2007 GMC Truck P0171 and P0174

rudy99 · **Joined:** Tue Jul 14, 2009 1:42 pm **Posts:** 4

Ok, I've searched the boards and can't seem to find a solution. My 2007 GMC 5.3 truck will not start the first crank (about 5 seconds) and starts great on the second try. The truck seems to run fine once it is fire up. I am not having the idle problems or stalling as some of the other posters have had. Any help?

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Skydrol · **Joined:** Wed Oct 08, 2008 11:32 am **Posts:** 165

You could have vacuum leak. Check the hoses for some that might be loose, torn, broken, etc... Make sure the air duct claps are tight and is not torn either.

Seems that un-metered air is added to what the computer calculated is the right ratio.

Could be the MAF sensor that is going bad.

Do not be changing sensors, most of the time is some else that makes them fail.

rudy99 · **Joined:** Tue Jul 14, 2009 1:42 pm **Posts:** 4

thanks sky. Update, I have 44psi of fuel preassure.

asecmt · **Posted:** Tue Jul 14, 2009 7:19 pm

Does the fuel pressure hold when you turn the truck off?

rudy99 · **Joined:** Tue Jul 14, 2009 1:42 pm **Posts:** 4

No pressure when I turn the key on. Pressure kicks up when I turn the engine on. Pressure stays fine until I turn it off and it drains immediatly. I'm guessing check valve at the pump but I hope I am wrong??

Thanks for your help in advance.

asecmt · **Posted:** Wed Jul 15, 2009 12:39 pm

If it bleeds down that fast and when it does start it does not run rough like a injector or fuel presure regulator is leaking but I would think that you would have misfire or rich codes not lean codes if this were the case. Sounds to me like it is the pump.

jeff compton · **Posted:** Wed Jul 15, 2009 1:49 pm

I think those trucks need almost 60 psi to start before the injector will open so I think everyone is right. You likely need a new pump. A new filter is always a good idea as well

Mohawkmtrs · **Posted:** Thu Jul 16, 2009 6:17 am

Fuel Pressure:

KOEO: 55-62 PSI
IDLE: 45-59 PSI

Sounds like a fuel pump to me as well.

2007 GMC Truck P0171 and P0174

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