Hard start when warm

[danocywg]

Hi everyone, I'm getting SUPER frustrated with an issue with my 2008 LTZ with 341,000km. Several months ago, I had an initial code thrown where it was indicating that my rear O2 sensors were failing (don't remember the code off-hand). So I took it to my mechanic, who has been really good to date. They check it out and tell me they're bad and that my cats are also running way hotter than they should. He also suggests replacing the front O2 sensors as well, since they don't appear to have been replaced before (at least not since I owned the truck). So we replace the four O2 sensors, spark plugs all around (they were due to be replaced) and the two catalytic converters...a few days later, check engine light comes back but this time it's throwing a P1133 and P1153 for the front O2 sensors. They do a leak test on the exhaust and nothing found, checked the intake and no leaks, Mass Airflow sensor tests okay. Clear the codes and lets me drive it for a few days to see what happens. I drove it for a few weeks and the code comes and goes, with no rhyme or reason. I look at my cheapy scan tool and it keeps getting triggered by what it lists as TID$80 and $81 Switches Units; the min is 76 and it's going down to 65 at times, throwing the code. So I give my mechanic the info and they scan it on their tool and they can see that as well, but when they check it, it's over the minimum. Take it back home and drive it with the CEL coming on and off every few days. Then a month later, my oil pressure sensor went out and take it to my mechanic. While doing the sensor, they're going to do the intake manifold gasket and are optimistic that will fix it as they had another GM that had the same codes and replaced the intake manifold gasket and fixed it. No such luck in my case as the code is back after it went through a relearn process (their words). Back to the garage and they went through everything again, they changed the spark plugs again, saying that they seemed to be fuel fouled, but that didn't change anything.

Now here's where things get even more frustrating...they check the fuel injectors and they tell me that all the injectors are streaming out fuel instead of it being a mist and they're certain that's going to fix the two O2 codes coming up. So I tell them to change the injectors and now not only do the codes not go away, it now takes several seconds for the truck to start...but not first thing in the morning. It starts without issue first thing but if I shut it off and start it 10-15 minutes later, it cranks for several seconds before it start up and sometimes, I'll have to try it a second time before it starts. Since they did that, I ended up replacing the Mass Airflow sensor and that seems to have made the P1133 code disappear. They sent my truck to have the PCM reprogrammed as they found a TSB for that problem. The P1153 code has not come back since the reprogram, but the hard starting issue continues. I know he's going to say that the fuel pump needs to be replaced next, but it NEVER started like that until they changed the injectors and I tend to think that there's a faulty injector that's dumping fuel when it shuts down. When it does finally start, there is a bit of black smoke from the exhaust, which isn't there first thing in the morning. Spark plugs and wires have been changed twice, throttle body has been cleaned and the mass airflow sensor has been changed. 

 

I was finally able to get my hands on a mechanical fuel pump gauge and here's my findings...

With the key on: 56 PSI
When running at idle: 44 PSI
5 minutes after shutdown: 68 PSI (still starts normally)
10 minutes after shutdown: 74 PSI (hard start)
20 minutes after shutdown: 14 PSI (hard start)

At WOT, the pressure goes up about 4 PSI then once I let off the throttle, it quickly drops to about 42 PSI then back to 44 PSI at idle.

 I suspect that the fuel injectors are leaking into the cylinders but my mechanic said he pulled the rail and there was no leaking.

[Jsdirt]

Holy parts cannon ...  Sounds like that shop never heard of, "Test, don't guess!"

 

My first thought after reading in the beginning is they replaced the upstream sensors with a subpar aftermarket brand. The only aftermarket brand I will use is NGK / NTK, or Bosch if the former isn't available. 

 

You need to find a shop that will test before firing the parts cannon at it. Guessing in the 21st Century is a VERY EXPENSIVE proposition, as you just found out. 

