Hot start issue- 18 GT w/ Procharger

[turnswrench]

Mine was fixed by moving the maf sensor to the pipe and getting a tune that matches that change.

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[Sawyerjames]

It amazes me that something (so frustrating) cannot be fixed. I'm going to continue to see if my tuner has any input to help

It is quite annoying, especially when you hit a dead end and the tuner you have been working with says they can't do anything. You can argue all you want, but that won't help fix the issue, and being told "it's okay" is not right, when no other car has ever done this and they have all been FI aftermarket (this is the first remote tune I have done though). I think the next option would be going with the GT350 pipe maf location, but I am confused on this as well because Procharger swears that tuners prefer the intercooler location for the best signal but changed to the gt350 pipe with new kits being sent out. I have seen that the pipe has helped some people's MAF issues, so it might be worth the try...

 

[t14mhall]

It is quite annoying, especially when you hit a dead end and the tuner you have been working with says they can't do anything. You can argue all you want, but that won't help fix the issue, and being told "it's okay" is not right, when no other car has ever done this and they have all been FI aftermarket (this is the first remote tune I have done though). I think the next option would be going with the GT350 pipe maf location, but I am confused on this as well because Procharger swears that tuners prefer the intercooler location for the best signal but changed to the gt350 pipe with new kits being sent out. I have seen that the pipe has helped some people's MAF issues, so it might be worth the try...

I agree, annoying for sure. I received an updated revision from my tuner and have full faith that if it's something he can fix via the tune, then he will. If it's design-related, then the choice will be live with it or pay more money for the GT350 pipe.

 

[ProChargerTECH]

Guys,

Its cause the fuel pump doesn't always prime.... (especially after a hot shut down)

Say you drive up to the gas station, pump some fuel, run inside, then come out to drive off.
Chances are the car will not fire the fuel pump again. If your cars check valve has allowed pressure to bleed off, it will stumble.

This can happen with stock cars, or any power adder cars.
It doesn't matter.

A quick log of the low side fuel pressure (before you start the car) will show this.
My car did it brand new off the showroom floor, and actually got a fuel pump replaced under warranty.

Thanks,
Erik Radzins


NOTE: I have also seen some tunes with very incorrect injector data in them, which also causes a big problem. Since hot starts are primarily port injection (cold is DI)

 

[Sawyerjames]

Guys,

Its cause the fuel pump doesn't always prime.... (especially after a hot shut down)

Say you drive up to the gas station, pump some fuel, run inside, then come out to drive off.
Chances are the car will not fire the fuel pump again. If your cars check valve has allowed pressure to bleed off, it will stumble.

This can happen with stock cars, or any power adder cars.
It doesn't matter.

A quick log of the low side fuel pressure (before you start the car) will show this.
My car did it brand new off the showroom floor, and actually got a fuel pump replaced under warranty.

Thanks,
Erik Radzins


NOTE: I have also seen some tunes with very incorrect injector data in them, which also causes a big problem. Since hot starts are primarily port injection (cold is DI)

Great feedback, thanks for sharing Erik. I have been dealing with it for a while now with no other issues. It is hard to replicate, but the way you described it is definitely what I am experiencing. That is wild, I have never had that on any NA or FI car I thought it was maybe a glitch somewhere in the tune, but not worth messing with things because every thing else is spot on...

 

[Bartly]

Guys,

Its cause the fuel pump doesn't always prime.... (especially after a hot shut down)

Say you drive up to the gas station, pump some fuel, run inside, then come out to drive off.
Chances are the car will not fire the fuel pump again. If your cars check valve has allowed pressure to bleed off, it will stumble.

This can happen with stock cars, or any power adder cars.
It doesn't matter.

A quick log of the low side fuel pressure (before you start the car) will show this.
My car did it brand new off the showroom floor, and actually got a fuel pump replaced under warranty.

Thanks,
Erik Radzins


NOTE: I have also seen some tunes with very incorrect injector data in them, which also causes a big problem. Since hot starts are primarily port injection (cold is DI)

It only happens to mine in the summer, never in the winter even if I get on it and get the head temps/engine bay hot. I also believe I hear my pump prime as soon as I push the clutch in before hitting the start button?

Wondering how the pump would only prime properly in the mild winters we have here.

 

[Jay-rod427]

It only happens to mine in the summer, never in the winter even if I get on it and get the head temps/engine bay hot. I also believe I hear my pump prime as soon as I push the clutch in before hitting the start button?

Wondering how the pump would only prime properly in the mild winters we have here.

Just a guess, but I'd bet the fuel prime times out based on time/engine temp. Only after so long, or so cold/cooled off will it prime. Otherwise it thinks it doesn't need to since the engine has ran recently. Especially with return fuel systems it rears its head because the regulator bleeds off all the pressure within 30 seconds or less.

 

[Bartly]

Just a guess, but I'd bet the fuel prime times out based on time/engine temp. Only after so long, or so cold/cooled off will it prime. Otherwise it thinks it doesn't need to since the engine has ran recently. Especially with return fuel systems it rears its head because the regulator bleeds off all the pressure within 30 seconds or less.

Sorta makes sense, I get that it could be something like that. It’s just odd to me that it is drastically different in the winter vs summer, and for winter I’m talking daytime highs 50-60F so not like it’s alaska. The way mine misbehaves in the summer is: first thing in the morning it always starts up perfect. If I get it up to temp and then park it for less than 20-30 minutes it will start perfect, but if i let it sit for an hour or more (even 9 hours sitting in my work parking lot in the sun) it will have the prolonged start/muffled sound. But if I open the hood and let it cool to ambient it will start fine. But come October it will and throughout winter/spring it will work fine and always startup instantly like it should. Temperature definitely has an effect on it.

Not sure how relevant this is to the conversation since mine is a 2016, doesn’t have the extra injection.

 

[Jay-rod427]

Sorta makes sense, I get that it could be something like that. It’s just odd to me that it is drastically different in the winter vs summer, and for winter I’m talking daytime highs 50-60F so not like it’s alaska. The way mine misbehaves in the summer is: first thing in the morning it always starts up perfect. If I get it up to temp and then park it for less than 20-30 minutes it will start perfect, but if i let it sit for an hour or more (even 9 hours sitting in my work parking lot in the sun) it will have the prolonged start/muffled sound. But if I open the hood and let it cool to ambient it will start fine. But come October it will and throughout winter/spring it will work fine and always startup instantly like it should. Temperature definitely has an effect on it.

Not sure how relevant this is to the conversation since mine is a 2016, doesn’t have the extra injection.

Mine's the opposite. The shorter it sits the worse it is.

 

[Bartly]

Mine's the opposite. The shorter it sits the worse it is.

Well that is just strange.

 

[Sawyerjames]

Well that is just strange.

haha I am in the same boat... the best way for me to duplicate is to drive for 20 minutes or so, park at a gas station and turn the car off, run inside to grab coffee or whatever (so maybe three minutes time) and then when I restart the car it stumbles to 500 rpms or less (sometimes the car has shut off) with a real muffled sound and then everything ramps up and it is good to go. It's more of an annoyance I guess, as I have been dealing with it for over 10,000 miles and no other issues. The strange thing is that I did not Procharge the car until after I put 10K miles on it and the car never came close to doing this when I was NA which makes me think it could be tune related or fuel pump boost related. Who knows...

 

[gimmie11s]

Mine does it too... TT car with MAF sensor in the upper IC pipe. Car otherwise runs perfect so i really dont care TBH.

Ive always figured it was fuel bleeding back down into the lines/tank being the car has a return system on e85.

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