99 4.0 and the dreaded EVAP system leak code

[any4xx]

I’ve been getting & clearing this code ever since buying my ‘99 a few months ago. Today I finally smoke checked the system. Zero leaks anywhere. I was even able to get enough (too much) pressure into the system that removing the gas cap was quite dramatic. It looks like the canister, a couple of the lines, and the filter are all fairly new. I’m guessing the previous owner replaced those.

My feeble mind tells me to try replacing the purge valve and/or the leak detection pump. Neither are horribly expensive, but my “guess” is that the pump makes more sense. But that’s twice to three times the cost of the purge valve. I don’t know if there’s a way to test these components. Help?

What say the experienced folks here?

Thanks for any and all advice.

 

[macleanflood]

On my 97 when I removed the purge valve next to my charcoal cannister...97 it's up under the hood...the valve wasn't clicking and it was full of charcoal from the failing cannister.

-Mac

 

[Moglocker]

I’ve been getting & clearing this code ever since buying my ‘99 a few months ago. Today I finally smoke checked the system. Zero leaks anywhere. I was even able to get enough (too much) pressure into the system that removing the gas cap was quite dramatic. It looks like the canister, a couple of the lines, and the filter are all fairly new. I’m guessing the previous owner replaced those.

My feeble mind tells me to try replacing the purge valve and/or the leak detection pump. Neither are horribly expensive, but my “guess” is that the pump makes more sense. But that’s twice to three times the cost of the purge valve. I don’t know if there’s a way to test these components. Help?

What say the experienced folks here?

Thanks for any and all advice.

Have you installed a new fuel pump recently,I didn’t have the big plastic nut tight enough.

 

[any4xx]

Have you installed a new fuel pump recently,I didn’t have the big plastic nut tight enough.

I have only owned it for a few months and have not replaced a fuel pump. But I’m guessing that if something like that was leaking I’d not be able to pressurize the tank with no smoke leaking out.

 

[any4xx]

On my 97 when I removed the purge valve next to my charcoal cannister...97 it's up under the hood...the valve wasn't clicking and it was full of charcoal from the failing cannister.

-Mac

That is definitely something worth checking. Thank you for the suggestion. I’ve got to be gone for a week so nothing will get done soon. I hadn’t considered removing those components and cleaning them out. I’ll definitely try that prior to replacing anything.

 

[Moglocker]

I have only owned it for a few months and have not replaced a fuel pump. But I’m guessing that if something like that was leaking I’d not be able to pressurize the tank with no smoke leaking out.

I couldn’t see mine leaking smoke until removed my fuel pump access panel,so

 

[any4xx]

I couldn’t see mine leaking smoke until removed my fuel pump access panel,so

I’ll leave that on the “things to check” list, but again, I was able to pressurize the tank so much that removing the gas cap created quite a cloud. I’ll be messing with the test pump and purge valve first, but will pull the tank to check that if neither of those components prove to be the problem.

 

[any4xx]

Okay Folks. I’m still stumped. I recently replaced the leak detection pump and the code still set after a few days. I then tried the purge valve. Same result. Every line going to the EVAP systems is tight and leak free. Today I dropped my fuel tank so that I could check all of the giblets there independent of the rest of the vehicle. Everything is tight and leak free.

The only thing that now comes to mind is that maybe the leak detection pump and/or the purge valve aren’t powering on at all? Each plug only has three wires. I’m guessing they are power, ground, and the feedback signal? Anyone know what colors are supposed to do what, and when? I’m thinking that neither of these receive power past the first few seconds of startup. But perhaps I’m wrong?

I’m not in a smog-testing area so if I have to look at the MIL forever it’s not the end of the world. But I like it when stuff works.

Thoughts?

 

[macleanflood]

Is the purge valve clicking? Use a screwdriver to the ear and listen?

On my 97 the charcoal cannister failed and the solenoid was full of charcoal pellets.

Wiring diagrams are in the Factory Service Manuals section 8w in the resources section. Checking voltage, etc as you mentioned would be an excellent step.

