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Warm start problems

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Gcundiff

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Hello, I'm needing some help on our new/used boat and hope you guys can she some light.

BOAT: 1999 5.0L EFI with 10 total hours but obviously has been in dry storage for years.

Engine starts cold perfect and runs fine. After sitting off for 30 min. or so, very hard to start, tries to fire and will occasionally idle for a second but seems to be starving for fuel. I don't think it's spark/ignition. I eventually got it to fire, gave it throttle and it ran fine for 30 minutes. Then after idling a bit, it coughed hard to get back up to speed. I put cheapo gas in it with E10, do the older 5.0 EFI's struggle with ethanol? Does it sound like vapor lock? Other fuel related ideas?

Thanks.
 
Does it sound like vapor lock?
Click to expand...
Perhaps...do you run it w/the bilge blower on all the time? You should and let it idle 5 mins. before shutdown after a long run. Did you replace the impeller when you got it? What temp does it run at? How much fuel was in the tank when you bought it...did you pump it out? Replace filters? Dump a double dose of Seafoam into the fuel tank and run it to near empty before filling it up...add a dose of fuel preservative for ethanol fuel to the tank first.
 
I completely drained the tank of its rotten fuel but didn't replace the fuel filter which I'm doing today. I didn't run the bilge blower at all. Should I? Temps looked fine all day and never deviated from normal. Will Stabil work for ethanol?
 
Run it all the time. Look inside the engine compartment at the air inlet to the bilge blower...one side should be blocked off. Remove the block and attach some duct to it and hang it in front of the flame arrestor so the engine is getting cooler air while under way. Use Stabil for ethanol. Fill the filter half full w/Seafoam and the rest w/gas to prime it. It will smoke like it's on fire but it will clean the entire fuel system. What do the spark plugs look like?
 
Gcundiff said:
Hello, I'm needing some help on our new/used boat and hope you guys can she some light.

BOAT: 1999 5.0L EFI with 10 total hours but obviously has been in dry storage for years.

Engine starts cold perfect and runs fine. After sitting off for 30 min. or so, very hard to start, tries to fire and will occasionally idle for a second but seems to be starving for fuel. I don't think it's spark/ignition. I eventually got it to fire, gave it throttle and it ran fine for 30 minutes. Then after idling a bit, it coughed hard to get back up to speed. I put cheapo gas in it with E10, do the older 5.0 EFI's struggle with ethanol? Does it sound like vapor lock? Other fuel related ideas?

Thanks.
Click to expand...

Hi, I had the same problem with my 1999 5.0L EFI.
It's probably your high pressure fule pump that is bad. When it is warm, the fuel turns into gas inside the pump and it stops working. When it cools down it will work again, but it can take hours depending on temperature.
You probably have to replace it. It is located at the right side of the engine, close to bottom front of the engine were the water is coming in.
Just follow the fuel hose from the fuel filter.
 
I'm having the same problem with my 502 MPI. Do you notice it shuts down when you go to idle or does it happen under way? Also, could this problem have anything to do with the charging system? I have twins and the charging system on the other motor seems to be faltering
 
I've been reading and studying this issue non-stop and based on many other threads at various sites, I'm convinced I have vapor lock issues. The motor is brand new with < 20 hours on it and there's some evidence someone else has tinkered with this same problem. I'm going to order the check valve kit and see if that works as I'm not too excited on getting stranded again trying the simple fixes that don't seem to be very successful anyway. I've found it online for $80 vs. $115 at dealer.
 
Listen to guyjg. His advice is sound. Let the engine run for a minimum of 5 Min. before shutting down if you intend to get underway shortly. Also, vacating the hot air by running the Bilge Blower works also. What Temp Thermostat are you running? Can you lower the Operating Temp a little? Al W.
 
If it does not have a number 160 stamped on it you have to heat some water and immerse it while watching it and a thermometer to see when it opens.
 
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