FJZ80 1997 EVAP problem/test/questions (1 Viewer)

[Readhead]

Hi all experts!
I faced a problem with the EVAP system. Recently when off-roading in high altitude I small a strong fuel smell. It came from the gas tank ( tank gas vapor pressure was very strong before I released the cap). I thought it was because of the Charcoal canister but I had replace it few years back with the VC120 and I had no issues at the gas station at normal height (like I had before the Charcoal canister replacement). No check engine light, so I did not check for codes.
I read the FSM and understood that in normal operation the gas vapor should be let into the engine by the EVAP system. In the FSM there is a simple test (see picture below): at normal engine temperature and RPM of 3000 there should be vacuum (suction) in the line between the VCV and the Charcoal canister. There was no suction at all.
The way I see it it can be defected VCV or TVV or maybe EVAP VSV. Is that right or I am missing anything?
The FSM explains how to test VCV and TVV but it require disassemble of these parts and test them off tool. No info about testing the EVAP VSV. The access is not great so I would like to see what I can debug easily first.
Is there any recommendations about how to debug it or how to disassemble these parts ?
I was searching the forum and find some info but not very relevant.
Any suggestions will be very welcome.

Thank you!

 

[DDiamelle]

Hi all experts!
I faced a problem with the EVAP system. Recently when off-roading in high altitude I small a strong fuel smell. It came from the gas tank ( tank gas vapor pressure was very strong before I released the cap). I thought it was because of the Charcoal canister but I had replace it few years back with the VC120 and I had no issues at the gas station at normal height (like I had before the Charcoal canister replacement). No check engine light, so I did not check for codes.
I read the FSM and understood that in normal operation the gas vapor should be let into the engine by the EVAP system. In the FSM there is a simple test (see picture below): at normal engine temperature and RPM of 3000 there should be vacuum (suction) in the line between the VCV and the Charcoal canister. There was no suction at all.
The way I see it it can be defected VCV or TVV or maybe EVAP VSV. Is that right or I am missing anything?
The FSM explains how to test VCV and TVV but it require disassemble of these parts and test them off tool. No info about testing the EVAP VSV. The access is not great so I would like to see what I can debug easily first.
Is there any recommendations about how to debug it or how to disassemble these parts ?
I was searching the forum and find some info but not very relevant.
Any suggestions will be very welcome.

Thank you!
View attachment 3855288

I just had the same experience. I was on a steep and relatively rough trail when I smelled gasoline. I opened the gas cap and vapor began hissing out. I removed it completely, and pressurized vapor came out for several minutes. I could even hear a gurgling sound as the vapor continued to release from the gasoline.

I had also replaced the canister with the VC120 a couple of years back and had had no problem until now. Anybody have any wisdom to dispense?

 

[Nframe]

VC120 cured mine of this.

 

[Readhead]

I just had the same experience. I was on a steep and relatively rough trail when I smelled gasoline. I opened the gas cap and vapor began hissing out. I removed it completely, and pressurized vapor came out for several minutes. I could even hear a gurgling sound as the vapor continued to release from the gasoline.

I had also replaced the canister with the VC120 a couple of years back and had had no problem until now. Anybody have any wisdom to dispense?

Did you run the test described in the picture?
I run some more test and found that the problem is with the VCV. It could not hold vacuum. The TVV is fine.
I’ll get the VCV today and update after installation

 

[Readhead]

VC120 cured mine of this.

FYI, had already replaced the canister to VC120 when I had pressure in the gas tank when fill gas in the gas station. This is different problem

 

[DDiamelle]

Did you run the test described in the picture?
I run some more test and found that the problem is with the VCV. It could not hold vacuum. The TVV is fine.
I’ll get the VCV today and update after installation

I haven’t tested yet, but will directly!

 

[DDiamelle]

FYI, had already replaced the canister to VC120 when I had pressure in the gas tank when fill gas in the gas station. This is different problem

Both TVV and VCV passed the test. I may need to replace the hoses and see what happens.

 

[Readhead]

Problem solved! Hopefully
I am no expert, the below describes what I had done to debug the problem. So, if you follow this thread, it is on your own risk. Make sure you know what you are doing and take all the safety measures.
As described earlier, I had perform the test described above (in the FSM) that indicate a problem in VCV or TVV ( BTW 1997 FJZ80 does not have EVAP VSV like 1996 or 1995).
The FSM suggest to remove VCV and TVV and test them off line. I did not want to remove them so I checked them installed.
I used manual vacuum pump to generate small vacuum (to generate >70 mmHg) - manual pump that used the bleed brakes fluid. I started with cold engine and engine turn off. Open the gas tank first to eliminate any pressure if exist, and close it again.
I connected the vacuum pump to the line connected to the TVV - see picture below

I pump using the vacuum pump to about 100 mmHg and was able to generate vacuum.
I used bike pump and connected it the the line going to the VCV - see below

If the system works well I should be able to flow air in the system from the bike pump to the line back to the canister when the engine hot but not when the engine is cold (in both cases the engine is turned off).
When the engine was cold I was not able to flow air (which is expected) but was able to generate vacuum in the TVV (which is good).
I concerted the disconnected lines back and heat up the engine to working temperature. Turn off the engine and open and close the gas tank cap again (to eliminate any pressure in the system)
Then, I connected the above setup. This time I was not able to generate vacuum with the vacuum pump. This means that the TVV function well but the lines to the VCV or VCV itself can not hold vacuum.
Now I waited till the engine is cold again and connected the vacuum pump directly to the VCV
To get access you will need to remove the INTAKE MANIFOLD STAY (I suggest to remove the top bolt but just release the bottom bolt ( it is a little pain to put it back again). Once released you can move the stay away from the VCV

The access to the pipe from the VCV to the TVV is not great so in order to disconnect the vacuum line attached to the VCV, I used a long right angle plier and put some plastic on it to protect the hose (see below) to pull it off.

The VCV could not hold the vacuum. Which means that it is defected.
I bought a new VCV (67$ incl shipment) - see below

https://partsouq.com/en/search/all?q=9092503192

I checked before installation that the new VCV function well (when under vacuum, it can flow air and when no vacuum, the air does not flow (see FSM).

I had installed it and now I need to check it in the high elevation.
Again, I am no expert, but I have not find any info about how to debug it in the forum, this is why I wrote the description of the my debug process.
Hopefully this can be useful (on your own risk...)

 

[Readhead]

Both TVV and VCV passed the test. I may need to replace the hoses and see what happens.

Interesting, are you saying the FSM system test fail but each component (VCV and TVV) works well? BTW which year is your FJZ80? in 1995/6 there is also EVAP VSV which may play a role.
In general if the hoses from to the TVV or from the TVV to the VCV leaks it can cause such a problem, but you can run a vacuum test for that.