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Extended engine crank time on my 2017 6 liter

SierraHD17

By SierraHD17
in Troubleshooting & Recalls

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SierraHD17 Senior Enthusiast

SierraHD17

Posted
Posted

So far it's intermittent which is why I don't want to be bothered with GM..... they are just going to say it's "normal" or "cannot replicate customer condition" unless I do the leg work for them.  So please refrain from the "take it in" comments...... thanks!

 

In recent times every once and a while the truck will crank a lot longer before starting.  Usually it's maybe 2 revolutions and it's running but then this sounds like the direct injected trucks and it will crank 6 or 8 times to get going.  I added fuel pressure to the scanner and it builds 550 kpa and holds it engine off but key on.  However taking it to start it will crank the longer duration before it lights off.  I thought it was only after sitting overnight but I just got it to do it with the truck just running, shut off and then restarted.  The scanner showed normal looking fuel pressure the entire time.  

 

Has anyone else had an issue or is there a TSB floating around for it?  

SierraHD17 Senior Enthusiast

SierraHD17

Posted
  • Author
Posted

For reference this only has occurred since the weather has warmed, not that I think it's related.  This morning the coolant temp when I got the truck to do it was sitting at 50 C or 122 F so it's not a "cold start" issue per say.

Logan Lanfear Enthusiast

Logan Lanfear

Posted
Posted

Well if you have good fuel it must be a spark issue or fuel delivery issue.  How many miles are on the truck?  I had a similar issue when my fuel pump was putting out too much pressure.  Once it does start, does it sputter or does it light right off?

SierraHD17 Senior Enthusiast

SierraHD17

Posted
  • Author
Posted

Truck has under 20000 miles on it.  Fuel pressure drops on engine crank to around 400 kpa which is basically 60 lbs.  It fires normally just sometimes takes longer than others.  Talking with others they are mentioning the cam phaser being out of position on start... but that should set a code which i am not seeing.

bgbdwlf2500 Enthusiast

bgbdwlf2500

Posted
Posted
5 minutes ago, SierraHD17 said:

Truck has under 20000 miles on it.  Fuel pressure drops on engine crank to around 400 kpa which is basically 60 lbs.  It fires normally just sometimes takes longer than others.  Talking with others they are mentioning the cam phaser being out of position on start... but that should set a code which i am not seeing.

DId you go from 87 to E85 recently? only time my truck has acted like that was when I hadn't read the ethanol content correctly

bgbdwlf2500 Enthusiast

bgbdwlf2500

Posted
Posted
5 minutes ago, SierraHD17 said:

Truck runs 94 octane premium and is custom tuned.  Ethanol % is around 11% like it should be with that fuel.

 

gotcha, just a thought as mine had very similar symptoms when it calculated the % wrong

Colossus Senior Enthusiast

Colossus

Posted
Posted

I had shorter crank time when running 91 octane vs 87 octane here at 5000ft.  (would be 93 vs 89 down at sea level) 

4x4Pete Enthusiast

4x4Pete

Posted
Posted

Have yoy tried it with a stock tune?  I doubt it would make a difference but rule it out anyway.  

SierraHD17 Senior Enthusiast

SierraHD17

Posted
  • Author
Posted

It's not tune related considering i have rewrote it and it's been on the truck since I bought it 8 months ago.  It's like the ops at work blaming a plc program lol.... they don't just go bad.  Hasn't done it in a couple days now so who knows what it's problem is or was.

mjm-1957 Enthusiast

mjm-1957

Posted
Posted

If your truck is a 2017 l96 it is flex fuel correct? Read document ID #4518520 . The second paragraph details the fuel delivery system and yours does not have a fuel composition sensor.

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