tired of the bullsh*t vapor lock!
 

502 EFI vapor lock issues.... any suggestions? maybe add a booster fuel pump before the water/fuel separator? or insulate the fuel lines? Getting tired of messing with it.... setting it on fire will be next! not really, but i would like to fix it. Boat has 2 502's in it and they both vape out.
thanks.
Kevin

Are you sure you can get enough fuel to that fire? :lolhit:

Run a line from the fuel-water separator back to the tank.

Do you have a mechanical pump on your sea pump?

If not there is a kit for this problem

i put a Holley electric pump between my gas tank and fuel water seperator. It was easy to do. Wired it to the ignition so when the key is on, its on, when i turn the key off, its off... You could also wire it to a switch, just remember to cut it off.... I havent had vapor lock sinse.

http://www.jegs.com/i/Holley/510/12-815-1/10002/-1

i dont remember if i put the "red, blue, or black" pump on. not sure it would matter either.

yes i do have mechanical fuel pump. I don't understand why i just can't
bypass that pump and add a low pressure electric fuel pump.

Boomer did you bypass the mechanical fuel pump?

Vapor Lock or Vacuum Lock?

I think of vapor lock where the fuel is getting too hot. Vacuum lock is where it won't flow because of inadequate relief venting not allow ing gas to flow from the tank- it creates a vacuum.

You can insulate the line, but if the gas is getting to hot it's sometimes from the manual fuel pump.

Wannabe

Best solution I have seen

"Hello I have a 1995 Formula 271. Basically the same issues, took another rout, $hit canned VST tank, sea water transfer pump, the whole 9 yards and started over. Run an Aeromotive fuel pump, (filters fore and aft the pump) -8an to the fuel rail, -6an on the return to the boats fuel tank, through a fuel pressure regulator set at 48psi. then to the tank. No more "cool fuel" or any other crap. The fuel from the tank is always fresh, you eliminate the fuel on the pressure side getting hot from the engine and just "circling round until you get on the throttle. It's clean and simple, your fuel rails should already be drilled for 1/4 mpt."

Courtesy pocketchange22

So basically replace everything with Tank -> Filter -> Pump -> Filter -> Rail -> Regulator -> Tank

If you don't want to jump right into hardware changes I have had good luck with adding Marvel Mystery Oil to the fuel. This apparently raises the vapor pressure of the fuel.

I believe its the lack of a return that causes the issue. The fuel vaporises in the rail.

ok maybe I'll try the mystery oil first..... thanks to everyone who are putting in
their two cents worth!

My uncle put a cheap primeing bulb,like what an outboard has spliced into his fuel line,it may be a little redneck but open the hatch give two or three pumps and 502 fires right up.

In the VST models, the pressure in the VST becomes higher than the pump can deliver, say 10psi in the VST vs 5-7psi max delivered. The top plug on the VST can be removed to relieve the pressure as a temp fix to get you home. I always leave mine finger tight so I can remove it.

I like the MMOil idea, probably good for the entire system anyhow as long as it is not too much.

I read up on the MMO and it says 4oz. per every 10 gallons.

Would a bypass type regulater and good fuel pump negate the problem?

This has been talked about a lot. If you have the VST tank, take the fuel rail return line off the vst tank and run it to your main gas tank instead. CP makes a nice piece that splices the fuel fill hose and allows you to run the return fuel line to it. Plug the fitting on the VST tank. Mine is a 96 502 mpi, and I had the same problems. I talked to the famous Eddie Young, and he suggested the above fix. Worked like a charm. Not a single issue since.

I have many posts on this and chased for ever. Run a fuel line from the VST back to the tank and cp does have a fitting you can splice in your fuel fill line to the tank. I had a guy weld another bung in it since I have twins. I will tell you this pull your mechanical pumps and check for wear on the arms.. There is supposed to be oil in the reservoir no one ever checks these.. I had one wore.. And the other was leaking. Only had 200 hrs on boat...

As Cloudmaster mentioned, just return the fuel to the tank instead of the VST and the problem will be fixed forever.....guarenteed. It is really simple to do. If you can't get to the fill hose to return it, then I can tell you how to make a fitting to put the fuel back into the tank. I have done more than I care to think about, so we know what works.
Give me a call if you have any questions. I can walk you through it.
Eddie

What about on the later 502's without the VST?

Had an issue last summer with both of mine vapor locking, especially after hard run and sitting for a bit.

I also read an article recently that claims ethanol fuel has a lower boiling point and can worsen an already bad vapor lock problem.

thanks Eddie when i get to that point I'll call you!

The later ones return to the fuel filter head. You can simply plug off that port on the filter head and just run the fuel line back to the tank.

Fuel with ethanol is more susceptible to vapor lock.

Eddie

My 502 mpi's will vapor lock with ethanol quite a bit and rarely vapor lock with regular fuel. Like Eddie said, you can run a return to tank or Merc also makes a kit with a booster pump that will cure the problem.

that merc EFI set up was B/S from the start even with all there updates(band aids) re plumb with a aero a1000 pump, a return regulator, good filter, and return to the tank...the way it should have been...

Eddie... my problem is.... the fill line for the fuel tank is right in the middle of the boat and the boat is 40 ft. long. Is there any any other way to return it without drilling, because the tank has about a 100 gallons of gas in it.
thanks,
kevin

There certainly is another way. Give me a call and I will be glad to explain it to you. It's hard to put into words to type here. Otherwise, I would just post it here. I've tried to explain it before and I don't think it made sense.

You can reach me anytime at 615-216-7449.
Eddie

Give Eddie a call, he knows his sh-t has helped me several times. He'll be doing my motors when the money fairy pays me a visit.

you can get a sending unit that fits your tank(depth) for a diesel, they have a return fitting already made in it...pretty simple..

Ezstriper that's a great idea! Are you sure it will work?

Do they make a sending unit with two return lines? For two motors feeding off the same tank?

I am sure you could easily make one into two with some fittings.

Pullled this up do to both of my '99 502's not starting every time they were shut off for a short while do to vapor locking and needing some clarification.

The return line going to my water/fuel separator...

There are 4 ports to the separator: main line IN, main line OUT, plugged port OUT, and a 2nd IN line. This 2nd IN (#16?) to regulator is the line I need to remove and plug the sep housing port, then reroute that hose to return to my tank, correct?
I have no unused bungs in the tank, just the sending unit and the 2 pickups for the 2 motors, so I'm going to have to tap into the fill hose with a tee. Do I need some type of check valve?
Can I tee both motors return lines together in the bilge and run a single line to the fuel fill hose?
What about that unused OUT port #3 on the sep housing? Can I use that instead of removing the return line or will that just create a recirculating condition with the pump running full time?
Thanks