IronManche87 Posted June 20, 2017 Share Posted June 20, 2017 Howdy all, So I'm stumped.. After hooking up my vacuum reservoir, the smog shop said it didn't change a thing.. My mom had taken it this time and she said he said something about it needing to be under 40k and it's over 60k... I have no idea what exactly the unit of measurement is... I've gone through and tightened all my hose clamps, new vacuum harness, blew smoke into the fuel vent hard line and it was good, don't have an exhaust or intake manifold leak, and I'm at a loss... Is there anything I can do myself to better diagnose or check out or a better/bunch of vacuum diagrams?? I have a Haynes manual that I'm going to read when I get off work today but was wondering if you guys had ideas or suggestions before I blow $350 to have the shop do it.. Thanks all! Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
Tex06 Posted June 22, 2017 Share Posted June 22, 2017 You need to find out what they're measuring. There's not enough info for a good troubleshooting session yet. Do they give you a printout in your state? Sent from my SM-G930T using Tapatalk Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 You need to find out what they're measuring. There's not enough info for a good troubleshooting session yet. Do they give you a printout in your state? Sent from my SM-G930T using Tapatalk Thanks for the reply tex! I live I'm California so super strict on smog.. They gave me a smog printout with the smog results as well as a simple pass or fail section for a lot of the systems but none were explained just a simple yes or no.. Passed everything but the evap with flying colors.. They said it's the tano not holding pressure but never said exactly what their unit of measurement was unfortunately.. Was really hoping someone on here had the answer to that question.. I know I need to just go ahead and drop the tank and inspect the vent hoses on top of the tank and ports. If I do end up needing the ports would Cherokee ones work?? Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
Ωhm Posted June 25, 2017 Share Posted June 25, 2017 Make sure your fuel cap is not vented. Easy check. Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 Make sure your fuel cap is not vented. Easy check.Thank you for the response! How would I check that? Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
Ωhm Posted June 25, 2017 Share Posted June 25, 2017 Should say "vented" somewhere on the cap. Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 I guess it is vented. There is a push vent one should I switch? Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 This is the push vent one Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
Ωhm Posted June 25, 2017 Share Posted June 25, 2017 You mean there's two different gas caps for the same vehicle. Don't know what to say. Maybe they both hold pressure. Also check your gas cap gasket. Sometimes a new one helps. Some else know about gas caps? Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 Same cap different style venting. I honestly have no idea how the one I have vents although the push vent one is straightforward. Gasket is good also Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
Tex06 Posted June 25, 2017 Share Posted June 25, 2017 I just removed my smog equipment on my '92. From what I understand the charcoal canister connects the fuel tank to the air filter housing. I don't believe it would hold pressure anyways. Sent from my SM-G930T using Tapatalk Link to comment Share on other sites More sharing options...
Ωhm Posted June 25, 2017 Share Posted June 25, 2017 Same cap different style venting. I honestly have no idea how the one I have vents although the push vent one is straightforward. Gasket is good also Sent from my LGMS210 using Tapatalk Your gas cap should not vent. Tex06 found this online: The EVAP test ensures that there are no leaks in the hose between the Gas Tank and Charcoal Canister... it that simple. The technician must clamp the end of the hose leading to the canister and pressurize the gas tank with Nitrogen via the EVAP test tool. The EVAP test tool will then calculate the drop in pressure due to any leaks. Technically there should be very little drop in pressure once the gas tank is pressurized. Should there be a pressure loss the machine will fail the EVAP portion of the smog test. Link to comment Share on other sites More sharing options...
IronManche87 Posted June 25, 2017 Author Share Posted June 25, 2017 Same cap different style venting. I honestly have no idea how the one I have vents although the push vent one is straightforward. Gasket is good also Sent from my LGMS210 using Tapatalk Your gas cap should not vent. Tex06 found this online: The EVAP test ensures that there are no leaks in the hose between the Gas Tank and Charcoal Canister... it that simple. The technician must clamp the end of the hose leading to the canister and pressurize the gas tank with Nitrogen via the EVAP test tool. The EVAP test tool will then calculate the drop in pressure due to any leaks. Technically there should be very little drop in pressure once the gas tank is pressurized. Should there be a pressure loss the machine will fail the EVAP portion of the smog test. Thats exactly it!! Okay so I definitely need to get the push button vent style then because they kept saying it wouldn't hold pressure at all but I always thought they needed to be vented to avoid spray from being over pressurized?? It's a new cap but it does day vented but no idea how it actually vents.. Thank you for the info sir!! I greatly appreciate the help!!! Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
ParadiseMJ Posted June 26, 2017 Share Posted June 26, 2017 OK, so if they're saying the tank won't hold pressure, it has nothing to do with the gas cap. It has to do with the lines that lead from the top vents (aka rollover valves) on the top of the tank, then the line that runs from the rollovers to the charcoal canister. The vac line that runs from the tank to the canister is broken, chafed, disconnected etc. They pressurize the tank itself (with their own cap adapter) to make sure that those two rollover lines or the tank valves are all continuous. It takes laying on the ground under the Jeep to trace those tank-canister lines and some blind feeling around. But it's fixable in a short afternoon. To find out if your rollover valves OR the lines are broken, you need to 1.) reach up to the top of the tank and feel that they are attached (the valve nipples are plastic and can degenerate, rot, break). 2.) the two lines come together in a T, make sure they're connected there into 1 (one) line. Then 3.) follow that line towards the firewall where it should connect to a steel line that runs about 10" up the firewall...then it turns into a rubber line again that connects to the charcoal canister. On the charcoal canister it might LOOK like there are three places for a vac line. One is plugged (fake). The larger of the three requires a larger vac line and that line should run to your intake, or at least to a port on the intake manifold. Then the fumes from your tank go through the charcoal canister and get sucked into the intake to get burned off. The vacuum lines on the drivers side of the engine bay are all about emissions. The ones on the passenger side are almost all about cruise and HVAC. Generally if you have EVAP problems, it's the lines on the driver side, unless it's a HUGE leak on the HVAC side. Rollover valves cost $25-$30 at the dealer, bulk vac line is cheap. You MIGHT want to drop the tank a little to gain better access. Link to comment Share on other sites More sharing options...
