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Old 09-26-2009, 15:56   #1 (permalink)
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The old pain, P0442

Yeah, I have that old pain, P0442, small leak in the fuel system's pressure test. OH, my car is a 99 Taurus plain Jane, nothing exotic.

Today I crawled under the car and cleaned a couple of rusted spots on the fuel vapor lines or at least what I thought were vapor lines. Next I painted those spots with Dow's 1500, a marine caulking compound that adheres to anything. Next I set the trip mileage to 0 to see how long it takes for this fault to reoccur and I reset the the fault with my computer.

I have had this fault on and off now for about a month or so. Each time I have reset it with my laptop because it does not clear itself. Question--- how often does the car's computer make the fuel vapor leak test??? Is this something that is done frequently or every 2-300 miles or so?

I did clean around the gas cap along and applied a thin film of grease to help make a good seal with the cap. I have not replaced the cap yet but that might be next if the fault reoccurs.

I dread having to take this to a shop of a smoke test to find the leak! Suggestions??

Thanks--

Foggy
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Old 09-27-2009, 18:44   #2 (permalink)
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Exclamation Re: The old pain, P0442

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Yeah, I have that old pain, P0442, small leak in the fuel system's pressure test. OH, my car is a 99 Taurus plain Jane, nothing exotic.

Today I crawled under the car and cleaned a couple of rusted spots on the fuel vapor lines or at least what I thought were vapor lines. Next I painted those spots with Dow's 1500, a marine caulking compound that adheres to anything. Next I set the trip mileage to 0 to see how long it takes for this fault to reoccur and I reset the the fault with my computer.

I have had this fault on and off now for about a month or so. Each time I have reset it with my laptop because it does not clear itself. Question--- how often does the car's computer make the fuel vapor leak test??? Is this something that is done frequently or every 2-300 miles or so?

I did clean around the gas cap along and applied a thin film of grease to help make a good seal with the cap. I have not replaced the cap yet but that might be next if the fault reoccurs.

I dread having to take this to a shop of a smoke test to find the leak! Suggestions??

Thanks--

Foggy
Don't grease the cap. If suspect, just replace. But... an internally leaking purge solenoid can cause an Evap leak code to set. Apply around 11 in. hg. of vacuum to the canister side of the purge solenoid with the engine off. It should hold vacuum, and not bleed down. If it bleeds down you need a purge solenoid. I can't find an exact description, but it looks very similar to Chrysler's Natural Vacuum Leak Detection system (NVLD). It checks for a small leak (P0456) during key off. Medium and Large Leak (P0442 and P0455 respectively) are done during engine running. Uses gas law as an operating principal. Ultimately, if you don't find any obvious issues then a smoke check is in order.
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Old 09-28-2009, 09:30   #3 (permalink)
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Re: The old pain, P0442

Thanks for your suggestions Tbird.

You mentioned fault P0442 to be a medium leak fault but I noticed that the fault code is described as a small leak. I mention that only because if this fault reoccurs now that I have "patched" a couple of rust spots, I would try connecting a vacuum pump to the test plug (or is this not the cannister side?) and see if the solenoid holds vacuum. I have a vacuum pump for doing the air conditioner so I should be able to configure a way to pull a small vacuum on that line. Yes--- I would avoid pulling too heavy a vacuum out of fear of collapsing the fuel tank.

It might even be worth just replacing the solenoid altogether.

Final question--- how often does the car's computer test for an evap leak? Is the testing ongoing at all times other than at times of full and near empty fuel conditions?

Thanks--

Foggy
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Old 09-28-2009, 20:39   #4 (permalink)
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Thanks for your suggestions Tbird.

You mentioned fault P0442 to be a medium leak fault but I noticed that the fault code is described as a small leak. I mention that only because if this fault reoccurs now that I have "patched" a couple of rust spots, I would try connecting a vacuum pump to the test plug (or is this not the cannister side?) and see if the solenoid holds vacuum. I have a vacuum pump for doing the air conditioner so I should be able to configure a way to pull a small vacuum on that line. Yes--- I would avoid pulling too heavy a vacuum out of fear of collapsing the fuel tank.

It might even be worth just replacing the solenoid altogether.

Final question--- how often does the car's computer test for an evap leak? Is the testing ongoing at all times other than at times of full and near empty fuel conditions?

Thanks--

Foggy
As I stated before, if the same as Chrysler's NVLD system, small leak is engine off, medium and large leak is engine running. P0442 with Chrysler was originally small leak, but was later changed to medium leak, because they wanted to monitor for .010 leaks. When vacuum testing the purge solenoid, disconnect the hose going to the back of the car (canister side) and connect the vacuum pump to the port on the solenoid.
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Old 09-29-2009, 10:37   #5 (permalink)
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Re: The old pain, P0442

Thanks Tbird--- I will keep you informed. My plan is to wait for a while to see if the "patching" solved the problme. If not, I will do my best to pump a vacuum on the solenoid.

More later--

Foggy
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Old 10-07-2009, 16:37   #6 (permalink)
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Re: The old pain, P0442

I put on 300 miles since I reste the computer...........guess what happened! You're right! The *&^%) light came back on. Tonight I stopped at an auto parts store and purchased a new gas cap. I want to do the simple things first before I get creative.

If the light comes on again, I will go after the solenoid. But while discussing solenoids, I just wonder if I can defeat the entire test and "fool the computer." Maybe I could just put a loop between the input and the output of teh solenoid and try that. Heck, this fault does not affect the engine's performance at all and there comes a time when goddie-goodies get carried away with "oh, we have to save the tree frogs!"

