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Thread: Hot Start Issue, Any Ideas?

  1. #1
    Supporting Member Turbo Mopar Contributor mcglsr2's Avatar
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    Question Hot Start Issue, Any Ideas?

    I have a 1987 Shelby CSX. The engine has a ported head, mildly ported header, full 3" exhaust, some boost modifications, is using the Mopar Performance ECU originally sold by Shelby, the P4529495 +20% 42lb injectors, adjustable FP regulator set for 25 psi at idle. I live in FL. The car starts right up runs fine most of the time EXCEPT for the following:

    If I'm driving around with the car at operating temperature and do a quick stop (say for gas) on a hot day, the car has a VERY hard time starting. I have to floor the gas and crank forever before it catches. Then after it catches, I have to sit there and nurse the idle for about 2 minutes. Now, if I do the same as above, but instead stop for a longer time (like an hour), the car starts right up without any of the idle hassles. The temperature sensors are all good and there are no trouble codes being set. I think what's happening is that there is too much fuel at hot start up on a hot day because of the larger injectors. Once the car is running and the closed feedback loop programming comes into effect, the ECU is able to reduce the injector pulsewidth and all is good.

    Does anybody have any other ideas or suggestions as to what might be happening and how to reduce or minimize this hot starting problem? I could just go back to the smaller stock T2 33lb injectors but I would rather not as I believe the car needs the extra fuel with the current mods. What do you guys think? And thanks in advance!
    Scott
    87 Shelby CSX #581

    The Car

  2. #2
    turbo addict
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    Re: Hot Start Issue, Any Ideas?

    Sounds like you need to get the fuel pressure back up and then do a custom calibration instead of "off the shelf" LM.

  3. #3
    Supporting Member Turbo Mopar Contributor mcglsr2's Avatar
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    Re: Hot Start Issue, Any Ideas?

    Quote Originally Posted by tryingbe View Post
    Sounds like you need to get the fuel pressure back up and then do a custom calibration instead of "off the shelf" LM.
    Thanks for the reply! Can you elaborate a little on what you mean by back up? Back up to what?

    Any suggestions on who does custom calibrations? Aries_Turbo?

    Any thoughts on what the actual issue is? I presume you are implying that there is not enough fuel present as you are suggesting to raise the fuel pressure?
    Scott
    87 Shelby CSX #581

    The Car

  4. #4
    turbo addict
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    Re: Hot Start Issue, Any Ideas?

    It is my opinion anyone who modify their turbo dodge should learn to do the calibration tuning themselves. The upgraded hardware is no good if the ECU is calibrated/tuned for the wrong hardware.

    The tuning software and calibration software are free.

    http://www.turbo-mopar.com/forums/sh...?45009-MPTuner
    http://www.turbo-mopar.com/forums/sh...or-LM-codebase

    As for tuning hardware, you'll need a socketed LM/SMEC, a Moates Ostrich, and a laptop then you're ready to tune in real time. Plenty of guides made in the last 10 years if you search.

    Stock fuel pressure is 3.8 bar/55 psi. I use a 3 bar / 43.5psi fuel regulator and you use a 1.7 bar / 25 psi. 1.7 bar is simply too low of fuel pressure for your car.
    https://www.enginelabs.com/engine-te...tem-questions/

    You need to get the fuel pressure back up to at least 40psi, then adjust your custom tune.

    In my opinion, using off the shelf ECU or adjusting fuel pressure to tune is out dated and inadequate in today's world. They both should be superseded with custom calibration that is custom to your engine hardware.
    http://www.turbo-mopar.com/forums/sh...+fuel+pressure

    If I was in your shoes, I'd get that based fuel pressure above 40psi, then use MPtune to adjust the custom calibration until I am happy how it runs.

  5. #5
    Rhymes with tortoise. Turbo Mopar Staff cordes's Avatar
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    Re: Hot Start Issue, Any Ideas?

    I might suspect fuel pressure too. 25psi could very well be vapor lock territory for you.

    Actually, are you talking 25psi static, or with vacuum on it? Thatís super low if itís static.

  6. #6
    turbo addict
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    Re: Hot Start Issue, Any Ideas?

