I have a 1995 454 mpi Inboard with hot/after running starting problems. It's not sending any trouble codes out except for a map sensor which I changed. It's runs great but it doesn't start at all if it's been running for a while. It won't even start if I hold the throttle open? though if you unplug the distributor module it will start in safe mode only and runs fine if you plug the module back in? The plugs, fuel pressure everything seems OK?? I'm lost? help anyone?

A friend with a 98 outlaw with 454 mpi motors had the same problem. Three trips to marine shops and it was never fixed. He ended up testing sensors himself and found that the thottle position sensor was bad. Use an ohm meter and check yours, might me the same problem.

When you say that the engine will start when you unplug the distributor module, do you mean the 4 pin connector on the distributor?

I think the first thing that you will need to determine is if the problem is fuel or ignition related. Check for spark when the no-start condition exists. An inductive timing light on a plug wire is one easy way to check.

Dave

Correct The four pin plug. If you disconnect the pug the computer runs in a safe mode for diognosis if I am not mistaken? I have checked spark at the time when the problem has occured and it still had spark and fuel pressure.

Something is not right here. The engine cannot start/run with the 4 pin connector disconnected. It may get spark, but the ECM will receive no reference signal (due to disconnected Reference-High circuit), it will not know that the engine is cranking, will not fire the injectors, and will not energize the fuel pump circuit.

Dave