P0300 after Dorman Fuel Inlet/rollover valve Repair

[dbailey75]

2003 Trailblazer Lt 4.2 2WD 137K miles, I’m not a mechanic but thanks to these forums and youtube videos over the last 2 years, I’ve been able to keep the truck going, VVT solenoid was my first repair, followed by front calipers, rotors, brake flex line, motor/transmission mount, Bilstein 4600 shocks/struts, transmission service, various sensors, list goes on.

Recently the fuel inlet showed signs of very small leak at the tank when inspecting the spare tire. Completed the repair using Dorman 577-106, reinstalled the tank along with a new pump, fuel pressure sensor, and fuel filter. Primed the pump, started right up, but running rough took a short drive, maybe 2 miles, check engine light came on, then started flashing. Car was running tip top before the repair. code P0300.

Thought maybe the new fuel pump was bad, reinstalled the original pump, same issue. P0300. Checked the fuel pressure at the filter/Shrader valve, 58 PSI. EVAP test were not completing, so I thought I had a leak, or maybe the tank repair was not correct. Dropped the tank again, purchased some stoppers, plugged the EVAP lines, tank holds pressure, no leaks from around the installed inlet/roll over valve, or from the fuel fill entrance, EVAP lines all hold pressure as well, charcoal canister on this model is under the drives seat and was not part of the EVAP pressure testing I performed.

Question, Dorman check valve says it’s only compatible with the ELX models, is this because GM's repair notice was mainly for those models? 2002-2003 SWB Trailblazers were part of the notice, https://www.tsbsearch.com/GMC/14423C. Or is there something different about how the EVAP/Fuel system works on an EXT compared to the SWB where this valve would not work? physically the unit installs with no issues, no different than the youtube videos.

Before reinstalling the tank, is there anything else I should check, before moving to it being an unrelated problem? Also want to note, very little gas was in the tank during the drive/idling, 2-4 gallons. I read somewhere, that for a full EVAP test to complete, I would need 15% or more of gas in the tank, which I was boarder line.

What are my next steps? I have a lowend scan tool Foxwell NT301

 

[mrrsm]

Welcome to GMT Nation...

Without trying to sound "TOO Sage"... in our collective experience... There are Only TWO Kinds of After-Market Fuel Pumps:

(1) Those that have FAILED...
(2) and Those that are GOING TO FAIL.

The wisdom that follows with this hindsight is to choose from the Fuel Pump List below...and focus on the one with the Red Arrow drawing your attention to it should the need arise post-diagnosis for its R&R:

2003 CHEVROLET TRAILBLAZER 4.2L L6 Fuel Pump & Housing Assembly | Shop Now at RockAuto

Fuel & Air Parts and More for Your 2003 CHEVROLET TRAILBLAZER at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

As for the P0300... That issue --might-- be related to a Bad Fuel Pump... (Doubtful right now... without gathering MORE Diagnostic Evidence) ...but if you had an Analog Fuel Gauge attached as per THIS recent On Topic Thread (Linked Below) ...you would be able to Monitor the FP Pressure dynamically while Test Driving the SUV and having the FP Gauge tucked under the Hood and laying close to the Windshield in Plain View.

BUT... Before doing that all over again... the simplest manner to Test for the P0300 Issue for Un-Metered Air causing Random LEAN Mis-Fire entering the inlet Air Stream is to get a Can of Starter Fluid Spray...

Then... while doing this Test OUTSIDE and with a Fire Extinguisher at hand... Lightly spray along the Left Side of the Engine Block adjacent the Top and Bottom of the Intake Manifold Flange near the Staggered 10mm Trapped Fasteners right along the Runners.

The Engine should be at Idle, In Park, with the Wheels Chocked and with the E-Brake "ON"... While You Immediately Listen for any indications of elevated RPM with --Short, Controlled Bursts-- (ala Sergeant Hicks in "The Aliens"). Do NOT Over-Do This Test!

This Test --MIGHT-- indicate the need to replace the Intake Manifold Triple Set of Figure "8" Gaskets... BUT ...First... Try Tightening up the asymmetric-staggered IM Trapped 10mm Floating Fasteners down using a MAX of only 89 Inch Pounds of Torque. Then, Start the Engine and Clear the Codes to see if that did "The Trick". Test Drive the SUV.

Visit THIS Link for a contemporary Thread concerning the CPAS and issues relating to the P0300 Code (and other Specific LEAN In-Cylinder Issues)... right along with instructions on how to set up a DURABLE Analog Oil Pressure Gauge....and the SAME Technique can be done with a similar Fuel Pressure Gauge connected up to the Schrader Valve on the Fuel Pressure Test Port!

