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99 Gmc wont start


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tritter
New User

Feb 3, 2012, 3:01 PM

Post #1 of 11 (2513 views)
99 Gmc wont start Sign In

99 gmc 5.7 4L80 TRANS 145k miles wont start have to add gas to throttal body to get it to start and then it has no power the more accelerate the more it bogs down and if sits for more the 5 minuets it wont start again it had a code of PO160 02 sensor. replace no codes has 50lbs fuel even wile driving ive cleaned the mas air flow sensor checked for vaccume leaks around in-take with WD40 ran lucas injector cleaner to tank several times anyone have any ideas?


Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 3, 2012, 3:08 PM

Post #2 of 11 (2505 views)
Re: 99 Gmc wont start Sign In

I believe fuel pressure need to stay above 58psi on this or it will bog down and won't start on its own lower than that. Watched one at 54psi and barely ran w no power,

T



tritter
New User

Feb 3, 2012, 3:14 PM

Post #3 of 11 (2501 views)
Re: 99 Gmc wont start Sign In

thnak, you think i could attach a pressurized fule can and attach it to the fuel line i could check your idea?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 3, 2012, 3:23 PM

Post #4 of 11 (2489 views)
Re: 99 Gmc wont start Sign In

You said priming this worked so pretty much this is a fuel pressure issue. Neat thought on pressuring up fuel rail with some device but never did that and would probably be inconclusive.

It just might get it to fire if you try that but would quit if not maintaining the pressure of fuel not air.

Chances are this needs a fuel pump and if you can nail that down do get a whole GM part as there are too many reports on failures of the aftermarket ones. I suppose a screwed up regulator for fuel could be the issue but hasn't been to me.

O2 sensor may be a problem but don't think it would prevent it from starting,

T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 3, 2012, 3:56 PM

Post #5 of 11 (2478 views)
Re: 99 Gmc wont start Sign In

Yep, your fuel pressure is too low. This engine requires a minimum of 55PSI to run



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



tritter
New User

Feb 3, 2012, 4:33 PM

Post #6 of 11 (2460 views)
Re: 99 Gmc wont start Sign In

pressurized the fuel rail regulator opening at 60psi took a old freon reclame jug put a quart of gas in it a pressurized to 59 lbs attached to fuel rail and it started right up is 60 psi about right for the regulator to start opening?


Tom Greenleaf
Ultimate Carjunky / Moderator
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Feb 3, 2012, 4:47 PM

Post #7 of 11 (2454 views)
Re: 99 Gmc wont start Sign In

Gotta hand it to you for some clever tricks and yes if you saw 60 psi it should have started if all else was well.

I think operating range is 58 to 62 psi for these. Hey it's a '99 so if (likely) fuel pump's ability it is pricey but not much choice.

Any vehicle with electric fuel pumps but seems to be more on this one THEY DON'T LIKE RUNNING LOW ON FUEL as that cools the pump so avoid that even if a takes a mortgage to fill it up!

T



tritter
New User

Feb 3, 2012, 4:55 PM

Post #8 of 11 (2441 views)
Re: 99 Gmc wont start Sign In

well gota go put my first born on e-bay so i can afford a fuel pump thanks for all for your help adding this site to my faves
again thanks


Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 3, 2012, 4:55 PM

Post #9 of 11 (2441 views)
Re: 99 Gmc wont start Sign In

It will vary with vacuum changes. The range is 60 to 66PSI.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.



Tom Greenleaf
Ultimate Carjunky / Moderator
Tom Greenleaf profile image

Feb 4, 2012, 2:28 AM

Post #10 of 11 (2413 views)
Re: 99 Gmc wont start Sign In

TRITTER - KEEP YOUR "FIRST BORN" AND DEAL WITH THE EXPENSE. Not free if you do that yourself. Hope gas tank isn't full but those can be drained so it doesn't crush you to take it out - oh boy,

T



Hammer Time
Ultimate Carjunky / Moderator
Hammer Time profile image

Feb 4, 2012, 4:02 AM

Post #11 of 11 (2408 views)
Re: 99 Gmc wont start Sign In

This is a pick up. It may be easier to lift the bed off to access the pump than it would be to drop the tank.



~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.







 
 
 






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