Ethanol percentage flex fuel

[gooffeyguy]

Been there, done that.

After you reload the stock tune, go into it and modify parameters and disable DOD and update the tune.

Sent from my SM-G930V using Tapatalk

 

[wsteele]

After you reload the stock tune, go into it and modify parameters and disable DOD and update the tune.

Sent from my SM-G930V using Tapatalk

I am just turning AFM back on, no tune per se.

 

[gooffeyguy]

I just saw that is what you basically did, and not using the diablo tune

Sent from my SM-G930V using Tapatalk

 

[gooffeyguy]

What would turning afm back on help accomplish?

Sent from my SM-G930V using Tapatalk

 

[wsteele]

What would turning afm back on help accomplish?

Sent from my SM-G930V using Tapatalk

It is only speculation on my part that something in the image Diablo loads when they turn AFM off might foul up how the Ethanol calc works. The only thing @kbuskill and I have in common with regard to the Diablo units is we both used them to turn AFM off.

 

[wsteele]

Well I, for one, am convinced. I think this also explains the intermittent extended crank that I sometimes experience.

I went ahead and ordered the fuel pump assembly from RA.

I went with the Delphi, as opposed to the "Genuine GM" because the Delphi comes with a Lifetime warranty as opposed to the Genuine GM's 24 month warranty.

I made sure to order the Flex fuel pump.

I guess time will tell if this was the right move.

Now to convince my son to put it in...

Sorry I missed this post. Did you check pressures at the rail?

I think I will go ahead and find my gauge and check the pressures, but will wait until I hear what happens with your pump swap before I do anything corrective in nature.

 

[kbuskill]

Sorry I missed this post. Did you check pressures at the rail?

I think I will go ahead and find my gauge and check the pressures, but will wait until I hear what happens with your pump swap before I do anything corrective in nature.

I haven't checked pressures at the rail.

I have seen the fuel pressure on the Tech2 and it was always real close to 43.5psi but I never watched it while accelerating hard or anything. I will definitely plug it in and do some observational testing before hand.

After reading the article that James posted, it just makes sense to me now. Knowing that the algorithm takes into account the injectors PWM, that the fuel pressure must be low.

I also have gotten a P1174 that randomly sets once in a while.

Low fuel pressure would also correspond with my truck not starting immediately all the time. Sometimes when I go to start it, either remotely or with the key, the starter motor will engage and the engine will spin over for an extended period of time before actually sputtering to life.

Most of the time the truck fires up almost instantly.

So with having these three symptoms I feel it is probably a safe bet that the fuel pump is on it's last legs. At almost 270k miles it certainly isn't going to hurt anything.

 

[kbuskill]

It is only speculation on my part that something in the image Diablo loads when they turn AFM off might foul up how the Ethanol calc works. The only thing @kbuskill and I have in common with regard to the Diablo units is we both used them to turn AFM off.

In my case I am actually running a custom tune from Lew @ Diablew, not just using it to turn off AFM, although that is one of the features in my tune.

 

[wsteele]

I haven't checked pressures at the rail.

I have seen the fuel pressure on the Tech2 and it was always real close to 43.5psi but I never watched it while accelerating hard or anything. I will definitely plug it in and do some observational testing before hand.

After reading the article that James posted, it just makes sense to me now. Knowing that the algorithm takes into account the injectors PWM, that the fuel pressure must be low.

I also have gotten a P1174 that randomly sets once in a while.

Low fuel pressure would also correspond with my truck not starting immediately all the time. Sometimes when I go to start it, either remotely or with the key, the starter motor will engage and the engine will spin over for an extended period of time before actually sputtering to life.

Most of the time the truck fires up almost instantly.

So with having these three symptoms I feel it is probably a safe bet that the fuel pump is on it's last legs. At almost 270k miles it certainly isn't going to hurt anything.

Reading my shop manual on the subject, it says 50-60psi, so if you are getting 43.5 that definitely is a problem and would call out a pump replacement.

If you happen to be using the Tech 2, could you take note of which menu and section you are at when you are reading the fuel pressure and post it back up? I looked and looked and couldn't find it anywhere. I suspect the 2007 model year doesn't communicate between the PCM and any fuel pressure sensor (maybe an internal sensor in the pump itself that the pump uses) as when I did the "all sensor" read on my dongle scanner, it lists 155 different sensor values, but fuel pressure isn't one of them. The shop manual calls out using a manual gauge on the fuel rail to test pressure, so again, I think the 2007 model year didn't get that ability, which is actually quite surprising giving how important fuel pressure is in an EFI engine.

Anyway, anxious to hear the results of the pump swap. I will check my pressure at the rail with a gauge here in the next day or so and will report the results.

 

[George B]

For the record:
I poked around my Tech2 looking for fuel pressure this morning with no luck either.