2001 Legacy Fuel deprived when hot - won't start or run

[KarolinaKid]

Just had to be towed in the first time in 20 years...And worse, I leave for a week at the lake in a week...help!

2001 Supra Legacy with Indmar 350 Chevy TBI...320 hp I think.

Cranks up at home and runs like a champ...purrs like a kitten. Get to the lake and launch...same thing...purrs like a kitten. Run all over the lake for half an hour or so, then stop for 30-45 minutes to let the kids swim. Engine is hot, temp had been holding normal at 175...but not over heating. When we went to crank up and get going it was hard to crank...started cutting out...died and would not start again...almost as if starved for fuel. This boat is in great shape...300 hours and looks new...clean engine...all hoses and wiring looks great.

Pulled engine cover and checked several spark plugs...all look good...wires all connect well and look new...no corrosion anywhere. Cap and rotor look good, dry. Coil sending spark...jolted me pretty good. Pulled a plug and tested spark...another jolt...good spark. We have fire! When turning over to crank, the injectors are pulsating a small inconsistent cone of fuel...not constant. Will not crank, but almost did a couple of times...towed in...got home...engine is cooled down...hooked up fake a lake and tried to start...cranks right up and purrs like a kitten. I notice the injectors spray a noticeably different large, consistent full cone of fuel. Only difference is cooler engine...suddenly not starved for fuel. Obvious fuel delivery issue when hot and after sitting a while. Reminds me of vapor lock on my old Chevelle big block 396.

Any suggestions? I will definitely change fuel filter, but cannot imagine that could be entire issue...it was replaced less than 30 hours ago. Fuel pump failing when hot? Electronics failing when hot? I'm stumped.

Any help would be much appreciated.

[KarolinaKid]

Research so far indicates higher content of alcohol (ethanol) in fuel along with poor design of fuel pump location can result in vapor lock during "heat soak" time. I hear Indmar has actually told people to poor cold water on the fuel pump and filter as a solution. Another solution is to install a second fuel pump in line further back away from the heat to assist fuel delivery during vapor lock. Toyota comes to mind for some reason here...

[motoman160]

I have a 2000 legacy with the mpi 330 motor and it had fuel pump that had a water supply to it and it would help keep the fuel cool well i guess they had aproblem with them rusting out on the inside and you would get water in your fuel. anyway indmar replced it with the new style no water around it and now it will vapor lock after sitting and it getting hot so i ran the fuel line different and hope that take care of it just thought this might help i know their different systems but maybe it will help

[rludtke]

Classic vapor lock condition.

Fuel injection is as susceptable to vapor lock as carburaters. The fuel in the injector lines down stream of the throttle body will boil or vaporize due to the heat under the engine cover. This typically happens after shut down, because the constant flow of new cold fuel prevents the fuel in the affected area from vaporizing. Once the flow stops, the fuel heats up. The vapor in the system needs to be purged, or the fuel needs to be cooled down. gasoline with alchohol makes it worse.

Opening the engine cover at shut down will help vent heat, but on a hot day that may not be enough. Icing the fuel pump can also help, but what a pain.

Search this site for discussions on this problem, i've seen many over the years.