00 evap emission Q

hey all,

2000, 178k miles, no CE light. but have had a creaking noise from the fuel tank at shut down for about a year (20k miles). scan tool showed a pending P1450 (excessive vacuum detected in the fuel tank). I verify this condition by pressing on the tank and the noise momentarily stops till it begins expanding again back to it's fixed shape.

i have the entire evaporative emission canister off. i can blow through the canister, through the canister vent solenoid, and dust separator up to the fill cap. odd mention: there is no smell of fuel in this assembly. only fuel smell came when i unhooked the canister from the tank tee.

if i blow through this line to the tank and purge valve, it's a slow release (maybe the vapor vent valves on the tank are small)- and i read the canister purge valve should normally be closed.

I followed the lines up just about to the PV where i lose sight from under the car. i can't believe a vacuum hose is disconnected since vacuum is obviously being created, and no fumes are coming from the car. could the PV be staying open when it shouldn't? or is the fuel tank pressure sensor bad (PITA repair)?

the CV solenoid looked toasted from corrosion so i have a new one coming. but i have a feeling this isn't the problem.

anyone chased this before or have suggestions?

If CV solenoid you means Canister Vent solenoid, then that might be your problem. If it's getting stuck the PCM might be sensing flow when there shouldn't be or viceversa. I would fix that and erase any existing/pending codes.

If you blow from the intake hose to the Fuel tank via the purge solenoid there shouldn't be any flow as this is a normally closed solenoid.

Best regards,

Oscar.

just to make sure were on the same page, here is what i'm reading from the ford workshop manual;

canister purge valve (PV) is normally closed.
canister vent (CV) solenoid is normally open.

from that and the diagrams i'm gathering that when the PV opens the engine's vacuum pulls the vapors from the tank and canister. and when things get too hot the CV's job is to vent when positive pressures exceed tolerance, allowing exit through the dust separator and up the line to the exit in the fuel cap cover area. what's happening in my case is the PV is allowing too much vacuum to be applied, slightly deforming the tank. i wonder if it's lazy and not closing off when it's supposed to. OR the fuel tank pressure (FTP) sensor is bad and not reading how much negative pressure is being created.

oscar, i will verify the PV line and advise.

Here's a full explanation of the EVAP system:

Enhanced Evaporative Emission (EVAP) System

The EVAP running loss system components consist of fuel tank, fuel filler cap, fuel tank mounted or in-line fuel vapor control valve, fuel vapor vent valve, EVAP canister, EVAP canister purge valve, fuel tank pressure sensor, canister vent solenoid, related wiring and fuel vapor hoses. EVAP running loss system uses inputs from Engine Coolant Temperature (ECT) sensor, Intake Air Temperature (IAT) sensor, Throttle Position (TP) sensor, Mass Airflow (MAF) sensor, Vehicle Speed Sensor (VSS) and Fuel Tank Pressure (FTP) sensor to provide information about engine operating conditions to PCM. The Fuel Level Input (FLI) and FTP sensor signals are used by the PCM to determine activation of EVAP Monitor based on presence of fuel vapor or fuel sloshing. Component descriptions are as follows:

Canister Vent (CV) Solenoid

The CV solenoid seals the EVAP canister from atmospheric pressure, allowing EVAP canister purge valve to obtain fuel tank target vacuum during the EVAP Running Monitor test.

Fuel Tank Pressure (FTP) Sensor

The FTP sensor is used to measure fuel tank pressure during EVAP Monitor Running Monitor test. FTP sensor is also used to control excessive fuel tank pressure by forcing the system to purge.

EVAP Canister Purge Valve

Normally closed purge valve controls the flow of fuel vapors from canister to intake manifold during various engine operating modes. When engine is shut off, vapors from fuel tank flow into canister. After engine is started, purge valve regulates fuel vapor flow by means of manifold vacuum and duty cycle signal from PCM.

Fuel Vapor Control Valve

The fuel vapor control valve is used to close the flow of liquid fuel to the EVAP canister purge valve or EVAP canister during refueling. Fuel vapor control valve is also used to prevent accumulation of liquid fuel in the fuel vapor hoses caused by overfilling fuel tank. On Escort and Tracer, the fuel vapor control valve also contains a liquid/vapor fuel discriminator. Purpose of the liquid/vapor fuel discriminator is to separate the liquid and vapor state of the fuel at the fuel tank vent and allow only the fuel vapor to move through the EVAP running loss system with the liquid fuel remaining in the tank.

