Troubleshooting an evap leak?

[kb01]

When a CEL comes on and the throws an evap leak code, what is a reasonable course of action for a mechanic to diagnose it? As a layman, my solution would be to put on a new gas cap and see if that works.

The reason I'm asking...

My sister called me last night. She had a CEL and went to her dealer. The dealer pulled the code and it was for an evap leak. To diagnose the cause, they ran a smoke test and lo and behold, it needed a new gas cap.

I can't help but feeling that she got taken advantage of. Any thoughts?

 

[RiceCake]

Throwing on a new gas cap would be a reasonable test, but a lot of shops, I can easily see, don't want to do 'seat of the pants' sort of jobs like that. If you throw on a new gas cap and have the customer leave to see if it fixes it, that customer could easily (dumbly) assume you know nothing when the CEL comes back on, and would head to another shop for a full diagnostic.

Technically smoking it is the correct way to properly diagnose the issue before you begin trying to fix it, but realistically its almost unanimously a good bet to just try the gas cap first. They did the full test, found the issue, and fixed it the first time, and there's nothing wrong with that honestly.

 

[LeakySeals]

Run a couple of bottles of techron concentrate plus through the system. Sometimes it can free a sticky valve. Never, ever stuff the tank after the pump clicks when fueling.

 

[bdcardinal]

Smoke test is a valid test.

 

[demarpaint]

Smoke test is the only way to go.

 

[AandPDan]

And if the gas cap hadn't fixed it you'd be out $20 something and mad at the shop for not doing a smoke test.

 

[Trav]

Yep she got hosed IMHO.
No need to change the cap at a shop or especially a dealer they should have a gas cap tester.

Many states that require emission testing require testing stations have to have one on premises by law in some cases.
They sold a smoke test job along with the labor. A tester will tell you within 10 sec if you have a bad cap.

Always test the cap before breaking out the smoke machine.
Edit: This is one of the more common units found in dealers and stations.

http://www.hickok-inc.com/catalog/products/fpt2600ex1-fuel-cap-pressure-test-kit.html

 

[stevejones]

I'm good with what the dealership did. What are the chances of finding a bad gas cap AND something else wrong (cracked hose, gasket leak, etc)?

Not only did the smoke test find the problem, but it validated the rest of the systems' integrity.

Originally Posted By: kb01
what is a reasonable course of action for a mechanic to diagnose it?

A: Smoke the system
Originally Posted By: kb01
As a layman, my solution would be to put on a new gas cap and see if that works.


A: That is why you are not a mechanic.

 

[Trav]

Let me explain my answer. I have no problem with the smoke test per se but doing a gas cap test first cuts out a lot of work and could save the customer some money.
I do have a problem doing extensive and somewhat expensive testing for cheap items that can be tested in seconds not even minutes.

Chances are pretty good it the cap immediately fails thats the source of the leak.
So lets say the dealer checked the cap and it was defective and said to the customer your cap tested bad and a new cap will probably take care of it.

We will charge you for the cap and check the cap as a courtesy. Drive the car and if you have any more trouble we will look into it further.

This little goodwill gesture goes a long way in creating customer trust and confidence and will probably generate repeat business.

 

[Scott_Tucker]

The problem with the 'just throw a cap on it an see if it works' mentality is that, once you have replaced the cap, you now have to go through a couple drive cycles for the evap monitor to set. If there is another problem, you've got to go back. Most people don't have time to keep going back to the shop, they just want it fixed the first time. The smoke machine gives definitive proof.

I think it was a totally legitimate diagnostic and the charges were justified. Do you go to the doctor when you feel sick, have tests done, and then dispute the charges because it was 'just a cold'?