Next, I could connect the line from the engine directly to the line going to the tank. To %^&* with the the test. Hey, after I get through driving this car its going to a bone yard anyway but the car runs so good, I intend to keep driving it and I have no intention of paying $500 big ones for a smoke test by a dealer.

More later!

Foggy
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Old 10-09-2009, 20:43   #7 (permalink)
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Exclamation Re: The old pain, P0442

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Originally Posted by foggysail View Post
I put on 300 miles since I reste the computer...........guess what happened! You're right! The *&^%) light came back on. Tonight I stopped at an auto parts store and purchased a new gas cap. I want to do the simple things first before I get creative.

If the light comes on again, I will go after the solenoid. But while discussing solenoids, I just wonder if I can defeat the entire test and "fool the computer." Maybe I could just put a loop between the input and the output of teh solenoid and try that. Heck, this fault does not affect the engine's performance at all and there comes a time when goddie-goodies get carried away with "oh, we have to save the tree frogs!"

Next, I could connect the line from the engine directly to the line going to the tank. To %^&* with the the test. Hey, after I get through driving this car its going to a bone yard anyway but the car runs so good, I intend to keep driving it and I have no intention of paying $500 big ones for a smoke test by a dealer.

More later!

Foggy
Can't fool it. The issue you have would be an INTERNAL leak inside of the purge solenoid. The solenoid operates normally, but when it's closed it isn't sealing properly. Shorting the purge solenoid wires together will set another DTC. Hooking a vacuum line to the tank vapor line isn't a good idea either, this would affect engine performance.
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Old 10-10-2009, 09:15   #8 (permalink)
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Re: The old pain, P0442

Well, I have the new gas cap on with only about 100 miiles on it. If it is going to fault, I expect it around 300 miles or so. By the end of next week I should know if I can get past 300.

Back to the solenoid for a minute...... just curious about this thing. I thought there was a vacuum on the tank provided through the selonoid with it in an open position. When it closed I thought a vacuum sensor located at the tank checked to see if the vacuum held and if not, it detected that a leak down was occurring, tripping the DTC.

I thought just removing the hoses from the solenoid and linking them together and leaving the wiring on the solenoid would fool it. But I guess that is not how it works.

Foggy
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Old 10-10-2009, 10:22   #9 (permalink)
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Re: The old pain, P0442

You probably fixed it with the new cap. I had the same problem with my Crown Vic. and the cap fixed it.


The EVAP Running Loss System Monitor relies on the individual components of the EVAP Running Loss system to apply vacuum to the fuel tank and then seal the entire EVAP Running Loss system from atmosphere. The fuel tank pressure is then monitored to determine the total vacuum lost (bleed-up) for a calibrated period of time. Inputs from the engine coolant temperature (ECT) sensor, intake air temperature (IAT) sensor, mass air flow (MAF) sensor, vehicle speed sensor (VSS), fuel level input (FLI) and fuel tank pressure (FTP) sensor are required to enable the EVAP Running Loss System Monitor.

If the bleed-up threshold is still being exceeded after three tests, a vapor generation check must be performed before DTC P0442 (small leak detected) will be set. This is accomplished by returning the EVAP Running Loss system to atmospheric pressure by closing the EVAP canister purge valve and opening the CV solenoid. Once the FTP sensor observes the fuel tank is at atmospheric pressure, the CV solenoid closes and seals the EVAP Running Loss system.

The fuel tank pressure build-up for a calibrated period of time will be compared to a calibrated threshold for pressure build-up due to vapor generation.

If the fuel tank pressure build-up exceeds the threshold, the leak test results are invalid due to vapor generation. The EVAP Running Loss System Monitor will pass and complete.

If the fuel tank pressure build-up does not exceed the threshold, the leak test results are valid and DTC P0442 will be set.
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Old 10-17-2009, 18:23   #10 (permalink)
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Re: The old pain, P0442

I DID IT!!!! I DID IT!!!

(I think)

OK this is what has happened. The gas cap? NOPE, same problem and I am about $20 poorer but it was worth the try.

I scrapped the pipes leading to the fuel fill and painted them. Others I coated with Dow Corning 520......no help, light kept coming on after I reset it.

Today, I jacked the rear of the car, placed jack stands under it for safety and decided that I had to find SOMETHING that at least resembled a leak. I looked and looked to no avail. Next, I printed some diagrams from a Ford maintenance disc that I have for the car to learn where I could find the Canister Vent Solenoid. Talk about easy??? Like heck!

One bolt supporting the plastic shelf that holds the canister along with the canister vent solenoid BROKE and the other bolt I removed using my Sawzall. When I got this thing down, I said WOW!!!! I found the canister solenoid!!! It was a rusty mess. I removed it and took it to my workshop and chiseled the caked, scalling rust off the thing. I was stuck because today is Saturday and there was no place for me to purchase a replacement.

Anyway, after awhile, I got through the scalling rust and thought I might be able to seal the thing. So I painted the solenoid with water based polyurethane, the stuff for wood finishing. Dried the solenoid with my heat gun and repeated the procedure several times. I put poly over everything! I even dumped some into the connector to seal the pins.

Put everything back together, used tie wraps to hold the plastic shelf containing the canister and then moved onto my next project. That was flushing the radiator and the heater core with the car running.

I finished all the outstanding jobs and now had everything back together and went into the house to grab my laptop to reset the MIL light. Got into the car AND THE LIGHT WAS OUT!!! OUT!!! OUT!!!

With my luck it probably will come back on. but I am going to find out by driving the car. New solenoid??? I don't think so.....if my poly coating job holds out. But I do think I have the thing solved.

I hope my experience helps others who run into this very difficult OBD2 fault condition.

Foggy

Last edited by foggysail; 10-18-2009 at 07:48. Reason: typo
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