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Thread: Hard Hot Start With Air Cleaner Installed

  1. #1

    Question Hard Hot Start With Air Cleaner Installed

    My Avenger MPI starts great cold and hot without an air filter installed.
    I installed an air filter it starts good cold but now it's hard starting hot.
    If I take the lid off the air cleaner it starts up with no problem. ???

  2. #2
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    Quote Originally Posted by copter View Post
    I installed an air filter it starts good cold but now it's hard starting hot.
    If I take the lid off the air cleaner it starts up with no problem. ???
    First, ensure the idle speed screw is adjusted to achieve an IAC Position of about 5% at hot idle.
    Remember to perform another TPS Autoset, whenever you adjust the idle speed screw on the throttle body.

    Second, you might need to increase the IAC Parked Position at that engine temperature (Idle ICF). See post #4 below.
    http://forums.holley.com/showthread....7913#post77913 (Related Cranking/Startup Tuning Post)

    Third, in the Holley EFI software (LINK), also look at the Coolant Temperature Enrichment %
    table and the Air Temperature Enrichment % table (both are in the Fuel ICF - Fuel Modifiers).
    The Coolant & Air Temperature Enrichment % tables are active immediately after starting the engine.
    http://forums.holley.com/showthread....6649#post66649 (Coolant Temperature Enrichment % Table Tuning)
    http://forums.holley.com/showthread....7913#post67913 (Air Temperature Enrichment % Table Tuning)

    If Learning has finished self-tuning the Base Fuel Table, you can tune the Coolant Temperature Enrichment & A/F Ratio Offset Tables.
    Usually, the Coolant Temperature Enrichment % & A/F Ratio Offset tables are too rich in the base calibrations.
    In my entire Coolant Temperature Enrichment table, I don't have a value higher than 130%. Everything is 130% (-5°F) to 100% (175°F-220°F).
    In my entire A/F Ratio Offset table (also in Fuel Modifiers), I don't have a value lower than −0.6. Everything is −0.6 (-5°F) to zero (85°F-220°F).
    I reconfigured my coolant temperature axis from -5°F to 220°F (Sensor Scaling/Warnings in System ICF), for more resolution in a realistic range.
    http://forums.holley.com/showthread....ing-Precedence (Additional Enrichment/Modifiers Information)

    Open the Holley EFI software "Help" Contents ("Help" drop down menu), and read "Step-By-Step Beginner's Tuning".
    In Step-By-Step Beginner's Tuning, see the "Idle Fuel vs. Temperature" graphical representation - Figure 8, Section 5.1.
    Under 400 RPM, the ECU only uses the Cranking Timing, Cranking Fuel (lb/hr) & IAC Parked Position % tables.

    EFI Software Help Information/Instructions:
    ‒ On the top Toolbar, click "Help" & "Contents". This opens all Help topics.
    ‒ When navigating the software, click "Help ?", drag it to any parameter and click again.
    ..This automatically opens the definitions for that specific parameter.
    ‒ Tuning information can be read by clicking the F1 key, when you're viewing any screen.
    http://documents.holley.com/techlibr...10555rev17.pdf (Holley EFI Wiring Manual & Diagrams)
    http://documents.holley.com/techlibrary_199r10544.pdf (Holley EFI Help/Instructions Overview)
    http://forums.holley.com/showthread....ents-Read-This! (Initial Checks & Adjustments - Read This!)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  3. #3

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    Danny, I have the street/strip cam tune programmed now. Do you think if I programmed it for the mild street cam it would help?
    The car is street driven only with a hydraulic roller cam with a duration of 244° @ .050". I'm thinking leaning it out with the mild street tune may help.
    What are your thoughts? Thanks.

  4. #4
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    Quote Originally Posted by copter View Post
    Danny, I have the street/strip cam tune programmed now. Do you think if I programmed it for the mild street cam it would help?
    Not likely; most of the starting parameters are the same anyway.

    I'm thinking leaning it out with the mild street tune may help. What are your thoughts?
    First, let's cover the basics:
    http://forums.holley.com/showthread....ents-Read-This! (Initial Checks & Adjustments - Read Steps #1-#6!)

    Second, ensure the fuel pressure is properly adjusted and the "Actual System Pressure" is accurately entered in Engine Parameters.
    With TBI, the Actual System Pressure is measured anytime engine is running (no vacuum reference hose), or key-on/engine-off pump running.
    With MPFI, the Actual System Pressure is measured with the vacuum reference hose temporarily disconnected, or key-on/engine-off pump running.

    Third, how does it fail to start? Just keeps cranking or initially fires, but immediately stalls? See below:

    Starting Issues - initially starts, but stalls immediately after:
    When it stalls, how does it die?
    Quick & clean (quick stall) = too lean*
    Spit & sputter (slow stall) = too rich
    Tune the After Start Enrichment accordingly.
    If engine stalls several seconds after starting, tune the Coolant Temperature Enrichment Table or After Start Decay Rate.
    May also be caused by using the wrong base calibration for the MAP sensor in use (Base Fuel Table excessively lean or rich).
    * If the tune is excessively rich, it can stall immediately after startup, due to flooding (extinguishing) the spark.

