to the engine while testing to see if the idle air control is not working properly.
What does it mean when a MerCruiser inboard engine cranks but will not turn on and begin to run. The starter activates and the crankshaft turns over but the engine will not fire.
I am also certain that the alternator and regulator are operating fine. What are other reasons for why my MerCruiser 5.0-liter engine will crank but does no start. Btw, it cranks healthy. It does not crank slowly, it just won’t switch on and begin operating. more
The battery is not damaged nor is the battery charge low. It is new battery and I had it tested. The battery terminals are free of corrosion and electrical connections are tight. The remote control lever is in the neutral position and I didn’t see any blown fuse.