Evap Leak Check Engine Light

[booradley21]

My mechanic and I have been struggling to pinpoint an evap leak on my ‘99 TLC. He did a smoke test and narrowed it down to the fuel sending unit and even after replacing it, the check engine light persists. Next step might be replacing the fuel tank. Any suggestions?

 

[Trunk Monkey]

What's the CEL code?

 

[booradley21]

What's the CEL code?

P0440

 

[ChiefKeef]

This is a long shot, and I saw you had a smoke test already--BUT, I would get intermittent EVAP codes for months randomly--come to find out my mechanic re-did my smoke the smoke test and saw i had a super slight leak from around my brand new gas cap--because my filler neck was actually "out of round" from years of fill-ups and the fuel nozzle, over time, messed up the shape of my filler neck and it wasn't sealing--even with a new cap. My solution has been for the past three years, getting up on my tip toes and "pressing down hard" when I put my gas cap on after a fill up, and that fixes it. I've still managed to throw a code or two when I've gotten in a hurry and not "pressed down hard", but I've cleared the code myself and its never been an issue. This may not be your thing but who knows.

 

[Les Summer]

This is a long shot, and I saw you had a smoke test already--BUT, I would get intermittent EVAP codes for months randomly--come to find out my mechanic re-did my smoke the smoke test and saw i had a super slight leak from around my brand new gas cap--because my filler neck was actually "out of round" from years of fill-ups and the fuel nozzle, over time, messed up the shape of my filler neck and it wasn't sealing--even with a new cap. My solution has been for the past three years, getting up on my tip toes and "pressing down hard" when I put my gas cap on after a fill up, and that fixes it. I've still managed to throw a code or two when I've gotten in a hurry and not "pressed down hard", but I've cleared the code myself and its never been an issue. This may not be your thing but who knows.

I have a similar problem with my new cap.

 

[GuitarsandMopars]

There's a process in Techstream that runs through a test of each component in the evap system. You listen to see if the valves make noise when they're activated by Techstream. I had a P0441 (evap incorrect purge flow), P0442 (small evap leak) and P0446 (evap vent control circuit), and replacing one of the vent control valves fixed all of the codes.

Here's a thread on the Techstream process.

Diagnosing EVAP system codes P0442 and P0456

(long post warning) In my journey to revive my new 2004 LX470, I've got P0442 and P0456 pending codes that are preventing the car from passing emissions. (They eventually turn on the CEL). I'm trying to diagnose the issue in this post and hopefully tap into the collective knowledge of forum...

forum.ih8mud.com

When I did the smoke test, there was some smoke coming from near the gas cap, but it was actually coming out of a nearby vent and was not a leak.