Fuel pump prime issue

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Andrew511
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Fuel pump prime issue

Post by Andrew511 »

Yesterday I couldn’t get the fuel pump to prime up when I first put it in the water. I ran it the night before and it was fine. It’s a 1 month old Carter pump new fuel lines new filter and all connections were tight. The filter is between the pump and the tank and the pump is only about 12-18” above the tank. It’s been working great every other time. I ended up having to take the “out” line off the pump that leads to the carb letting it fully prime and then slid the fuel line back on and it ran fine the rest of the day even after a 2+ hour stop to fish. Could the pump be going bad? Or do I need to add a squeeze ball somewhere for this situation? DD 350 carb

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Slidin Gator
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Re: Fuel pump prime issue

Post by Slidin Gator »

Andrew511 wrote:Could the pump be going bad? Or do I need to add a squeeze ball somewhere for this situation?
No, probably not.

Yes.

Add 1-2 feet of fuel line in a loop at the pump inlet and you will probably never have this issue again. Keep the primer bulb in the package and stuffed in the spares box for when you actually do need it.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

SWAMPHUNTER45
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Re: Fuel pump prime issue

Post by SWAMPHUNTER45 »

We always mount an electric pump low, the inlet / outlet should be level or lower to the tanks bottom.
You probably caught air and it lost prime. A primer ball would be an option.

swamper2
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Re: Fuel pump prime issue

Post by swamper2 »

Isn't there a check valve in the pump to keep fuel in it?
16ft alumitech/406sbc/2.38w/3-80in.R's

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Slidin Gator
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Re: Fuel pump prime issue

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swamper2 wrote:Isn't there a check valve in the pump to keep fuel in it?
Some do, some don't, "It's a Carter Pump" does not really nail down the pump, Carter makes a whole bunch of pumps. The float in the carb also acts as a check valve. Given that it lost prime initially (after sitting at least over night) but then worked the rest of the day can mean that a piece of trash in the line held the check valve open until it was flushed out, or there is a small air leak in the suction line.

Given that it primed up after pulling the line off the carb leads me to believe this particular pump has limited self prime lift. Further, the carb float must have been stuck closed and needed a little fuel pressure to open up.

A loop of fuel line on the pump inlet (looping above the pump) holds fuel at the pump inlet in the event of a suction line leak and allows the pump to prime up quickly. It would also be worth checking the self prime specs of this specific pump. The pump needs to be located less than the self prime height relative to the bottom of the tank so it can self prime when the tank is almost empty.

The filter on the suction side makes things worse, decreasing suction lift. It is not good idea to put a water separating filter (assumed,
not specified) between the tank and pump, the pump will pump water just fine, you just want to keep the trash out. A trash screen filter should be located between the tank and pump and the water separator between pump and carb. It is also helpful to place the trash screen above the pump (in the loop) to hold more fuel for start up priming.

Swamp is right that mounting the pump low, at/near the bottom of the boat, eliminates priming issues. However, Coast Guard regulations require an anti siphon valve, or an electric shut off valve (that opens when ignition is on) at the tank outlet if the fuel lines run below the top of the tank to prevent the tank from siphoning into the hull due to a fuel line leak. The Facet Gold Flo pump is one particular pump that includes such a valve internally. An anti-siphon valve is basically a check valve with a cracking pressure higher than the head height of the tank so the pump has to pull a suction for fuel to flow. These valves essentially eliminate the advantage afforded by mounting the pump low, an electric shut of valve does not create back pressure, but can fail in it's own right.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.

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