Instruction/ maintenance manual of the product 950 Holley
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COMMANDER 950 TOTAL ENGINE MANAGEMENT SYSTEM ELECTRONICS AND FUEL INJECTION MANUAL 199R-10149-5 NOTE: These instructions must be read and fully understood before beginning installation. If this manual is not fully understood, installation should not be attempted.
2 INTRODUCTION ................................................................................................................................................... 4 1.0 TERMS & DEFINITI ONS OF FUEL INJECTION MANAGEMENT SYSTEMS ....................
3 9.0 REQUIRED ADDITIONAL EFI TUNING ......................................................................................................... 36 10.0 ALPHA-N TUNING .....................................................................................
4 INTRODUCTION Thank you for your purchase of the Holley Commander 950 Fuel Injection System. This tuning manual is designed to take all of the guesswork out of tuning your Commander 950. Holley is dedicated to providing products for our customers that not only outperform your expectations, but also are easy to install and tune.
5 Appendix 7 covers the description of fuel injection systems, including : combustion principles and air/fuel ratios, emissions and performance, and engine management systems. These engine management systems consist of: air management, fuel management, and ignition timing management.
6 1.3 Multi -Point Fuel Injection (MPFI) A multi point fuel injection systems meters the fuel to each cylinder individually via the fuel injector located just upstream of the intake valve.
7 1.6 Fuel Injectors There are basically two approaches in delivering the fuel to the engine: • Above the throttle plate as in throttle body injection • In the intake port toward the intake valves as in multi -point injection The fuel injector is continuously supplied with pressurized fuel from the electric fuel pump.
8 § 3 Ball-on-a-stick injector . This metering design is mostly used in the director plate application. The seal is achieved between a conical seat and a spherical plunger. The director plate has the function of metering the fuel and generating the required spray geometry.
9 1.9 Idle Air Control Valve (IAC) The IAC is located in the throttle body of the TBI and MPFI. The valve consists of a stepper motor that adjusts the position of its pintle to vary the bypass air during idle and of idle conditions.
10 1.13 Electric In -line Fuel Pump The function of the electric fuel pump is to deliver pressurized fuel to the fuel injection system. The ECU activates the fuel pump relay to operate the fuel pump when the ignition switch is in the On or start position.
11 1.16 Main Fuel Filter The function of this filter is to eliminate any contaminants after the fuel pump. These are either small enough to pass through the fuel filter of the pump inlet or are generated by the fuel pump.
12 O 2 Sensor Voltage 1.21 Open Loop Open loop defines the engine operation where the fueling level is calculated by the ECU with only the input signals from the throttle position sensor (TPS), from the coolant and/or air charge temperature, and from the manifold absolute pressure (MAP).
13 The Air Temperature Sensor monitors the temperature of the incoming air. This tells the ECU what the outside temperature is and allows the ECU to adjust the fuel for this. The Coolant Temperature Sensor tells the ECU the temperature of the engine and will add extra fuel when the engine is colder, just like the choke on a carburetor.
14 2.1 Speed Density 1. Engine speed (1000 RPM) and manifold pressure from the MAP sensor (38 kPa) are read by the ECU. From these values, it obtains a number from the base fuel map (32). 2. The ECU then looks at the reading from the Air Temperature Sensor and may modify the fuel value.
15 2.2 Alpha-N An Alpha-N system is similar to a speed density EFI system, except that for step 1, the ECU will look at engine speed and the position of the Throttle Position Sensor, instead of the MAP Sensor, to determine the value from the base fuel map.
16 3.0 SKILL LEVEL REQUIRED Installation of the COMMANDER 950 intake system and the ECU requires approximately the same level of skill and experience to replace or service an induction system consisting of a carburetor and conventional intake manifold (as well as basic wiring skills for the installations of the ECU).
17 5.1 Step -by-Step Wiring Harness Installation NOTE: It is advised to leave the battery completely disconnected until the installation of the entire system is completed. 1. ECU MOUNTING – The ECU should be mounted as far away from the ignition box as is feasible (minimum 6”).
