I recently had been getting a P0452 (low evap pressure inside tank) code and P0300 and have been trying to diagnose since. I pressure tested before but I didnt have any issues at the time. I did a pressure test again today and had a startling discovery.

If I remember reading correctly, from the article Swartlkk has posted before, it should maintain a psi of 55 or so after the key is on/engine off. I tested both with key on and key off. These are my results:

60 PSI - Immediately after turning key on/off
55/56 PSI - about 1 - 2 seconds after key on/off
35 PSI - 2 Minutes
28 PSI - 3.5 Minutes
22 PSI - 5 Minutes
17 PSI - 6.5 Minutes
14 PSI - 8 Minutes
10 PSI - 10 Minutes

Also, I checked inside the intake plenum and noticed it was damp as if gas has leak in there. A very strong smell is also present.

Any ideas what it might actually be? or where I can start to check? My gut feeling is screaming injectors.

 

replace your spider injector assembly upgrade mpfi unit, much better and less prone to failure.

 

Fuel pressure regulator is leaking. You can replace it without replacing the whole unit.

Part 2 -'Spider' Fuel Injector Test, Fuel Pressure Regulator Test: GM 4.3L, 5.0L, 5.7L

 

Is there a way to test the regulator? I am thinking about pulling the intake this weekend to scope things out prior to making any purchases.

 

Ha, I just posted a link with more tests you can do.

 

I see that now. Lol. Thanks for the link, giving it a thorough reading.

 

all depends on where its leaking at the rear of the mainfold than yes its the FPR but if its leaking on either side than its the injector. sure you could replace just one but i can guarantee the rest will fail shortly after and at that point it would have been cheaper to just replace the unit. but its your call just my 0.02c

 

I agree about replacing it all at once rather than piece by piece.

Burned: In that link you sent I noticed that the test mentioned that if it drops to 0 within seconds then I have a problem in the assembly. But mine drops off slowly or would that be considered within seconds? Or am I misinterpreting the test?

 

before replacing the spider,check the pressure at the inlet of the fuel filter....if it still drops the check valve in the pumps bad. if it holds then go ahead and change the spider.


edit....wow.....i totally read the part about the plenum flooded and still typed that....Yep. bed time for me.

 

haha I feel you on that one chris.

So I take your edit as a way of saying that its more than likely not the fuel pump?