IronManche87 Posted June 26, 2017 Author Share Posted June 26, 2017 OK, so if they're saying the tank won't hold pressure, it has nothing to do with the gas cap. It has to do with the lines that lead from the top vents (aka rollover valves) on the top of the tank, then the line that runs from the rollovers to the charcoal canister. The vac line that runs from the tank to the canister is broken, chafed, disconnected etc. They pressurize the tank itself (with their own cap adapter) to make sure that those two rollover lines or the tank valves are all continuous. It takes laying on the ground under the Jeep to trace those tank-canister lines and some blind feeling around. But it's fixable in a short afternoon. To find out if your rollover valves OR the lines are broken, you need to 1.) reach up to the top of the tank and feel that they are attached (the valve nipples are plastic and can degenerate, rot, break). 2.) the two lines come together in a T, make sure they're connected there into 1 (one) line. Then 3.) follow that line towards the firewall where it should connect to a steel line that runs about 10" up the firewall...then it turns into a rubber line again that connects to the charcoal canister. On the charcoal canister it might LOOK like there are three places for a vac line. One is plugged (fake). The larger of the three requires a larger vac line and that line should run to your intake, or at least to a port on the intake manifold. Then the fumes from your tank go through the charcoal canister and get sucked into the intake to get burned off. The vacuum lines on the drivers side of the engine bay are all about emissions. The ones on the passenger side are almost all about cruise and HVAC. Generally if you have EVAP problems, it's the lines on the driver side, unless it's a HUGE leak on the HVAC side. Rollover valves cost $25-$30 at the dealer, bulk vac line is cheap. You MIGHT want to drop the tank a little to gain better access. Thank you so much ParadiseMJ!!! Luckily I work at O'Reillys today and I already found the part number for it!! I had no idea what exactly they were called and was going to ask lol thank you!! I had dropped the tank before and thought they were good but old. Perhaps one might have popped off or broke/torn. Will be dropping the tank and inspecting. I have almost no gap so can't even get my hand up there to feel but shouldn't take very long! I'm hoping I'll be able to get the rollover valves into work by the end of today and be able to just swap it all out tomorrow afternoon after work! You all make learning and working on my truck interesting and fun!! As much of a headache it can be at times x.x but I'd rather learn how to diagnose and fix it myself!! Thank you all once again!!! Hopefully will have good news by tomorrow night!! Will keep everyone updated!! Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
ParadiseMJ Posted June 27, 2017 Share Posted June 27, 2017 If you have to...or are going to change out the rollover valves...pull the old ones out carefully so they don't separate the rubber/plastic and metal. Also, when installing the new ones, orient them they way you want the nipples facing, put some Vaseline or oil in the grommet and just poke it in. If you put them in and then want to pull them out again, the metal part can still come apart and half can drop into the tank. Witness, me: I still have a bottom half floating around in my tank from 6 years ago. Link to comment Share on other sites More sharing options...
IronManche87 Posted June 27, 2017 Author Share Posted June 27, 2017 If you have to...or are going to change out the rollover valves...pull the old ones out carefully so they don't separate the rubber/plastic and metal. Also, when installing the new ones, orient them they way you want the nipples facing, put some Vaseline or oil in the grommet and just poke it in. If you put them in and then want to pull them out again, the metal part can still come apart and half can drop into the tank. Witness, me: I still have a bottom half floating around in my tank from 6 years ago. Thank you for the tip and heads up!! Much appreciated!! Sent from my LGMS210 using Tapatalk Link to comment Share on other sites More sharing options...
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