18 1. BLACK WIRE - Connect the black wire to a solid chassis ground with the ring terminal provided. The best place to connect is the negative side of the battery. 2. RED WIRE - Connect the red wire directly to the positive side of the battery with a ring terminal provided.
19 Crank Trigger CD Ignition Systems – The Commander 950 can control the timing on any engine that uses a crank trigger (magnetic or Hall effect) and capacitive discharge ignition box.
20 6.3 Software Operation and Navigation The Commander 950 is a Windows-based software. It functions the same as all other windows software. Pull-down menus are selected with the mouse. These are then opened to view the various tables. Software Data Capture – When a window is opened, the software checks for the ECU.
21 Mouse Free Navigating – Often it is easier to not use the mouse when operating a laptop. The C950 software can be operated without the use of a mouse. From the main window, press “Alt” and then the underlined letter of the window or menu you want to open (i.
22 NOTE: There is a vacuum line going to the fuel pressure regulator. This is needed to compensate for vacuum present in the intake manifold. Make sure you always use this vacuum line.
23 Figure 5 Engine Parameters Screen Record your selection in the spaces provided. __________Cylinders – Pick 4, 6, or 8 __________Port Fuel Injection or Throttle Body Injection – Select Multi-Por.
24 9. ¨ SAVE PARAMETERS It is recommended that you save your map to the computer hard drive anytime you make changes, that way you can always go back to a previous version. At this time you should save that map that has the correct engine parameters.
25 Check the following sensor outputs. After each, record the value in the space provided. ¨ __________MAP (Manifold Air Pressure) – The manifold air pressure when the engine is not running should be between about 88 and 94 with the engine not running.
26 8.0 STEP-BY-STEP BASIC TUNING The following is a step-by-step guide to perform basic tuning that will be required with all applications. TIPS: - Tune one parameter at a time. Don’t change things unless you know what they do. - Follow the instructions.
27 2. CHECK TIMING If the ECU is getting an RPM signal, the next best thing is to make sure that the ignition is firing. To check this, connect a timing light to spark plug #1, and make sure that it is firing while it is cranking. If it is, try to see approximately what the timing is on the harmonic balancer.
28 Figure 9 Startup Enrichment Table 4. STARTUP / STARTS AND STALLS If the engine starts and then stalls, it most likely needs more air and/or fuel. There are several areas that may need tuning that relate to fuel. For simplicity’s sake, at this time, we are going to stay in one area, the main fuel map.
29 Figure 11 Example of Fuel Map with Graphical Representation TIP: This red box will move around. Notice where the red box is when the engine starts. If the engine stalls, leave the key on and increase the values in the area where the engine was trying to idle.
30 Figure 12 Spark Map with Engine Idling When the engine is running, the area that it is getting its timing advance from will be highlighted in red. The advance is also shown in the data monitor ( spk adv). With a timing light, check the advance at the crankshaft.
31 Figure 13 Fuel Map Showing Proper IAC Position For more information on how an IAC works, see Appendix 1—Idle Air Control . 7. FUEL MAP TUNING (LOW SPEED) The next step is to adjust the base fuel map. The method used requires that an oxygen sensor is installed and operating properly.
32 Figure 14 Engine Idling with Proper O 2 Mod The number should be about 85 -100 when tuned properly. This means the base map is slightly richer than 14.7:1, which will promote good driveability. If it is over 100 it is lean and if it is less than about 85-90 it is too rich.
33 Figure 15 Example of Smooth Fuel Graph To modify the graph, move the pointer by using the arrow keys. When you want to raise or lower a point, hold the shift key down and use the arrow keys to raise or lower a point one value at a time. Holding the Control (Ctrl) key and using the arrow keys changes the value by 5.
34 GOOD! DRIVE TO ANOTHER AREA ON THE FUEL MAP “O2 Mod” ON THE FUEL MAP IS… LESS THAN 85 MORE THAN 105 SUBTRACT FUEL PULSE WIDTH* AND SMOOTH SURROUNDING CELLS** BRING UP THE SPARK MAP DOES THE E.
