Chrysler guys Explain Difference btwn leak detection pump

Posted By: cjs69mope

Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 04:31 PM

Hello I was wondering if any Chrysler technicians can explain why does Chrysler call their Evap emissions valve a leak detection pump ?
I have many years of foreign car experiance and most manufacturers call their evap valve a canister close valve.
I was just wondering this because i was working on a 2004 dodge caravan and was wondering why the three wires to the valve? One must be a sense input but don't have a diagram . most of the foreign cars have a two wire so testing is easy just supply ground to close or open it and you can pressure test the system . Any info would be great thanks .

Posted By: teflon

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 06:07 PM

Pin 1 is ground, pin2 is NVLD switch signal and pin 3 is NVLD solenoid control. NVLD stands for natural vacuum leak detection. As the vehicle cools, the fuel tank naturally contracts creating a vacuum on a seal container. When this occurs the switch closes in the NVLD signaling to the PCM there is no leak.

This is what a 2004 Caravan has. A LDP is used on older vehicles and actually builds pressure in the evap system and monitors time to determine if a leak is present.

Newer vehicles use an ESIM, emission system integrity monitor.

Posted By: JohnRR

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 08:02 PM

perfect timing on this topic , I have an 04 grand cherokee , got a P0455 code for gross leak. took it in they smoke tested it and found a decayed hose in the back at the evap can ??? fixed , cleared all is good , till yesterday it came back ???

Should I replace he gas cap since what I found online pointed to that as being the cause of this ?

Posted By: denfireguy

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 08:16 PM

Quote:

perfect timing on this topic , I have an 04 grand cherokee , got a P0455 code for gross leak. took it in they smoke tested it and found a decayed hose in the back at the evap can ??? fixed , cleared all is good , till yesterday it came back ???

Should I replace he gas cap since what I found online pointed to that as being the cause of this ?

If you took it to Autozone or OReilly, they would have first sold you a gas cap. The dealer did you a favor to actually trouble shoot the problem. I discovered this the hard way with my Durango. Yeah, I bought two gas caps (dummy me) and then dug into the FSM that directed me to the bad hose under the car. Oh, and the emmission check place told me I needed a new gas cap too after they tested it. The hose repair fixed that too.
Craig

Posted By: JohnRR

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 08:37 PM

Quote:

Quote:

perfect timing on this topic , I have an 04 grand cherokee , got a P0455 code for gross leak. took it in they smoke tested it and found a decayed hose in the back at the evap can ??? fixed , cleared all is good , till yesterday it came back ???

Should I replace he gas cap since what I found online pointed to that as being the cause of this ?

If you took it to Autozone or OReilly, they would have first sold you a gas cap. The dealer did you a favor to actually trouble shoot the problem. I discovered this the hard way with my Durango. Yeah, I bought two gas caps (dummy me) and then dug into the FSM that directed me to the bad hose under the car. Oh, and the emmission check place told me I needed a new gas cap too after they tested it. The hose repair fixed that too.
Craig

That's all well and good , but it's BACK .

The original repair was under the used car warranty and that ran out right after I had it supposedly fixed , it took 2.5 hours last time. I'm not going to pay 95/hour to sit around and wait for them to TRY something else ...

Posted By: Dartsport540

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 09:10 PM

I have had at least 5 customers, Grand Cherokees with that code , for evap leak. There are 2 hoses or 3 hoses going from the gas tank to the evap canister, located behind the drivers rear wheel. 2 of the hoses dry rot and crack. If you can get up in there with a small mirror you can see the hoses being cracked where they go over the barb on the lines. Just replace both hose, not to easy to get at.
1st vehicle that I did, I only replaced the cracked line that I 1st saw . It came back a week later with the same code. I did a little better searching with a small, retactable mirror. Then I saw small cracks in the other hose. Now I just replace both hoses everytime, that I find 1 cracked.

Posted By: cjs69mope

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 09:24 PM

Quote:

Pin 1 is ground, pin2 is NVLD switch signal and pin 3 is NVLD solenoid control. NVLD stands for natural vacuum leak detection. As the vehicle cools, the fuel tank naturally contracts creating a vacuum on a seal container. When this occurs the switch closes in the NVLD signaling to the PCM there is no leak.

This is what a 2004 Caravan has. A LDP is used on older vehicles and actually builds pressure in the evap system and monitors time to determine if a leak is present.

Newer vehicles use an ESIM, emission system integrity monitor.

Thanks but are you saying that the system performs the test when the Eng and key is turned off ?
I always thought for the monitor to set it would have to be driven on the interstate above 50 mph with approx 1/2 tank of fuel .
for a certain time and the monitor would reset ?

