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07chevy 2500 hd starting issue..please help


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Chevyfreak1
User

Jul 19, 2014, 9:59 AM

Post #1 of 23 (1591 views)
07chevy 2500 hd starting issue..please help Sign In

I have a 2007chevy2500 hd 6.0 it cranks and runs fine when cold but when it gets warm it cranks over 4 or 5 times and I cut key off and it turns over three or four more times and cranks and runs fine mechanics around here are parts changers .I need someoneto chime in that understands engine diagnostics..I have changed and did the following new fuel pump ,fuel pump reg it's built on the pump ac delco. Fuel pump relay .cleaned maf and throttle body. Evap purge solenoid and evap canister and solenoid .just cannot figure out anything else it could be it doesn't throw any codes. I have money but just hate to waste it on parts changing that don't help truck has 60000 miles thanks any help or suggestions would be appreciated


kev2
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Jul 19, 2014, 11:12 AM

Post #2 of 23 (1581 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

 The use of a professiona; scanner is important - we want to see ALL modules.
check fuel pressure - yes I saw you had a new fuel pump. check fuel pressure anyway.

Tell us - is vehicle STOCK? no aftermarket parts ie remote starter or added alarm?


Chevyfreak1
User

Jul 19, 2014, 11:19 AM

Post #3 of 23 (1577 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

I checked it it was a little over sixty with key on. I was wondering if could be crak sensor or something else it runs great I pull my bassboat with no loss of power ..I can't explain it


Chevyfreak1
User

Jul 19, 2014, 12:31 PM

Post #4 of 23 (1566 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

The vehicle is stock ..


Discretesignals
Ultimate Carjunky / Moderator
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Jul 19, 2014, 12:44 PM

Post #5 of 23 (1563 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Was that the fuel pressure when the problem was occurring?





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Chevyfreak1
User

Jul 19, 2014, 12:45 PM

Post #6 of 23 (1559 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Not sure a mechanic was checking it and said it wouldn't hold what should it be off and running


Discretesignals
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Jul 19, 2014, 1:03 PM

Post #7 of 23 (1557 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Key on engine off the fuel pressure should be 50-60 psi.


Quote
Important: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

1. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 minute.






Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.


Chevyfreak1
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Jul 19, 2014, 1:25 PM

Post #8 of 23 (1554 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

He put a airtex pump on it 1st and it didn't fix it I checked pressure then it was dropping 7 psi in 5 min they went back and put a Delphi in it and now its back to its old tricks ..it cranks fine when I first get in it then i drive it for a little bit and cut it off and go to crank again it acts up once it cranks it run fine as far as I can tell...


Discretesignals
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Jul 19, 2014, 1:36 PM

Post #9 of 23 (1551 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

The fuel pressure needs to be verified while the problem is happening.

Those symptoms don't sound like fuel is bleeding back into the tank. If you have delayed starting after the vehicle had sat overnight, that would be a more likely scenario for excessive fuel drain back.

If you still have excessive fuel pressure bleed off when you shut it off, then you might consider something such as a leaking fuel injector.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jul 19, 2014, 1:42 PM)


Chevyfreak1
User

Jul 19, 2014, 1:39 PM

Post #10 of 23 (1547 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Wouldn't the truck smoke real bad if the injector was leaking that is when u start it ..that just what I read somewhere I am not disputing your word I appreciate your input on this matter..


Discretesignals
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Jul 19, 2014, 1:49 PM

Post #11 of 23 (1543 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

You should still make sure you have good pressure when the problem is occurring before checking for the possibility of leaking injectors. Your problem may not have anything to do with the fuel delivery system, but you have to eliminate that before heading in a different direction.



Quote
Wouldn't the truck smoke real bad if the injector was leaking that is when u start it


Depends on how bad it is leaking. If you still had excessive fuel pressure drain off, you could install a shut off valve in place of the fuel filter. Pressurize the system and then close your valve. Watch the pressure and see if it holds in the rail. If it does, that probably eliminates leaking injectors.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jul 19, 2014, 1:49 PM)


Chevyfreak1
User

Jul 19, 2014, 2:58 PM

Post #12 of 23 (1530 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

My fuel filter is built on to fuel pump assembly doesn't have one on the frame rail...could a crank sensor also cause this or a throttle pos sensor without throwing a code.


Discretesignals
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Jul 19, 2014, 3:18 PM

Post #13 of 23 (1527 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

It's possible, but if the crank sensor wasn't working when it got hot, you wouldn't have spark or injector pulse.

You would need to verify cam and crank sensor signals at the PCM using a oscilloscope or graphing multimeter while cranking the engine while the problem was happening to verify signal integrity. You also might be able to watch RPM data on a scan tool data stream to see if the PCM is getting RPM information from the crank sensor.

A TPS sensor wouldn't cause something like that, unless it was showing WOT during cranking putting the PCM into clear flood mode. If it were doing something like that, which is rare, you would see that in the scan tool data stream.





Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.

(This post was edited by Discretesignals on Jul 19, 2014, 3:21 PM)


kev2
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Jul 20, 2014, 4:27 AM

Post #14 of 23 (1506 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

you must exhaust the BASICS before replacing components...
ok vehicle is stock great
fuel pressure is 60psi thats good

what was the result of scan?
lets try a fuel pressure leak down- key on observe pressure rise- key off observe if pressure drops. post results


Chevyfreak1
User

Jul 20, 2014, 6:16 AM

Post #15 of 23 (1497 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Iam going to take it to a mechanic that supposed to be good so everyone says tomorrow. Ill let y'all know what. They say ..if they don't find it I don't know what I am gonna do i just can't understand why it cranks fine first thing then after you let it get up to operating temp it want s to act up cranking ...


kev2
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Jul 20, 2014, 7:43 AM

Post #16 of 23 (1492 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

it will require testing - as mentioned FUEL leakdown is a possibility the procedure was posted-
SCANNING it is a must do with computer controls- not the same as code reading...

A thought - Important- Does this engine have AFM ?


(This post was edited by kev2 on Jul 20, 2014, 7:44 AM)


Chevyfreak1
User

Jul 20, 2014, 7:45 AM

Post #17 of 23 (1490 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Whats that (afv)?


kev2
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Jul 20, 2014, 7:48 AM

Post #18 of 23 (1489 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

AFM = Active Fuel Management
(I corrected typo)


Chevyfreak1
User

Jul 20, 2014, 8:01 AM

Post #19 of 23 (1486 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

I dont think it does thats where it switches from 8 cylinder to 4 cylinder how would u know


kev2
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Jul 20, 2014, 9:14 AM

Post #20 of 23 (1482 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

I would guess the owner would know-
Otherwise the 8th character of the VIN# would ID the engine.


Chevyfreak1
User

Jul 20, 2014, 9:18 AM

Post #21 of 23 (1479 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Its a U if that helps haven't had this vehicle along time


Chevyfreak1
User

Jul 22, 2014, 5:30 AM

Post #22 of 23 (1459 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

ok mechanic just called me back he has had fuel pressure gauge on truck keep in mind new delphi fuel pump key on 55 psi key off pressure starts dropping it probably dropped 7 lbs just in a few minutes ...but how does the truck start good when cold the symptoms only occur after it warms up is the engine in a different start mode when its cold...


Chevyfreak1
User

Jul 25, 2014, 3:36 PM

Post #23 of 23 (1437 views)
Re: 07chevy 2500 hd starting issue..please help Sign In

Can I pull the fuel rail an check for a leaking injector myself ..with the key on and system pressurized






 
 
 






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