Fuel Flow Issues

Sawdust

Sawdust

Jim from Kentucky
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I got my Simplicity 7117H that has been repowered with a Kohler 20hp Magnum out the other day. It’s always ran perfect but recently started bogging down when under load like going up a slight hill. It also would not take full throttle.

I noticed the fuel filter wasn’t filling up like it normally does. I seen a few pieces of debris in the tank so I removed the tank, shook the debris out, the tank was clean, I installed a new tank grommet, new fuel lines, and new filter. Once I hooked everything back up no fuel flow even blowing in the tank to create a little pressure. Once I disconnected the fuel line at the pump fuel started flowing out of the hose.

Can there be a vapor lock maybe between the exit side of the fuel filter and pump or pump going bad.

Even when the engine is running there’s just enough fuel in the filter to keep it running unlike before the filter would stay full of fuel. All of my other tractors once the fuel shutoff valve is open the filter will fill up, not this one.
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No Doug this is mounted on top of the engine. I messed with it again yesterday and just got more confused. I can’t get hardly any flow coming into the filter when it’s all hooked up. When I disconnect the line at the pump it flows as it should. When it’s running there’s just enough fuel flowing in the filter to keep it running at idle. When I raise the throttle it will empty the filter then start stalling.
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Two thoughts - is the filter designed for a gravity fuel system or pressure fed fuel system (fuel pump)? Some filter elements will not allow fuel to flow with just gravity and need a smidge of pressure for fuel to pass through the element. Could also be a bad filter or the bowl inside the carb is not vented somehow. If there is a drain on the bottom of the carb bowl to drain fuel (some do some don't) you could open that enough so fuel flows out and then see if fuel then flowed through the filter ok. Just a couple of suggestions.
 
29 Chev said:
Two thoughts - is the filter designed for a gravity fuel system or pressure fed fuel system (fuel pump)? Some filter elements will not allow fuel to flow with just gravity and need a smidge of pressure for fuel to pass through the element. Could also be a bad filter or the bowl inside the carb is not vented somehow. If there is a drain on the bottom of the carb bowl to drain fuel (some do some don't) you could open that enough so fuel flows out and then see if fuel then flowed through the filter ok. Just a couple of suggestions.
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Yep. What he said.
 

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29 Chev said:
Two thoughts - is the filter designed for a gravity fuel system or pressure fed fuel system (fuel pump)? Some filter elements will not allow fuel to flow with just gravity and need a smidge of pressure for fuel to pass through the element. Could also be a bad filter or the bowl inside the carb is not vented somehow. If there is a drain on the bottom of the carb bowl to drain fuel (some do some don't) you could open that enough so fuel flows out and then see if fuel then flowed through the filter ok. Just a couple of suggestions.
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CRF6179 said:
Yep. What he said.
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Yeah Stew and Rick I don’t normally use an element type filter for a mechanical pump only on the gravity flow. I’m just trying all my options before I replace the fuel pump or take the carb off. I’ve tried the screen type and two different types of the element type with the same results. It’s like there is an air pocket restricting the fuel from entering the filter enough for the pump to pull from. I priced the aftermarket pumps and they are only around $15. and the rebuild kits are just a few dollars less so I don’t see any point of rebuilding it. Kohler pumps are around $45. both are probably China made.
 

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If I'm not mistaken you should be able to remove the line between the pump and the carb and gas should flow out. I put a filter similar to the one you are using on the 18hp Briggs twin on the snow blower and I don't think it ever filled with gas while running the engine last winter. The engine ran fine. The only way for the air to get out of there if the intake side is highest is back up the fuel line into the tank unless the discharge end of the filter is higher than the incoming side. Mine is intake high but the air wouldn't go back into the tank. Haven't checked it recently.
Some tanks have a screen inside the tank that might keep the air from venting.
Hope you get it figured out.
 
Great minds think alike guys. Yesterday I eliminated the filter and it still has the same symptoms. It runs fairly well at slow to mid range throttle at mid speed. As soon as I go full throttle and higher speed it bogs down. I’ve been researching the fuel pumps on these. A lot of aftermarket pumps at half price for the OEM Kohlers. The problem is several bad reviews for all of them being both are China made.

Im going to shelf this for awhile I got too many other things going on right now. This is one of my several grunt tractors. I use it mostly for just the rear tine tiller and the boom bar. Thanks everyone for your help. I’ll keep you posted when I get back to it.
 
The fuel tank may have cruddage in the bottom.. Drain it and take a look-see. Also, if the fuel line is old it could be degraded / collapsing. If so replace it and verify you have good flow.. Eliminating the filter is just a recipe for plugging the carb. JMHO..

Good Luck!
 
WNYtractortinkerer said:
The fuel tank may have cruddage in the bottom.. Drain it and take a look-see. Also, if the fuel line is old it could be degraded / collapsing. If so replace it and verify you have good flow.. Eliminating the filter is just a recipe for plugging the carb. JMHO..

Good Luck!
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As I mentioned in the beginning of my post I removed the tank and only found one small piece of debris and other than that it was really clean. I replaced the tank grommet, and replaced the fuel line also but still the same problem. This is why I didn’t care much about having no filter just for testing.
 
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Well I had a couple of honey do things this morning in the yard so my time outside was over around noon. My curiosity got the best of me needing to feel better about replacing the fuel pump so I took the old one off. Sure enough it looks bad. The diagram is hard, the check valves are rusty with clogged screens, and the rubber on them looks brittle. I feel better now about replacing it.
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Cvans said:
I'd be the same way Jim. I wouldn't quit thinking about your problem until I had a handle on it.
Looks like it's time for a pump even if that wasn't all of your problem.
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I woke up in the middle of the night thinking about this. Chris it’s one of those feel good things whether it’s the problem or not. Lol
 
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