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Slow and Sluggish Start 2015 Silverado 2500HD

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SilveradoNewbie New Member

SilveradoNewbie

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Hoping to get some help. The dealership has been no help. About two months ago my gas 2015 2500HD started to start kind of sluggish. Overtime it would crank longer and longer when cold. Got to the point where it was taking 5+ seconds to fire up. Went to the dealership and after $110.00 they told me my throttle body plate was loose. They guy insisted if I didn't fix it ASAP it could break off and ruin my engine. After taking it home I removed the throttle body, which was indeed loose, cleaned, tightened and put it back on. I did notice as I shook the plate there was zero carbon build up where it used to sit on that middle rod. I used that as a guide when tightening it back up. Obviously that didn't fix the problem. I'm not even 100% sure it was loose before I went to the dealership but there is more to that story. I'm still in the same place with the long cranks, however about a week ago I did find a solution to alleviate the problem. I noticed if I turned the key on then back off a couple times before I start the engine it fires up right away every time. Does anyone know what could cause this? Thanks

Edited by SilveradoNewbie
CamGTP Senior Enthusiast

CamGTP

Posted
Posted (edited)

When you turn the key on and off like that, you are running the fuel pump through it's prime cycle. The more you do it the better your fuel pressure is likely getting.

 

Hook up a fuel pressure gauge to the fuel rail, the first prime of the system should already get you above 50psi and it should stay there without bleeding back to nothing right away. If you hook it up, prime it and only get 20-30psi that is an issue. Then after say 2-3 primes it reaches 50+ psi, I'd say you've found part of your issue.

 

I would do this test first as it's cheap or free if you own  a fuel pressure tester.

Edited by CamGTP
TRKLGND Enthusiast

TRKLGND

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Are you using E85?  That can cause extended cranking times when cold. It did on my 2017 2500HD 6.0L.

SilveradoNewbie New Member

SilveradoNewbie

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2 hours ago, paracutin said:

Are you using E85?  That can cause extended cranking times when cold. It did on my 2017 2500HD 6.0L.

I'm not using E85. I was actually going to try it but it didn't make a lot of sense economically. How did it go for you?

 

3 hours ago, CamGTP said:

When you turn the key on and off like that, you are running the fuel pump through it's prime cycle. The more you do it the better your fuel pressure is likely getting.

 

Hook up a fuel pressure gauge to the fuel rail, the first prime of the system should already get you above 50psi and it should stay there without bleeding back to nothing right away. If you hook it up, prime it and only get 20-30psi that is an issue. Then after say 2-3 primes it reaches 50+ psi, I'd say you've found part of your issue.

 

I would do this test first as it's cheap or free if you own  a fuel pressure tester.

Thanks! I actually have a fuel pressure tester so I'll try that throughout tomorrow when I start up. I'll let you know how it goes. 

TRKLGND Enthusiast

TRKLGND

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Posted (edited)
13 hours ago, SilveradoNewbie said:

I'm not using E85. I was actually going to try it but it didn't make a lot of sense economically. How did it go for you?

 

I'm in central Illinois.  For me, the price difference between E10 and E85 had to be about .60/gal for it to be cost effective.  Even then, running E85 means more frequent fill-ups and my time is worth something.  I did not notice any more power (the power difference in my 1500 with the 5.3 was noticeable) but the idle was smoother.  The truck just seemed to run better.  For that reason I ended up using it even when it was not really cost effective.  It actually ran better on E85 than 91 or 93 octane.

Edited by paracutin
  • 1 year later...
brewguy101 Enthusiast

brewguy101

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On 10/9/2019 at 3:45 PM, SilveradoNewbie said:

Hoping to get some help. The dealership has been no help. About two months ago my gas 2015 2500HD started to start kind of sluggish. Overtime it would crank longer and longer when cold. Got to the point where it was taking 5+ seconds to fire up. Went to the dealership and after $110.00 they told me my throttle body plate was loose. They guy insisted if I didn't fix it ASAP it could break off and ruin my engine. After taking it home I removed the throttle body, which was indeed loose, cleaned, tightened and put it back on. I did notice as I shook the plate there was zero carbon build up where it used to sit on that middle rod. I used that as a guide when tightening it back up. Obviously that didn't fix the problem. I'm not even 100% sure it was loose before I went to the dealership but there is more to that story. I'm still in the same place with the long cranks, however about a week ago I did find a solution to alleviate the problem. I noticed if I turned the key on then back off a couple times before I start the engine it fires up right away every time. Does anyone know what could cause this? Thanks

Did you ever find the cause of this problem?

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