Re: The Insanity Project - New Pics
So here's what was happening;
I had a p0455 that wouldn't go away since fall. I replaced the gas cap and the canister but still had it, making it another problem. It also threw p0300 stumbles when it rained or after a high pressure car wash, but it stopped when winter came and just the p0455 remained. Tank area always smelled of gasoline, too.
When the weather started warming up again and it rained, it would p0300 again - making me wonder wtf rain had to do with a p0300...bad electrical connection or ground? So I ripped down all the electrical connections to the injectors, the grounds, and the plugs, cleaned them and put them back together, and replaced the plugs...problem stuck around when it was raining, but it always took a while...an hour or so of driving in the rain and then it wouldn't go away when it got dry for a day or so.
Once my gauges were installed, I noticed this pattern (which led to my diagnosis).
Low fuel in the tank would equal low fuel pressure, and a lean condition with a stumble below 1/8 tank. The lower the fuel level, the lower the fuel pressure. Full tank would stay at 57-58psi, half tank would be around 40 at WOT, quarter tank would be down around 20, and lean combined with crazy high exhaust temps - my plugs were BURNED.
Lean w/p0300 stumble
Over 3/4 tank
WOT at 3/4 - look at the EGT - Almost 1,400.
All this led me to believe that it had to be a rusted out and destroyed fuel sending unit - constant massive evap leak message, with fuel pressure varying depending on tank level along with a crazy lean condition when almost empty (from too much air getting into the fuel sent to the engine coupled with the low pressure condition).
So I dropped my gas tank and found this;
Looks like 12 winters of buildup without maintenance may have killed my sender. Yep. I can see the gasket without removing the sender. There is the massive air leak as well as an explanation of how it stumbles in the rain (high humidity with extra air getting in the fuel send is basically water in the gas. I drive 300-600 miles per week and fill up from multiple stations so I knew it wasn't bad gas).
Oh hey, was this my locking ring? Tried to find one on rockauto, amazon and gm sites - none available. Check the local ac delco outlet, 12 days if they can find one. Check the dealership, none in the area, none in the system. Nationwide search was the only option.
What. The. Fuck.
So I cleaned it up, to find...4 of 5 locking ring retainers have rusted away
I started looking for new 04-05 tanks...out of stock, zero aftermarket support...and no wrecks locally with in-tact rings (all suffered the same fate as mine in varying degrees). $750-1k plus shipping for a new tank shipped in from elsewhere. Locking ring did arrive to the dealership so there was that on my side.
I pumped out the rest of the gas, let it dry in the sun, then vacuumed the shit out of the interior of the tank with a shopvac.
I'm not sinking $1k into a gas tank without any other issues than the lack of locking ring support (especially since it will just do the same thing without maintenance in 10 years) so I popped in the new sending unit, gooped around the gasket with permatex blue fuel resistant gasket dressing and sealer, pressed it in, got the locking ring on the one side and then used 2 #10 stainless panhead screws to hold 2 of the other tabs down evenly. Then I dumped 2 full tubes of permatex around it in 4 coats over 2 days to get this result;
Problem fixed. No more p0455, no more stumble when it rains, and a solid 57-58 psi regardless of fuel level in the tank. EGT is back down around 1250-1300 at WOT instead of 1400+, no more crazy lean fuel mix