Valve cover gaskets...need some input. (2003 GMC Envoy XL 4.2L)

2003 GMC Envoy XL 4.2L I6 278,000 miles Greetings all! I have been long awaiting the opportunity to replace my leaking valve cover gaskets, and yesterday presented such an opportunity. Continuing the job today, I finally removed the valve cover. However, when removing the intake manifold to...

gmtnation.com

Spot On Link ... for more information on Diagnosing the P0300 Issue:

SOLVED! - code P0300. What to do next?

This is on my 2007 4.2l, 270,000+ mile TB. Short story made long. I added about 12 gallons of possibly bad fuel. My truck sat a few hours and when I went to drive it, it went about 1/2 mile, lost power, barely running, and a flashing cel. Stalled and would not start. I added some heet and pumped...

gmtnation.com

 

[dbailey75]

Welcome to GMT Nation...

Without trying to sound "TOO Sage"... in our collective experience... There are Only TWO Kinds of After-Market Fuel Pumps:

(1) Those that have FAILED...
(2) and Those that are GOING TO FAIL.

The wisdom that follows with this hindsight is to choose from the Fuel Pump List below...and focus on the one with the Red Arrow drawing your attention to it:

2003 CHEVROLET TRAILBLAZER 4.2L L6 Fuel Pump & Housing Assembly | Shop Now at RockAuto

Fuel & Air Parts and More for Your 2003 CHEVROLET TRAILBLAZER at Reliably Low Prices. Fast Online Catalog. DIY-Easy. Your Choice of Quality. Full Manufacturer Warranty.

www.rockauto.com

View attachment 114895

As for the P0300... That issue --might-- be related to a Bad Fuel Pump... (Doubtful right now... without gathering MORE Diagnostic Evidence) ...but if you had an Analog Fuel Gauge attached as per THIS recent On Topic Thread (Linked Below) ...you would be able to Monitor the FP Pressure dynamically while Test Driving the SUV. BUT... Before doing that all over again... the simplest manner to Test for the P0300 Issue for Un-Metered Air causing Random LEAN Mis-Fire entering the inlet Air Stream is to get a Can of Starter Fluid Spray...

Then... while doing this Test OUTSIDE and with a Fire Extinguisher at hand... Lightly spray along the Left Side of the Engine Block adjacent the Top and Bottom of the Intake Manifold Flange near 10mm Trapped Fasteners right along the Runners.

The Engine should be at Idle, In Park, with the Wheels Chocked and with the E-Brake "ON"... While You Immediately Listen for any indications of elevated RPM with Short, Controlled Bursts (ala Sergeant Hicks in "The Aliens"). Do NOT Over-Do This Test!

This Test MIGHT indicate the need to replace the Intake Manifold Triple Set of Figure "8" Gaskets... BUT ...First... Try Tightening up the asymmetric-staggered IM Trapped 10mm Floating Fasteners down using a MAX of only 89 Inch Pounds of Torque. Then, Start the Engine and Clear the Codes to see if that did "The Trick". Test Drive the SUV.

Visit THIS Link for a contemporary Thread concerning the CPAS and issues relating to the P0300 Code (and other Specific LEAN In-Cylinder Issues)... right along with instructions on how to set up a DURABLE Analog Oil Pressure Gauge....and the SAME Technique can be done with a similar Fuel Pressure Gauge connected up to the Schrader Valve on the Fuel Pressure Test Port!

Valve cover gaskets...need some input. (2003 GMC Envoy XL 4.2L)

2003 GMC Envoy XL 4.2L I6 278,000 miles Greetings all! I have been long awaiting the opportunity to replace my leaking valve cover gaskets, and yesterday presented such an opportunity. Continuing the job today, I finally removed the valve cover. However, when removing the intake manifold to...

gmtnation.com

Spot On Link ... for more information on Diagnosing the P0300 Issue:

SOLVED! - code P0300. What to do next?

This is on my 2007 4.2l, 270,000+ mile TB. Short story made long. I added about 12 gallons of possibly bad fuel. My truck sat a few hours and when I went to drive it, it went about 1/2 mile, lost power, barely running, and a flashing cel. Stalled and would not start. I added some heet and pumped...

gmtnation.com

Thanks for the quick reply, I can confirm I purchased the Bosch Fuel pump which I plan to reinstall prior to reinstalling the tank (put the original pump back in after the initial P0300). Can we take some steps back to the fuel tank, and rollover valve, EVAP. Would the Dorman Rollover valve cause any issues mentioned, EVAP hose are in good shape, no visible crack/kinks. There's still the question of the Dorman rollover valve being compatible the SWB. once we check this off the list, I'll put the tank back in trailblazer for further troubleshooting.

