intermittant will not strart issue? 4.3L Merc 1999

[FishHog]

had this boat for 3 years now. Been running fine, one morning last year, it wouldn't start. Used the kicker to go fishing and took most of the day before it finally fired up. Thought it must have been flooded, and never had a repeat so I stopped worrying about it.

now today, same issue.

It almost fires, you can tell if wants to start, fires once or twice, but then just keeps turning over. Has new plugs, wires, distributor last year. Had good compression last year (didn't test it again today, but have no reason to think it has changed).

Carb looks wet, so let it air out for quite awhile, and still one start.

any suggestions as to what my problem could be?

thanks,

FishHog

 

[Watermann]

Re: intermittant will not strart issue? 4.3L Merc 1999

As you know there needs to be 3 things, fuel, air and spark to start her up. I would start trouble shooting fuel first since you did a tune up recently.

It wouldn't hurt to go back over the ignition system checking everything if the fuel checks out.

 

[achris]

Re: intermittant will not strart issue? 4.3L Merc 1999

Re-check the compression anyway. It doesn't take long and costs nothing. And it should be the FIRST step in any diagnosis of engine problems. Next check you have spark and it's firing at the right time, then check the fuel system....

The correct procedures and steps does not change because you checked it last year, or last week for that matter. Plenty can (and does) happen in a few hours of runtime...

1. Compression.
2. Spark, and at the right time.
3. Fuel/air.

Chris......

 

[Bondo]

Re: intermittant will not strart issue? 4.3L Merc 1999

Ayuh,.... When was the last time the Fuel Filters were changed,..??

 

[FishHog]

Re: intermittant will not strart issue? 4.3L Merc 1999

Ayuh,.... When was the last time the Fuel Filters were changed,..??

Changed them in the fall before I winterized. First start was last week on the muffs. Yesterday was supposed to be the first on the water day but no start.

agree achris, will go through that tonight, ran out of time last night. Was just hoping someone might have had a similar problem and idea. Ran fine all last year with the exception of one day in the spring when it did the same thing. Once it started it ran fine the rest of the year right up until I put it away for the winter. Started fine last week, no go yesterday. Seems strange to me, but I will start checking the list. Hopefully I find something.

thanks for the help guys.

 

[FishHog]

Re: intermittant will not strart issue? 4.3L Merc 1999

so the good news is I got it started. the bad news is I can't figure out exactly why.

tested spark at the cap, it jumped 1/2 inch, but didn't seem as bright and strong as I expected. It was fairly bright out, but seemed more orange/yellow than blue. But went ahead and pulled all plugs, they all looked fine. Checked compression all good right at 160-165 on all. Put new plugs in since I was planning to anyway. Checked that I had fuel being injected into the carbs on advance of throttle, seemed good and strong. Checked all spark plug wires and seem great, all tested well with ohm meter, they are only 1yr old. All were tight and in place.

once I put it back together I decided to try it again and it fired right up like it typically does. Must be the plugs, that is all that changed, and it didn't even hesitate to start.

so I went over the old plugs again and they all look good to me. If I didn't have new ones, I wouldn't replace them based on looks. So, I'm happy its running, but can't say I'm confident that I fixed anything. Especially considering the fact that the same thing happened last year and I finally got it running on the same plugs and it ran the rest of the season on those plugs right up until I winterized it in the fall.

guess I'll keep a spare set of plugs handy, but I'm not convinced that is really my issue.

 

[MikDee]

Re: intermittant will not strart issue? 4.3L Merc 1999

What spark plugs did you use?

 

[FishHog]

Re: intermittant will not strart issue? 4.3L Merc 1999

acmr43lts

 

[Watermann]

Re: intermittant will not strart issue? 4.3L Merc 1999

Sure hope it's not your ignition module giving the intermittent problem with fire.

 

[FishHog]

Re: intermittant will not strart issue? 4.3L Merc 1999

I hope so too. having a hard time beleiving it was just a sparkplug. I would expect rough running with a bad plug but not a "no start".

 

[Watermann]

Re: intermittant will not strart issue? 4.3L Merc 1999

Yeah I agree with that, never have witnessed it myself either and spark plugs are pretty darn simple devices.

There may be some directions out there on testing the module but intermittent failures would make it a challenge.

 

[dingdongs]

Re: intermittant will not strart issue? 4.3L Merc 1999

Replace ignition sensor under cap.Mine failed a few times leaving me stranded and this was the cause.normally gives a few warnings first and then just fails.Run through the tbV stticky and this will enevitably b the cause.cheap off fleabay.I now carry a spare but get a rotor arm too as these are stuck on and usually break when removing as there loctited down.

 

[Watermann]

Re: intermittant will not strart issue? 4.3L Merc 1999

What dingdong said, last year I had the same thing happen on my 5.7 L Chev motor, it wouldn't start, then started and ran for a while before giving up completely. I pulled the distributor to clean up all the rust that had invaded and replaced the ignition sensor to fix it. That was of course after scratching my head for a while.

 

[airshot]

Re: intermittant will not strart issue? 4.3L Merc 1999

Had a similar problem on my 3.0 a couple years back, found some water in the fuel, replaced filter and drained tank, worked well for a couple weeks then started all over again, after doing all the testing and not really finding much other than a suspected weak spark I just replaced the coil on a whim and never had the issue again.