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Vapor lock?


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Three times now this year, after running the boat for awhile, then shutting it off and going to eat for an hour or so, it starts and runs about 5 secs then shuts off. Then it'll fire off but won't stay running. First two times it took about half an hour then it fired and stayed running. Last time I opened engine compartment and put blower on, and it was okay in 10-15 minutes. Someone mentioned possible vapor lock. What could be causing this? Otherwise runs fine. 

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Cause?  Uhhh... vapour lock.  Gasoline gets overheated and vapourizes.  Get a secondary pump and/or insulate the pump and lines.  And cool the boat (lift engine lid, add fan etc.)

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It seems to be more prone to happen if you are using ethanol fuel.  If you can avoid it (easier said than done around here), you might have better results.

Growing up, we had a sterndrive with a Merc 350 that would do the same thing.  When we started using premium fuel, that took care of the problem as well.

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Yep, probably vapor lock.

Pour cold water (you can use an empty can of your favorite beverage, dunk it in the lake, and pour lake water in a pinch) over the fuel pump.

It wasn't until 2007 that Indmar/Malibu started putting the fuel pump inside the fuel tank.  That way, the fuel pump itself is insulated from the heat inside the engine compartment, and the fuel in the fuel lines and fuel rails distal to the pump  is under enough pressure that even ethanol fuels don't cause vapor lock.

But, with my boat, as I suspect with yours, the Pierburg electric fuel pump is mounted in a circumferential metal clamp that connects directly to the engine block.  It gets heated up not only by the air temperature within the enclosed engine compartment, but also by conduction from the block itself.

The best solution, for me, to resolve this recurrent problem was to install a secondary low pressure fuel pump mounted closer to the gas tank, which pressurizes the fuel in the line between the tank, through an inline fuel filter, and on up to the primary fuel pump.  Since then, I have tried to get my boat to vapor lock several times (shutting her down after a morning run, keeping the hatches closed, and not even turning on the blower, for 30-45 minute stretches).  So far, I have had no further problems. YMMV.

FWIW, I purchased this one from Bake's:  https://www.bakesonline.com/indmar-fuel-pump-vapor-lock-prevention-kit.html

Others have gone a cheaper route by purchasing the pump, connections, and fitments individually.  Still others have managed by wrapping the fuel lines and insulating the fuel pump with heat-resistant materials/shields.

Good luck.

 

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Don't waste any more of your time and effort, just add the secondary pump and be done with it...I fought it for far too long.  Now it starts right every time.

There are a ton of posts/threads on this, but just know there are several ways to accomplish this, ranging from $100 and up.

 

 

Edited by formulaben
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Sounds like a common problem I've run up on. The Carter P4389 is $70 Amazon Prime. And so I need 1/4 inch to 1/2 inch brass hose fittings, maybe at NAPA, or the hardware store? ?And the wires will just piggy back onto the same wires going to main pump? Does it matter which side of the filter it goes on? I saw someone say between filter and main pump. Does it matter if there's more room on the other side?

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Looking at reviews for Carter pumps, lots of people complaining that their quality has gone way down. Any other recommendations for diy low pressure pumps where I don't have to buy the $500 kit from Bakes or skidm?

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30 minutes ago, DaleHardy said:

 Does it matter which side of the filter it goes on? I saw someone say between filter and main pump. Does it matter if there's more room on the other side?

FWIW, I mounted mine between the tank and the fuel filter.  I figured, otherwise, that inline fuel filter is also a potential source for bubble formation (thin metal, containing heated-up ethanol).

Besides, when doing it the way I did, I didn't need any additional fuel line.  I just cut that segment of fuel line from the tank to the filter, after a mock up of where I was gonna mount the new pump, and used the remainder of that cut fuel line to run from the new pump to the fuel filter.

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The kit I ordered came with instructions from Indmar Products.  I just reread them.  Here are a couple of tidbits:

"Before installing this kit it is important that all other factors that promote vapor lock have been addressed.  The second fuel pump will not be effective if ALL of the other factors have not been rectified.  Plugged fuel filters, sticky anti-siphon valves, kinked fuel lines, obstructed fuel pick-ups, obstructed bilge vents, faulty bilge blowers, and fuel with high ethanol content all contribute to vapor lock. . . .

"The additional fuel pump should be installed as close to the fuel tank as possible.  If there is an in-line fuel filter between the tank and high pressure pump, the secondary pump should be installed before the filter to allow the pump to push fuel through the filter. . . .

"Use Teflon tape or pipe thread sealant when installing the barbed fuel line fittings."

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3 minutes ago, srab said:

The kit I ordered came with instructions from Indmar Products.  I just reread them.  Here are a couple of tidbits:

"Before installing this kit it is important that all other factors that promote vapor lock have been addressed.  The second fuel pump will not be effective if ALL of the other factors have not been rectified.  Plugged fuel filters, sticky anti-siphon valves, kinked fuel lines, obstructed fuel pick-ups, obstructed bilge vents, faulty bilge blowers, and fuel with high ethanol content all contribute to vapor lock. . . .

"The additional fuel pump should be installed as close to the fuel tank as possible.  If there is an in-line fuel filter between the tank and high pressure pump, the secondary pump should be installed before the filter to allow the pump to push fuel through the filter. . . .

"Use Teflon tape or pipe thread sealant when installing the barbed fuel line fittings."

Thanks. That is useful info.

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  • 2 weeks later...

I'm having the same issue on my "94 Echelon with Merc 350.  After the engine warms up, the fuel pump which is front left of the engine, gets really warm to the touch.  I put a heat shield on it last summer on the back side of it which seemed to help but the issue happened again last night.  When I cool it down with cold water it fires back up and has no issues.  I'm going to add a second layer to the heat shield and use 100% gas and see if that helps before looking into the secondary pump; which sounds like works well.  I'll update...

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Cheapest/easiest solution: prop your engine cover open with a small block of 2x4. This seems to work on our 06 Response. We used to get vapor lock in the summer when we would sit and swim for awhile. This was WITH one of those Carter pumps that I guess the previous owner had installed, but it was after the fuel filter on the starboard bow side of the engine near the crank sensor. So sounds like not ideal installation of the Carter pump.

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