It's not the gas cap.

The hoses from the rear axle box seem fine.


What am I supposed to check here?

 

Low on the firewall on the right(passenger)side.

 

Thanks. What is the thing near the rear axle then?

 

The hoses from the rear axle box seem fine.

 

What am I supposed to check here?

 

Do we have the same car?
There is nothing low on the firewall on the passenger side.
You can not even see the lower part of the firewall.

 

"Do we have the same car?"

Nope mines a '96 XJ. My canister is on the firewall.

There should be a schematic of the system on a sticker under the hood. Mine is near the brake booster. Check for any damaged,disconnected,or lose fittings,hoses,system parts. If all looks good you may need to have a smoke test done.

 

Any help? Any feedback on the posted photos?

 

Ok, zero clue how to diagnose this.
Neither did the mechanic who just fixed my brakes.

Any help?

 

If nothing is obvious, take it to a shop who will perform a "smoke test", which was already mentioned byEZEARL. This test introduces smoke into the evaporative system and then seeing where it escapes.

Any competent shop should be able to do this for you. Pay the nice man.

 

The box by the real axle is the EVAP canister. Check the other side of those three connections for splits by feeling them or using a mirror. One tube goes back to the gas tank. That metal tube can rust out. That metal tube connects to a plastic tube at the top of the gas tank. Check that connection.
The other two lines run along the driver's side of the vehicle to the engine compartment. There are a couple of connections along the way. The smaller line runs to the intake manifold and the larger line runs to the leak detection pump. (Your second picture) You need to inspect those lines for cracks and/or separations at the connection points. The smaller line goes from plastic (underneath the vehicle) to metal (transition to engine compartment)to plastic. The connections are underneath the driver's seat and low on the firewall in the middle of engine compartment. I'm not sure about the connections on the line to the leak detection pump.
I hope this helps.

 

Repaired a cracked Evap line near the leak detection pump, replaced a O2 sensor, and replaced the gas cap. Check engine light came back on after each repair, after about 20-40 cycles. Before I try to inspect the Evap lines beginning to end, any other suggestions?

 

That evap box in the rear has molded mounts that hook into that metal shell. Take it down and inspect it for snapped mount tabs and cracks.

To help diagnose this as a leak or a faulty Leak detection pump disconnect the large S shaped hose coming out of the LDP that connects to the ridgid plastic line running to the back of the Jeep. Then plug the 2 open ends with plastic thimble caps.

The LDP will now only pressurize that S hose. If a gross leak code still occurs the LDP has an internal failure.

 

Thank you very much, I needed a little direction to proceed.