New Fuel Pump Confusion

[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.

 

[Tiger Small Engine]

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.

Either new fuel pump is bad, you have fuel pump hooked up incorrectly, or fuel line running back to fuel tank is clogged.

 

[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

 

[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.

 

[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

 

[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.

 

[Tiger Small Engine]

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

Never have seen, or heard of this “one way check valve.” Just saying.

 

[ILENGINE]

Never have seen, or heard of this “one way check valve.” Just saying.

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.

 

[ILENGINE]

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

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.

 

[slomo]

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.

I can smell fuel vapors driving my car with the windows up when passing a gas station.