 

[Vikas]

The way shop approaches a problem depends upon if the customer is paying for it or it it is a warranty job. You can bet your paycheck that if this was under warranty, the manufacturer would NOT have paid for the smoke test before replacing the cap. This is how it would have gone:-

1) Customer complains about the CEL and brings it in.
2) Shop puts the scanner, notices the small evap leak code and then re-tightens the cap and sends the customer on the way after clearing the code "No charge" and "bring it back if the light comes back on"
3) After the fuel tank drops to 3/4, the light comes on
4) car is back to the dealer
5) this time he changes the gas cap, erases the code and sends him away, charges the manufacturer for the new cap
6)...

 

[Vikas]

Of course the real question is:-

Would OP have done the same thing or would he have replaced the cap himself before visiting the dealer? Could his sister have done the same thing?

You visit the dealer and then you have to pay.

 

[demarpaint]

Originally Posted By: Trav


Always test the cap before breaking out the smoke machine.


Reading this thread again you're right. If the gas cap passed the test then smoke check the car, my bad.

 

[yonyon]

My general routine for EVAP leak codes:

-Look at and feel the cap. 4/5 of bad gas caps are obvious upon this type of inspection. 2/5 bad gas caps will show up on the official state-sanctioned gas cap tester that I have access to. The gas cap tester never identifies the gas cap that just plain doesn't fit on that car.

-Test gas cap with gas cap tester.

-Quick visual inspection of vapor lines - this finds maybe 1/10 leaks and we're less than 5 minutes in at this point. If it's a Chrysler vehicle this finds maybe 9/10 leaks.

-When practical, an application specific "does this vehicle have a vapor leak at this time?" test is used. 1/3 of cars can be shown not to have a current leak so there's no need to waste time on a smoke test.

-Check for vehicle-specific common problems.

-Try a new gas cap.

-If practical, an application specific "does this vehicle have a vapor leak at this time?" test is used. If the leak went away, it's time to stop looking.

-Smoke test.

-If the problem is still not found, now really get into it.

Smoke is pretty late in the list, but definitely is useful and finds problems.

 

[bdcardinal]

Originally Posted By: Vikas
The way shop approaches a problem depends upon if the customer is paying for it or it it is a warranty job. You can bet your paycheck that if this was under warranty, the manufacturer would NOT have paid for the smoke test before replacing the cap. This is how it would have gone:-

1) Customer complains about the CEL and brings it in.
2) Shop puts the scanner, notices the small evap leak code and then re-tightens the cap and sends the customer on the way after clearing the code "No charge" and "bring it back if the light comes back on"
3) After the fuel tank drops to 3/4, the light comes on
4) car is back to the dealer
5) this time he changes the gas cap, erases the code and sends him away, charges the manufacturer for the new cap
6)...


Nope, that would violate Ford's FIRTFT warranty schedule. FIRTFT stands for Fix It Right The First Time. The situation you showed would not be allowed under Ford's warranty policies. The technician MUST properly diagnose with screen shots on the IDS provided in order for the dealer to be reimbursed for the repair. Continued violations of warranty procedures can result in a dealer losing their ability to perform warranty work at the worst or else they can have a situation where Ford will require EVERY warranty repair to have prior approval which can take from a few minutes to a few weeks to get authorization. Besides being parts certified, I have taken all the certifications for Service Advisor and Warranty Administrator. Also in CA, the repair you suggested would violate the Bureau of Automotive Repair regulations for performing smog repairs without proper documentation of a smog component requiring replacement. Shops have been forcibly shut down for repeated repairs like that without proper evidence of a part needing replacement.

In a customer pay situation I could see the Advisor saying " Mr/Mrs Customer there is an evap leak, the most common cause is a faulty gas cap. We can replace it, clear your code and see if it returns. However there is a chance there are further issues that must be addressed and we will have to spend more time and money diagnosing the problem if that situation arises."

 

[Vikas]

Thanks for FIRTFT, I was not aware of it.

Getting back to OP's problem realistically none of the real EVAP codes ever show up during the warranty period. it is too early for to rear its ugly head.

Ask me how I know :-(