EVAP canister problems

Tiny
FRANKIEDONNN
  • MEMBER
  • 2001 DODGE RAM
  • 5.2L
  • V8
  • 2WD
  • AUTOMATIC
  • 121,689 MILES
Hi, the fuel trims go negative 30 at idle when the EVAP purge comes on. But if I pinch off the EVAP purge line, LT trims improve to negative 7 and ST varies positive and negative within the zero range. It seems to be pulling fuel from the tank, but I don't understand why yet. Thanks for you help. Frank
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Tuesday, August 13th, 2019 AT 6:51 AM

15 Replies

Tiny
ASEMASTER6371
  • EXPERT
Good morning,

This indicates the solenoid is no good. The solenoid is normally closed until the PCM commands the EVAP system test.

Common failure.

I would replace the solenoid and retest.

Roy
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Wednesday, August 14th, 2019 AT 3:40 AM
Tiny
FRANKIEDONNN
  • MEMBER
Hi, Roy,

Thanks for your response. The solenoid is working because I can feel it operating. It starts operating about 5-mins after starting from cold. Should it come on at idle or only when driving? Another thing is; once it runs the first cold start and purges and goes off, it turns on again, if I stop the engine and restart it. I feel that it is staying on too long and running too often. Something I did not mention before is that I can't get the EVAP. Nor the catalyst monitor to run no matter how many times I do the drive-cycle. Can this problem also be caused by a bad LDP reed-switch? Is the gas tank EVAP line suppose to be open the purge solenoid when the pump is running? Thanks for your help. Frank.
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Wednesday, August 14th, 2019 AT 4:13 AM
Tiny
ASEMASTER6371
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Just because the solenoid is working does not mean it is good.

I would replace it and retest.

No to the catalyst monitor. The purge has nothing to do with the current issue.

Roy
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Wednesday, August 14th, 2019 AT 4:27 AM
Tiny
FRANKIEDONNN
  • MEMBER
Well, I had already bought a new purge solenoid but it did not appear to be making any difference. So I reinstalled the old one just to get a comparison. So on your suggestion, I put the new one on again ran the engine and the purge came on: The LT went to negative 25 and back to negative 14. After I stopped the engine and restarted, the trims are now at negative 7. I suppose it is normal for the engine to run rich when the solenoid is purging, but I have never seen it go to negative 25 to 30 before, that is why I decided to ask for some help. There is still a problem, because the EVAP-. Monitor won't run; does that have anything to do with the reed switch Roy? The LT trims have been running negative 10 for months and I figured it was an exhaust manifold leak and/or, the EVAP-system: I think I fixed the exhaust manifold leak but I am not sure about the whole EVAP system. What do you think? Thanks, Frank
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Wednesday, August 14th, 2019 AT 5:42 AM
Tiny
ASEMASTER6371
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Can you do a bay test with your scanner for the EVAP system?

Roy
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Wednesday, August 14th, 2019 AT 6:54 AM
Tiny
FRANKIEDONNN
  • MEMBER
I never heard the term bay-test before but if you mean to control components with the scanner then the answer is no. My scanner is the Innova 31603 just a simple one for now. Sorry, Frank. I have a test light, a VOM, vacuum gauge. Collecting tools a little bit at a time Thanks Frank
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Wednesday, August 14th, 2019 AT 7:32 AM
Tiny
ASEMASTER6371
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A scan tool that has bidirectional commands allows you to do tests. The bay test for the EVAP system would be in there.

It will tell you if there is an issue with the system. That's why you need to have this done to see if there is a component failure in the system.

The EVAP monitor will run after an 8-hour sit and takes about 15 minutes to complete. See if it clears the next time you start it in the morning. You can not turn it off during the test.

Roy
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Wednesday, August 14th, 2019 AT 9:08 AM
Tiny
FRANKIEDONNN
  • MEMBER
Okay, but what do you mean by 'clears'?
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Wednesday, August 14th, 2019 AT 9:20 AM
Tiny
ASEMASTER6371
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The monitor on your scan tool. It most likely is reading not ready at this time. When the monitor runs and completes, if there are no issues and it passes, then it will say ready.

Roy
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Wednesday, August 14th, 2019 AT 9:23 AM
Tiny
FRANKIEDONNN
  • MEMBER
Thank you. I'll try it tomorrow morning. Frank
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Wednesday, August 14th, 2019 AT 9:29 AM
Tiny
ASEMASTER6371
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You are welcome.

Roy
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Wednesday, August 14th, 2019 AT 9:32 AM
Tiny
FRANKIEDONNN
  • MEMBER
Good morning Roy. Well, I ran the engine until warm. The trims were normal at idle negative 7. If I raise the RPM with the purge-valve off the trims improve, while if I raise the RPM with the purge running, the trims go more neg. I took it for a drive and the trims got as neg as 20 at some points. Aren't the trims suppose to stay in the 10% range no matter what the speed is? Thank you, Frank
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Thursday, August 15th, 2019 AT 7:07 AM
Tiny
ASEMASTER6371
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Long term trims should stay constant at around 0%. They may vary from -5 to + 5 at idle.

Roy
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Thursday, August 15th, 2019 AT 8:46 AM
Tiny
FRANKIEDONNN
  • MEMBER
Yes, but they should also stay in the positive and negative 10% range at all engine speeds and vehicle speeds. Right?
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Thursday, August 15th, 2019 AT 10:14 AM
Tiny
ASEMASTER6371
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That's a little high but acceptable, yes.

Roy
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Thursday, August 15th, 2019 AT 12:19 PM

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