I cleaned up a mechanical fuel pump I had and had it all hooked up and ready to go. Started the motor and it was getting gas to the carb just fine... Except it started spewing gas out of the two small holes at the base of the pump below the diaphragm.





I can only assume this is because I have a bad diaphragm that needs replacement?

One caveat tho is that the inlet hose is fed with gas by an electronic pump that gives about 4-6psi. Could this be the issue? Gonna try to bypass the electric pump and feed the gas straight from the tank to the mechanical pump as soon as I can.

Deerio,
Only one way that fuel can get to the bleed holes below the diaphram. Through the diaphram. You have a crack or pinhole in the diaphram that it is getting through. I'm not familiar with what the diaphram looks like (post a photo) but I'd hold it up with light behind and look for pinhole or crack. If there's a metal disc on both sides, the leak may be in the diaphram between the plates or close to the central rod and not be visible. I believe that this is the pump with five screws holding the two halves together. I have one of these with a bad diaphram that I'll be tearing down later and trying to repair.

I'd dedicate several hours to digging around on the net looking for a automotive fuel pump rebuild service to either have it rebuilt or acquire a generic diaphram assembly and fit it to the Japan pump. I'm sure that there are a few.

I expect that the electric pump is pushing fuel through the diaphram and out the bleed holes. It will also end up in your crankcase oil if you let it run for long.

Steve

Welps, I had the mechanical pump hooked up directly to the fuel source and unfortunately it was still squirting out thru those small vent holes. So I guess it wasn't the because of electric pump after all.

I guess it's time to rebuild the mechanical pump with a new diaphragm and valves!

I think that there are some of the British valves that will work in the Japanese pump. Don't know about the diaphram. 'Lil Truckie' posted on this a while back when he was working on one. Maybe he will pipe in here., or you can check out his posts over the past few months.

Steve

They are still available new and should have a rebuild kit available.

You can use an L series fuel pump and swap the arm.

Here is the E1 pump on Amazon (M70035 is the PN): http://www.amazon.com/Carter-M70035-Mec ... B000C01APW

I do remember reading that the Carter pump was available but as far as I know whatever stock is left is probably whatever is left. If I can't find a rebuild kit then maybe I'll just go back to using an electric pump with a regulator.

Its a good time to get the Carter pump and buy a few rebuild kits for it or a bunch depending on how much they are...... atleast to keep a stock in hand.

In the past I have used this one Carter Electric pump and has proved worthy to use on a variety of applications (sorry for the long link):
http://www.amazon.com/gp/product/B000BZ ... 0D3QBWQ9GP

This pump feeds at a consistant 4psi and I have used it on my 85 Chevy Motorhome 33ft to push fuel near the tank mount all the way up to the 454ci V8 and it was happy to supply 300hp.

Same pump used in my Datsun 620 L16 motor.

Love it cause it comes with inline filter attached so you wont void warranty accidentally.

Also if the mechanical pump was installed but not leaking (take diaphram out and seal holes internally), you could keep it hooked up and feed it with the electric pump and it will flow through it without issues.