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New Fuel Pump Confusion

#1

M

masterdrago

Issue with fuel at carburetor. None out when fuel line open into bucket. No fuel in filter. Replaced filter. Able to blow thru lines from carb to tank. The small line under air filter that goes to fuel tank is one way check valve - good flow from tank to inlet housing below air filter. no flow toward tank.
Checked vacuum at the bottom line of pump to engine. 0"-5" pulsed vacuum - same as neighbors FS730V which runs good.

The markings on the new pump have me confused. On my old one, the bottom left barb when mounted on the engine is the inlet from fuel tank, while the upper right barb is the outlet to the carburetor.

The new one has arrows on the rear that indicate reverse flow?? Meaning it flows backwards from the OEM??

Did I damage it hooking up backwards?
View attachment 590818

No fuel to carburetor no matter how I hook it up. Have pulsed 0-5" vacuum on the tube connected at bottom. No obstructions in all new tubing, pickup line to tank, or new filter. No poor connections or air leaks. Check valve in tank tube goes to under air filter clear and allows air from tank to connection.

Just no fuel to carburetor.

I'm completely stumped.

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#2

Tiger Small Engine

Tiger Small Engine

masterdrago said:
Issue with fuel at carburetor. None out when fuel line open into bucket. No fuel in filter. Replaced filter. Able to blow thru lines from carb to tank. The small line under air filter that goes to fuel tank is one way check valve - good flow from tank to inlet housing below air filter. no flow toward tank.
Checked vacuum at the bottom line of pump to engine. 0"-5" pulsed vacuum - same as neighbors FS730V which runs good.

The markings on the new pump have me confused. On my old one, the bottom left barb when mounted on the engine is the inlet from fuel tank, while the upper right barb is the outlet to the carburetor.

The new one has arrows on the rear that indicate reverse flow?? Meaning it flows backwards from the OEM??

Did I damage it hooking up backwards?
View attachment 590818

No fuel to carburetor no matter how I hook it up. Have pulsed 0-5" vacuum on the tube connected at bottom. No obstructions in all new tubing, pickup line to tank, or new filter. No poor connections or air leaks. Check valve in tank tube goes to under air filter clear and allows air from tank to connection.

Just no fuel to carburetor.

I'm completely stumped.
Click to expand...
Either new fuel pump is bad, you have fuel pump hooked up incorrectly, or fuel line running back to fuel tank is clogged.


#3

M

masterdrago

The issue turned out to be with the fuel cap. New one solved. All the pumps work if I flip left to right following the arrows and mount ~1.2 inches out from mower. The old pump even still works. Just a bad fuel tank cap. My neighbor had never heard of this either. It had me mystified for days. It even solve the intermittent dying mid mow after 20-30 minutes.

Also solved the issue in post at https://www.lawnmowerforum.com/threads/dies-choke-very-touchy.79518/#post-511460


#4

A

Auto Doc's

Yep, as fuel is used air is drawn in through the cap vent. If the cap vent is plugged the fuel tank will go from atmospheric pressure down into a vacuum due the fuel pump suction. The tank will not allow fuel to flow if it has a vacuum.


#5

M

masterdrago

Tiger Small Engine - "fuel line running back to fuel tank" from just under the air filter - is a one way (check valve - allowing only air "FROM" the fuel tank but not "TO" the tank. It is clear. Check valve works.

Auto Doc's - I was under the impression that the line from under the air filter to the tank check valve served that purpose. Did not know pertaining the fuel tank cap. When I removed the cap and cranked, immediately saw fuel enter filter and proceed to carb, then started right up. Temporary fix - drill hole in cap with screen to prevent debris in fuel. Mowed ~90 minutes to test. All good. Now I have several extra el-cheapo pumps:cool:


#6

A

Auto Doc's

The EPA and engineers are so anal about making sure fuel vapors cannot escape into the atmosphere that it is almost an obsession.

In reality, simply filling up a vehicle at the gas station releases more fuel vapor that any mower will ever release.


#7

Tiger Small Engine

Tiger Small Engine

masterdrago said:
Tiger Small Engine - "fuel line running back to fuel tank" from just under the air filter - is a one way (check valve - allowing only air "FROM" the fuel tank but not "TO" the tank. It is clear. Check valve works.

Auto Doc's - I was under the impression that the line from under the air filter to the tank check valve served that purpose. Did not know pertaining the fuel tank cap. When I removed the cap and cranked, immediately saw fuel enter filter and proceed to carb, then started right up. Temporary fix - drill hole in cap with screen to prevent debris in fuel. Mowed ~90 minutes to test. All good. Now I have several extra el-cheapo pumps:cool:
Click to expand...
Never have seen, or heard of this “one way check valve.” Just saying.


