496HO random issue vapor lock or ???
 

2002 496HO 227hrs "0M084807" with random issue and not sure if it's vapor lock or something else. starts fine and runs as it should except when trying to restart after short off time (about 10-15 minutes) after running for about an hour. Starts but runs down on cylinders, sometimes restart again and all is well, sometimes if I let it idle for a few minutes returns to normal running. Using VV mobile today shows no faults, battery voltage running 13.8v From memory I think it happened about this time last season when temperatures were 80's to low 90's. I think engine has cool-fuel 2 system? We only have ethanol 10% fuel up here and maybe vapor lock. What are the symptoms of vapor lock or any other ideas what's going on?

thanks

Don't think its VL because its only been off 15 minutes or so. VL takes time for fuel to heat soak and fuel boils into vapor

Your motor has cool fuel and also a boost pump.

I'm thinking the pump may be having some issue getting fuel to flow at pressure. I would start by checking pressure at the rail, should be 43 psi

Have you checked the manifolds and risers? A leaking manifold will cause misfires after sitting a few minutes and dripping back into the cylinder

Simple qualifier - do you raise the hatch and let the heat heat escape during the 10-15 minute shutdown?

Alldodge is pointing you in the right direction IMHO.

UPDATE from this AM:

Fuel PSI builds instantly on startup. 41psi
Shut down holds PSI about 35lbs well over 20 minutes then I stopped monitoring.
NO faults
Has run fine for the last 17hrs without any issues
From memory this is same issue which started about same time last season once it's got hot with temperatures in upper 80's to low 90's.
I'm going to replace both PCM and fuel ump relay because I think they are getting too hot even after 10-15 idling.

Wondering if it's the PCM/ECM after heating up???

Don't think its the ECM
Original issue was
Need test equipment hooked up to determine what is happening when it does it again

Since there is time involved and a restart after a short time it could be a restriction in the feed (tank, anysiphon, filter, line, vent line). The tank vent line if restricted would cause the issue. When tank was full it wouldn't take long to draw a vacuum. As fuel is used up it would take longer to draw a vacuum

Will check next time out and open fuel cap to check for vacuum
I did notice ECM/PCM doesn't detect misfire? May not have that ability??

Just got back from an evening cruise for over an hour and RPM was no more than 3500 along with several stop/engine starts.
Ran great, no issues. Also temperatures were only mid 80's.
Will check for vacuum in tank next time out.

Bump....

Update since last 7/18 posting and have ran about 6 hrs runtime on engine. and kept engine under 3500rpm and never had the issue. Today ran about 4000-4400rpm for maybe 1/2 mile at most. Shut down, immediately restarted and was felt like down on cylinders same as before. Waited 10 minutes and all back to normal. Going to do a scan and check faults, which never was, and history scan.