2002 mercruiser firing problem??

[lucky7's]

I have a 2002 mercruiser 6.2 mpi. It seems the timing keeps messing up. I did a head job about a month ago because i burned up some intake valves on the starboard side because the intake manifold gasket on that side failed. Have it fixed and it ran great for about 10 hours of use.. Now it wont start like it is firing too soon and hangs up when trying to crank. When i pull the lead off the coil it turns over smooth. So i know its not hydrolocking ( no water in cylinders)even pulled spark plugs . when i hook the coil back up it binds like its firing wrong. I know it has not jumped timing because all my marks line up and it was running great!! Also whats weird it did this when i first tried to start it after the engine work and i found out it was off by a gear on the distributer.(seems like its doing the same thing) Got it lined up right and it ran great!! Ran like 50 gallons through it one weekend and like 100 through the next month and the next weekend wet to start it and its firing messed up and binding and popping .. Fuel pressure is good!!! No movement on distributer because i checked my scribe marks!! lined it up on #1 tdc and its lined up perfectly with how it shows in the manual!! ( i have the factory service manual) ......... Could it be the crankshaft position sensor or maybe a cracked distributer cap or even the map sensor???.... Man this is crazy!!! What else is there... I have great spark.

 

[cr2k]

Re: 2002 mercruiser firing problem??

Possibly carbon tracking in the dist cap. Are all the plug wires on and seated at both ends?

Also check the centrifugal advance is it smooth? (turn the rotor and see)

 

[dubs283]

Re: 2002 mercruiser firing problem??

check for water in the fuel by pulling off water separator filter

 

[lucky7's]

Re: 2002 mercruiser firing problem??

Already checked water separating filter and replaced. I checked the distributer cap for cracks and carbon. Looks pretty clean but a hairline crack is all it takes i guess. Also no advance on this distributer its electronic controlled

 

[lucky7's]

Re: 2002 mercruiser firing problem??

I found out what the problem was. It was a cracked or faulty distributer cap. I cross referenced it to a 98 GMC sierra pick up truck with a 5.7 liter engine. If anybody ever needs one of these they have them at autozone for 36$. Even though I could not see any carbon tracks or an apparent crack. I put the new one on and it cranked right up. It must of been binding because it was firing two cylinders at once. The crack must of been between the plastic where you cant visually inspect.