    The ECU will adjust fueling +/- 25% you added 20% larger injectors, cut the fuel pressure by over half and then added mods that give you probably 15% more air flow. Turn the fuel pressure back up to 55psi with the vac line disconnected and enjoy. Get a wideband and make sure the wot fuel is ok. I'd guess it to be pretty lean.

  7. #7

    Re: Hot Start Issue, Any Ideas?

    Sounds like the car is rich (clear flood mode to start hot.) Cold you need more fuel so the engine can tolerate extra fuel, but hot it can't.... Once you get it started the O2 sensor feedback is probably leaning out the injectors. Check the the short and long term fuel adapters. I be there negative...

    I would check and see if the fuel pressure regulator is leaking. If you pull the vacuum line off, do you smell or see fuel? Key on and see if any squirts out...

  8. #8
    Supporting Member Turbo Mopar Contributor mcglsr2's Avatar
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    Re: Hot Start Issue, Any Ideas?

    Quote Originally Posted by tryingbe View Post
    It is my opinion anyone who modify their turbo dodge should learn to do the calibration tuning themselves. The upgraded hardware is no good if the ECU is calibrated/tuned for the wrong hardware.

    The tuning software and calibration software are free.

    http://www.turbo-mopar.com/forums/sh...?45009-MPTuner
    http://www.turbo-mopar.com/forums/sh...or-LM-codebase

    As for tuning hardware, you'll need a socketed LM/SMEC, a Moates Ostrich, and a laptop then you're ready to tune in real time. Plenty of guides made in the last 10 years if you search.

    Stock fuel pressure is 3.8 bar/55 psi. I use a 3 bar / 43.5psi fuel regulator and you use a 1.7 bar / 25 psi. 1.7 bar is simply too low of fuel pressure for your car.
    https://www.enginelabs.com/engine-te...tem-questions/

    You need to get the fuel pressure back up to at least 40psi, then adjust your custom tune.

    In my opinion, using off the shelf ECU or adjusting fuel pressure to tune is out dated and inadequate in today's world. They both should be superseded with custom calibration that is custom to your engine hardware.
    http://www.turbo-mopar.com/forums/sh...+fuel+pressure

    If I was in your shoes, I'd get that based fuel pressure above 40psi, then use MPtune to adjust the custom calibration until I am happy how it runs.
    Quote Originally Posted by cordes View Post
    I might suspect fuel pressure too. 25psi could very well be vapor lock territory for you.

    Actually, are you talking 25psi static, or with vacuum on it? Thatís super low if itís static.
    Quote Originally Posted by GLHNSLHT2 View Post
    The ECU will adjust fueling +/- 25% you added 20% larger injectors, cut the fuel pressure by over half and then added mods that give you probably 15% more air flow. Turn the fuel pressure back up to 55psi with the vac line disconnected and enjoy. Get a wideband and make sure the wot fuel is ok. I'd guess it to be pretty lean.
    Thanks for all the replies everybody! And yes, the 25 is NOT static, it's about 40psi with the vac line disconnected. So it sounds like what I need to do is set the FPR, vac line disconnected, to about 55psi and see how things go from there.

    Regarding the custom tune, I don't at all disagree with what is being said about doing it myself, etc. The issue right now is time, as in lack of. So ideally if I can get the car running reliably right now (though maybe not with as much power or efficiency as it could be) that is sufficient. Then later when time is available I can look into getting a tune, creating a tune, etc.

    Also, if it helps anyone here, the car does already have a wideband on it. So if information is needed from that to help address the issue, I can provide it.
    Scott
    87 Shelby CSX #581

    The Car

  9. #9
    turbo addict
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    Re: Hot Start Issue, Any Ideas?

    I had to add 55% more fuel at idle when I added a ported head and tubular header to my car. Everywhere else swapped from about being 10-15% rich to 10-15% lean when looking at the adaptives. So about a 30% change.

  10. #10
    Boost, it's what's for dinner... Turbo Mopar Staff Aries_Turbo's Avatar
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    Re: Hot Start Issue, Any Ideas?

    I can make a base tune file and email it to you based on your engine setup (a bit of an educated guess) but you will need to burn the chip and do the fine tuning.

    I can show you the tables to change and explain the tuning philosophy that works with these ecus.

    Brian

    Quote Originally Posted by turbovanman
    This one is easy, I have myself to blame, I rush things, don't pay attention to gauges when I should, change to much stuff at once then expect miracles, the list is endless.

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