Mercruiser 350 MPI won't start
 

This is driving me nuts.


I've got a 2003 350 MPI that ran rough in the spring, would cough over 2000ish for hours of run time, eventually stopped running. Had zero desire to run, changed crank sensor and coughs like it wants to run again.


Checked fuel pressure at rail, 40 psi

Changed plugs (very black), cap and rotor (not too bad but not great)

Connected to MEDS software, only faults are normal ones for systems not used on this engine. Did the IAC test, I can hear it. Can watch the computer read oil pressure coming up as I crank. The only quirk is that the software says about 70% engine load and I'm running tests with the engine off. Knock sensor reading is 1700 and the software doesn't have data with it to tell me what it should be.

Checked #1 is TDC and rotor is at #1 with Balancer showing 0 so I believe timing is at least close and hasn't jumped.


I have a good port engine, may try to put starboard ECM over to see if it fails on the port. I did find the ECM kept looking connection with software and believe it to have been a bad pin connection at the main harness plug. Just spread out the pins a bit and it seems ok.


I'm getting back in it today, looking for suggestions.

Whats the motor serial number?
Don't know much about MEDS but did look it up on line

Did we check for spark ? And strong spark ?
If there isn’t, Won’t take long to swap coils from engines.