Fuel pump (suction)
 

I currently have a Mallory fuel pump that apparently is a pusher not a puller so I need to prime it to the the fuel to pump. My question is does anyone have any idea on a good pump that will pull the fuel up to it. Problem I have is it's hard to get mounted under the tank so I run out of fuel when the tank level is below the pump level which happens to be about 1/3 to 1/2 tank. Thanks for any help. It's a carb 502. 415 hp.

Only pump that will pull uphill with any consistency are the old school diaphragm or Weldon Electric.

Suggest checking the antisiphon valve on the tank. Its the barbed fitting that the rubber fuel line connects to.


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Yup. ^^^^^

Also, the following based iff my old crusty hardening brain so please double check.....your Mallory could have a gerator type pump which is more efficient on the output side, but less effecient at ‘pulling/lifting fuel up lines’ then the vane type. Vane type is mire noisy then gerators.

As a fyi, many marine companies on carb’d sbc’s and liw hp 454’s that don’t have block provisions for mechanical pumps, use the Marine Carter Electric pumps. They are vane type, again, if I remember correctly.

Hope this helps, and please do a quick study in case my memory mixed up.

One of the Holley pumps will lift 18", I just forgot if it was the red, blue or black.

Weldon pumps advertise that they can pull as well as pump, unlike most electric pumps. I used a Weldon mounted on the block and it pumps like a beast.

I run mallory 140's. This is what I did. I mount the pumps as low as I can in the bilge. I then run a loop in the delivery hose that will keep fuel in the line to allow the pump to prime and create a vacuum.
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I did that's been replaced with a regular barbed fitting clear through no valve

So you're saying you removed the anti-siphon valve and have issues with it siphoning?

yes correct

The valve you removed is there to eliminate the issues you are having. Why did you remove it? Once primed the Mallory pump will lift fuel to an extent.

It was removed before I got the boat your saying I should install one?

While I would admit that the antisiphon valve would help the issue, but this would only help on restarts. Once the pump has fuel it should be able to keep pumping, unless the lift (height) is to great for its design. Vane pumps should be at least level with top of the tank and having a dip in the line can help

The antisiphon valve is a USCG safety regulation so if the fuel line breaks or leaks, it will not siphon all the fuel out of the tank.

Can you make a bracket to mount the pump on which allows it to be placed lower. The bracket will allow it to be removed/installed with screws higher, but the bracket lets it be lowered.

Similar to installing a bilge pump under the motor and using an aluminum plate to place it low, but the screws into the stringers beside the motor for easier access

Throwing another curve, wouldn’t be terribly uncommon for fuel pickup in tank to have a crack in it and not pick up fuel when the level gets to that height.

yeah I checked that it's good I'm thinkin I'll have to try running the line down below the tank

Is a low pressure block mounted diaphragm pump running into a high pressure electric fuel injection pump an option? I am thinking about doing this as I don't want to mount my electric pump so low that a flooded bilge could submerge it.

that was my concern

Doesn't need to be below the oil pan just even or bit below the top of the tank.

The cool fuel module is mid way of the oil pan (behind motor mount), so about even with the starter. Even if there was a leak large enough and the pump was lower then the pan, marine pumps are water proof

Post some pics of what your working with, this way there could be some real discussion of the issue(s)

I had to do what Rookie did (see his drawing above) when I used a aero motive pump many years ago. They said I didn’t need go, but I did. The fuel left in the loop and thus the pump, made it work correctly.

What Mallory pump are you running? I run Mallory 140's. I just went and looked at my Scarab and the pumps are mounted even with the top of the fuel tank. My loop does go down to about halfway down the tank.

140 bottom of unit which is where the pump is right about level with half tank

Here is what I am planning to avoid a suction problem from the high pressure pump.

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yeah I'm just running a carb so I dont have a high pressure pump and I dont have a mech pump provision on my block. Hopefully I need a high pressure pump on my new boat👍

You could use a water pump mounted fuel pump. That is what I am doing.

You should start a new thread on that. I see some things that should be changed up.

‘I’m listening, what do you see wrong with this?