HELP: Mercruiser MPI stalls after sitting when engine is warm

[ryanicko]

Hey everyone I'm looking for some advice or help. I have a 2002 Chaparral 216 SSI with the Mercruiser 5.0L MPI engine. The boat always starts right up when I take it out each day (engine cold) and runs fine no stalling or sputtering while running at any speed/rpm.

Now here is my question: When I turn it off for awile maybe 15 mins to 1 hour after running the engine for at least a half hour (engine warm) it stalls when I try to restart the engine. The engine turns over and usually runs for 1-5 seconds before stalling. I usually have to try to start it 10-15 times before it will restart. It will eventually always restart so far, but this isn't normal and it is going to burn out my starter.

The batteries are both new and all guages are running within normal limits. I bought this boat a few weeks ago and had the outdrive serviced and the oil changed. I would like to get everyone's suggestions before I pay a marina to start replacing parts that might not need it.....Thanks

 

[Pete104]

Re: HELP: Mercruiser MPI stalls after sitting when engine is warm

You have to have the PCM scanned for fault codes on this unit. Your IAC valve most likely went south. It controls the idle on EFI motors.

 

[ryanicko]

Re: HELP: Mercruiser MPI stalls after sitting when engine is warm

I figured out the problem incase anyone else is having this same issue. My one way check-valve that stops the hot water from flowing back into the engine block was defective. This was allowing the hot water back into the engine to cause a vapor lock issue. Since the valve was replaced, I have not had any problems.

 

[Fun Times]

Re: HELP: Mercruiser MPI stalls after sitting when engine is warm

I figured out the problem incase anyone else is having this same issue. My one way check-valve that stops the hot water from flowing back into the engine block was defective. This was allowing the hot water back into the engine to cause a vapor lock issue. Since the valve was replaced, I have not had any problems.

Thanks for this important update.

Because in my personal unconfirmed opinion, I would only guess probably anywhere between quarter to half of the possible fuel vapor lock questions regarding 2002 to current Mercruisers MPI's that come up this time of year could very well possibly be due to an defective one way check-valve in the cooling system like yours.

I see this as a little tough to diagnose with confidence. So by chance would you be able to elaborate a little bit more information of how you where able diagnose it was in fact a bad check-valve for future reference? Thanks.