Warm Start Problems

[mcsc1]

Updating this.

Replaced fuel pump again since it has a warranty. Didn’t change anything. It was, however, a different looking pump than originally put in.

Swapped MAF from my wife’s Yukon and nothing changed.

When cranking, the dash shows volts going below 12. After firing it sits around 14 or slightly less.

I’m beginning to think it may be a spark issue as I’ve tried everything else and found no leaks. But the 1 thing that I go back to is the “clear flood mode” working sometimes.

 

[Doubeleive]

Updating this.

Replaced fuel pump again since it has a warranty. Didn’t change anything. It was, however, a different looking pump than originally put in.

Swapped MAF from my wife’s Yukon and nothing changed.

When cranking, the dash shows volts going below 12. After firing it sits around 14 or slightly less.

I’m beginning to think it may be a spark issue as I’ve tried everything else and found no leaks. But the 1 thing that I go back to is the “clear flood mode” working sometimes.

my next chioice in the parts cannon would be the fuel pump control module.
you can get them cheap enough (even used) but it will need to be programmed to the vin
it sucks that is only a "warm start" issue as that makes a official diagnosis more difficult, from what I have read it could "maybe" also be the cam position sensor based on it being affected by heat? not sure that could just be another rabbit hole
it could even be a electrical connection somewhere

 

[mcsc1]

my next chioice in the parts cannon would be the fuel pump control module.
you can get them cheap enough (even used) but it will need to be programmed to the vin
it sucks that is only a "warm start" issue as that makes a official diagnosis more difficult, from what I have read it could "maybe" also be the cam position sensor based on it being affected by heat? not sure that could just be another rabbit hole
it could even be a electrical connection somewhere

Thanks for all the suggestions. I too have thought control module but having it programmed to the vin doesn’t sound fun or cheap.

One spark plug smelled like raw fuel where the others all smelled like burnt fuel. So that could be my issue.

We’ve tried checking grounds in the engine bay and cleaned everything up a little. But nothing changed after doing that.

I had thought cam position sensor, but I hate just throwing parts. I’m unable to leave it for more than a day due to needing it for work.

 

[mcsc1]

Also, before getting the AFM turned off I was getting a p3400 code for afm malfunction. May be related, may not be.

 

[Fless]

A cylinder balance test, and an injector balance test, might show an imbalance in the spark or fuel delivery. Even if it's not tested when the issue occurs, one of those might show a weak point.

Also, look at individual misfires with live data to see if one cylinder or bank is acting up.

What do your short- and long-term fuel trims look like?

 

[Doubeleive]

a tech2 would probably be helpful, they pay for themselves in the long run. there is a owners map thread maybe someone near you has one

 

[mcsc1]

A cylinder balance test, and an injector balance test, might show an imbalance in the spark or fuel delivery. Even if it's not tested when the issue occurs, one of those might show a weak point.

Also, look at individual misfires with live data to see if one cylinder or bank is acting up.

What do your short- and long-term fuel trims look like?

Can that be done using a scan tool? If not I may have to rely on a shop to do that as I don’t have the tools for it aside from the scan tool.

 

[Fless]

It will need to be done with an advanced scan tool like a Tech 2 or another with bi-directional capability.

Some scan tools let you look at live data (like misfires) and most will show fuel trims.

 

[Sam Harris]

I may have missed it, but what brand fuel pump did you put in (and replace a second time)? We’ve seen a good amount of non OEM pumps failing out of the box.

 

[j91z28d1]

definitely needs the correct cranking fuel pressure.

put a gauge on it and cycle the. key a few times till pressure comes up and then crank it


we had a truck at work that would bleed down the fuel pressure when off, it would build when primed but take a sec, before that happened if you stated cranking instantly without pausing for a sec to build pressure, it would crank for a long time and then act like it was flooded put once it did start.

the fix was turn the key on, wait a second and then crank. fired every time. from tuning cars, cranking fuel is a bit of a hassle to get right. I guess being a bit low and then flooding it messed it all up. now this was a older truck with a return style system and the ecm doesn't know the fuel pressure like these. so not sure what it would do. but worth a try