Fuel feed issue

18 HP opposed twin 3 screw fuel pump won't suck up the fuel, it was running OK couple weeks ago then a few days later I tried to start it, wouldn't draw fuel up to the carb you could see it gurgling in the filter so I took the pump apart and found one of the diaphragms was torn at one of the screw points, so I got a rebuild kit for it today, cleaned everything inside and out of the pump and carb, set bot mixture screws 1 1/2 turns out from lightly seated no it won't draw any fuel through the filter, it does run as long as spraying starting fluid or gas directly into the carb

Hmmm, is the vaccuum line for the pump hooked back up correctly? Springs back in place for the diaphragm?

Yes& yes

Is there possibly a clogged fuel line? Like maybe between the filter and the carb or something.

or also I've had happen where the fuel line gets a pin hole in it and it looks like it's pumping but it's not and when you try to re prime it she's a no go

All new fuel lines, filter and shutoff valve. And yes the valve was open and no the fuel wasn't in backwards

If I remember correctly, seems like one of the adjustment screws was backed out around 6-8 turns from lightly seated. Is this common with these oppies?

It was this one

it varies from motor to motor and carb to carb but as a perfect example I had 2 5 hp one lung briggs one had the main jet backed out three turns the other needed 5 1/2 best advice is set it back where it ran before and go from there

Don't mean to but didn't realize didn't have a pic of it in the phone

That mixture screw in the picture is the main fuel jet screw. Altough the adjustment of the screws shouldn't affect the fuel pump, it will still pump fuel regardless of the settings. On a side note, where do you have that line on the bottom of the pump going to?

-Just so you know the lower port is the vaccum port, and the one on the side is the fuel inlet port.

Good, that's how they're hooked up

Oh really? It sorta looks like the fuel line is hooked up to the bottom port, haha.

needle valve stuck closed in the float bowl?  very unlikely but it's an idea

Thanks, I'll be sure to double check that in the morning.

usually a tap from a ratchet will free it up if you do it while cranking also it's been a really long time since I had an oppy in my life is it possible there's more than one way the internals can go together I know the carb on my chainsaw is diaphragm run and it can go together a half dozen ways or better

Did you fill up the bowl with gas during reassembly? Just pull the top off while it’s all still in the tractor and dump about half cup to a cup of fuel in the bowl to prime everything

Take the fuel pump off and make sure none of the little check flaps are folded over. I've had that happen and prevent it from pulling fuel.

And this sounds really dumb, but suck on the fuel inlet(with the carb as dry as possible). If you can pull any air through, then you have a problem with the diaphragm.

Another thing to consider is that the plastic fuel pump body warped slightly and isn't sealing. I had it happen once.

Sucked on the line earlier, no give, diaphragms are good


Thanks CraftsmanQuad didn't think of that, will do that tomorrow

Make sure your pulse line isn't cracked or leaking too.

I assume you're working on your MTD, is the valve on the bottom of the tank open? I noticed my tank has a shutoff valve there.

Yes the valve is open, are you talking about the line going to the crankcase?

Yep. That's the one that actually provides power to the pump

Yep, fuel and crankcase lines were hooked up properly

Got her running today, adjusted both high and low idle mixture screws out, put some go juice in the float bowl and blew out the fuel line. It only runs on half choke and pops pretty bad until it's good and warm then smooths out some, still pops just not as bad

Sounds like you need another carb cleaning.