Hard start

[Angler21]

Please help!!   2008 GMC Sierra. 4.8.  Replaced fuel pump and FSM last year. Replaced evap solinoid last week.  Truck doednt want to start.  Turns over on first try. Then starts on second try.   Could it be a fuel sensor on fuel rail? 

[CamGTP]

Check fuel pressure at the rail with a mechanical gauge, verify that it's within spec per GM. I don't have the spec handy at the moment.

 

If you can prime it twice and it runs first try, that could be a possible pressure issue.

[Angler21]

Thanks.  I will.  Now it’s losing power on hills and service stabilitrac comes on then goes off

[SC Tiger]

10 hours ago, CamGTP said:

Check fuel pressure at the rail with a mechanical gauge, verify that it's within spec per GM. I don't have the spec handy at the moment.

 

If you can prime it twice and it runs first try, that could be a possible pressure issue.

It's right around 50-55 PSI I think.

 

10 hours ago, Angler21 said:

Thanks.  I will.  Now it’s losing power on hills and service stabilitrac comes on then goes off

How does it run once it does start?  Can you disable Stabilitrac and see if that improves anything?

[Angler21]

I can turn stabiltrac off but that doesn’t seem to help 

[riverbanks]

Check tsb 11273b,see if your vehicle is covered

[Angler21]

I think it’s past the 10 years. However I’m going to get ahold of GM and see 

[Angler21]

So the 20 amp fuse doesn’t register as having power   Truck is running. Fuse for fuel pump shows no power but does not look burnt

[SC Tiger]

On 6/27/2019 at 3:15 PM, Angler21 said:

So the 20 amp fuse doesn’t register as having power   Truck is running. Fuse for fuel pump shows no power but does not look burnt

Make sure you have the right fuse.  These things won't run without the fuel pump running.  Easiest way - pull the fuse (with the truck off) and see if will still run.

 

Assuming the pump is good, it might be the fuel pressure regulator.  If I understand the system right, this thing is supposed to balance the fuel delivery based on engine throttle.  A cracked diaphram will make it run rich at idle, but I think a bad spring will cause issues at open throttle.  Replacement (Auto Zone/GP Sorenson) is about $65.

 

Would explain pressure issues.

 

On 6/27/2019 at 1:07 PM, Angler21 said:

I can turn stabiltrac off but that doesn’t seem to help 

Answers that.  Not sure of the modern systems, but older Stabilitrac-type systems worked by reducing power when they detected slippage.