I have changed my purge valve solenoid cause of a P0446 code. Worked great for about two or three weeks then came back on again with the same problem. I'm not sure how to fix it anymore. Any help would be nice.

 

TheRider91, P0440 means that the PCM has detected a malfunction in the EVAP system. This could possibly mean there is a leak somewhere, but not necessarily. One of the many possibilities is a faulty fuel tank pressure sensor. The sensor is mounted in the fuel pump module, which more than likely came with the used fuel pump you had installed. That might explain why you started having problems after the fuel pump was replaced.


The GM factory shop manual diagnosis flow chart for P0440 is 4 pages in length, (one of the more difficult DTC's to diagnose). https://blazerforum.com/forum/diagno...plained-35145/ One of the more sophisticated diagnostic tools used is a smoke machine, not something the weekend DIYer has at his disposal.

As mentioned in previous posts, there are several systems that the PCM "monitors". Some are continuously monitored, some only once per drive cycle. They are viewed on a capable scan tool as "I/M Readiness" and indicated as "complete" or "incomplete". All of the monitors must run and pass their test for the I/M Readiness to indicate "complete" before an inspection facility can "pass" the vehicle. The drive cycle must be duplicated exactly as outlined in the General Motors Driving Cycle for all monitors to run and complete their tests. If the drive cycle is not duplicated exactly as outlined, certain tests will not run, thus the I/M Readiness will indicate "incomplete" and the vehicle will immediately fail the inspection. During normal driving it may take weeks or even months for a specific monitor to run and complete its test. Each test has certain parameters that must be met or the test will not run. For example, the EVAP monitor can only run when the fuel level is between 15% and 85%, (that explains one of your situations with a full tank). Hope this helps.

 

Ah.. the Hook has some good info there.

Are you sure you didnt damage / crack the nipple on the front tank vent, like I did {and some other guys, as well}?
That would cause that problem I believe. I fixed mine .. the right way. search 'hit bump fixed' under my name

BTW.. with used FP, should always use the tank press sensor off your prev pump to avoid that possibility of installing the bad with the good.
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Added for future readers: The doughnut gasket/spacer/seal for the fuel pump should be cleaned and lubed with silicone grease if you are going to reuse it.
Check carefully for lingering gas smell on first stop after fill up. That is a good clue for one or other being the problem

 

Good point on the vent fitting, if it's a 4 door. On the 2 door, the fitting is part of the fuel pump module and it's tough to break it. You really have to work at it, but it can be done

 

Well luckily by some grace of God the SES light stayed out for almost 200 miles and I finally got it inspected. Unfortunately, it came back on about 50 miles after, so thank you for the info. Guess I've got at least a year to fix this problem, and whatever other ones inevitably rear their ugly heads by then...