    Notes - starts & runs, but potentially could be better:
    If it starts worse, with the throttle cracked open, it's too lean.
    If it starts better, with the throttle cracked open, it's too rich (or throttle blades were closed too far.)
    The Cranking Fuel (lb/hr) & IAC Parked Position % are the "cranking air/fuel ratio". Tune these tables.
    Adjust the idle speed screw on throttle body, to achieve an IAC Position of about 5% at hot idle.
    Some engines start better with more timing while cranking (Cranking Timing in Ignition Parameters).
    Ensure the ignition timing is synchronized: http://forums.holley.com/showthread....ing-Holley-EFI
    Sequentially injected engines will always crank slightly longer for the ECU to receive the cam sync signal.
    The new Quick Start "Fuel Prime Percent" feature works very well, but be careful; too much % will start fine cold, but not hot.

    • You can only tune the Startup Enrichment parameters after the Learning has self-tuned the Base Fuel Table and if the Coolant Temperature Enrichment & A/F Ratio Offset tables are acceptable. This is because the aforementioned parameters & tables are modifiers of the Base Fuel Table. Exception: Cranking Fuel (lb/hr), Cranking Timing & IAC Parked Position %, because they function independently under 400 RPM (or whatever your "Crank To Run RPM" is). FYI: The "Crank To Run RPM" parameter (in Ignition Parameters) is not your actual cranking RPM when starting the engine.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  5. #5

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    The fuel pressure is set at 42 psi. When I start it hot, it fires for a split second, then just turns over until I feather the throttle and it starts.
    It does not stall after it starts.

  6. #6
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    Quote Originally Posted by copter View Post
    When I start it hot, it fires for a split second, then just turns over until I feather the throttle and it starts.
    Then it's too rich. Try decreasing the Cranking Fuel (Startup Enrichment - Fuel ICF) and/or increasing the IAC Parked Position (Idle ICF) at that engine temperature. However, this can only be performed after the Learning has finished self-tuning the idle area of the Fuel Table, which it probably has by now.

    TIP: For most engines, the amount of lb/hr idle fuel (Base Fuel Table +/− Learn Table) should also be a good starting point for the hot Cranking Fuel cells (hot restart).
    This may not apply to non-vacuum referenced fuel pressure regulator applications due to their higher fuel pressure at idle, cruise, light acceleration & deceleration.
    As a result, their lb/hr idle fuel values (Base Fuel Table) are lower in comparison, and since there's no engine vacuum when cranking, the correlation isn't the same.
    Exception: TBI fuel pressure regulators (with injectors above throttle blades) aren't vacuum referenced because the injectors aren't subjected to intake manifold vacuum.
    https://www.vaporworx.com/documentat...re-regulators/ (Vacuum Referenced Fuel Pressure Regulators)
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  7. #7

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    I dropped the Cranking Fuel from 25 to 20, drove it around until it got to 180°, cut it off, and 10 minutes later it fired right up. I'll see what happens in the next few days and let you know if that was the problem. Thanks! Danny, have you ever thought of getting a 1-800 number? LOL!

  8. #8

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    Quote Originally Posted by Danny Cabral View Post
    First, ensure the idle speed screw is adjusted to achieve an IAC Position of about 5% at hot idle.
    Danny, is the 5% adjustment rule true for throttle bodies that already have a orifice through the butterfly plate? My stock LS1 has roughly a 1/8" bypass hole in the plate already.

  9. #9
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    Quote Originally Posted by Thumper28 View Post
    Danny, is the 5% adjustment rule true for throttle bodies that already have a orifice through the butterfly plate? My stock LS1 has roughly a 1/8" bypass hole in the plate already.
    Yes. The engine idles with a specific amount of airflow, whether it has a bypass hole or not.
    May God's grace bless you in the Lord Jesus Christ.

    '78 BRONCO: 508" stroker, TFS heads, 11:1 comp ratio, Dominator MPFI & DIS, cold air induction, Spal dual 12" fans/aluminum radiator, dual 3" exhaust/Magnaflow mufflers, Moroso vacuum pump, Accusump, engine oil & trans fluid coolers, 100HP progressive dry direct-port NOS, A/C, LenTech Strip Terminator wide-ratio AOD/2500 RPM converter, 3:1 Atlas II, modified Dana 44/60-lockers-4.10s, hydroboost/4-disc brakes, ram-assist/heim joint steering, Cage long radius arms, traction bars, 4" Skyjacker lift, 35" mud tires

  10. #10

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    Quote Originally Posted by copter View Post
    I dropped the Cranking Fuel from 25 to 20, drove it around until it got to 180°, cut it off, and 10 minutes later it fired right up.
    I'll see what happens in the next few days and let you know if that was the problem. Thanks!
    Danny, have you ever thought of getting a 800 number? LOL!
    I know it's an old topic, but 20 lbs/hr Cranking Fuel hot seems like a lot, because I've got only 4.5 on mine. Was engine hot, and it fires right up?

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