4.3 MPI Crank No Start / No Spark

[DazzaP]

Hi All
I'm at a total loss. I'm pretty good with engines, etc., but this has me beat, and I bet it's something simple. Back story below...
We were out boating last summer, testing rpm on a new prop, so the top speed run was all good for 5 minutes, then the engine cut out. Checked the engine had oil leak, so I guess the oil pressure switch did its job; I suspect it split the hose. Wouldn't restart, so got towed back.
Ive replaced the oil pressure switch, pressure sensor, complete ignition coil and module, dizzy cap.
Ive spent a few hours now trying to diagnose the issue but drawing a blank; everything checks out, but what seems strange is, as per the drawing attached Im loosing voltage to the top plug pink wire when its plugged in, but according to the diagram, tI shouldn't be as its spliced at junction 108.
You can hear fuel pump kick in and prime..
Or any other ideas please.

 

[Fun Times]

Engine serial number and what year is your application?

 

[Candy Gramformongo]

The old rule of thumb is that if you have three things, compression, fuel and spark, it will run. You say "everything checks out," but one of those three things is missing. So keep checking. Compression is not usually a problem in an engine that was recently running, so check that last. Spark you can check by pulling a wire at a plug and watching it jump a gap to ground while you crank. So if that checks, my bet is fuel.

Also, two things rarely just coincidentally go wrong at the same time without being related. Assume the no start condition is related somehow to the no oil situation.

 

[DazzaP]

Engine serial number and what year is your application?

0M35389 Sea ray 190 Thanks

 

[Fun Times]

Your serial number appears to be missing one number possibly in near the beginning sequence as adding a number to the end suggests the engine to be a 350MPI engine model...Also wondering if the stern drive was Alpha or Bravo model as the Alpha has a shift interrupter switch that might be activated somehow that could cause odd issues that one would need to be aware of while inspecting things out.

I was more concerned with the year to help ensure you're using the right diagnostic manual and if your model used the Camshaft sensor or not. I saw you believe the engine to be a 2001 someplace else so you should be OK with things you are using to keep going at this.

Have you pulled out and inspected the fuse and fuse wiring & pin connector and maybe tried another fuse to ensure all is okey there before moving on down the line? Carefully wiggling the wires to see if power comes and goes. Continuity test with a multimeter would be next on the list to try.

Are you getting any spark? Does the RPM gauge seem to move up while cranking the engine over to start?... If not, most of a no spark signal starts at the Crankshaft sensor found near the bottom of the front timing cover area 'all other things in normal working order of course.

 

[DazzaP]

The old rule of thumb is that if you have three things, compression, fuel and spark, it will run. You say "everything checks out," but one of those three things is missing. So keep checking. Compression is not usually a problem in an engine that was recently running, so check that last. Spark you can check by pulling a wire at a plug and watching it jump a gap to ground while you crank. So if that checks, my bet is fuel.

Also, two things rarely just coincidentally go wrong at the same time without being related. Assume the no start condition is related somehow to the no oil situation.

No Spark

Your serial number appears to be missing one number possibly in near the beginning sequence as adding a number to the end suggests the engine to be a 350MPI engine model...Also wondering if the stern drive was Alpha or Bravo model as the Alpha has a shift interrupter switch that might be activated somehow that could cause odd issues that one would need to be aware of while inspecting things out.

I was more concerned with the year to help ensure you're using the right diagnostic manual and if your model used the Camshaft sensor or not. I saw you believe the engine to be a 2001 someplace else so you should be OK with things you are using to keep going at this.

Have you pulled out and inspected the fuse and fuse wiring & pin connector and maybe tried another fuse to ensure all is okey there before moving on down the line? Carefully wiggling the wires to see if power comes and goes. Continuity test with a multimeter would be next on the list to try.

Are you getting any spark? Does the RPM gauge seem to move up while cranking the engine over to start?... If not, most of a no spark signal starts at the Crankshaft sensor found near the bottom of the front timing cover area 'all other things in normal working order of course.

Sorry yes just found out that number 6 on my number keypad isn't working, add it to the list of something not working. Story of my life at the moment. It is 0M635389.

Looked at the shift interrupt switches purple wires, tested them by applying forward and reverse throttle then trying to start, wouldn't even crank so I'm guessing this is correct?

Tested the 3 fuses all were good.
No spark at all, removed the crank sensor yesterday and tested seemed ok.
Didn't check though rpm guage when cranking will check that today thanks.
Much appreciated with all the help.
I've got a feeling it needs to go get plugged in for diagnostics.

 

[Fun Times]

Sounds kind of correct though you'll want to also do a visual as well to the switch mounted on the shift plate of the engine to make sure it's center in the V 'and ohms test the switch to make sure it's working properly when physically moved say by hand and watching the meter...It will be item number 18 but with the purple wires mentioned, you found it... https://www.mercruiserparts.com/bam/subassembly/31500/8550/280

The reason the engine didn't crank over when selecting forward neutral reverse is there is another switch in the shifter handle controller that keeps the engine from cranking in gear for safety reasons of not spinning the prop while someone is still near it say swimming, etc..

