chem_man

MADMech -

Have you checked the fuel pressure on the new fuel pump? It needs to be in the 50 - 57 psi range.

Did you change the fuel filter when you changed the fuel pump?

Have you re-seated the ignition coils onto the spark plugs?

I know you said that you purchased the ignition coils from Advance Auto and that they were Bosch. Are they actually branded Bosch and come in a box that had the Bosch name, or is that what the counter person said at Advance Auto, and the coil actually came in a Carquest box?

MADMech

the coils actually came in a Bosch box. They weren't individually boxed, they were all wrapped up in one big box. I'm gonna go over everything again today, and verify that everything is right. I did not change the fuel filter, as the previous owner told me they had just had it replaced about 3 months ago. I'm going to look at it and verify that it's good. I'm also going to verify fuel pressure from the new pump as well. Will let everyone know what the outcome of all the checking and rechecking is. Thank you for all the help, I really do appreciate it.

chem_man

OK, sounds good.

Just to let you know, I have never seen Bosch ignition coils for these vehicles.listed in any online catalog I have used (rockauto.com, Advance, O'Reilly, Bosch's online aftermarket catalog, carparts.com, partsgeek.com, etc).

I do know that Bosch is an OEM supplier and they do sell various aftermarket parts, but I am concerned that you might have gotten counterfeit parts. There are a lot of junk ignition parts out there, If you paid less then ~$40 per ignition coil, I would be concerned that you got a low quality Chinese knock-off.

I admit I do not keep rack of all the part brands/manufacturers out there, but I am familiar with the one's that manufacturer/sell quality parts and where to get the best price on them.

Good Luck!

MADMech

I did change the fuel filter when I replaced the pump, the pump is functioning as it should. I did verify that the coil packs I received are knock offs. I purchased a set of coils from my local chevrolet dealership and put them in. I no longer have a P0300, however I'm still having a rough idle and Smelling fuel. I did a smoke test of the entire evap system and no leaks are prevalent. I'm still searching for the cause, but at this point I'm not sure what else it could be. So unfortunately I'm a confused as I was when after I bought the trailblazer.

chem_man

Sorry to hear about the counterfeit ignition coils. I hope you reported that Advance Auto Parts store to corporate! There is no excuse for them to sell such crap!

Well, regarding the rough idle, my suggestion is to add a bottle of Techron Complete to your fuel tank and drive the fuel system clean. Do this a couple of times for best results. As far as the fuel smell goes, where exactly on the TrailBlazer do you smell it (engine compartment, by the bottom of the driver's door, etc.)?

Another thing to check is the fuel pressure regulator which is located behind the alternator and is mounted about where the engine block meets the valve cover. Make sure the vacuum line is intact, and then remove the vacuum line from the fuel pressure regulator's nipple and see if gas runs out of either the vacuum line or the nipple. If gas runs out, you need to replace the fuel pressure regulator.

Regarding your fuel trims, are you able to monitor them in real time? (Also, if you can, then set the scanner up so that both the short term and long term fuel trims are reported as a percentage.)

Good Luck!

MADMech

From sitting in the trailblazer starting it and the exciting the drivers for i can smell gas as soon as i open the door, but if you pop the hood it's pretty prevalent as well... and yes i have a scan tool, it's not the greatest but i should be able to view the fuel trims in real time. The fuel pressure regulator is new and not leaking when the vacuum line is disconnected. I emailed advance auto corporate office, am still awaiting a response.

chem_man

OK on the fuel smell. With the engine running, look over the fuel lines and see if you see any drips. Also, check the EVAP purge valve on the driver's side of the engine located about halfway back and halfway down to make sure it is not cracked and that it is operating properly. I'm attaching a diagram that shows the fuel lines,




I hope Advance responds positively soon.

Good Luck!