312-8 fuel issue

[Jwright3190 15]

I rebuilt my carb, new fuel lines and new fuel filter last year. The year before I replaced the fuel pump. After I use my mower for about 15-20 minutes it runs out of fuel. The fuel filter is empty. If I let it sit for about a half hour it will fire right up and do it again. I’m leaning towards the cheap Amazon pump I bought. I thought about installing an electric pump but I don’t understand how it dont over fill the carb.

[Lagersolut 734]

47 minutes ago, Jwright3190 said:

I rebuilt my carb, new fuel lines and new fuel filter last year. The year before I replaced the fuel pump. After I use my mower for about 15-20 minutes it runs out of fuel. The fuel filter is empty. If I let it sit for about a half hour it will fire right up and do it again. I’m leaning towards the cheap Amazon pump I bought. I thought about installing an electric pump but I don’t understand how it dont over fill the carb.

Did you check or replace the fuel shut off at the tank ? They have a fine mesh screen inside the tank - your problem sounds more like a clogged screen or a bad fuel cap not venting . 

[Jwright3190 15]

2 hours ago, Lagersolut said:

Did you check or replace the fuel shut off at the tank ? They have a fine mesh screen inside the tank - your problem sounds more like a clogged screen or a bad fuel cap not venting . 

I will check both tomorrow! Thank you!

[Ed Kennell 41,800]

9 hours ago, Lagersolut said:

a bad fuel cap

Yeah that, just loosen the cap and try it.

[953 nut 59,784]

9 hours ago, Lagersolut said:

bad fuel cap not venting . 

As fuel is removed from the tank a slight vacuum will be created if the tank isn't vented. The more fuel is used the greater the vacuum until it reaches the point where the fuel pump can no longer overcome it,      then everything stops.

[peter lena 9,233]

@Jwright3190https://www.amazon.com/CarBole-Universal-2-3-5P-S-I-Operating-Self-   have a couple of these in use for years , this is the TYPE YOU WANT , NOT  the , fuel filter looking one , very solid , low pressure  its self regulating , ignition switch hook up , don.t worry about carb , not an issue , have this on my  ignition switch , when you go to start  , its on , added a single LED  green bulb to my dash , to verify  operation . check out tank for debris , typically  ethanol  gas eats  rubber hose , two choices , buy ethanol free gas or add a STA BIL  fuel storage  to your gas , to stop hose break down , would also recommend , replacing existing gas line , in line fuel filters  will show you what's going on  , one close to tank  the other close to carb . agree with @Lagersolut verify tank venting , we have all delft with this issue , its a learning experience , personal experience has been , fault free . pete  

[Jwright3190 15]

Cleaned my gas cap with degreaser. It ran for over an hour with no problem! Seems like that was it! Thank you everyone for the help!

[Ed Kennell 41,800]

15 hours ago, Jwright3190 said:

. I thought about installing an electric pump but I don’t understand how it dont over fill the carb.

The float activated halve in the bowl is what controls the fuel  in the carb.

Actually, all the fuel pumps pulse, mechanical, and electric run all the time.    The electrics can be controlled with an on/off switch and some of them will turn off with an internal pressure switch.

The real advantage of the electrics is they start pumping when you turn the switch on.   No need to crank the engine to pump fuel to the carb.   This is a real advantage with the tractors that have the fuel tank located under the seat.   With time the fuel leaks back to the tank and the pump loses its prime requiring a long crank time to get the fuel back to the carb.    The electric pump should be located below the fuel tank so it never loses prime.

Edited May 10 by Ed Kennell