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Thread: Two issues after starting engine on new Holley ECU.

  1. #1

    Smile Two issues after starting engine on new Holley ECU.

    Hello Newbie here: I have two first try issues when starting the engine with the Holley ECU.
    First the engine is being run on an engine test stand (not a dyno). Just for setting up a nice idle and approximate timing tables and good guesstimate fuel tables and such for eventual tuning adjustments on dyno. I'm attempting to see if the Learn feature will retune a base file for this engine that is close enough to get the engine onto the dyno for a safe start to corrective tuning.

    The engine is a 588" big block Chevy with IR stack EFI Kinsler injection.
    The engine is equipped with a 24X reluctor and sensor and a 1x camshaft sensor. The engine is coil on plug LS Firing Order and using LS coils, LS MAP, CTS, ITS, TPS, Holley FPS and Oil pressure sensor, two 2-wire knock sensors and a single Holley Bosch WBO2 sensor and a GM LSx 4-wire stepper motor IAC. The camshaft is a low lash solid roller 256°I-268°E duration at .050" and has .720" I & .740" E valve lift on a 114.5° LSA and is installed straight up no advance or retard. Uses 60 lb/hr Siemens Deka 1V injectors and should when properly tuned be about 900HP @ 7000 RPM and 840 lb/ft of torque.

    My first issue is that the ECU, engine 12 volt & fuel pump relay is powered by a panel switch and a push button operates the starter to start the engine with power switch on. The ECU runs the fuel pump for 5 seconds, but when the engine is started from the push button the fuel pump does not re-energize and the engine idles for about 30-40 seconds until the fuel pressure drops to low and the engine slows,,stumbles & stalls, sometimes backfiring slightly. I assumed that the ECU senses engine start and starts the power back to the fuel pump, but this does not seem to be happening. WHY is the question? With switch on the power stays at the fuel pump relay and at the ECU power to sensors, coils & injectors. So why not also to fuel pump relay output to pump? I rewired a temp 12 volt all the time to the fuel pump relay with the wire from the ECU fuel pump circuit disconnected and started the engine and the engine runs and continues to idle.

    My second issue is that the Holley base calibration I used is for a 500-600 cubic inch big block and the engine will idle at about 750 RPM where I set idle IPO with some hunting 700-800 RPM. The WBO2 reading seems way too fat with reading hovering around 9.0 to 10.0 for an AFR. The TPS has been synced and is at 0% off and at idle and the MAP reads about 70-75 kPa at idle down from its 101 kPa reading when engine is off. The IAC is staying close to 45% and seems to be supplying most of the air with the IR blades nearly shut at 0% TPS. The initial timing for cranking is set at 25° and it pretty much stays close to that when idling. Not being an experienced EFI tuner how should I make some changes to both fuel and timing tables to bring the idle WBO2 readings closer to a 12.5 to 14.0 reading with no engine load that it sees on the test stand? I know this should be accomplished by reducing fuel lbs/hour in the fuel table and possibly using more or less timing in the at the idle RPM areas.

    I know this is not a common EFI engine combination, engine size and intake system, so I know I'm in pretty new uncharted territory here. But I hope to be as good an EFI tuner as I'm engine builder. It's basically an LSx engine with IR injection ON STEROIDS! So any help & learning I can get here on the forum will be greatly appreciated! Thanks, Ray

  2. #2
    Join Date
    Dec 2009

    Default (Initial Checks & Adjustments - Read Steps #1-#6!) (Holley EFI Tuning Tips & Information)
    May God's grace bless you in the Lord Jesus Christ.
    '92 Ford Mustang GT: 385" SBF, Dart SHP 8.2 block, TFS TW 11R 205 heads, 11.8:1 comp, TFS R-Series intake, Dominator MPFI & DIS, 36-1 crank trigger/1x cam sync, 160A 3G alternator, Optima Red battery, A/C, 100HP progressive dry direct-port NOS, Spal dual 12" fans/3-core Frostbite aluminum radiator, Pypes dual 2.5" exhaust/off-road X-pipe/shorty headers, S&W subframe connectors, LenTech Strip Terminator wide-ratio AOD/2800 RPM converter, M4602G aluminum driveshaft, FRPP 3.31 gears, Cobra Trac-Lok differential, Moser 31 spline axles, '04 Cobra 4-disc brakes, '93 Cobra booster & M/C, 5-lug Bullitt wheels & 245/45R17 tires.

  3. #3


    Stack injection is tough to setup because the change in air is huge with a small change in throttle. You may want to consider doing a remote tune session with me. You learn a lot as you watch me do what I have to do to keep the engine happy. and

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