92 Mercruiser 5.7 random stall help!!

[jeff.nelson83]

Ok here we go, 1992 cobalt 206 5.7 v8 thunderbolt IV ignition. Engine serial #0D709843 carb rodchester quadrajet

The problem, at random the engine stalls! Some times it will stall at idle and some times it will stall in gear. I dont run the engine above 3100 rpm and it will stall at any range. It is random! Some days it wont happen and other days it will happen 2-4 times in a day. If it stalls while drive above 2000 rpm it will do it for 1-3 seconds and it usualy comes out of it and will not kill the engine but if it happens while at an idle or just in gear i will kill the engine but it will restart everytime.

What i have done.

Replaced the coil, pickup sensor in the dist., cap and rotor. I have disconnected my tach to make sure it is not back feeding voltage to the coil. New water seperating filter checked the tank vent and pickup for restriction and looked in the fuel tank for crap, checked the mechanical fuel fump vent line for fuel and all is good. I use 89 alchol free gas at the marina. Carb was rebuilt over the winter.

I am having a hard time diag the problem because it is random and the boat with start right back up. I think it is ignition related and not fuel. But i am looking for some insight on the problem, any recommendation would be helpfull or help with testing the problem out.

 

[jeff.nelson83]

Re: 92 Mercruiser 5.7 random stall help!!

Also the boat runs great, starts great.

 

[camalot]

Re: 92 Mercruiser 5.7 random stall help!!

It does sound electrical!!

I would check the purple wire for 12v when it does it again, do the gauges do dead at the same time?
Things I would check: run switch on the remote controls, ignition switch, shift interrupter switch the plug going into the ignition amplifier.

Royal PITA problems like this, if the ignition fuse doesn't blow at least you know there is no short!!

 

[jeff.nelson83]

Re: 92 Mercruiser 5.7 random stall help!!

Well I hooked up a 12v light bulb on the purple wire(+ SIDE OF THE COIL) last night to see when it stumbles if the light goes out or not.

 

[ktbarrentine]

Re: 92 Mercruiser 5.7 random stall help!!

I had a random stall similar (not exact) like this that was caused by intermittent open in the 20A fuse at the ignition switch. Changed out the fuse and holder for a waterproof blade type and no longer have the problem.

 

[jeff.nelson83]

Re: 92 Mercruiser 5.7 random stall help!!

Thanks for tip. Keep them coming IBoats!

 

[Bondo]

Re: 92 Mercruiser 5.7 random stall help!!

Well I hooked up a 12v light bulb on the purple wire(+ SIDE OF THE COIL) last night to see when it stumbles if the light goes out or not.

Ayuh,.... Did it,..??

 

[Volphin]

Re: 92 Mercruiser 5.7 random stall help!!

Check the wiring and grounds. Wiggle that wiring around and try to reproduce the issue. Are you sure you are getting fuel when this happens? Anti Siphon valve can and do cause regular stalling, but usually when they suck closed they stay that way until restart.

 

[Volphin]

Re: 92 Mercruiser 5.7 random stall help!!

Hesitant to call it a module problem, but if a man had one laying about, I'd plug her in and give it a go.

 

[achris]

Re: 92 Mercruiser 5.7 random stall help!!

I like the light idea. That will tell us if the problem is supply or fire side of the coil. My initial thought was shift interurpt switch. I have seen a few that get a bit of water on them and can cause exactly this type of problem....

Chris........

 

[jeff.nelson83]

Re: 92 Mercruiser 5.7 random stall help!!

@volpin, checked all the grounds and i do mean all of them. while under way i have wiggled wired, tapped on switches and levers. The Anti Siphon was working fine took it apart and checked it, looked great. But i hink it is an igntion module issue too but i dont want to spend $300 on a chance.

@achris, going to also hook a 12v light up to the + and - side of the coil so when or if it stalls the light will stop blinking.

I will let you guys know tonight, going out to wakesurf.

 

[NHGuy]

Re: 92 Mercruiser 5.7 random stall help!!

Check the shift interrupt switch. Also check that the lower shift cable is perfect. When that cable is bad you can get problems shifting or shutting down.

 

[jeff.nelson83]

Re: 92 Mercruiser 5.7 random stall help!!

Well we went out to the lake this weekend and it didn't act up once. I am starting to think that maybe it was the anti siphon valve but only time will tell. I removed the valve to test and we will see if it keeps going.