2003 mercruiser 4.3 issues

[Transamman78]

Hello. I have a beautiful 2003 rinker 192. 4.3 mercruiser. Last year it started to have issues running. It would start then quickly die and have a terrible time starting but would die and start a few times until it would start and run like a champ all day. Doesn't seem to be fuel because the carb always pumped. The tach would also jump all over while running but the engine wasn't actually fluctuating. I went to start it for the first time this year and it just cranks. Fuel is good and I even tried starter fluid. I checked and I'm getting no spark out of the coil. I checked the coil and it is good. Starting to get pretty bummed out. Any similar stories?
Thanks

 

[nola mike]

What ignition system do you have? Regardless, first thing would be to try disconnecting your tach from the coil and cleaning all of your electric connections including grounds.

 

[alldodge]

The tach would also jump all over while running but the engine wasn't actually fluctuating.

Disconnect the gray wire from the Tach

 

[Transamman78]

What ignition system do you have? Regardless, first thing would be to try disconnecting your tach from the coil and cleaning all of your electric connections including grounds.

Thunderbolt v. There are only 2 wires going to the coil. 1 purple and one grey. Should there be an additional for the tach?

 

[Scott06]

take gray wire off tach first if needed This is thunderbolt ignition trouble shooting guide https://www.boote-forum.de/attachment.fphp?attachmentid=114582&d=1231576181

 

[dubs283]

1 purple and one grey. Should there be an additional for the tach?

grey wire is for the tach

issue sounds typical of a failing/failed ignition sensor in the distributor, there is a good troubleshooting guide for the thunderbolt system which can easily detect most failed component(s)

 

[Transamman78]

grey wire is for the tach

issue sounds typical of a failing/failed ignition sensor in the distributor, there is a good troubleshooting guide for the thunderbolt system which can easily detect most failed component(s)

So I have 12 volts to the positive side of the coil. When I pulled the red/white wire off of the ignition sensor I only showed .2 volts. This should indicate a pad sensor right? It should show 12v without cranking it?

 

[poconojoe]

I have the same engine, same year.

A couple of years ago I used that troubleshooting chart and had to replace the ignition sensor in the distributor. The old one from the factory was a plain, exposed circuit board! The new one was a sealed, encased unit.
It was not difficult to do and it wasn't expensive. I think it was $35-$40 US dollars.

I also replaced the rotor, cap, plugs and wires.
I figured, give it a good tune-up.
I had trouble getting the old rotor off of the shaft. I think the factory glued it on! I had to cut it in pieces to get it off.

Follow that troubleshooting chart. It's very good.

 

[Transamman78]

Ok. After diagnostics I found I needed a new ignition sensor. Replaced that, cap, rotor,wires and now I have great spark. Still no starting even with starter fluid. I'm at a loss. Maybe fouled plugs could stop it from starting?

 

[alldodge]

now I have great spark. Still no starting even with starter fluid

Have great spark and it won't even hit with either, just cannot believe that. The gas and either must be water

How did you test for spark, and was it white or blue?

 

[Transamman78]

Have great spark and it won't even hit with either, just cannot believe that. The gas and either must be water

How did you test for spark, and was it white or blue?

Blue spark. Tested plugs with a spark tester. Did the same with lead coming from the coil.

 

[alldodge]

Good spark
Good fuel
Will not hit, not even a backfire

I got nothing

 

[Transamman78]

Good spark
Good fuel
Will not hit, not even a backfire

I got nothing

Swapped plugs and it runs like a champ now. Thanks everyone

 

[poconojoe]

Swapped plugs and it runs like a champ now. Thanks everyone

Wow!
That's great!
At least you ended up with a great tune-up.
You'll be good for a while.

 

[alldodge]

Swapped plugs and it runs like a champ now. Thanks everyone

Won't even backfire, and now it runs
glad to hear your running but