Engine won't start once warm up, 6.2 MPI.

P

pierpressure

New Member
Feb 17, 2014
21
Miami, FL
Boat Info
Amberjack 290 2002
Engines
Mercruiser 6.2L , Bravo III.
I have a 2002 MX 6.2L MPI, This is an intermittent issue whereby after running the boat for a couple hours on water and turning off, she fails to start back up. I can hear the fuel pump priming, the engine fires for about a second and then stalls out. After sitting for a while 20 minutes or sometimes up to 1 hour, it starts up. Once it starts, I'm golden with no hesitations at idle, full throttle, etc...... It only happens after I turn it off, Any ideas? :huh:
 
Vapor lock. Do a search and you'll find alot of information on it.
 
The starter slave solenoid can cause similar issues. Sometimes loose connections and sometimes a bad slave solenoid. It is a cheap part by boat standards. There are threads on the subject in the forum.
 
IAC control valve could also be the issue.
 
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Classic vapor lock issue. My 02 5.0l mpi(base same eng) would sometimes do the same thing at times. You can install a boost pump for the fuel to try and help. Merc has a kit I believe.
 
I have the same enigines. My port engine is a total B***h to start once it is warmed up. My engines came with the boost pump (2003) but I still get vapor locked. Ill stay tuned to this thread. I have been fighting this for 2 years now. Ive had mechanics look at it and they scratch their heads. It's only when it is warmed up.
 
On an air cooled 2 stroke I had the same problem. I solved it by replacing the fuel line with a thicker one and running it as far away from the engine heat. Figured the thicker line would insulate the gas from heating and giving it some slack near the engine would help keep it cool. Took a year to figure that out.
 
this could be another example of how the rising and radiating heat from 'heat soak' from a shut down hot engine gets trapped in the engine compartment and does all kinds of nasty things to electronics and fuel in the supply lines.......without a way to evacuate the heat from the engine compartment the engine heat will heat everything up in the compartment to the point issues such as vapor lock can happen.... a hot engine will continue to get hotter and hotter to a point immediately after it is shut down because there is no coolant circulating inside the water passages to cool it down....then you are forced to wait until the heat dissapates naturally before things return to normal....i have had personal experience on my boat with this where the heat was affecting my electronic ignition module....to help with my engine heat problem i added two small squirrel cage blowers (120 cfm each) in the engine compartment that pull in cooler outside air into the compartment....i can turn these fans on for a few mins and force cooler air into the lower section (bilge) of the compartment which forces heated air out of the compartment through the compartment vents in the transom.....

as a side note i used to own an older Jaguar XJ6 and frequently spoke to owners of XJ12....the XJ12 was notorious for vapor lock for this same reason....it was huge V12 engine in a VERY tight engine compartment and the heat from the engine would cause the fuel in the supply line to vaporize (boil) causing vapor lock because the heat could not escape the compartment fast enough to keep the temp down.....

cliff
 
Hi guys, just thought I'd let you know for some of the small block engines, there's a check valve kit you could install (Merc part # 21-862271A1) that may help with some of the vapor lock issues. Some newer engine models may already have the valve while some older models may not. We had a good discussion about it on marineengine.com a few years back. http://www.marineengine.com/boat-forum/showthread.php?390380-Vapor-lock-or-what. You'll be able to find a Mercruiser service bulletin link about fuel vapor lock. Another Merc marine tech mentioned he's done a lot to some sea ray models. Hope this helps, Good luck.:smt001 P.S, all the advice given thus far could very well be the hot starting problem. Oh and if you have a big block Merc 7.4 - 502 MPI, one trick is to figure out a way to remove the fuel return line from either the filter base/housing or at the VST depending on engine model and direct it back into the fuel tank or some have had success mixing marvel mystery oil in the gas per the instructions on the can. Helps keep the pump cooler plus last longer.
 
Try idling the engine for about five minutes before shut down. Also run the Bilge Blower while underway all the time and for ten minutes after slowing. Al W.
 
First of all, thank you for all the advise, it's definitely a vapor lock problem and I think the problem started last month, I normally use non-ethanol 90 or regular 87 octane with 10% ethanol, last month I fueled at a marina (Monty's in south beach) they had 93 octane (non-ethanol) and that's when my problems started, I never fuel at the marina ever ($5.65 per gallon it's not good for my blood pressure), but after researching about my problem I read about the fuel issue in another forum, Mercruiser rated my engine for 87 octane 10% ethanol max, so I will do that test in a couple of week (will refuel with 87 and add some stabill) that should helps, if not, I'm removing the fuel cooler and cleaning it or replacing it. And if that solve my problem, I will be running my blowers constantly for now on, I think running the engine for few minutes before a long run it should help as well. Great advise
 
I'm sorry, it took me a while to come back but just to close this case, the problem was Vapor lock due to bad fuel (from monty's marina at Miami Beach) I believe it probably had too much alcohol, depleted the tanks and refueled with good fuel and problem it's gone. forever (I hope)

Thank you for all the people that took the time to respond.

Cheers.
 
Pierpressure did this fix the issue?


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I had something similar... chased the issue for ages... was combo of IAC and the fuel cooler lower water hose fitting being so corroded it was barely flowing... check cooler and IAC..
 
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