Fuel Vapor Vent Valve

Fuel vapor vent valve assembly is mounted on top of fuel tank and is used to control flow of fuel vapor entering the fuel tank vapor delivery line to the EVAP canister. The head valve portion of the fuel vapor vent valve prevents fuel tank from overfilling during refueling. The fuel vapor vent valve also has a spring supported float that prevents liquid fuel from entering fuel tank vapor delivery line under severe handling or a vehicle rollover condition. See Fig. 23.

EVAP Canister

Vapors from fuel tank are stored in EVAP canister. With engine running at RPM higher than idle, vapors are purged from EVAP canister back into the engine for combustion.
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About the PV line, check lines as much as you can. The fuel smell is only present when the Purge valve is stuck, has broken lines or the line from the fuel tank to the canister is broken. Since you don't smell any fuel your problem might be likely on the other side, the vent solenoid, which you said it's bad. I would replace it, after all with that condition it will give problems sooner or later in case it doesn't solves your problem...

Oscar.

an update

replaced canister vent solenoid. no difference- fuel tank still makes the creaking noise at shut off.

oscar, i haven't verified the PV line yet. i didn't look forward to removing the cowl but i will be replaceing that next. it has a duty cycle- perhaps it's gotten lazy and isn't reducing the vacuum load to the system when it should.

only other items left in this puzzle are the fuel tank pressure sensor or the fuel tank itself.

The evaporative emission canistor purge valve is mounted on the firewall at the rear of the engine compartment.
It is on the driver's side .....very close to being inline with the PCV valve in the rear valve cover on the 3.8L motor.

This is a bad picture, since my hand is blocking most of the purge valve.....but you can see the power brake booster on the right and part of the purge valve showing from behind my hand.
http://inlinethumb03.webshots.com/14530/2248514960011220610S500x500Q85.jpg (http://rides.webshots.com/photo/2248514960011220610nQqNdh)

It is really hard to get a good picture back there, particularly with the big upper intake manifold on the 3.8L motor.
I had taken this picture to show the routing of the hose for my catch can in the PCV line.
I looked through my pictures and this is the best that I could find.
I sold the vehicle almost a year ago, or I would have been able to go out and get a picture.

There is a vaccum present on one hose going into the purge valve whenever the motor is running.......coming from the upper intake manifold.
It sounds like that is OK, as your indication is of too much vaccum.
The other vaccum line, that goes back to the canister, should only get vaccum when the PCM sends the signal to the purge valve.

You can barely see it in my picture, but on the front of the purge valve.....on the top is what looks like a cap.
Under that cap is a felt type of air filter.
I read someplace that if this filter becomes clogged, it can cause the valve to not function properly.

To aid with wiswind's picture here is a link

http://www.oreillyauto.com/site/c/detail/MOT0/CX2183.oap?pt=02211&ppt=C0018

it doesn't shows the component mounted in the engine compartment but it will give a good idea.

Try running the van a little with the PV disconnected, you'll have the CEL on and very likely you'll notice a fuel smell after you turn the engine off but that way you can see if the creaking persists or has gone away. You can also measure resistance across the terminals and you should see 30-38 Ohms.

Oscar.

hey guys, thank you.

i just replaced the fuel tank cap- no difference. so i will dig into the PV next. oscar you are correct, the new PV ohms at 31.3

i had driven with the entire evap canister assy removed and there was no noise.

i'll keep you all appraised.

I once had to replace my fuel pump ... and on the replacement unit, the pressure sensor was bad. I could have easily checked it with a voltmeter before installation ... just didn't expect it to be problem on a new unit. Had to drop that dang tank again.

It's more likely your problem is the valve or sensor near the engine I would think.

I once had to replace my fuel pump ... and on the replacement unit, the pressure sensor was bad. I could have easily checked it with a voltmeter before installation ... just didn't expect it to be problem on a new unit. Had to drop that dang tank again.

It's more likely your problem is the valve or sensor near the engine I would think.

how did you know you had a problem with your FTP sensor? P452, 453?

I don't remember the code exactly ... but since I had just replaced the pump/sender unit, the pressure sensor was high on my short list. It turned out to be "open" circuit. But I had to endure looking at that CEL for 12k miles, as there was no time left for further repairs before embarking on driving vacation.

I kinda remember it being P1450.

purge valve has been in for 700 miles. first few shutdowns i thought i had it fixed. but i hear it again. maybe it's a softer, slower creaking.
fwiw.