I purchased a 2004 Avalanche about a month ago and bought it with a faulty fuel pump sending unit. I planned on just buying the sending unit but I busted the old pump pulling it out. So I ordered a brand new AC-Delco unit and installed it. Hooked everything up and fired up the truck. It ran fine for about 10-20 seconds, then began to act like fuel wasn't flowing to the right places, it started to run extremely low rpms, almost stalling.

I shut the truck off and came back to it the next day and it would barely start. It'd fire up, and then stall. So I assumed it was just the fuel pump, no big deal, new parts sometimes are defective but I checked pressure in the lines with a pressure gauge and it was showing 52PSI. I then checked the ground and power to the pump, both are nice and constant.

Let me stress this, the truck ran fine before I replaced the pump. I replaced the pump because of the gauge issue and the fact that I messed up the old one.

I then assumed a couple more things, at first I was thinking the fuel filter was clogged but I crawled under the truck and couldn't find the freaking thing. I did some research and from what I can tell, the filter is inside the tank on these Avalanches? If true, that is the stupidest thing I've ever heard of but anyways...

Before I pulled the pump out, I removed the relay and ran the gas out of the system. My hunch was that I stirred up dirt and grime and all that crap and it plugged up my injectors. This assumption was further confirmed (at least that's what I thought at the time) with the engine code it was throwing. I was getting a misfire to one of the cylinders that would be last on the rail to get fuel.

I pulled the injectors out and let them sit in Fireball injector cleaner for a couple hours. It was very very dirty after just a couple hours so I dumped out the crap and refilled my container with fresh solution and let it sit overnight. There was significantly less crap in the solution after soaking the second time. Satisfied with the results, I put the injectors back into the fuel rails and installed them back into the truck. It took a good deal of force to get them to seat back into the intake manifold but me and a buddy got them to seat in to where there was no room between the mounting plates and the engine and the bolts holding them on went in easily. FYI, I didn't force it in with the bolts!

Then I primed the pump by cycling the key on and off several times and attempted to start the truck. It cranks over but will not fire. Occasionally while cranking over it will almost fire but it will not start. I used a screwdriver to check pressure by sticking it in the pressure valve and a heck of a lot of fuel sprays out and it's pressurized so fuel is getting to the rails. What am I missing? It's doing the same thing it was doing before I cleaned the injectors. I believe it turns over with a bit less hesitation now but it still doesn't fire.

Again as I said, the truck ran fine before I changed the pump. Also of note is that the previous owner of the truck cut an access hole in the floor to get to the fuel pump so I didn't drop the tank and consequently could not have messed up any wiring or lines coming from the tank and because the pump is putting out plenty of pressure, it's all good there!

Any ideas as to what I'm overlooking?

 

UPDATE: Today, I bled the lines using the bleeder valve on the fuel rail and there was definitely air in the system. I'm assuming taking the fuel rails out would be the cause of that. I could hear and see air bubbles in the fuel that sprayed out. I did this a total of 6 times (cycling the key to get fuel to the rail and bleeding it out). The last time, the valve sprayed out with a ton of pressure and the fuel looked good.

But, it still doesn't start. I honestly cannot figure out what else in the system could go wrong. What else can I check?

 

I've got a problem with my 04 Avalanche braking. When slowing down, everything is fine, until the vehicle is almost stopped (under 5 mph) then the vehicle pulls to the left just a bit, feels like the left front brake is going on harder than the rest. I didn 't notice it until last night but just when the above happens, I can see an instantaneous dimming of the dash lights, almost like a blink in duration that seems to coincide with the pull to the left. Any ideas are welcome. I doesn't fell like the ABS is activating, (ie no pulsing) but hard to really tell that as I'm almost topped when it happens.

 

at what point did you think it might be a good idea to reply to a 5 year old post about a issue not even related one bit to your issue?

 

where exactly is the bleeder screw post pic

 

If you’re still needing an answer, the “bleeder” is actually a fuel pressure test port and is located on either the fuel rail crossover tube or the passenger side rail.

Removing the engine cover will help to see it.