Vapor Lock In Port Injection Application

[krue0101]

Hello,
I am working on an industrial application with a port injected gasoline engine and am having vapor lock issues due to the temperature of the bulk fuel and inlet vacuum. Due to design constraints I am not able to flood the inlet of the fuel pump or use an in-tank pump. I am also stuck with a bulk fuel temp of 135° F, due to design constraints. Does anyone have any ideas how I can keep the fuel from vaporizing in the inlet fuel line? Is there a such thing as a pre-charge or lift pump for unleaded gasoline?
Any help would be appreciated.

Thanks J

 

[patprimmer]

Can you pressurise the tank

Regards
pat pprimmer@acay.com.au
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[richdubbya]

Are their design constraints on fuel line size? The larger the line the lower the vacuum. Also a return line to the tank will prevent the fuel from being stagnant in the line if it is picking up heat there. Insulating the lines helps a lot if they are exposed to added heat. Make sure the tank is well vented.

 

[WGJ]

Judging from your description of the system, patprimmer is right - try pressurising the fuel tank to reduce the depression between the tank and the fuel pump inlet.

Most electric FI pumps intended for frame/chassis installations need either a gravity feed or an in-tank lift pump. Some mechanisms don't respond well at all to any depression in the connection between the bulk fuel storage and the pump inlet - gasses evolve easily with reduced pressure and the pump will lose prime and generate noise. The roller cell types (e.g. Bosch) are the worst.

I would be inclined to try pressurising the tank, just slightly, and using a gear-type ('gerotor') pump in a frame/chassis-mount package as, in my experience, the gerotors can generate a reasonable 'lift' and if, as suggested earlier, you can contrive to keep the bulk fuel temperature down, a reliable fuel supply can be established.

Walbro is the pump I have in mind.

Try

http://www.gnttype.org/techarea/fuelsystem/walbroflow.html

for some flow data and some pump dimensions.