Jump to content

SierraHD17

Extended engine crank time on my 2017 6 liter

Recommended Posts

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?  

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites

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?

Share this post


Link to post
Share on other sites
Posted (edited)

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.

Edited by SierraHD17

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

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

 

Share this post


Link to post
Share on other sites
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

Share this post


Link to post
Share on other sites

This one's physical alcohol sensor seems pretty bang on.  No such thing as e85 here so the most it sees a swing of is null to 10%.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

Alcohol sensor on a 6.0??

  • Like 1

Share this post


Link to post
Share on other sites

Yeah it's under the cab in the fuel line.  It's not a gmt900 with its inferred bullshit.

Share this post


Link to post
Share on other sites

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

Share this post


Link to post
Share on other sites

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.

Share this post


Link to post
Share on other sites
Posted (edited)

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.

Edited by mjm-1957

Share this post


Link to post
Share on other sites

Maybe it's not related to the tune, but once you dork with it, there's a good chance the dealer will blame it on the tune.  

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now


×

Important Information

By using this site, you agree to our Terms of Use.