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Go Back   Chevy TrailBlazer, TrailBlazer SS and GMC Envoy Forum > 2002 - 2009 TrailBlazer/Envoy Tech > 02-09 Vortec 4.2L I-6 Engine and Drivetrain > OEM Issues

OEM Issues Original Equipment Repairs and/or Problems

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  #1  
Old 07-25-2008, 07:13 PM
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pjaneiro pjaneiro is offline
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2002 Chevy TrailBlazer LT
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fuel pump no longer working

Ok here's the story, as i was driving home last night, the abs light and brake light appear and the tb felt sluggish a bit, further down the road i needed to really try to press on it so it could move again, this morning, no lights but the tb cranks but will not start, no codes either, ok do a fuel pressure check nada no pressure at all , ok so i thought fuel pump dead right ? bought a fuel pump from a scrap ward, tb started, then after 30-40 sec sputtered and died, hmm bad fuel pump ? ok get another one....same thing but this time faster, 20 sec then dies nothing unable to start it up, i replaced the fuel filter, just in case maybe it was clogged, same thing, i now have 3 pump in my garage, that are plugged and nicely pouring water onto a nice bucket, so i know my pumps are working fine...

is there a fuel cutoff feature on the tb ?


Please help....

anyone has the electrical schematic for the fuel pump ?

thanks
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  #2  
Old 07-26-2008, 09:30 AM
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bump...
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  #3  
Old 07-26-2008, 10:29 AM
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I THINK that a fuel pump relay is involved in some way. I am looking in the oweners manual now. yes relay 41 on my 07 tb. I am not sure where the power comes from for fuel pump power but with the key on there should be power on the load side of the relay and at least power on one of the coil sides of the relay at least for a few seconds after key is turned on. Coil power might go away if the computer doesnt see the engine turning over because of accedent portection. Also instead of power on the coil side the computer may control the ground side of the coil. Try switching with a good relay first. I don't have any wiring diagrams or we could walk right through this problem. PS possible ign switch. Have you tried one? Hope this helps in some small way. Jay
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  #4  
Old 07-26-2008, 10:36 AM
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Every Vehicle has a "roll over switch" AKA Fuel cut off switch. Its usually located in the passenger kick panel. See if its tripped by chance.
If not, is there power getting back to the pump? There should be a 5V referance wire that comes on with ignition.
Like it was said above, swap a relay around and try that.
And if that doesn't work........
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Old 07-26-2008, 10:55 AM
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Relays have been switched already, first thought, what pisses me out is usually i can find quickly these issues, but this one...NADA...checked the relays power, man the tb is weird, it will automatically switch over ground signal and whatnot if you reverse the relay as for the switch, i have found nothing, neither in my haynes manual or anywhere else...

I NEED HELP !!!!!
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  #6  
Old 07-26-2008, 11:13 AM
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Perhaps your TB just doesn't like driving in Montreal......or maybe thats just me.
So the relay is fine, fuse is ok im guessing, so its probably not shorting out.
All long as the roll over switch is ok, you will need to hunt down a diagram for the wiring at the fuel pump and make sure all the right signals are getting there. Im not at work, so anyone else have access to Alldata?
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  #7  
Old 07-26-2008, 11:28 AM
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You disconnect the battery and replace the fuel pump and it runs for 20-40 seconds, correct? Now if you disconnect the battery, wait a couple of minutes and reconect, will it start and run a few seconds? If so, something is telling the PCM to turn off the fuel pump. If this true, then it is not a relay, or fuse, or wiring. Is there a pressure sensor on the fuel line telling the PCM that there is pressure in the fuel system? I am not a lot of help, but it is a thought.
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  #8  
Old 07-26-2008, 11:38 AM
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Here is a couple of Fuel System Diagrams:
Click image for larger version

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  #9  
Old 07-26-2008, 12:47 PM
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Quote:
Originally Posted by brendanpower View Post
Perhaps your TB just doesn't like driving in Montreal......or maybe thats just me.
So the relay is fine, fuse is ok im guessing, so its probably not shorting out.
All long as the roll over switch is ok, you will need to hunt down a diagram for the wiring at the fuel pump and make sure all the right signals are getting there. Im not at work, so anyone else have access to Alldata?
I keep reading about the rollover switch...where is this damn switch !!!! I can't find squat !!!! not in teh haynes manual, or the users manual....
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  #10  
Old 07-26-2008, 12:56 PM
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2002 Chevy TrailBlazer LT
Forest Green Metallic 4.2L I6 4X4
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Location: Montreal, Quebec, CANADA
Posts: 899
thanks for teh schematics, i am going to try out taking out the relay and shooting the 12v straight into the the relay connector connected to the gray wire, we will see how that goes....

For the montreal driving part, i would'nt be surprised, already that this is a U.S truck i am sure it hates the canadian gas, that's the only thing i have going on, i have a fellow tb'er that has a constant 15-16 mpg driving city only, and i barely hit the 12mpg mark....but when i go to the u.s HELLO !!!! 15-16 mark....

i wonder where are the diffs...

Also i am sure that if i were to visit bagdad or irak, i would probably find less pot-holes there than here... i would say my average hole per foot is 100
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