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2004 gmc envoy_slt_xl
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Discussion Starter · #1 ·
Hello,
I have an 04 enxoy xl with the 5.3L Engine. I have had it 5 months, it has 118000 miles, never had any issues or quirks.

not new to working on cars but new to GMC

Have been researching for a WHILE, so not an easy fix, or not as common problem as it seems.

the symptoms are common however:

Cranks, wont start (mostly wont start).

pretty much ruled out security and trans-lock. Could be the ignition switch but i am leaning twoards fuel or air sensor problem.

Car DOES start, very rarely. Usually only if it is or has been hooked to another battery (although i am sure its a good battery, i can crank for hours after the charge has been pulled off, and its pretty new.)

When it doesnt work:
it will crank (i hear fuel pump prime, starter is turning the engine) but no firing)

sometimes: it will crank and fire (only for half a second doesnt even sound like all 8 cylenders fire before it dies)

sometimes: it will crank and start, but will only run if i keep it around 1500+ on the tach

rarely: it will start and run fine (took it for a test drive today)


things i have done to try to diagnose:
fuel filter
made sure pump was priming
checked that there was fuel in the rails by removing the pressure sensor on the driver side of the block
checked for spark
checked the oil
cycled ignintions more than 10 seconds (with key off and/or out) to bypass security
tried strating in neutral
cleaned throttle body (not extensively but enough to get it going)
made sure throttle was activating the plate in the throttle body.

wierd occurences:
had it running well, on a very very cold day, for about 10 mins, open the hood and it dies.
after I have gotten it running, whether i keep it charging or take the charger off and run my own battery, it starts and runs fine (engine hot) if i leave it for an hour and try to start again (with and withoug battery charger) it does not work
every time i remove and replace the little fuel pressure sensor, it cranks next time


help!!!!
thank you!!!
 

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Registered
2004 gmc envoy_slt_xl
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2 Posts
Discussion Starter · #2 ·
update... and still broken

alright, so i dropped the tank, tested the pump, tested the relay, changed the ingition switch.
donnt have a security light but still tried bypassing the passlock.
what else can cut the power to the pump?
when i applied power directly it ran, and i tested the harness with the DMM and got 5v on the sending unit contacts and 0 on the pump contacts.....
any ideas?
 

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4 Posts
Hello,
I have an 04 enxoy xl with the 5.3L Engine. I have had it 5 months, it has 118000 miles, never had any issues or quirks.

not new to working on cars but new to GMC

Have been researching for a WHILE, so not an easy fix, or not as common problem as it seems.

the symptoms are common however:

Cranks, wont start (mostly wont start).

pretty much ruled out security and trans-lock. Could be the ignition switch but i am leaning twoards fuel or air sensor problem.

Car DOES start, very rarely. Usually only if it is or has been hooked to another battery (although i am sure its a good battery, i can crank for hours after the charge has been pulled off, and its pretty new.)

When it doesnt work:
it will crank (i hear fuel pump prime, starter is turning the engine) but no firing)

sometimes: it will crank and fire (only for half a second doesnt even sound like all 8 cylenders fire before it dies)

sometimes: it will crank and start, but will only run if i keep it around 1500+ on the tach

rarely: it will start and run fine (took it for a test drive today)


things i have done to try to diagnose:
fuel filter
made sure pump was priming
checked that there was fuel in the rails by removing the pressure sensor on the driver side of the block
checked for spark
checked the oil
cycled ignintions more than 10 seconds (with key off and/or out) to bypass security
tried strating in neutral
cleaned throttle body (not extensively but enough to get it going)
made sure throttle was activating the plate in the throttle body.

wierd occurences:
had it running well, on a very very cold day, for about 10 mins, open the hood and it dies.
after I have gotten it running, whether i keep it charging or take the charger off and run my own battery, it starts and runs fine (engine hot) if i leave it for an hour and try to start again (with and withoug battery charger) it does not work
every time i remove and replace the little fuel pressure sensor, it cranks next time


help!!!!
thank you!!!
I hate when folks suggest this but here goes. Check your grounds. Since it runs sometimes and does goofy stuff like shuts off when you open the hood maybe it's a marginal ground that is affected by vibrations or temperatures or maybe even earthquakes in China. Having a 2004 Envoy I found that these Chevs/GMCs are notorious for having crappy ground connections.
 

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Here's where you should be looking .... I'll quote you:

" ......wierd occurences:
had it running well, on a very very cold day, for about 10 mins, open the hood and it dies.
after I have gotten it running, whether i keep it charging or take the charger off and run my own battery, it starts and runs fine (engine hot) if i leave it for an hour and try to start again (with and withoug battery charger) it does not work
every time i remove and replace the little fuel pressure sensor, it cranks next time"

That suggests .... even without capitolization (and your post is the only exemption to English Rules of Capitolization I'll bother reading this week) -----> you might have a thermal-electrical problem.

I'd be testing or substitute to test the fuel pump relay.

FWIW -----> NEVER OPEN THE HOOD ON A RUNNING ENGINE. It gets scared ... now it's psychologically damaged; it will need analysis (the engine, not you ... mebbee) with serious couch-time.

FWIW #2 ----> Relays don't mind if you open the hood at all.

AND -----> What's with the charger and battery combination here? Is there something you're not saying?

AND #2 -----> Why are you just throwing oddball (read: expensive) parts at this?

AND #3 -----> It is not required to spend all your Covid Stimulus money on this car. Diagnose it first, THEN buy the correct parts and send me the balance of the check 'cause you were going to spend it all anyway ... right?
 
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