Help with my dad's 04 Blazer

**Sweet Chops** · 11-25-2009, 05:30 PM

Truck: 2004 Blazer 4x4 4.3 43,000 miles
When the truck is cold, like if it sits over night or at work it will turn over a few times and will not start. If he turns the key back then tries to start it will start up. It has been happening for about a week. On tues day he got a SES light. I went over on wed. when he got home from work to read the code. the SES light was for bank 1 and 2 lean condition. The truck was warm when I was over their so it started right up. I ran a scan w/ my HP tuner and everything looks fine. Truck feels like it is running fine also. Just starting hard. Temp outside has been low 40s to mid 50s if that matters.

Any Ideas?

Thanks,
Anhalt

**SeVeReDiStOrTiOn** · 11-25-2009, 05:37 PM

Weak fuel pump? Try letting it prime a little longer and se if it's still hard starting...checking the fuel pressure wouldn't hurt either.

**01 SS Vert** · 11-25-2009, 05:44 PM

I had the same truck, but never had that problem.

**Sweet Chops** · 11-25-2009, 05:47 PM

From what I have been reading the Fuel Pressure should be 55-60. Does that sound right?

**SeVeReDiStOrTiOn** · 11-25-2009, 05:54 PM

Originally Posted by Sweet Chops

From what I have been reading the Fuel Pressure should be 55-60. Does that sound right?

Yea that sounds about right for the normal port injection setup

**01 SS Vert** · 11-25-2009, 06:14 PM

yeah, mine read 58 psi off the fuel rail.

**Smkn_TA** · 11-25-2009, 06:19 PM

Next time, turn the key as far as he can without starting it, on my truck this cycles the fuel pump. I do this three times, and then the fourth time I start it up and have full pressure before it even cranks over.

**Sweet Chops** · 11-25-2009, 06:27 PM

I will try that thur when I go over there for turkey. If it starts with no problems does that mean the pump is bad, or what?

**importhater81** · 11-25-2009, 06:29 PM

It should have 55-60psi with key on engine off and hold pressure.If it primes to 55-60psi and then drops right away it could be a leaking fuel pump check valve,injector or regulator.Other causes of lean codes are vacuum leaks,low fuel pump volume,faulty o2 sensors or maf sensors.Also check the breather tube from the passenger side valve cover and make sure it didn't come loose off of the air intake above the throttle body,that will sure as shit set a lean code with no driveability issues.

**Sweet Chops** · 11-25-2009, 06:35 PM

The o2 seamed very lively when I did the scan. I also would have thought the truck would run a little rough it it had a bad MAF. On thing that did catch my eye was that the LTFTs were off quite a bit. about 20-25% off. Not sure if that matters. the STFTs were very close to 0 within 5%

**02cetransam** · 11-25-2009, 06:42 PM

My buddy has an 02 Envoy 4x4. He has had a starting problem since he bought it (about 8 months ago from a dealer who wont do anything about it). Intermittently, it will not start. It will just turn over. Some times it will start the second time and sometime it will take 10-15 times. Sometimes you have to wait 20 mins then try again and then it will finally start. Its been a huge pain in the butt. So far he has changed the following: ignition switch (brand new GM), fuel pump (brand new GM), wiring harness that connects fuel pump (brand new GM) and it still does the exact same thing. He would tap the gas tank and then the SUV would start so he was confident it was the pump or connector. Apparently, its common for the connectors to corrode at the pump. He has cleaned the major ground straps and disconnected the car started. Same thing. Its been a nightmare for him.

**0rion** · 11-25-2009, 07:19 PM

Originally Posted by Sweet Chops

Truck: 2004 Blazer 4x4 4.3 43,000 miles
When the truck is cold, like if it sits over night or at work it will turn over a few times and will not start. If he turns the key back then tries to start it will start up. It has been happening for about a week. On tues day he got a SES light. I went over on wed. when he got home from work to read the code. the SES light was for bank 1 and 2 lean condition. The truck was warm when I was over their so it started right up. I ran a scan w/ my HP tuner and everything looks fine. Truck feels like it is running fine also. Just starting hard. Temp outside has been low 40s to mid 50s if that matters.

Any Ideas?

Thanks,
Anhalt

sounds like the fuel pump is on the way out to me. Could also be the "spider" that distributes fuel to the injectors. Open the tb and shine a light in the intake and see if the sides of the intake are washed down with fuel. My gut says fuel pump though.

Originally Posted by 02cetransam

My buddy has an 02 Envoy 4x4. He has had a starting problem since he bought it (about 8 months ago from a dealer who wont do anything about it). Intermittently, it will not start. It will just turn over. Some times it will start the second time and sometime it will take 10-15 times. Sometimes you have to wait 20 mins then try again and then it will finally start. Its been a huge pain in the butt. So far he has changed the following: ignition switch (brand new GM), fuel pump (brand new GM), wiring harness that connects fuel pump (brand new GM) and it still does the exact same thing. He would tap the gas tank and then the SUV would start so he was confident it was the pump or connector. Apparently, its common for the connectors to corrode at the pump. He has cleaned the major ground straps and disconnected the car started. Same thing. Its been a nightmare for him.

the first step to this would be to properly diagnose it. His parts list so far looks like a guessing game. Check fuel pressure when the truck acts up and see what it is. Check for voltage at the pump. It's just a process of elimination and the guessing game can get expensive. Could also be something simple like a relay that's being overlooked but the only way to know is to start checking the pressure and voltage and follow those where they take you.

**02cetransam** · 11-25-2009, 07:34 PM

k thanks. i will let him know.

**0rion** · 11-26-2009, 05:13 AM

Originally Posted by 02cetransam

k thanks. i will let him know.

GM fuel pumps are known to fail. The s-series seem to have the biggest problems with them. I'm actually pretty shocked that him replacing his pump didn't fix it because they're extremely common to fail. The other common issue is that spider assembly. Those are just known to leak. Did he replace his pump or did the dealership and was it the dealership he bought it at? Have him go buy a gauge (~$20) and when it acts up again have him check the fuel pressure and see what it says. Also, have him listen for the pump to prime when he turns the key on. If he hears the pump prime but still doesn't have pressure he might have a bad pump out of the box.

**Sweet Chops** · 11-27-2009, 09:17 AM

ok I checked the fuel pressure and here are the #s.
Key turned forward but not running 60psi
Truck running 55psi.
The SES light turnd back on and here are the code.
P0171 Fuel Trim System Lean Bank 1
P0174 Fuel Trim System Lean Bank 2
I am going to replace the fuel filter.