The P0446 is a problem in the EVAP system unrelated to fuel pressure or leakdown. Follow the flow chart in this link: https://blazerforum.com/forum/diagno...plained-35143/


Fuel pressure & leakdown:
In your tests, the fuel pressure increased after the pump shut off due to heat transfer from the engine to the fuel lines, which skews the results of the leakdown test. Check it again after the engine cools down. When you initially turn the ignition to the RUN position, (don't start the engine) the pump should run for ~2 seconds and then shut off. Pressure must be checked during the 2 second time frame while the pump is running. Must be 60psi to 66psi. When the pump shuts off, pressure should drop slightly and hold. It must remain above 55psi for at least 10 minutes. All we really need is the pressure when the pump is running, and again at the 10 minute mark.

 

Went out for a test drive, and Blazer responded well. Easy crank, and smooth idle. Good acceleration, and plenty of power climbing, or passing. Have driven ~40miles with no SES light. Although after reading the thread you posted a link to in regards to P0446 I'm sure I have not met all conditions for VCM to run that DTC. I will have to take the Blazer into a shop to resolve the 446 because I do not have the facilities/equipment/reasorces to run the necassary tests.

I have already returned the Pressure Test Kit. In the second test these conditions where met. Pump running 60psi, 10 min. after pump off 55psi. The reason I did the third test (with engine running) was because my repair manual states that Fuel System pressure should reduce by 3 to 10 psi from orginial key on pump running reading. Which held true psi reduced from 55 to 52. If you feel that a retest is needed, due to engine temperature skewing the results, I will do so. However, it will have to wait a bit now as I will not have a chance to work on the Blazer again for a week or so.

Thank you,

 

Went out for a test drive, and Blazer responded well. Easy crank, and smooth idle. Good acceleration, and plenty of power climbing, or passing. Have driven ~40miles with no SES light. Although after reading the thread you posted a link to in regards to P0446 I'm sure I have not met all conditions for VCM to run that DTC. I will have to take the Blazer into a shop to resolve the 446 because I do not have the facilities/equipment/reasorces to run the necassary tests.

I have already returned the Pressure Test Kit. In the second test these conditions where met. Pump running 60psi, 10 min. after pump off 55psi. The reason I did the third test (with engine running) was because my repair manual states that Fuel System pressure should reduce by 3 to 10 psi from orginial key on pump running reading. Which held true psi reduced from 55 to 52. If you feel that a retest is needed, due to engine temperature skewing the results, I will do so. However, it will have to wait a bit now as I will not have a chance to work on the Blazer again for a week or so.

Thank you,

 

Ryan-- Just read through your thread, and I had the same issues with my 2001 2-dr Blazer. Same fault codes too...

I replaced:

cap, rotor, wires, plugs, Magnaflow FULL exhaust system, fuel pump, gas tank cap, fuel filter, gas tank vent hose, filler neck to tank hose, fuel pump to fumes box hose, canister purge valve, vent solenoid, and vapor canister ALL AC DELCO parts!

Today-- I still have a gas smell when I fill up the tank EVERY TIME and the mileage stinks! and the check engine light came back on.

I think the new Magnaflow exhaust system is tripping the check engine light to come on, PLUS I added a cold air intake system, so that must be tripping the light too...

My only other thought for me, *(and maybe for you too) is to replace the spider fuel injector assembly in the intake manifold.

 

Ryan, with a hot engine, the results can be misleading. If you experience problems, check it again, cold. GM does not publish any "engine running" fuel pressure specs for this engine. There are far too many variables involved. Be very cautious when using aftermarket repair manuals. They are very general and cover several model years. Specs, diagnosis & repair procedures and illustrations vary greatly depending on model & year. If you want accurate and complete information, GM "dealer issue" shop manuals are available online, sometimes Ebay has new and used sets. 3 separate manuals with over 3,000 pages, covering one model year! Good stuff.

P0446 is specifically related to EVAP vent valve operation. The most common cause is dirt entering the valve or an electrical problem, bad ground, broken wire etc. Cheap & easy to replace it, but best to check it out first.

 

Good to know! I do suspect an electrical problem in relation to the P0446, because there is some kind of voltage leak to the fuel gauge. Any time I turn on my turn signals / flashers the needle of the fuel gauge will 'jump' back and forth by varing amounts depending on the level of fuel in the tank, presumably due to the voltage values corresponding to different fluid level and how it relates to the amount of voltage leaking into that line. I have dropped the tank 4 times in the last ~3 years for a couple of reasons but I have never been able to find the 'leak'. I am thinking that it is most likely in the middle of a loom in the dash due to the fact that the dash is where those two systems would cross in close contact, and that I have looked fairly closely at all electrical connections and looms that are by the tank and, say, rear signal light. Although I must say that I'm not at all sure of a proceedural way of narrowing in on it. My SES light did come on again today on my way to work, but I have not had a chance to read the codes. I really would like to purchase a SCAN tool but I just can't justify the expense right now. I will try to make it by the parts store on Thursday to read the codes.

As always Thank You for all the help,

 

The rear turn signals ground at the left "D" pillar, near the tail light housing. The level sender grounds at the left rear corner of the frame crossmember. Might be good places to check first. The EVAP vent solenoid is grounded inside the PCM, so it's not related to the level sender & turn signal issue.