 

Pressure looks good, but that bleed down isn't normal. An injector balance test using a BI-DIRECTIONAL scan tool and a fuel pressure gauge will confirm any injector issues 100%. Why they would even pull the rail to check this is mind blowing to me. If it doesn't have a Schraeder port, one can be installed. 

[danocywg]

1 hour ago, Jsdirt said:

Holy parts cannon ...  Sounds like that shop never heard of, "Test, don't guess!"

 

My first thought after reading in the beginning is they replaced the upstream sensors with a subpar aftermarket brand. The only aftermarket brand I will use is NGK / NTK, or Bosch if the former isn't available. 

 

You need to find a shop that will test before firing the parts cannon at it. Guessing in the 21st Century is a VERY EXPENSIVE proposition, as you just found out. 

 

Pressure looks good, but that bleed down isn't normal. An injector balance test using a BI-DIRECTIONAL scan tool and a fuel pressure gauge will confirm any injector issues 100%. Why they would even pull the rail to check this is mind blowing to me. If it doesn't have a Schraeder port, one can be installed. 

I was told that they only use the ACDelco O2 sensors as they've had problems in the past with aftermarket ones on Chev/GMC trucks. I'll talk to them and get them to do a balance test; I know they have a SnapOn bi-directional scanner, so they should be able to do that no problem. I honestly suspect they didn't actually pull the rail off to see if the injectors were leaking. The rail definitely has a schraeder port as I used it to get my readings.

[newdude]

2 hours ago, danocywg said:

I know he's going to say that the fuel pump needs to be replaced next, but it NEVER started like that until they changed the injectors and I tend to think that there's a faulty injector that's dumping fuel when it shuts down. When it does finally start, there is a bit of black smoke from the exhaust, which isn't there first thing in the morning. Spark plugs and wires have been changed twice, throttle body has been cleaned and the mass airflow sensor has been changed. 

 

I was finally able to get my hands on a mechanical fuel pump gauge and here's my findings...

With the key on: 56 PSI
When running at idle: 44 PSI
5 minutes after shutdown: 68 PSI (still starts normally)
10 minutes after shutdown: 74 PSI (hard start)
20 minutes after shutdown: 14 PSI (hard start)

At WOT, the pressure goes up about 4 PSI then once I let off the throttle, it quickly drops to about 42 PSI then back to 44 PSI at idle.

 I suspect that the fuel injectors are leaking into the cylinders but my mechanic said he pulled the rail and there was no leaking.

 

If you turn the key on you have 56psi If I read this correctly?  What happens if you leave the key on and engine off and watch the gauge for a couple minutes?  Does it hold 56psi?  Does it drop?  

 

Here is GM's test procedure on the fuel system  I bolded a couple bits.  To truly do a couple of the steps, there is the need to bleed air with a proper scan tool that can command the function.  I put the one for trucks with the Fuel Pump Flow Control Module as most every Tahoe/Suburban/Avalanche of that year have one:

 

 

Quote

 

Circuit/System Testing

 

Ignition OFF, all accessories OFF, install the CH-48027 Digital Pressure Gauge . Refer to Fuel Pressure Gauge Installation and Removal.

 

Ignition ON, engine OFF, command the FPCM Fuel Pump ON with a scan tool.

 

Verify the fuel pressure is between 345–690 kPa (50–100 psi) with the pump running.

 

Engine idling at the normal operating temperature, Verify the FPCM scan tool Fuel Rail Pressure Sensor parameter is between 296–310 kPa (43–45 psi).

Note:

• The fuel pump may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.
• DO NOT start the engine.