Posted By: 70Cuda383

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 09:26 PM

Quote:

Quote:

Quote:

perfect timing on this topic , I have an 04 grand cherokee , got a P0455 code for gross leak. took it in they smoke tested it and found a decayed hose in the back at the evap can ??? fixed , cleared all is good , till yesterday it came back ???

Should I replace he gas cap since what I found online pointed to that as being the cause of this ?

If you took it to Autozone or OReilly, they would have first sold you a gas cap. The dealer did you a favor to actually trouble shoot the problem. I discovered this the hard way with my Durango. Yeah, I bought two gas caps (dummy me) and then dug into the FSM that directed me to the bad hose under the car. Oh, and the emmission check place told me I needed a new gas cap too after they tested it. The hose repair fixed that too.
Craig

That's all well and good , but it's BACK .

The original repair was under the used car warranty and that ran out right after I had it supposedly fixed , it took 2.5 hours last time. I'm not going to pay 95/hour to sit around and wait for them to TRY something else ...

HAVE you checked/replaced your gas cap? the gascap is such a common cause, that on the 04 Durango I had, it would actually flash "gascap" or "check gascap" (I cant remember exactly now) on the Odometer, telling to to check it and make sure it's snug/tight. after so many re-starts with the same "code" it would then trigger the check engine light, because it ASSUMED that you checked the gascap and fixed it, meaning that there's another leak somewhere else.

frustrating thing about the gascap is that any time you open it to fill the tank, you might not get a good seal when you put it back on.

if it's NOT the gascap, I'd take it back and complain, sure it's out of your used car warranty now, but if they just fixed it, then you should be in the "your repair didn't work" grace period.

afterall, it might be a different hose, or maybe the technitian who did the repair botched it up and it's leaking at the same hose?

Posted By: JohnRR

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 10:02 PM

Quote:

I have had at least 5 customers, Grand Cherokees with that code , for evap leak. There are 2 hoses or 3 hoses going from the gas tank to the evap canister, located behind the drivers rear wheel. 2 of the hoses dry rot and crack. If you can get up in there with a small mirror you can see the hoses being cracked where they go over the barb on the lines. Just replace both hose, not to easy to get at.
1st vehicle that I did, I only replaced the cracked line that I 1st saw . It came back a week later with the same code. I did a little better searching with a small, retactable mirror. Then I saw small cracks in the other hose. Now I just replace both hoses everytime, that I find 1 cracked.

Thanks , I'll crawl under it if I can't get them to fix it when I go in for an oil change .

Posted By: 383man

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/19/12 11:31 PM

Quote:

Quote:

Pin 1 is ground, pin2 is NVLD switch signal and pin 3 is NVLD solenoid control. NVLD stands for natural vacuum leak detection. As the vehicle cools, the fuel tank naturally contracts creating a vacuum on a seal container. When this occurs the switch closes in the NVLD signaling to the PCM there is no leak.

This is what a 2004 Caravan has. A LDP is used on older vehicles and actually builds pressure in the evap system and monitors time to determine if a leak is present.

Newer vehicles use an ESIM, emission system integrity monitor.

Thanks but are you saying that the system performs the test when the Eng and key is turned off ?
I always thought for the monitor to set it would have to be driven on the interstate above 50 mph with approx 1/2 tank of fuel .
for a certain time and the monitor would reset ?

What Teflon said is dead on right. The LDP is just that a pump and it pressurizes the system and then the NVLD and ESIM both use vacum to test for leaks. There are many different emission systems on the car that test many different ways. Some like EGR need to be driving down the road and some will need to be above a certain mph for a certain amount of time and so on. Thats why many emission systems may only test themselfs once a week or so depending on how you drive.
For your question is yes it will test with the eng off but it will not turn the lite on untill it fails so many times and the car is running. It will also run a backup test with the car running as it will close the tank vent and then open the purge solenoid to pull a vacum and see if the NVLD switch closes and then see how long it stays closed. One thing to remember is if you have the check eng lite fixed and the tech erases the codes with a scanner he also erases all the PCM self test results and thats why they tell you to drive it for a week so hopefully it will run all of the test again so when the emission people look at your car they see all the test have run and passed. Ron

Posted By: Rick_Ehrenberg

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/20/12 04:45 PM

I've seen quite a few rusted tank filler pipes, too.

Rick

Posted By: teflon

Re: Chrysler guys Explain Difference btwn leak detection pump - 01/20/12 05:56 PM

383man and Mr. E are correct. The PCM runs the small leak test at engine off and key off to test for a .010" leak. Yes the filler necks were known to rust and leak, a smoke test will find that quickly.