4.3 gi runs real rich

[mad obsession]

I folks, great site,
I have an 1998 four winns 278, twin 4.3 tbi, my issue is port engine runs rich, and misses quite a bit, new plugs, cap /rotor checked, IAC changed, temp sender changed, still not effective, lots of carbon behind the boat(unburnt fuel,) also lots of fuel smoke, can not seem to figure out the issue, I am trying to figure out if it is calling for a cold condition(full fuel) i am stumped, any advice would be great,
motor is 43fbpbyc branded cobra, but it is a 98 so I believe it is late model omc(transition years I am told)

 

[Monte1961]

Re: 4.3 gi runs real rich

have you checked compression or or done a leakdown test just to see if there might be another issue that may be causing the? How about the O2 Sensor also controls fuel mixture. Things that come to my mind are IAC, Temp Sensor, O2 Sensor & EGR Valve. Make sure you have no vacumn leaks on the TBI.

 

[mad obsession]

Re: 4.3 gi runs real rich

well, did some more investigating, started looking at parts diagram, noticed the previous owner swapped fuel pumps, only he had the high pressure pump on the filter side(lift pump) and there was hi press. at throttle body side, thought that was odd, so I swapped my low pr. from the other engine, no start, I pretty much established that hi pressure at throttle body was not working, and someone put a hi pressure at the lift pump to compensate and the boat would run, does that make sense, I get the rational, but not the fix, boat still runs like crap but it does run, I am finished for the night, but may end up swapping computers to see, i also want to put my spare Hi pressure in the right place and re use the low pressure to see if it cleans all up....anyone have anything to add, that would be awesome

LD