35 To tune WOT, find a safe place where the vehicle can be accelerated to legal speeds. Again, you need one person driving and one person tuning and monitoring. Open the main fuel map. The sensor that needs to be monitored carefully is the oxygen sensor voltage output.
36 GOOD! MAKE ANOTHER RUN TO DOUBLE-CHECK TUNING WATCH THE “O2 (V)” VALUE ON FUEL MAP (RED OR YELLOW) LESS THAN 0.75 (GREEN) MORE THAN 0.85 STOP IMMEDIATELY! ADD FUEL PULSE WIDTH IN LEAN AREAS* AND SMOOTH SURROUNDING CELLS STOP IMMEDIATELY! BRING UP THE SPARK MAP DOES THE ENGINE PING? ** NO (GREEN) BETWEEN 0.
37 NOTE: In the idle air control motor, there is simply a valve that lets extra air into an engine. It is used to raise the idle when an engine is cold and to maintain a desired rpm when a vehicle with an automatic transmission is placed in gear. You must set the throttle plates to provide the majority of the airflow at idle to an engine.
38 B. AE Correction vs. Coolant Temperature – The second line down says “AE correction vs. Coolant temperature”. These numbers are to modify the TPS based acceleration enrichment when the engine is colder. Just like the coolant temperature modifiers, a number 110 for example adds 10% more acceleration enrichment fuel.
39 GOOD! MAKE ANOTHER RUN TO DOUBLE-CHECK TUNING. THEN PROCEED TO MEDIUM LOAD TRANSIENT TUING DOES THE ENGINE REV SMOOTHLY? NO RAISE LEFT 6 BOXES OF THE “Pulse Width – Rate of Change of TPS” TABLE 0.
40 DOES THE ENGINE HEISTATE OR STUMBLE? RAISE LEFT 6 BOXES OF THE “Rate of Change of MAP Sensor” TABLE 10 UNITS* YES * Most of the time, fuel pulse width needs to be added to these tables if the engine doesn’t rev smoothly. A lot of fuel needs to be added before the engine stumbles due to too much fuel.
41 3. Spark Advance - The next area that can be reviewed is the spark advance map. The base spark maps provided should provide a good performing baseline but are conservatively low for some applications and may need less for others. Optimizing timing is very important for best idle, peak safe power, and best driveability.
42 Also make sure you listen for engine knock, especially in the peak torque area when you are changing timing. If you drag race, sometimes putting in more timing in the map area where you stage and launch will help 60 foot times.
43 Figure 24 Poor Spark Map at Idle Figure 25 Poor Fuel Map at Idle and Cruise.
44 C. As was mentioned before, another key for best idle is to adjust the throttle plates so the idle air control motor is not open much or at all when the engine is hot and in neutral. To do this, look at the data monitor and the IAC Position. It should read 10-15 with the engine at the programmed desired idle.
45 Desired Idle – The engine idle speed will be controlled by the ECU and can be changed at different temperatures. If the engine is cold, the idle speed will need to be higher than if the engine is warm for best idle stability. These values are very specific to each application.
46 TIP: As a guideline a TPS position that is between 2/3 and 3/4 throttle usually works fine for naturally aspirated engines. This is an important value, but does not need to be exact down to 5 or 10 numbers. A supercharged or turbocharged engine will have this value set much lower.
47 Figure 30 Air and Coolant Temperature Modifier Table Figure 30 shows an example of the coolant temperature enrichment table. With the Commander 950, you enter a number that multiplies whatever fuel value you are using from the base fuel map (based on the RPM and load of the engine).
48 Figure 31 Fuel Map Showing Coolant Mod and Afterstart Mod After Engine Start To tune the Coolant Temperature Enrichment, make sure the vehicle sits overnight to completely cool down. Start the vehicle. If it stalls, start it again. Try to keep it running for a few seconds with the gas pedal.
49 GOOD! START THE ENGINE THE NEXT MORNING TO RECHECK SETTINGS** DOES THE ENGINE STALL IN THE FIRST 2 SECONDS? YES INCREASE AFTERSTART ENRICHMENT 5% AT THAT ENGINE TEMP* ADD 5% MORE COOLANT TEMP ENRIC.
