Engine won't start after running and sitting. Vapor lock?

I have a 2001 Launch with the 5.7L Indmar 350 EFI direct drive. Have enjoyed 10 straight summers of perfect worry free use until this season. When I start my boat up in the mornings and go out everything is fine, but when I park it in the afternoon for a few hours it will not restart. It is as if the engine is deprived of fuel. If it does start, it will barely idle for 10-30 seconds then die. A couple of times it would even start and idle at various speeds by itself before eventually dying. The first time it happened was the first day I had it in the water so I had not changed the fuel filter yet. I bought one during the week and put it on the next Saturday morning before going out. Again it started right up and operated fine all morning, but same problem when I went to run it in the evening. This made me think I had bad gas or water had accumulated in the tank. That week I bought another filter, some HEET water treatment, and topped the tank off with 15 gallons of premium fuel. Added all of these things the next Saturday morning and the boat started right up and ran amazingly well, but same problem when I went to take it out in the evening. I had done some research on the topic and it sounded like vapor lock so I stored it with the clamshell open this time to try to prevent the 'heat soak' but it didn't help.

I have seen various threads on similar things happening but few definitive answers. Everything from vapor lock to bad gas to bad fuel pumps. Hopefully someone in the Supra community can help me nail it down. If it is vapor lock why would it just start to be an issue now? Fuel pumps appear to we working fine also so I would hate to start replacing unncessary parts.

Thanks in advance!

Is it possible for you to take off your air cleaner, have someone turn the key while you watch the fuel spray out of the jets into the throttle body? Would hopefully eliminate a fuel issue if it is pumping gas and turn more toward spark/electrical which could be more difficult to diagnose.

Vapor lock is infrequent in injected motors but possible. I would check the fuel pressure and Mls sure you have adequate pressure when the issue arises. Also you can use a squirt little with fuel in it to see if it will run on it. This will tell you if it is fuel delivery or not. Make sure you have a fire extinguisher on hand.

Is this TBI ? If so then u have a electronic fuel pump correct ? Fuel pressure 32 lbs or above ?

Does the motor miss or chug when it is running for those 30 secs , have u tryed to manaually pump fuel ?
Pressure regulator ok ?

There are somethings to check just off hand .. But I have heard of people pulling fuel line and pumping into a bottle to check tell
Tell fuel flow .. Rent a gauge , check pressure

IZELT - I actually did this last weekend and the injectors are spraying just fine.

If it is a spark/electrical issue why would it only happen a few hours after sitting, then work fine after a day or week of sitting?

Yep, EFI system with electronic pump. The motor doesn't miss or chug, it just gradually stops getting fuel then dies. Eventually it doesn't start at all.

I haven't tried manually pumping fuel or testing pressure yet, but I did look at the injectors under the air cleaner and they are spraying just fine when attemping to crank the engine.

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Originally Posted by lively

Is this TBI ? If so then u have a electronic fuel pump correct ? Fuel pressure 32 lbs or above ?

Does the motor miss or chug when it is running for those 30 secs , have u tryed to manaually pump fuel ?
Pressure regulator ok ?

There are somethings to check just off hand .. But I have heard of people pulling fuel line and pumping into a bottle to check tell
Tell fuel flow .. Rent a gauge , check pressure

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Resistance increases with heat so if it is a bad connection to start with but still working then gets hot and doesn't then that maybe a issue. Sounds like it isn't a fuel issue though. Get it to act up then check the coil then plugs for spark.

Thanks guys.

I actually emailed Indmar directly yesterday and just got a response:

"Sounds like fuel vaporization in the fuel line between the tank and pump. It6 could be you got a tank of winter blend fuel that is designed to vaporize at a lower temp to help with cold starting issues in the winter. We had a prettuy mild winter so it is possible there may be a lot of left over winter blend fuel. Try buying fuel from a different source ... someplace that sells a lot of fuel and see if that makes a difference. You are changing the fuel filter and that is good. The harder the fuel pump has to pull to get fuel from the tank, the lower the vaporization temp of the fuel. You may also want to check the anti-siphon valve in the fuel tank and make surtre it is not stickingand causing a restriction in the fuel system."

I guess I will try to completely purge the system of any possibly bad fuel before I start taking things apart...

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Originally Posted by GA2001Launch

Thanks guys.

I actually emailed Indmar directly yesterday and just got a response:

"Sounds like fuel vaporization in the fuel line between the tank and pump. It6 could be you got a tank of winter blend fuel that is designed to vaporize at a lower temp to help with cold starting issues in the winter. We had a prettuy mild winter so it is possible there may be a lot of left over winter blend fuel. Try buying fuel from a different source ... someplace that sells a lot of fuel and see if that makes a difference. You are changing the fuel filter and that is good. The harder the fuel pump has to pull to get fuel from the tank, the lower the vaporization temp of the fuel. You may also want to check the anti-siphon valve in the fuel tank and make surtre it is not stickingand causing a restriction in the fuel system."

I guess I will try to completely purge the system of any possibly bad fuel before I start taking things apart...

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winter blend fuel ?? BAHA HA AH Aha .. man where do u get that stuff ? i have a work truck that could use some of that hard start fuel ? really where you get that ? ask him !! see what he says lol .. its a combustion engine ... not a wonka vator ! ... rent a gauge and check your pressure man .. i have seen several electronic fuel pumps work fine for days and then start crapping out for no reason ..

if it was me i would buy some line and run a straight pull from the pump to the engine . lol im still laughing at his response .. and maybe they do sell it .. but hell be a first for me .. but i dont think that is the issue ...

If it was we would all be asking the same questions and there would be a lot of cars on the side of the street.

As mentioned already, if it isn't fuel, then next would be fire. (spark). If it was me, next I would take a spark plug and disconnect the coil wire, plug in a spark plug and have someone turn it over while watching for a spark. That should eliminate the wire to coil if it works. (hold the plug to the block with a pair of covered handled pliers/channel locks). If that worked, then I would do it with each plug wire off the distributor cap in the same fashion. On ours, the distributor cap was corroded. Replacing it this week before the holiday.

Thanks, I'll give it a shot.

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Originally Posted by jzelt

As mentioned already, if it isn't fuel, then next would be fire. (spark). If it was me, next I would take a spark plug and disconnect the coil wire, plug in a spark plug and have someone turn it over while watching for a spark. That should eliminate the wire to coil if it works. (hold the plug to the block with a pair of covered handled pliers/channel locks). If that worked, then I would do it with each plug wire off the distributor cap in the same fashion. On ours, the distributor cap was corroded. Replacing it this week before the holiday.

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Please let me know what you did to fix this I'm dealing with it now myself. Thanks

I have the exact same problem with my '97 comp black scorpion motor. Has anybody got a definite solution?

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Originally Posted by Wingler

Please let me know what you did to fix this I'm dealing with it now myself. Thanks

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Its common for some of the boats built before 2007 to vapor lock when using fuel with ethanol. The fuel pump is mounted to the engine block and will vapor lock on very hot days. There are several old threads addressing the issue. The quick fix is to use ethanol free fuel or pour cold water on the fuel pump when it happens. The engine will immediately start after you do that, this is what I do on days where the outside temperature is 90+. Sounds silly for boats this expensive but it works. The permanent fix is to have a low pressure pump installed between the tank and high pressure pump. Several people on this forum have done it themselves. I heard Indmar was covering that during the warranty period, since then they have fixed the issue.

Hope this helps.