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Mercruiser 5.7 MPI cold start floods

Paintblend

New member
I have a 2000 Mercruiser 5.7 new long block, new out drive , had injectors cleaned and tested, when i first start it cold it floods black smoke boils, i have to open throttle about 20% to keep it running and in a approximately 2 min it clears up and runs fine,,,,, after it gets heat in it it will start easily and run good,,, but cant get rid of cold start flooding,,,,, changed IAC and TPS no help,, what now,, new fuel pump with new engine,, pressure is 42 to 44 lbs when hit key then drops to around 20 and holds help

open for suggestions:rolleyes:
 
First off, this would have been better off being posted on the Mercruiser Page...

That said, based on your description (fuel pressure dropping), I'd suspect one or more of the injectors are stuck open...
 
sorry i am a newbee,,, i did send the injectors and had them checked and cleaned,, how would i know or how could i check to see if they are leaking,, the pressure goes to approx 42 lbs when switch is turned on or the system is charged and then drops and holds on around 22 lbs,,, and as soon as the engine gets warmed up or gets some heat in it,, you can turn it off and let it set for a dew minutes and it will hit quickly and idle fine , over and over it is like something is telling it to flood at cold start up
 
The bleeding has stopped,, all that was needed was an 805218T - Engine Temperature Sensor

replaced this part and if fired up like a new motor,,, wait it is a new motor,,,, the sensor must have been giving an erroneous message to the ECM and was dumping the fuel in it ,, it now starts at the hit of the switch,,,,, LOVE IT
 
If the ECT provides a 'low' value to the ECM, the ECM will call for a wider pulse width from the injector and give you a rich mixture.....so glad you got that resolved.

I'm inclined to think the rail pressure should be higher than 22PSI running; as long as the engine revs up under load, that may be all your particular engine needs.

Good luck.
 
Thank you,, I'm sorry i was not clear on the fuel pressure, it is much higher with the engine running,, the 22 lbs is just the hold pressure, when the switch is first turned on the pre charge goes to 42 and then drops to 22 with out starting the engine,, it does increase with the engine running

thanks again for the explanation of how the sensor works,,
 
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