Fuel Vapor Lock again...........
 

I know there has been a lot of talk on here about this problem. Mine is a mild build 500hp 96 502mpi. Twice today I had vapor lock that would shut down the engine. Both were after a 15 minute slow no wake run through the channel.

I'd really like to remedy the problem, but don't know if there is anything i can do. It would be real nice to just get the cool fuel system, but don't know if that's possible.

One idea I had was to reroute the fuel line from the front of the motor and either route it to the back of the motor, or up further using new AN aluminum lines. Don't know if it would work or not............... It's pretty embarrasing to get up on plane, and then have it quit and come back down. I'm sure glad i have the back exhuast flappers as well as the internal rubber flappers as two lines of defense to keep the water out of my cylinders when that happens.........

You can take the fuel line return and remove it from the filter, buy 2 fuel fill adapters the size of the fill hose and return the back that way into the tanks or if you have another pick-up on the tank return there. You could also use the vent line if you can get close enought to the fuel tank.

Anyone else come up with a fix?

Once its running it should not vapor lock. Vapor lock generally happens after running the boat and turning it off. The heat in the engine compartment evaporates the fuel in the lines.

mine is doing it after a 15-20 minute slow no wake. Engine bay is getting heat soaked. blower on or not........

The sure fire way to fix it is to return the fuel to the tank. This will absolutely stop the vapor locking.
Eddie

Can you elaborate on this?

I was also thinking of abandoning the steel fuel line routed in front of the motor, and making up an rubber fuel hose with fittings and routing away from the motor. I would think the change from steel to rubber in itself would help the fuel temps in the line.

You cannot use rubber fuel line for a marine engine. Against USCG rules.

One easy way is connect this to your fuel fill line then connect the return fuel line to it.

http://www.cpperformance.com/detail.aspx?ID=980

That is definitely worth a try. Anywhere else a fuel line is close to the engine?

It creates a constant flow of fuel throughout the system instead of a "dead-head" style system where the fuel sits in the lines for a prolonged amount of time in an idle situation.

http://www.ellison-fluid-systems.com...uel_system.gif

That's interesting. So basically the fuel that is getting too hot running around the motor will be constantly on the move instead of being stagnant. I understand the theory. I guess I don't know how the return is hooked up now with the VST tank. Would I just want to hook the return to the vent lind of the tank vs. the fill?

Any possibility of running lean at WOT due to returning to the tank vs. whatever method is being used now?

It won't run lean because it will have constant fuel flow as well as more steady fuel pressure. This system still has to have a regulator in line to maintain the proper line pressure (a fuel log style regulator works great). Typically it will be just after the carb inlets on the return side. This keeps the pressure constant but also allows the fuel to reach the carbs in whatever capacity needed. As far the return line entering the tank, you will more than likely have to make a new entry to maintain the proper ventilation. One of the performance shop guys on here could give you a better diagram and layout for your application. Good luck.

Yeah, your confusing me somewhat, i have the MPI, what do i need to do.

My mistake cloudmaster, I missed the mpi and was under the impression it was carburated based on the post about the return system. I'm not certain but I believe the mpi already has a return style system due to the level of fuel pressure required to run. I have extremely limited knowledge on fuel injected systems won't be of much help. Sorry for the confusion, just trying to help.

Was everyone elses's post on a carb model or MPI? What do I need to do for an MPI?

I'm going to try this.............

Cloud,
Before you re-rig, I think your idea of just doing a quick test with a temporary rubber fuel line in place of the steel line might work.
Ben

Plan on it, West Marine has rubber fuel line USCG and NMMA approved. Gonna loose the metal line and reroute it.

I'm probably gonna do the fuel return switch as well.

Also going to add a couple of vents just to get some more air into the engine compartment, i don't think there is enough.

None of this would matter if i don't sit in slow no wake channels. But i do, so something has to be done.

The MPI's just return the fuel to the water sep filter and not tot he tank.

He said he has the VST system. The only thing I have read about them is that the screen in the VST tanks clogs up all the time.

If i want to check this screen out, what seal or oring would i need to put it back together. Only thing i saw was some $80+ kit with the orings..........

vapor lock
 

you have to remember that the cause is engine heat and heat soak in the engine bay. try turning on your bilge blower to exhaust extra air and heat. the fix is to keep the bilge cool.

No doubt, i agree. Eliminator doesn't have much at all in the way of venting. I am going to try and add some venting through the lower back seat area.

I usually run with my blower fan on all the time. It's not enough though. Maybe there are better blowers now that move more air? Not sure. I'm sure mine is '96 technology.

I have not religiously lifted the hatch cover 8 inches or so when in the channels but will be doing that as well. I still think the rubber lines will help out with the fuel temps as well.

I don't have/never had a VST system, so I don't know the specifics. I have read a lot about an internal sceen that gets clogged and needs to be cleaned out periodically.

It's something worth checking into for sure. Just saw it looked like i had to spend 80 bucks for an oring to put the cover back on......... seems kinda crazy

If you are careful you can reuse the o ring seal in the vst cover. My experience is that it stays in the groove machined in the cover. I keep one just in case but have not had to use it.

Jerry.