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Discussion Starter #1 (Edited)
For those that have a fuel return system installed, have you experienced any problems? I've been driving the car for a while and just recently received a "check fuel cap message" even though the cap was tight. I checked the code with the HIM/HDS and it indicated DTC P0456 (Evaporative Emission (EVAP) System Very Small Leak (.02 inch)) was triggered. I cleared the code and then used the HIM/HDS to perform the EVAP test (takes about 25 minutes or so from start to finish). Once complete, everything passed and it appeared to be an intermittent problem.

A few days later, the same DTC was triggered. I read a little more and evidently one of the ways the DTC can be triggered is if you are running too high of a fuel pressure on the system. The car is currently set to run at 48psi at idle where it increases 1psi for every 1psi of boost referenced.

I'm going to be testing each of the EVAP components with the HIM/HDS in order to determine what component had failed. In any event, has anyone else has experienced the same issue?
 

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I haven't had any probs yet. I'll keep an eye out for that though.
 

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Discussion Starter #3
The EVAP leak detection system uses a vacuum retention (decompression) method (0.09 inch monitor) when the engine is running and an engine off natural vacuum (EVON) method (0.02 inch (EVON) monitor) when the engine is off. I the problem that I have is with the EVON method which detects leakage from the change in fuel tank pressure via the fuel tank pressure (FTP) sensor. Should be an easy fix, but I won't be able to get around to looking at it for a few days.
 

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Could any of the return line hoses be loose causing a leak at the top of the tank?

"Fresh fuel has a higher volatility that will create greater pressure/vacuum. The optimum condition for testing is less than a full tank of fresh fuel. If possible, to assist in leak detection, add 1 gallon of fresh fuel to the tank (as long as it will not fill the tank), just before starting these procedures"
 

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Eric its weird they say that "P0455, P0457, P0497 are judged as OK" Maybee I am misreading it I will go re-read it.

Once required conditions for the monitor are met, the engine control module (ECM) applies vacuum to the EVAP system line from the purge control solenoid (PCS) valve through the fuel tank, and monitors the variation of the FTP sensor output to detect a “0.09 inch leak”
 

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Discussion Starter #6
Highrev1 said:
Could any of the return line hoses be loose causing a leak at the top of the tank?
I doubt it, but will check anyway. For the return line, I am using AN fittings. On the fuel tank unit, I am using a bulhead fitting with a nylon washer on top and a nut on the bottom. The top of the fuel tank unit was also drilled and tapped for the bulkhead fitting. I used the nut and nylon washer just to make sure that the fitting got a good seal. When installing the fuel tank unit into the car, I also made sure that the gasket was not pinched and was seated correctly before tightening the lock ring.

When driving, I cannot smell gas inside of the car however I noticed that my miles per gallon quickly went to the crapper. After parking the car in the garage overnight, I can smell gas in the air when outside of the car, but not on the inside of the car. I think it may be a problem with the EVAP canister. I was also thinking that the fuel return hose might have had a pinhole leak however, I used the HIM/HDS to turn the fuel pump on for a few minutes and could not locate any gas leaks.
 

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Discussion Starter #8
Highrev1 said:
Eric its weird they say that "P0455, P0457, P0497 are judged as OK" Maybee I am misreading it I will go re-read it.

Once required conditions for the monitor are met, the engine control module (ECM) applies vacuum to the EVAP system line from the purge control solenoid (PCS) valve through the fuel tank, and monitors the variation of the FTP sensor output to detect a “0.09 inch leak”
I read that as well, however the DTC that I got was P0456.

Your second paragraph is referring to Step 0 which is part of the vacuum retention method (evidently this part is okay, but I am really not sure...I did not get a DTC for this one, but would could explain why my gas mileage has gone to the crapper). Steps 1 and 2 are part of the EVON method that triggered the DTC.
 

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I can't see in the pic:(
But...How about the purge valve and the vacume lines in the engine bay? There all tight and secure without any leaks? I know those purge valves have weak NIPPLES and like to break off easily ;)
 

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Discussion Starter #11
Thanks...I'll try to check later and also look at the freeze frame data to see what was recorded to lead up to the DTC.

* You must spread some Reputation around before giving it to Highrev1 again. *
 

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Could just be a normal issue it does state Depending on usage of vechile???

If a vehicle’s fuel fill cap is loose or missing, and the ECM/PCM detects an EVAP system leak when it runs the EVAP monitor, the CHECK FUEL CAP message appears on the information display when the engine is started. A temporary DTC is also stored in the ECM/PCM’s memory. If this happens, there’s really no need for the owner to bring the vehicle in for service. All he or she has to do is shut off the engine and make sure the fuel fill cap is in place and it’s properly tightened (it’s one or three clicks, depending on what’s written on the cap).
Although the owner can cycle the message from the display with the reset button (the actual button name varies by model), the temporary DTC that’s setting the message is still there. This means the message never really goes away. It can be cycled back with the reset button, and it comes on again if the ignition switch is cycled or the engine is restarted. This message keeps coming back until the EVAP monitor runs again and it finds no EVAP system leak. This could take several days, even weeks, depending on how often the vehicle is driven.
If, when the next EVAP monitor runs, the cap wasn’t tightened or there’s another EVAP system leak detected, the MIL comes on and the message goes off. A permanent DTC is now stored in the ECM/PCM’s memory. If the owner now tightens the cap, the MIL should go off after the next EVAP monitor run, yet, this could still take days or weeks. If the MIL is still on after that monitor run, then it’s time to bring the vehicle in for service. If the vehicle comes into your shop with the fuel cap message or the MIL on, make sure the fuel fill cap is in place and properly tightened. Record the DTC, then clear it with the HDS, and run the EVAP system function test. If there’s still a problem, press on with normal troubleshooting.
 

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Discussion Starter #13
The DTC was a temporary one where no freeze frame data was stored. I ran the fuel pump through two five minute cycles while I checked all of the connections and hoses for leaks. All were secure and no leaks were detected. I then popped the cover where the fuel tank assembly is located and noticed that the 45 degree fitting that was screwed into the bulkhead fitting had rotated a bit. The fitting to bulkhead connection was tight, but the bulkhead worked itself loose about 1/3 of a turn separating itself ever so slightly from the top of the fuel tank assembly. This must have happened over time when driving over bumps, etc. where the part was subjected to minor vibrations.

I took the bulkhead fitting out, cleaned all of the connection points, and scuffed the connection point surfaces. I then applied JB Weld to the threads on the bulkhead fitting, reassembled, verified the JB Weld seal, and will let the part sit overnight. This will permanently fix the problem. :thumb:

Thanks for your help Greg.
 

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Discussion Starter #14
Problem solved...It was a minor leak around the bulkhead fitting on top of the tank assembly. I used JB Weld on the top and bottom of the fitting to ensure a tight seal. Here are some PICs for reference:





 
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