 

[mrrsm]

More Wisdom on that subject from @Mooseman via THS Thread:

NEED HELP - EVAP Rollover Check Valve Failure (ICV),

Hey yall, So the mysterious EVAP code is coming from a failed Intake check valve also known as the rollover valve on the fuel tank. I have seen kits online by Dorman to fix this problem, however it says they are only for 2002-2004 year models. I have an 08 97x, does anyone know if A) I can use...

gmtnation.com

Remember that there are Quite A Few Things that can be causing the P0300 (some of them are well-thrashed-out in the link I posted above). These can involve a Failing COP (Coil Over Plug) caused by excessive LEAN Fuel Conditions that will throw P0301-P0306 Codes.

Of course, we have already covered the Fuel Pump as being one of them. Un-Metered Air *Sneaking* past a Leaking Intake Manifold and getting by the PCM's Controls and Sensors is another problem.

Also... a Failed EFI can cause the Fuel to --NOT-- Atomize-Mist when poorly actuating leaving Hard-2-Combust Liquid Fuel Droplets to enter inside the Cylinder instead. If this persists, the condition know as "Poisoning The CAT" will occur due to the Excessive Raw Fuel Burning Up inside of the CAT Canister and excessively Raising its Temperature.

If specific cylinders are having very high Mis-fire Counts, the COP working above the Spark Plug might already be in trouble due to the High Voltage Climb on the Secondary Coil trying to bridge the Spark Plug Gap without the help of having enough Hydro-Carbon to Air Mixture....hence "The LEAN F/A Problem"

What happens over time is that the HV Secondary Coil Voltage will Oscillate --excessively-- back and forth get through and into the Primary Coil side and Over-Heat it to the point of creating a Short Circuit. Lean Fuel Issues Cause COP FAILURES... NOT The Other Way Around.. Ordinarily, COPs and EFIs Do NOT Fail as Complete Sets.

Installing the --Wrong Spark Plugs-- can do the same thing. Once the Excessive Voltage backs up through and into the Primary side of the COP...it will seek to find Ground on the OUTSIDE of the Plug instead of Firing INSIDE of the Cylinder.

You will know this is happening if you find evidence of Black Carbon via Electrical Tracing along the Rubber COP Insulation Boot and BLACK TRACING LINES ALONG THE SPARK PLUG CERAMIC INSULATOR.

 

[Mooseman]

The check/rollover valve definitely would not cause a misfire. I think it's just coincidental you got a misfire at the same time as the tank valve repairs. You have to do some misfire diagnosis. First, you have to see if one particular cylinder is causing it as sometimes it won't set a particular cylinder misfire (i.e. P0306) until it has run a while without being reset.

Thought maybe the new fuel pump was bad, reinstalled the original pump, same issue. P0300. Checked the fuel pressure at the filter/Shrader valve, 58 PSI. EVAP test were not completing, so I thought I had a leak, or maybe the tank repair was not correct. Dropped the tank again, purchased some stoppers, plugged the EVAP lines, tank holds pressure, no leaks from around the installed inlet/roll over valve, or from the fuel fill entrance, EVAP lines all hold pressure as well, charcoal canister on this model is under the drives seat and was not part of the EVAP pressure testing I performed.

Reason Evap isn't completing is that it takes a lot of driving time and specific temperatures and fuel levels to get it to complete. For the time being, I would leave aside anything regarding Evap as that would not cause misfires. Fuel pressure you need to check that the pressure holds after priming not-running for a while and that it continues to be good while running.

This thread has lots of info on chasing down misfires:
Very slight miss/misfire at idle

 

[dbailey75]

The check/rollover valve definitely would not cause a misfire. I think it's just coincidental you got a misfire at the same time as the tank valve repairs. You have to do some misfire diagnosis. First, you have to see if one particular cylinder is causing it as sometimes it won't set a particular cylinder misfire (i.e. P0306) until it has run a while without being reset.


Reason Evap isn't completing is that it takes a lot of driving time and specific temperatures and fuel levels to get it to complete. For the time being, I would leave aside anything regarding Evap as that would not cause misfires. Fuel pressure you need to check that the pressure holds after priming not-running for a while and that it continues to be good while running.

This thread has lots of info on chasing down misfires:
Very slight miss/misfire at idle

thanks for confirming the tank repair is not the cause of the P0300, put the tank back in with the new fuel pump, there were no issues with previous pump prior to fixing the inlet check valve leak other that it was 21 years old. Will change gears and start trouble shooting the misfires. also added more gas, should have 5 or so gallons.

 

[dbailey75]

Updated: I had previously purchased 6 Delphi coils earlier in the year, at the time I only had an issue with code P0306, after trouble shooting, and moving the misfire from cylinder 6 to 5, I replaced the bad coil. Issue solved and called it a day. Last night I installed the other 5 coils, all is well again.

Gas and electricity at 2 things I do not like to work on.

I'll report back in a month on the inlet/check valve fix. I know other youtube mechanics were also curious about the compatibility of the Dorman check valve, other than the tanks being different sizes, the placement of the inlet/check valve is in the same location as far as I can tell on most all models, unable to think of reason why it would not work for other models.