Here are your engine parts for this model,

https://www.mercruiserparts.com/4-3l-mpi-alpha-bravo-0m615000-thru-0w3

Your serial number appears to suggest the engine may be newer than 2001 and closer to the late 2002 - 04 range...What year is the boat it's in?

Next time you're in there, take aa look to see if there is a wire plugged in the back of the distributor sensor sticking out..Some models don't while later models do you use that sensor. I don't believe yours does but still need to know...Also wiggle the main engine wiring harness in that area and lightly tap on (and swap out) the relays to see if symptoms change might any.

You fall within the following service guide though it doesn't seem to be an exact issue here..., https://www.crowleymarine.com/sb/2/10455

No warning horns sounding to help suggest a fault code?

Describe the oil leak...Did it spray oil all over the engine that might have gone somewhere it shouldn't have causing an odd issue not to start?

Technically the oil psi switch doesn't turn off the fuel pump directly like a carburetor engine model but does affect the ECM that may shut down or at least seem to shut down the engine "in our own panic mode" as it drops available power quickly depending on over all situation.

 

[DazzaP]

Sounds kind of correct though you'll want to also do a visual as well to the switch mounted on the shift plate of the engine to make sure it's center in the V 'and ohms test the switch to make sure it's working properly when physically moved say by hand and watching the meter...It will be item number 18 but with the purple wires mentioned, you found it... https://www.mercruiserparts.com/bam/subassembly/31500/8550/280

The reason the engine didn't crank over when selecting forward neutral reverse is there is another switch in the shifter handle controller that keeps the engine from cranking in gear for safety reasons of not spinning the prop while someone is still near it say swimming, etc..

Here are your engine parts for this model,

https://www.mercruiserparts.com/4-3l-mpi-alpha-bravo-0m615000-thru-0w3

Your serial number appears to suggest the engine may be newer than 2001 and closer to the late 2002 - 04 range...What year is the boat it's in?

Next time you're in there, take aa look to see if there is a wire plugged in the back of the distributor sensor sticking out..Some models don't while later models do you use that sensor. I don't believe yours does but still need to know...Also wiggle the main engine wiring harness in that area and lightly tap on (and swap out) the relays to see if symptoms change might any.

Yeah no plug into the distributor.

You fall within the following service guide though it doesn't seem to be an exact issue here..., https://www.crowleymarine.com/sb/2/10455

Just tried no luck

No warning horns sounding to help suggest a fault code?

Sorry, I'm new to this boat. Two beeps.

Describe the oil leak...Did it spray oil all over the engine that might have gone somewhere it shouldn't have causing an odd issue not to start?

I can't be sorry I didn't see it; it looked low down, though, with no oil high up. I was hoping to get the engine to start to find where the oil came from.

Technically the oil psi switch doesn't turn off the fuel pump directly like a carburetor engine model but does affect the ECM that may shut down or at least seem to shut down the engine "in our own panic mode" as it drops available power quickly depending on over all situation.

Thanks For the thorough reply.
I just probed the pink wire 12v that goes into the ICM while it was plugged in. I had 12v, but as soon as I turned on the ignition, I lost the 12v. I have no Idea why??

 

[Fun Times]

Yeah no plug into the distributor.

Just tried no luck

Sorry, I'm new to this boat. Two beeps.

I can't be sorry I didn't see it; it looked low down, though, with no oil high up. I was hoping to get the engine to start to find where the oil came from.

Thanks For the thorough reply.
I just probed the pink wire 12v that goes into the ICM while it was plugged in. I had 12v, but as soon as I turned on the ignition, I lost the 12v. I have no Idea why??

I don’t have full access to the manual but I had a quick glimpse at another service manual before my laptop battery died that had the splice numbers in it and I Believe 105 may go to the main power relay so if that is correct then possibly when you turn the key on, you may get power for a little bit then it shuts itself off via the relay….in your manual you are able to use/see, look for the chart of the splices as they have a description of what each number represents…there’s about 10 of them that start with 101, 102, etc..

Next time try turning the ignition key on maybe a few times to see if the 12v comes back at all...< or/and bump the key to start again and again while testing......Again, Swap Around Relays.

The list below in the photo is from SM 33 for the big block 496 or more known for the PCM while yours is the ECM… check to see if they are the same numbering system in SM 36.

 

[Fun Times]

Two beeps.

Need more info when available on this? When at first key up cycle you may get a beep or 2...But if you leave the key on and keep getting beeps here and there, then there is a code and needs a scan tool to see what's going on.

Could also try pushing in the center throttle only button, 'open the throttle anywhere from1/4 to full throttle and even pump the throttle a number of times to see if the engine needs more air (or less fuel at certain percentage times) ((cylinder flooding)) to start while cranking over the engine. Is your battery new, strong, 12.5+ volts with 800 - 1000 cold cranking amps rating?

Just to help confirm methods, where and how are you checking for spark?

Where abouts is your location?

 

[QBhoy]

Hi. I’d check the following in this order

Kill switch (sorry. Had to ask)
The new coil. Are they getting continuity to earth back to the battery where they are mounted.
The new cap. Is it installed properly. Is it just a new cap or a new whole assembly ? Are you getting a spark from the king lead from coil to diz ?