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Mercruiser 4.3 starts but won’t stay running

Tyoung1969

New member
Greetings All,

I have read a number of posts about this issue, and have followed all the advice I could find, but still can’t find my issue. Engine starts fine but dies in a few seconds. I bypassed the oil switch and can hear the fuel pump running, unhooked the fuel line to the carb and have a lot of fuel pumping into a bottle, I jumped the red to the purple on the ignition switch. I have 12 volts to the coil, I’ve checked every wiring connector I can find, but still have the same results. Starts, just won’t stay running. Also changed the water separator filter. Checked the lanyard. Have fuel going through the venturies. This is driving me insane! Any other advice would be greatly appreciated!
 
When it is dying, are you working the throttle to engage the accelerator pump? Does that keep it going at all? I suspect that the carb is jacked up in some way that you are draining the fuel bowl and it's not getting filled up fast enough.
OR, you are getting so much fuel that it's literally putting out the fire
OR you are sucking up water mixed with gas so that you get some fuel in there but the float bowl eventually gets full of water and konks out.
In any event, it's a fueling issue since you clearly have spark. And air.
 
It will start without giving it gas if you crank it a little longer that usual. I will look at the choke and see if I can tell what’s going on. Thanks for your help!
 
It dies out whether I give it throttle or not. Both replies are leaning towards the carb, so I guess that’s where I’ll start next. I appreciate the advice!
 
take a fuel sample, see if there is water in the fuel, if thats ok, while having someone else cranking/starting it, spray carb cleaner down the throat of the carb, see if it stays runnning longer than is has been withougt the cleaner. if so, the carb should be investigasted further
 
I think it is 12 volt from key. when you are cranking 12 volt is fine but when the key is in on mode 12 volt is interrupted. I had same problem and ignition fuse was not contacting. Cleaned the fuse and everything was fine. One indication is when engine dies, all gauges go dead too. follow 12 volt coming to ignition key to engine.
if it was the carb, engine would be running with more throttle.
 
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take a jumper wire and go from the circuit breaker on the intake to the pos side ofthe coil, see if it stays runnnig.
 
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