A light bulb just appeared over my head!!

Just read a posting from Donbrew about P0451 or P0454. He posted, I'm assuming from a repair manual, stating that if there is a restriction in any of the vent lines it can lead to the fuel vapors not being bled off fast enough and cause cause zeroing problems with the sensor.

So let me ask this. When I compression fitted the nylon line to the steel line I used a brass compression fitting along with a brass insert on the nylon side to keep it from crushing. I did not use the brass insert on the steel side of the line. I was told the plastic type (sharkbite type) would not work from nylon to steel. I remember saying to myself how restrictive that little insert looked to be but wasn't concerned about it beings the line was only for vapor. I did the same means with the fuel line, brass insert on the nylon side and nothing on the steel side. I did not have the proper connectors at that time to make a straight run on either line.

Also, the code doesn't come up everyday. It's like every other or maybe even every two days or so. Should i redo these lines in hopes this could be the problem? I'll just get rid of the remainder of steel line and replace with nylon and get the right connection and compression fit it with the sharkbite type fitting. This way there should be no restriction in the line.

What fuel line kit did you install? Inspect the connection to the EVAP canister both electrical and air lines , it’s possible there’s a bent pin
You tested the EVAP purge solenoid valve under the hood, did tge new vapour line connect directly to it or did you cut the lines to size and install a coupling?

did not use a kit. bought 25ft roll of 3/8 nylon. Kept original lines from basically drivers floor up to engine. Connected my lines at that point with compression fittings. Pressed the old fittings from what i took off onto the new nylon tubing to mate up to the canister.

yes, tested purge solenoid under hood. when i take the purge line off solenoid and close vent at canister, i put my vac tool on purge line and can not pull a vac.

The canister is open so that’s why no vacuum

The canister is closed and commanding 20% on the purge solenoid. I'm watching the data stream on the FTP sensor with car running. Here's where it gets weird for me. Before i even ran the seal/purge test from scanner I looked at the data on the sensor. It was reading -8.000mmHG and voltage was at 2.45v. Shouldn't vacuum be closer to zero and voltage like 1.5v? The car wasn't even ran yet and was sitting all night. My understanding is you start the seal/purge test and start the car and you should start seeing negative vacuum building. Voltage should also start climbing as vac increases. I'm not see an increase in vacuum or voltage but instead it's the opposite. It's going from -8, -7, -6 etc and voltage goes from 2.45, 2.40, 2.35 etc. If it's pulling a vacuum shouldn't negative numbers go more negative and voltage numbers go more positive? This is acting like it's relieving vacuum but it's pulling vac through the purge solenoid. WTH!!!!

I manually checked for vacuum on the purge line by shutting vent solenoid and putting my mighty vac tool on. I didn't think it was pulling vac because the guage on the tool wasn't showing anything. I think thats just because the area i'm trying to pull vac on is so big (fuel tank) and would take about a gazillion hand pumps on the mighty vac. The numbers on the FTP sensor all acted the same way. Also confirmed the release of air from the mighty vac after pushing the relief valve.

I'm removing the compression fittings tomorrow and getting rid of the brass ferrules on the inside of the nylon vent line. I'm doing the same with the fuel supply line as well. I'm convinced it's restricting the lines.

I would expect that overnight cool would develop a vacuum from a zero pressure baseline.

It's a fluid dynamics fact of life the the brass ferrules you’re concerned about will cause pressure drop during flow. No way it’s significant though. That it causes a problem in the vent line isn’t even plausible.

That’s why. I don’t recommend compression fittings for fuel and vapour line repair.

fixed the vapor line today and used the shark bite type connector to join the two lines. Did drop the tank again just to double check things and good thing I did. The nylon supply line from the fuel pump somehow got kinked when I put the tank back up last week. It was kinked bad too, almost completely blocked. I really can't believe the car was running. Was noticing a lot of surging and rough idle but i just thought it was related to the code.

So I fixed that by running a whole new nylon line again but took the time to shape the line with a heat gun. Worked out great! I grabbed a new FTP sensor just in case I need to put that in. I tested the resistance on the sensor that is in fuel pump and get the same thing on the new sensor so no point in replacing a perfectly good sensor. I'll take the new one back and get my money back. It wasn't insalled.

Put it all back together and primed fuel pump. Put the scanner on and did the seal/purge test. That dang thing is still reading -8.000 mmHG and 2.45V. I commanded purge to 10% and closed seal. I watched the numbers go backward again from -8 to 0 to 11.0mmHG and the voltage steadily decreased from 2.45v to I believe it was .9V. I open the seal and numbers quickly return back to -8 and 2.45V, on linear slope of course.

So, it appears the evap system is doing what it's supposed to do BUT why do my numbers do the complete opposite of what I've seen everyone else's scanners do? Like starting at 0 and ending somewhere around -12 for vac and 0 - 2.5V. Are these numbers some kind of set starting point for this brand of OBD2 scanner and maybe the function is opposite? Is there a set standard for OBD2? I only finished up like an hour ago and haven't done any driving with the car. I've no idea yet if it will throw the P0451 yet. Besides, it seems like that code is set prior to cold start ups. Can the computer system set a code without the car running? Like after you shut car off? It never happens when i'm driving.

FYI, I can blow through all vent openings in canister as well as the vent lines on fuel tank.

Many of the EVAP tests run after shutdown/over night. This is the source of some "parasitic drain" complaints.
It is enough to know that the purge valve is normally closed and the vent valve is normally open. Too much data is dangerous.