1. Ignition ON, engine OFF, command the FPCM Fuel Pump ON with a scan tool and observe the fuel pressure gauge while the fuel pump is operating. Verify the fuel pressure is between 345–690 kPa (50–100 psi).
   • If the fuel pressure is greater than the specified range, replace the fuel tank fuel pump module.
   • If the fuel pressure is less than the specified range, test, inspect, and repair the items listed below. If all items test normal, replace the fuel tank fuel pump module.
   • Restricted fuel feed pipe
   • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections.
2. After the fuel pump is turned OFF, verify the fuel pressure stabilizes between 500–599 kPa (72–87 psi).
   • If greater than the specified range, replace the fuel tank fuel pump module.
3. After the fuel pump is turned OFF, verify the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.
   • If the pressure decreases more than the specified value, perform the following procedure:
   1. Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief.
   2. Install the J 37287 Fuel Line Shut-off Adapter between the fuel feed pipe and the fuel rail.
   3. Open the valve on the J 37287 Fuel Line Shut-off Adapter .
   4. Ignition ON, command the FPCM Fuel Pump ON with a scan tool and bleed the air from the CH-48027 Digital Pressure Gauge .
   5. Command the FPCM Fuel Pump ON and then OFF with a scan tool.
   6. Close the valve on the J 37287 Fuel Line Shut-off Adapter .
   7. Monitor the fuel pressure for 1 minute.
      • If the fuel pressure decreases more than 34 kPa (5 psi) within the specified time, locate and replace the leaking fuel injector(s).
      • If the fuel pressure does not decrease more than 34 kPa (5 psi) within the specified time, replace the fuel tank fuel pump module.
4. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 minutes.
   • If the fuel pressure decreases more than the specified value, replace the fuel tank fuel pump module.
5. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027 Digital Pressure Gauge . The fuel pressure should not drop off during acceleration, cruise or hard cornering.
   • If the fuel pressure drops off, test, inspect, and repair the items listed below. If all items test normal, replace the fuel tank fuel pump module.
   • Restricted fuel feed pipe
   • Inspect the harness connectors and the ground circuits of the fuel pump for poor connections
6. If the fuel system tests normal, refer to Symptoms - Engine Controls.

 

 

Edited February 25, 2020 by newdude

[tlaw91]

I’d be doing a voltage drop test on them there battery cables, which should honestly be a maintenance item in ur year truck.

 

Spec is 200mv or less

 

-GM Tech

 

 

Sent from my iPhone using Tapatalk

 

[danocywg]

On 2/25/2020 at 12:01 PM, newdude said:

 

If you turn the key on you have 56psi If I read this correctly?  What happens if you leave the key on and engine off and watch the gauge for a couple minutes?  Does it hold 56psi?  Does it drop?  

 

Here is GM's test procedure on the fuel system  I bolded a couple bits.  To truly do a couple of the steps, there is the need to bleed air with a proper scan tool that can command the function.  I put the one for trucks with the Fuel Pump Flow Control Module as most every Tahoe/Suburban/Avalanche of that year have one:

 

 

 

He told me that their diagnostic testing showed that the fuel pump was the problem, so they changed it and it hasn't been a problem since they've changed it, at the garage. I get it home and go out 45 minutes later and it STILL hard starts and the smell of fuel is pretty heavy. If there's a silver lining, it doesn't seem to do it ALL the time after the initial start in the morning now, but this is getting ridiculous now.

[newdude]

29 minutes ago, danocywg said:

He told me that their diagnostic testing showed that the fuel pump was the problem, so they changed it and it hasn't been a problem since they've changed it, at the garage. I get it home and go out 45 minutes later and it STILL hard starts and the smell of fuel is pretty heavy. If there's a silver lining, it doesn't seem to do it ALL the time after the initial start in the morning now, but this is getting ridiculous now.

 

You've got fuel odor?  Can you see any sort of leaks anywhere?  What condition are your fuel lines in?  Can you see any fuel leaks anywhere?   

 

Hard starts could come from a bad purge valve too.  If its venting emissions vapors during cranking when its not supposed to  (so valve stuck open) that can cause a hard crank.  Typically you will get an emissions code with a bad valve though, and it might happen only when filling the tank.  

 

I did find this as well but if I read your original post, you already did injectors correct?

