Boat eating fuel pumps

[Seafarer31]

I have a palmer gas motor and the fuel pump gets very hot and shuts down. I have replaced the stewart warner pump twice and even tried another brand. THe pump runs fine for about and hour then starts making a knocking sound and I am guessing this migh be vapor lock. I replaced the fuel filter and regulator and nothing seems to resolve the problem. Any ideas?

[mikeg516]

You may have gunk in your fuel. There should be a fuel filter between the tank and the pump. A Stewart Warner is self lubricating which means if it runs dry it will sieze up. There is also a screen inside that can clog.

[timebandit]

Are you using one of these?

STEWART WARNER

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Electric Fuel Pumps

Pumps assure quick starts, eliminate surging, flooding, and starving. All pumps assure battery-saving quick starts by delivering gas the instant ignition switch is turned on. Also see our Marine Application fuel pumps.

82050 Series is a powerful piston type pump which brings solid state reliability to fuel pumps. One moving part. Built in filters eliminate the need for other filters in line: microcarbon filter dissipates water; magnetic filter traps metallic particles. Gas line connection 1/4" internal PT.
235 Series has built-in screen. Gas line connection: 1/8" internal PT. Not to be used with alcohol based fuels.

Electric Fuel Pumps

Kit	Characteristics
82050	12V neg gnd. 7 psi
82501	12V neg gnd. 5 psi
82502	12V pos/neg gnd. double insulated 7 psi
82504	24V pos/neg gnd. 7 psi
235A-D	12V pos/neg gnd. 5 psi
235B-D	6V pos/neg gnd. 5psi

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[sailingdog]

Hmm... I notice that says it isn't to be used with alcohol-based fuels... but most of the gasoline nowadays is E10 at a minimum, and has 10% ethanol by volume.

[erps]

Another possible source for heat is poor electrical connections. Maybe the terminals that connect to the pump have resistance? Touch 'em while the pump starts heating up to further narrow down where the heat is coming from.

[Seafarer31]

Thank for the suggestions, here is a little more info. I have replaced the fuel filter, blown out the fuel lines from the carburetor back to the tank, replaced the electrical connectors, replaced the fuel regulator and even added a pressure gauge between the pump and carburetor. When the pump starts knocking the pressure gauge shows a drop in fuel pressure and the needle starts jumping.

What I have not done is replace the fuel line from the tank to the fuel pump or inspected the tank itself. To try to eliminate the tank as the problem I disconnected the fuel line and just dropped it into a gas can and I still have the problem. The only thing not replaced is the fuel shut off valve that is before the fuel filter.

This is the configuration, fuel tank > 10 to 15ft fuel line > shutoff valve > fuel filter > fuel pump > pressure regulator > pressure gauge > carburetor. In addition, the fuel tank sits about two to three feet higher than the engine itself.

This seem simple to me but I must be missing something since I cannot resolve the problem.

Thanks in advance for suggestions

[cardiacpaul]

alrighty, here goes.

use the smallest pump you can. You have no "lift" and the pump is "over running" so to speak. The palmer is basically an internation "cub" and "cub lo-biy" engine. it sips fuel, doesn't guzzle. One or two lbs of pressure should do it.
Of course, make sure your fuel lines are clear, and the elec. conns. are solid (both sides)

[timebandit]

There are two kinds of eletric fuel pumps----

Hummers are pump for electronic fuel injected engines that have a return to the tank. They are a gear type pump that run all the time and depend on fuel flow to keep them cool. These pumps kinna make a humming sound when running. If you are running this type of pump it will overheat in a short while if just ideling or running it without the engine on.

Clickers are pumps for most carb type engines. They are a demand type pump and only run when the pressure drops below about six pounds of pressure. These pumps make a clicking sound when they are pumping. An arrow on the top of this pump points to the carb or at least the OUT fitting should be conected to the carb. This is the pump you should be running.

Sounds like you may have the pump installed backwards.

Rick

[Rockter]

If the Stewart Warner pump gets to (say) 5 psi, the pump switches off. Typically, with your hand on the pump, it should run intermittently... say a wee burst every 5 seconds, or so, dependent on fuel demand.
I suspect that the pump has perforated the diaphragm, though that is unusual so early in the life of it. If the diaphragm perforates, the pump will run and run, though mine did not overheat when it failed. It lasted 15 years, at least, pumping diesel.
Be wary of pump overheating when pumping gasoline. It sounds a bit risky to me.

[timebandit]

Added a pressure gauge between the pump and carburetor. When the pump starts knocking the pressure gauge shows a drop in fuel pressure and the needle starts jumping.

Pumping from carb to tank?

To try to eliminate the tank as the problem I disconnected the fuel line and just dropped it into a gas can and I still have the problem.

Blowing bubbles in the gas can? Pump in backwards.

This is the configuration, fuel tank > 10 to 15ft fuel line > shutoff valve > fuel filter > fuel pump > pressure regulator > pressure gauge > carburetor. In addition, the fuel tank sits about two to three feet higher than the engine itself.

Disconect everything from the shut off and check if you have fuel flow. If there is ressemble and than remove the pressure regulator (you dont need it).

With the fuel tank as high as it is you dont even need a fuel pump.

Rick