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Blinking check engine light

Tiny
DAREN4
  • MEMBER
  • 2003 CHEVROLET TRAILBLAZER
  • 4.2L
  • V8
  • 4WD
  • AUTOMATIC
  • 150,000 MILES
Recently replaced fuel pump (in tank) since engine light blinks periodically and rough idle store diagnostic computer reads 0300.
Sunday, April 11th, 2021 AT 11:08 AM

4 Replies

Tiny
STEVE W.
  • MECHANIC
  • 13,465 POSTS
Hello, was the pump replaced after the P0330 in response to it? P0300 is random multiple misfires. A common cause for that is a lean fuel mix, either from low fuel pressure or more common a large vacuum leak. The extra air gets in behind the mass airflow sensor and causes the misfires because it's making it run lean. You can test for a leak using a couple methods, one is to use something like carburetor cleaner and spray the area at the base of the intake manifold and then around and over any of the vacuum lines, you are listening for the engine to suddenly change RPMs, then look in that area for a bad line or fitting.

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge
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Monday, April 12th, 2021 AT 6:13 PM
Tiny
DAREN4
  • MEMBER
  • 3 POSTS
No. The top of my fuel pump was leaking gas so I had to lower tank in order to replace the in tank pump. Replaced twice because the first pump, the gas gage float was different then the original and gave a false reading but ran fine. Took it off again to put on original equipment when I put it on this time, it wouldn’t start and there was a huge puddle of gas on the floor! Come to find out one of the snap fittings to the pump wasn’t secure. Secured it went and started again started but with misfire been that way ever since January 13, 2021 it still runs good but you can feel the rough ideal and I fear it will end up damaging my engine if I don’t address it. Thank you for answering me!
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Tuesday, April 13th, 2021 AT 4:42 AM
Tiny
DAREN4
  • MEMBER
  • 3 POSTS
It's why I believe it has something to do with lowering the tank. It ran fine when I first thought the tank had a hole in it, I would smell gas and when I filled the tank smell would get worse so I decided to take tank off. That’s when I noticed what was causing the smell and replaced pump. Before that I had no problems with the truck.
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Tuesday, April 13th, 2021 AT 5:25 AM
Tiny
STEVE W.
  • MECHANIC
  • 13,465 POSTS
Okay, then you need to check the fuel pressure, it's possible you have a bad pump or low power to it. This has some of the information on testing it. For your truck you need to see 45-55 PSI with the pump on and a drop of no more than 5 PSI after 1 minute of the pump turning off.
https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator
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Tuesday, April 13th, 2021 AT 11:14 AM

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