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Auto Go
Auto Go, ASE Certified Technician
Category: Jeep
Satisfied Customers: 849
Experience:  ASE Master certified, ASE certified Undercar Specialist, ASE Advanced Engine Performance certified
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Having had a smoke test run on the fuel tank, the check engine

Resolved Question:

Having had a smoke test run on the fuel tank, the check engine light is still on but now the fuel tank is very difficult (timewise) to fill. Why might this be????
Submitted: 7 years ago.
Category: Jeep
Expert:  Auto Go replied 7 years ago.
Hello and welcome to Just Answer!

EVAP problems are difficult to diagnose sometimes. Since your fuel filling problem happened after the smoke test was done, I'd say there has to be a problem with the vent control system. What you need to do is disconnect the vent hose that goes from the fuel tank to the NVLD assembly (natural vacuum leak detection). Here is an image showing where it is and what line needs to be disconnected. If the fuel will fill ok when the line is disconnected, then replace the NVLD. This part has a fairly high failure rate.


notice the NVLDs location in relation to the fuel tank. That should help you locate it. It's not going to be easy to get the hose off, but it's likley that the vent valve is stuck in the NVLD not allowing the tank to vent as you fill the tank. Fuel tanks no longer vent into the atmosphere, they vent through the charcoal cannister to capture fuel tank vapors instead of letting them go off into the atmosphere. Then when the computer determines that the time is right, a purgbe solenoid will open and engine vacuum will draw the vapors from the cannister to the enigne and the vapors are burned in the engine.

Since the problem came about after they tested the system, either the valve is stuck or something didn't get plugged back in or lines were hooked up improperly.

thanks and let me know if I can help you any more.
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