 

 

Quote

 

#PIP4450E: Intermittent Extended Crank After A Hot Soak - May Have A Possible Starter Noise As Well - keywords debris dust grind fuel hard idle injector inlet long module no noise pump rail repeat rough starting - (May 20, 2009)

Subject:	Intermittent Extended Crank After a Hot Soak - May Have a Possible Starter Noise As Well
Models:	2007-2009 Chevrolet Avalanche, Silverado, Suburban, Tahoe
	2007-2009 GMC Sierra, Yukon
	with 5.3L E85 Engine (RPO LC9 or LMG)

---

This PI was superseded to revise the title line to reflect a potential starter noise that can occur as a result of the extended crank. Please discard PIP4450D.

---

The following diagnosis might be helpful if the vehicle exhibits the symptom(s) described in this PI.

Condition/Concern:

Some customers may complain of an intermittent extended crank when restarting their engine after a hot soak (typically 30-60 minutes). This may be the result of a fuel injector or fuel pump concern. Typically, no DTCs will be stored upon inspection and if this is related to a fuel injector concern, the technician may notice that the engine starts quicker if they press the accelerator pedal.

 

In some instances, the engine may have a brief rough idle after this occurs. If the engine RPM decreases too much when it is idling rough, the starter could engage again as a result of the smart-start feature described in the latest version of 03-06-03-001. If this occurs, some customers may also comment on a brief starter noise shortly after the vehicle starts.

Recommendation/Instructions:

If this complaint is encountered, perform the Hard Start Diagnosis in SI and repair as necessary. The Hard Start Diagnosis will also link to the Fuel System Diagnosis and Fuel Injector Diagnosis in SI. Typically, one of these procedures will isolate a fuel injector or fuel pump concern if the fuel pressure is obviously low, slow to build, or bleeds down quickly after the fuel pump stops running.

 

If the procedures above do not isolate a cause for this concern because the fuel pressure is not obviously low, is not slow to build, and does not bleed down quickly after the fuel pump stops running, perform the following suggestions:

1. Allow the engine to run until operating temperature is achieved and turn off the engine.
2. As a safety precaution, disable the fuel injectors and ignition coils by pulling the INJ-A and INJ-B fuses in the UBEC.
3. Follow SI procedures to lift up the fuel rail, leaving the fuel feed line connected and all fuel injectors installed.
4. Place card board or a shop towel under all fuel injector tips.
5. Use the Tech 2 to pressurize the fuel system while in the KOEO (key on, engine off) position.
6. Close the hood and allow the engine to hot soak for the period of time described by the customer (typically 30-60 minutes).
7. Open the hood and inspect the tips of all fuel injectors. If a single fuel injector has dripped, or is ready to drip, replace just that fuel injector. If more than one has dripped, or are ready to drip, replace all of the fuel injectors. Cleaning the fuel injectors will not correct this fuel injector concern.
8. Follow SI procedures to reassemble the engine, install the INJ-A and INJ-B fuses, clear any DTCs that may have set as a result of having the fuses removed, and re-evaluate the concern.

Please follow this diagnostic or repair process thoroughly and complete each step. If the condition exhibited is resolved without completing every step, the remaining steps do not need to be performed.

 

 

 

Edited May 27, 2020 by newdude

[danocywg]

I thought there was a leak originally but nothing that can be seen anywhere. After it finally starts, I can smell fuel about 5 seconds after and goes away after a minute or so. On a normal start, I don't notice the fuel smell. I think at this point, I'm going to take it to a dealer and have them do a proper diagnostic on the fuel system. 

[ava]

On 6/1/2020 at 12:42 PM, danocywg said:

I thought there was a leak originally but nothing that can be seen anywhere. After it finally starts, I can smell fuel about 5 seconds after and goes away after a minute or so. On a normal start, I don't notice the fuel smell. I think at this point, I'm going to take it to a dealer and have them do a proper diagnostic on the fuel system. 

did you get a chance to figure this out, i have exactly the same issue with my 2010