evap leak detected

i recently changed my fuel pump on my 2015 tacoma and a couple weeks later an emissions code fired. It's also slowly losing fuel mileage when i drive. has anyone ran into this problem just after changing the fuel pump?

 

check your hoses on the tank, might have left one disconnected

usually the fuel cap seal dies over time but doing the pump might have disrupted something

 

Could be a seal on the tank, could be a hose, could be something unrelated like a gas cap or purge valve.

It sucks because its a bear to change those pumps.

Did you use a new oring?

I lubricate them with silaglyde and I lubricate all connections to make sure they seal. We did lots of pumps in 2020-21

 

Also remember that one of the built in test for the Evap system is the odb test where it randomly performs a pressure test of your tank to determine if it is sealed. the logic for this test wont allow it to be performed unless your gas tank is less than 75 percent full. randomly (i think 5 hours after engine coolant temp is back below 95F) while the truck is turned off and this condition exists, it will command the evap pump to pressurize the tank then perform a leak down measurement by watching the rate of leakdown... they want 75 percent or less fuel so there is a headroom for air during the test. thats why a bad cap or a disconnected line will cause the evap test to leak at a faster rate than allowed

this is probably why you didnt get the test fail yet, maybe your full level wasnt in the window yet for it to perform the test did you immediately fill the tank after changing your pump and did the test only fail after the truck sat overnight with he fuel level below 75%? you probably have a line not connected good or cracked and it may not be a line thats below the fuel level, but a vent line part of the evap system or ecology design going to the charcoal canister

the purpose of that canister is to absorb fuel fumes so they arent vented to the atmosphere and then when you first turn your vehicle on, the system takes and injects those fumes into the intake to burn them off
this is usually injected after the throttle body and maybe this is affecting the fuel mixture being its a leak after the map sensor.

i would check the lines going forward to the engine that send the fumes to the engine to be burnt off when you start up. you may have a vacuum leak/ fuel vent line leak i dont know the tacoma specifically, but in general it sounds plausible that its a line from the tank to the charcoal canister and then to the intake manifold somewhere

maybe someone else can expand on this

are you a V6 or a 4 ?

 

here you go.....

 

I think that is for a 4 cyl, but basically same kind of design on the 4 and the 6

i know this sounds funny because you didnt do work at the purge valve location all you did was change the fuel pump, but ..... maybe your purge valve is stuck open? ......your evap test would fail because the pressure would constantly bleed off thru the purge vale being open all the time and your fuel economy would be compromised because of the added vacuum leak being unmetered by the fuel air mixture control system

are you getting any other codes on the ODB system beside the evap leak test failing?

 

If you hadn't just been in there doing a fuel pump I'd say try a new cap, clear codes and give it couple weeks.. but you'll probably have to pull the tank back down and double check your work.

Purge valve leaks are fairly common but i wouldn't go throwing parts just yet. Double check your fuel pump work..

 

i completely agree with not yet throwing parts at it yet. but the thing im curious about is when you say you are .. and ill quote you..."SLOWLY LOSING FUEL MILEAGE"

The tank area shouldnt be related to that.


for now, can you elborate on what you mean by "slowly losing fuel mileage"?

and also.....

why did you have to change the pump?.... what prompted that? .... what lead up to that decision to change it?.... was it simply a complete pump failure or did you change it for some other reason maybe related to fuel economy?


also, how are you determining MPG ? using a scanguage? or just calcualting by mileage since last fillup vs amount of fuel pumped to fill it back up?