Would not run after sitting for an hour

[Last Dollar]

Engine ran great all day. After turning it off and sitting for an hour it did not want to start. It would miss and studder but would not rev up, just quit. Tried 3 times before it finally stumbled back to life and then ran great the rest of the day. It's a 2003 5.0 MPI. I did notice an odd exhaust smell when it was struggling to run like it was flooded?? I've had this boat 9 years and never has it done this. I've had the famous Idle air control valve fail twice and now even carry a spare. This is a whole different problem. Could the fuel pressure regulator be intermittent??

 

[paulswagelock]

Sounds a lot like vapor lock but the temps might not support that theory.

 

[Last Dollar]

Never experienced it on this boat so I don't think it was vapor lock, the temperature was in the 80's anyway. I just think something stuck or failed temporarily then corrected itself...........only to get worse or return at the most inconvenient time!!!!

 

[ColoSR]

My boat (2003 6.2L MPI) did this, turns out that my fuel pump was going bad. It has the Cool Fuel 2 plus the vapor lock helper pump. Its in the shop right now to replace the CF2 unit. Fuel pressures were fine in the shop, but would drop from 40ish to 30ish psi under load. They had to put it on the dyno to figure it out.

Using the blower at low speeds and after you shut down helps with the problem. I found that I could start it by put it in neutral and moving the throttle all the forward, you just have to pull it back quickly once it fires. Also, it will run with just one of the pumps. My main pump became intermittent at the tail end of last year, I could get to about 2,000 RPM with just the helper pump.