1996 4.3 what kind of ignition?

[Poppy19]

Does a 1996 4.3 engine with a carb have electronic ignition?

Here's the issue as my son describes it.

The engine starts and idles fine for about 5 minutes, and then turns off like someone turned the key OFF.

He can increase the throttle, and it will run for a shorter period of time.

If he goes FULL throttle, it dies instantly.

______________________________
regarding the full throttle issue I suggested that he look for a dead man switch, that may be getting activated.

I recall in some older Ford broncos that if the engine runs fine, and then it is like someone reached over your shoulder and turned the ignition key OFF, the problem is often the pick up coil inside the distributor. IIRC after it cools off, it'll start and run like before.

Now I don't recall the issues with the ignition control module in some slightly newer engines.

IF it doesn't have electronic ignition, I'm barking up the wrong tree.
Thanks in advance for any help/suggestions.

Poppy

[mmwjr]

This vintage engine has the Mercruiser Thunderbolt V ignition system. Under Documents of this site you will find the Mercruiser manual for this engine which contains a troubleshooting guide. The issue could be the coil or the ignition sensor in the distributor. Although when you mentioned dieing when accelerating sounds like a bad accelerator valve in the carburetor.

[Poppy19]

Thanks Mike,
He just had the carburetor rebuilt by a gent who guarantees his work.
When you stated accelerator valve, is that the same as the accelerator pump?

I'll have to look into how to troubleshoot the ignition sensor.
Thanks again.
joe

[mmwjr]

Yes Joe accelerator pump.

[Poppy19]

Mike,
It's a season later and I would like to update this thread.
Last year, I bought the pick up coil / ignition sensor inside the distributor and had it sent to my son's house for him to swap it in. By then he was disgusted, and had the boat trailered to a marine mechanic. He did a little work on it and told my son to bring it back next year, or pull the engine and sell it.

Last weekend, my son had a couple of back yard mechanics come over and give it a try.
When I got there, they were already at it, trying to start it with ether.
I brought a spark tester, and there was no spark. I had them test the coil for 12V to the coil... none. They jumpered battery power to the coil, and it started up!

We adjusted the air/fuel mixture and it ran better, and then stumbled and died. While it was stumbling, they continued to fool with the jets, until it wouldn't start again, except with ether.

They pulled the top of the carb off and reset the floats.

I had suggested that we check fuel pressure. One guy had a fuel pressure gauge and a bunch of adapters and hoses (quite the set). I left for a bit and when I returned they were pouring fuel into a funnel connected to a hose.

Somewhere along the line they discovered a piece of paper in the fuel line clogging it.

The engine started, they adjusted the jets, and it is running great!

[mmwjr]

Hi Joe, glad to hear it’s running. So you still need to resolve the power to the coil issue? This comes from the I terminal of the ignition switch.

[Poppy19]

Thanks Mike, I'll make a note of that.

I haven't spoken to him all week, so I don't know if he did any additional work on it.

He also has an issue that it pumps water INTO the boat while the ear muffs are on and the engine is running. That is actually a more important issue. I don't know if he worked on that yet. I hope it is a simple fix.

[mmwjr]

Water leaking into to the boat while running on muffs is either a hose issue or a crack in the block or exhaust.

[Poppy19]

He had it winterized at the end of the season last year. I'm hoping that the engine has freeze out plugs that the mechanic may have pulled.
I don't want to hear that he has a cracked block!