Fuel delivery problem or Vacuum lock?

[ND Crownline]

I have a 99 Crownline with a 502 Merc. engine Serial # 0L310155 drive number 0L157098 if that helps anyone. My problem is this when the boat is cold it starts and runs just fine. But once I drive it for a while and shut it down and let it sit any more than 30 min. when I go to restart it will start but not run very long and sounds like its not getting fuel. After a few seconds it will stop running then it will not restart at all. I can cycle the key and hear the fuel pump run, and it sound like it wants to start but will not. I can play with cycling the key and messing around with it for 30 min. berfore it will run again. Once it runs again I have no problems unless I let it sit again for more than 30 min or less than 2 hours. I have replaced the fuel pump, water pump, and thormostat and a few other little things, but it still seams like a vacuum lock or something? what else should I be looking at? Anyone had any problems like this before?

thanks for any help or suggestions

 

[Farmer3315]

Re: Fuel delivery problem or Vacuum lock?

I have a 99 Crownline with a 502 Merc. engine Serial # 0L310155 drive number 0L157098 if that helps anyone. My problem is this when the boat is cold it starts and runs just fine. But once I drive it for a while and shut it down and let it sit any more than 30 min. when I go to restart it will start but not run very long and sounds like its not getting fuel. After a few seconds it will stop running then it will not restart at all. I can cycle the key and hear the fuel pump run, and it sound like it wants to start but will not. I can play with cycling the key and messing around with it for 30 min. berfore it will run again. Once it runs again I have no problems unless I let it sit again for more than 30 min or less than 2 hours. I have replaced the fuel pump, water pump, and thormostat and a few other little things, but it still seams like a vacuum lock or something? what else should I be looking at? Anyone had any problems like this before?

thanks for any help or suggestions

I've been dealing with EXACT same issue with a 350 mag. I know this sounds stupid but next time it does it try having someone pull you about a 100 feet or so and then try it. Mine will fire up every time. I don't know what it does but it has worked at least a dozen times and failed none. I just checked fuel pressure on mine and thinking its running a little low so I might try a new pump. Good luck and please let us know if you figure it out

 

[Failproof]

Re: Fuel delivery problem or Vacuum lock?

Electric fuel pump, heat soak, and todays **itty fuel. As soon as you shut down it starts to perc. Add to that the vaccum needed to break the check valve, and its instant vapor lock. Why towing it would affect anything i dont know but dont doubt it one bit. Nothing surprises me with boats!

 

[Dshow]

Re: Fuel delivery problem or Vacuum lock?

There are several things you can do to help vapor lock, the air in the engine compartment is getting to hot so you need to keep it cool.
1. Leave the blower on all the time to keep the air circulating.
2. Idle the engine a little bit to cool it down before shutting it down.
3. I had totes on either side of my engine taking up air volumn which I reduced their size.
4. My 2 air vent to the engine compartment had plastic inserts with only 2, 3" holes of which I only has one blower hose. I removed one insert and cut the other down to only allow for one hose. I get much better air flow now...
5. Make sure your blower hose has no kinks which reduce air flow.
6. If possible, open the engine lid after shutting down if your just sitting there.
7. Merc has a bulletin regarding vapor lock. If you have a cool fuel system, they sell a check valve to keep the hot engine water from draining back down into the cool fuel system and heating your fuel.

 

[ND Crownline]

Re: Fuel delivery problem or Vacuum lock?

Thanks for the reply's, Dshow I do idle down for a bit be for I shut down, but will let it run a while longer, I also have a case that goes around the sides of the motor that has holes cut into it about 12" square, that you can snap on these covers with pockets for storage, I leave them off trying to get more air in. I will also look at my air vents and see if there is something that I can remove. I did get the service bulletin form Farmer. Thanks again for any help

 

[dollarten]

Re: Fuel delivery problem or Vacuum lock?

Are you using an ethanol blend fuel ? If so the high evaporation of this type of fuel will cause starting problems I once had the problem with ethanol blend fuel and switched to a non ethanol blend and had no more hot start problems

 

[ND Crownline]

Re: Fuel delivery problem or Vacuum lock?

I am gong to check with the owner of the marina on the lake that I keep the boat on, but the guy working the dock said its 91 octane, but when ever I do pull the boat out of the lake I always put or fill up with 91 and try to make sure that it does not have ethanol blend. Does anyone know if adding ocatane boost or some other additive will work or help?

thanks

 

[ND Crownline]

Re: Fuel delivery problem or Vacuum lock?

Thanks again for all sugestions, I did let the motor idle down longer when stoping and also lifted the engine lid for a while, this along with getting fuel at another marina and I did not have any issues this past weekend. I am thinking of pulling the boat out and having a check valve put it so the hot water cant drain back down as the service bulletin talks about. Has anyone else done that? did it help?

thanks

 

[Banando]

I had the same problem its the check valve on top of fuel tank looks like air hose fitting it starts to seize up put a regular fitting on it havnt had any more issues