-Mac

 

[any4xx]

I don’t want to risk jinxing myself, but I think that @Moglocker had the answer. When I dropped my tank a few days ago everything was tight. So tight that I was afraid that I was going to break the pump retaining ring getting it off. Even though everything was holding pressure I decided to go ahead and remove the pump to check the seal. Not only was removing it a nightmare, but after way too many tries I had all but given up on trying to get the ring to screw back on. It was like the ring was about 1/8” smaller than it should have been and I just couldn’t get it started straight. I decided to grease the threads on both the tank and the ring to see if I could get it back on. That worked and I was able to tighten it down and put everything back together. I was disappointed that I couldn’t find anything obvious to fix.

But fast forward to today. Three days later and my MIL has not come back on. Could it be that my fuel pump wasn’t installed tightly enough but the tank assembly would still hold pressure & smoke? Again, I’m hesitant to declare victory this soon, but for now it seems that simply removing the pump and reinstalling it might have just been the magic fix.

 

[Moglocker]

I don’t want to risk jinxing myself, but I think that @Moglocker had the answer. When I dropped my tank a few days ago everything was tight. So tight that I was afraid that I was going to break the pump retaining ring getting it off. Even though everything was holding pressure I decided to go ahead and remove the pump to check the seal. Not only was removing it a nightmare, but after way too many tries I had all but given up on trying to get the ring to screw back on. It was like the ring was about 1/8” smaller than it should have been and I just couldn’t get it started straight. I decided to grease the threads on both the tank and the ring to see if I could get it back on. That worked and I was able to tighten it down and put everything back together. I was disappointed that I couldn’t find anything obvious to fix.

But fast forward to today. Three days later and my MIL has not come back on. Could it be that my fuel pump wasn’t installed tightly enough but the tank assembly would still hold pressure & smoke? Again, I’m hesitant to declare victory this soon, but for now it seems that simply removing the pump and reinstalling it might have just been the magic fix.

You most likely fixed it,people don’t realize that you have to grease those threads to get the ring tight enough to make a good seal,did you use a lock ring tool?

 

[any4xx]

You most likely fixed it,people don’t realize that you have to grease those threads to get the seal tight enough,did you use a lock ring tool?

Sadly, I didn’t have access to the proper tool so I just did the alternating-ridge-tap thing to keep the retaining ring rotating smoothly until I felt it was seated as firmly as necessary. But I’m DEFINITELY going to have the lock ring tool before I ever try that again. What a nightmare.

 

[any4xx]

Ugh… MIL came back on. When I had the housing out of the tank I was surprised at just how loose the top center section felt. It was very easy to turn and to properly clock once the main housing was tightly mounted. I suspect that my leak is at that junction.

The Jeep runs great and I’m not inclined to pull the tank any time soon just to turn the MIL off. At some point I’ll do it, but for now I’ll just live with it. Fortunately I’m not in an area that requires emissions testing.

Did I mention, “UGH!”

 

[Moglocker]

Ugh… MIL came back on. When I had the housing out of the tank I was surprised at just how loose the top center section felt. It was very easy to turn and to properly clock once the main housing was tightly mounted. I suspect that my leak is at that junction.

The Jeep runs great and I’m not inclined to pull the tank any time soon just to turn the MIL off. At some point I’ll do it, but for now I’ll just live with it. Fortunately I’m not in an area that requires emissions testing.

Did I mention, “UGH!”

You have to use Grease on the threads and use a tool made to tighten the ring down,mil will be gone.

 

[any4xx]

You have to use Grease on the threads and use a tool made to tighten the ring down,mil will be gone.

Once seated should the center be easy to turn?

 

[DirtyDesertRat]

This may be heresy, but...ignore it?

I had a stupid evap leak indicator on my 2008 Fusion. I ignored it for a year, maybe two...or so.

I finally crawled underneath, and found that the cheesy plastic evap tank had been whacked and had a big crack. So it was easy enough to replace, and that fixed it.

 

[Moglocker]

Once seated should the center be easy to turn?

I don’t recall mine turning inside

 

[hear]

Whats this tool that we apparently need? Link?

 

[Moglocker]

https://www.amazon.com/Lisle-63000-Fuel-Tank-Lock/dp/B0079GPYA4?tag=wranglerorg-20