WH520

312-8 fuel pump

13 posts in this topic

Hi everyone, it's been awhile since I've been here. I'm having some issues with my 93 312 with the 12 horse Kohler.

 

Last weekend I went to start it and it wasn't firing at all so I sprayed some carb cleaner in the carb and it fired up for a second but wouldn't restart. I pulled the fuel lines off the fuel pump and had gas going to the pump. I left the line off the pump on the side that goes to the carb and turned it over and gas came shooting out. I hooked the line back and it started right up and ran great for the hour it takes to mow my yard.

 

Fast forward to this weekend. I went out to mow the grass and it's doing the same thing again, not firing. I pulled the line off the pump and turned it over but this time there is no gas being pumped out.

 

I tore the pump apart and from what I could tell everything looked ok. I could hear the check valve clicking on the inlet side when I blew into it. I tried sucking on the outlet side but I couldn't hear anything. I didn't get very good suction on it though because, well, gas fumes don't taste very good lol.

 

Does anybody have any suggestions? Is there a rebuild kit for these or can you still buy a fuel pump? I tried looking them up but didn't have much luck.

 

Thanks guys, sorry for the long post!

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Do you have a good supply of fuel to the pump?      The tank shut off valves have a screen inside the tank that gets clogged.

If the valves in the pump are sealing properly, you should be able to blow air through the inlet but not through the outlet...a bit safer than sucking on the inlet.

New pumps are available for around $40.   NAPA, Jacks small engine, Amazon, etc.

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ID: 3   Posted (edited)

That's good to know, I didn't know there was a screen there. 

 

As a matter of fact I did try blowing in the outlet and no air came out. I had forgotten I did that.

 

When I took the line off coming from the tank no gas would come out while I held the line straight up and down (like the position it would be in connected to the pump) It would only start to come out when I got it almost horizontal with the engine. It seemed to be a pretty steady stream coming out though. 

Edited by WH520

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You should take the float bowl off the carb while you are at it. After dumping out the old gas, take some spray brakekleaner and spray up in the bottom of the carb to clean the float area. Wear safety glasses so you don't get the stuff in your eyes and dry your eyeballs out.

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ID: 5   Posted (edited)

remove the fuel pump, it's easy, , remove the gas lines, remove two screws on the front of the engine block.  take it apart, slowly and carefully ( 4 screws) don't mess with the gasket..note the position of the input and output check valves, take them out,  clean them and put them back in "snug" same as they came out. Before you remove them note if the input check valve is slightly "unseated". 

 

In all honesty this is about a 20 to 30 min ordeal but if you are not pulling gas from the fuel tank you need to check it. Also be sure your gas line/filter  is  fresh and the fittings are indeed TIGHT.

 

I have had this exact same issue many times and fought the battle only part way.  I finally decided to install a new gas line, new filter, new HOSE CLAMPS , removed the fuel pump, serviced the check valves   and all is well. Engine starts on a half a crank every time now, as it should.

 

But I am replacing the fuel pump/ check valves soon. After all they are 30 years old !  If the fuel pump loses prime it's very difficult to get it back 

Edited by Tonyp
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Hi guys, I figured I'd give an update. I ordered a new pump from NAPA and installed it yesterday and it fired right up! 

 

Now I've got an issue with one of the deck spindles, always something lol

 

Thanks everybody for your help.

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ID: 7   Posted (edited)

Hi guys, thought I'd give an update and ask a question. 

 

I replaced the fuel pump last fall and mowed my yard twice before the new pump quit working on me. 

 

So fast forward to a few weeks ago. I ordered another fuel pump, replaced the fuel lines and put a new petcock on the tank. The tractor fired right up and was running good. Again, I mowed the yard twice and now it's not pumping fuel again. It's getting a good fuel flow from the tank to the pump. 

 

Whats the the chances of getting 2 bad pumps and only getting 2-3 hours out of them ? Am I doing something wrong on installation? 

 

I just ordered another pump off eBay, I thought I'd try to get some tips off the experts here. 

Edited by WH520

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ID: 8   Posted

:confusion-confused:   Are you using ethanol free gas?  If not, go to buyrealgas.com and find a station that sells it. Ethanol will kill the fuel system on small engines. Another possibility would be the vent in the gas cap, if the vent is bad the fuel leaving the tank will create a slight vacuum that the pump can't overcome.

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ID: 9   Posted

I forgot to mention I also got a new fuel cap since the old one was cracked. 

 

I have been using ethanol gas, there is a station not far from me that sells non ethanol, I've just never tried it. Maybe I'll drain the gas out of the tank and fill it up with non ethanol when I put the new pump on. 

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Do the pumps work when you pump the levers by hand?   If they do, you may have a worn cam lobe.  Go electric.

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I did try pumping them by hand but wasn't getting any suction. 

 

However, on the current pump when I plugged both the inlet and outlet I would get a puff of air come out of both sides. 

 

Electric is my next step if I have the same problem with the new pump, I was just wanting to try to try to keep it original if I could. 

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Electric is the way to go!   :handgestures-thumbupright:

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Got the new pump and installed it today. It started right up and I let it ran for half an hour.

 

I'll let you guys know if it still starts when I go to mow the yard in 3 weeks. So far I've only been getting 2 weeks out of them lol

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