#8

ILENGINE

ILENGINE

Tiger Small Engine said:
Never have seen, or heard of this “one way check valve.” Just saying.
Click to expand...
I agree. It sounds like the rollover vent valve is not working because if this mower has the vapor recovery line connected to the air filter housing then the fuel cap not venting wasn't the issue because the fuel cap wasn't vented to start with. Direct atmospheric vented fuel caps were EPA regulated out in 2012.


#9

ILENGINE

ILENGINE

masterdrago said:
Tiger Small Engine - "fuel line running back to fuel tank" from just under the air filter - is a one way (check valve - allowing only air "FROM" the fuel tank but not "TO" the tank. It is clear. Check valve works.

Auto Doc's - I was under the impression that the line from under the air filter to the tank check valve served that purpose. Did not know pertaining the fuel tank cap. When I removed the cap and cranked, immediately saw fuel enter filter and proceed to carb, then started right up. Temporary fix - drill hole in cap with screen to prevent debris in fuel. Mowed ~90 minutes to test. All good. Now I have several extra el-cheapo pumps:cool:
Click to expand...
The rollover check valve is a 2 way valve and is only supposed to stop venting when turned upside down. So the non venting fuel cap wasn't suppose to vent. You have a check valve issue not a fuel cap issue.


#10

S

slomo

Auto Doc's said:
The EPA and engineers are so anal about making sure fuel vapors cannot escape into the atmosphere that it is almost an obsession.

In reality, simply filling up a vehicle at the gas station releases more fuel vapor that any mower will ever release.
Click to expand...
I can smell fuel vapors driving my car with the windows up when passing a gas station.


#11

M

masterdrago

ILENGINE said:
The rollover check valve is a 2 way valve and is only supposed to stop venting when turned upside down. So the non venting fuel cap wasn't suppose to vent. You have a check valve issue not a fuel cap issue.
Click to expand...
ILENGIN, I appreciate the help. I had pulled that plastic valve out on first checking. I had no idea what it was for as I'm ignorant of ICEs. It clearly acted as a one way valve (you call it "rollover"). Found it at Partstree.com. When I suck on the line below the fuel filter, I can draw gas vapor from the tank. However, if I blow on that line, it is definitely shut off. Are you saying I should be able to pass air either way? It acts like a check valve and it can be shaken up and down (makes noise) when pulled out of the tank. So a new one breaths either way unless upside down?


#12

ILENGINE

ILENGINE

masterdrago said:
ILENGIN, I appreciate the help. I had pulled that plastic valve out on first checking. I had no idea what it was for as I'm ignorant of ICEs. It clearly acted as a one way valve (you call it "rollover"). Found it at Partstree.com. When I suck on the line below the fuel filter, I can draw gas vapor from the tank. However, if I blow on that line, it is definitely shut off. Are you saying I should be able to pass air either way? It acts like a check valve and it can be shaken up and down (makes noise) when pulled out of the tank. So a new one breaths either way unless upside down?
Click to expand...
That is how they are supposed to work. The idea is to allow tank venting to remove the vacuum created by fuel leaving the tank, to allow vapor recovery so that it can be burned, and prevent fuel spillage if the mower tips over. Most of the time they never seem to work correctly.

I was just playing with an old one earlier, and it was restricting flow in both directions, except when turned upside down and then had unrestricted air movement in both directions.


#13

M

masterdrago

ILENGINE said:
That is how they are supposed to work. The idea is to allow tank venting to remove the vacuum created by fuel leaving the tank, to allow vapor recovery so that it can be burned, and prevent fuel spillage if the mower tips over. Most of the time they never seem to work correctly.

I was just playing with an old one earlier, and it was restricting flow in both directions, except when turned upside down and then had unrestricted air movement in both directions.
Click to expand...
Now that is strange. Plus the picture of the rollover valve for my mower on PartsTree does not look anything like mine. Anyway, by venting the cap, any issues with the rollover valve are inconsequential. I do not mow on anything but mostly level 5 acres. Now my latest problem is that in my haste to get the tall grass mowed,I hit a root. Appeared to be no damage. Did not stop the mower, but when I shut down the blade and went to idle, the Kawasaki began surging slowly with a small backfire infrequently. Bet I nearly sheared the flywheel key. Now timing is off. Fun! Fun! I'll try to have a look in a few days. It continued mowing strong after the root encounter. Just surging and some slight backfire.


#14

M

masterdrago

ILENGINE, the fuel cap (OEM) "is" vented. And the rollover valve is only one way "to" the connection under the air filter. I added more venting to the cap by drilling a small hole and added a screen to prevent debris. Dirt and dust must have clogged the original air path in the cap. New hole fixed the issue. No one I've talked to has ever mentioned a clogged fuel cap causing the dying as in post https://www.lawnmowerforum.com/threads/dies-choke-very-touchy.79518/#post-511460 and most recently zero pumping of fuel to the carburetor.

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