50 Afterstart enrichment is found in “Fuel” and then “Startup Enrichment”. There are three parts of this area that deal specifically with afterstart enrichment. They are: Ø Afterstart Enrichment – Works the same way as the coolant temperature enrichment.
51 a large increase in fuel. This makes the fuel map very uneven. This causes poor driveability that is hard or impossible to resolve with mapping. If this same engine were mapped using speed density operation, this large change in airflow would create a large change in the position of the fuel map.
52 Figure 34 Typical Alpha-N Fuel Map Mapping is the same as speed density from the aspect that the area on the base fuel map that you are obtaining fuel map values from will be highlighted in red. Drive the vehicle at different throttle positions and engine speeds to modify the fuel map as needed.
53 11.0 D ATA LOGGER Figure 35 Main Datalogger Screen The Commander 950 includes a data logger that serves many useful purposes. It can be used for logging runs at the dragstrip or used to analyze data when tuning a vehicle. To start the data logger, first select “File”, and “Log Data”, after the datalogger is opened.
54 After you enter a filename hit “OK”. The “Trigger” screen below (Figure 37) will appear. Figure 37 The trigger screen (Figure 37) allows you to start the data logger immediately or wait for a trigger point. The trigger point is a selectable input such as RPM, TPS, and more.
55 Figure 38 TIP: If more than 5,000 data points are taken, the software will automatically split them up into separate files. 5,000 data points amount to 5-8 minutes depending on the computer. TIP: For example, if you take 15 minutes of data and name the data file TEST, you will have 3 separate files automatically saved.
56 APPENDIX 1 COMPLETE SOFTWARE OVERVIEW Appendix 1 provides a description of all the software functions. It is not intended to describe how to tune an engine, but rather to provide one section that details all the different screens that will be used.
57 DATA MONITOR – Used for monitoring real-time engine parameters Both the Main Fuel Map and Spark Map screens have a readout of real-time engine parameters above the graph.
58 Fuel Graph – This is a graphical representation of the fuel cell values. When properly tuned, the fuel map should be smooth. The graph mode can be used to refine the fuel values into a smoother curve. You will want to view some of the supplied fuel maps to see what a fuel graph should look like once finished.
59 Afterstart Holdoff – These parameters control the number of revolutions the ECU waits before adding the afterstart fuel enrichment. Afterstart Decay Rate – Rather than deleting the afterstart enrichment after the afterstart holdoff period all at once, the ECU allows the user to program the speed of decay.
60 AE of MAP vs. Coolant Temperature (%) – Colder engine temperatures may require different transitional fueling requirements. This table allows the user to tailor the synchronous fueling to the engine temperature.
61 Figure 44 Figure 45.
62 Idle spark control – These parameters allow the ECU to adjust the idle spark timing to control the engine idle speed. This function can be turned on or off. The P term : adjusts the timing to assist in idle stabilization. The D term : compensates for overshoot.
63 Hardware Settings ( Hdwr Settings) Figure 48 Engine Parameters Engine Parameters – Base engine parameters that must be adjusted before the engine is started. Number of cylinders - Select from 4, 6, or 8 cylinders. Only even-fire engines can be used.
64 Inductive Pickup – Use with a magnetic pickup crank trigger. See Appendix 10 for wiring specifics. Ford TFI – Use with Ford TFI electronic distributors. Allows for the Commander 950 to control ignition timing. Requires adapter cable PN 534-139, which is included in Ford 5.
65 Rev. limiter high RPM – At this rpm, the engine will stop injecting fuel to limit the speed of the engine in an attempt to protect the engine from self-destruction.
66 Figure 51 Idle Air Control Desired Idle – The engine idle speed will be controlled by the ECU and can be changed at different temperatures. If the engine is cold, the idle speed will need to be higher than if the engine is warm. This is because the oil will be thick and the friction internal to the engine will be greater.
67 Hot Start Delay – The amount of time the engine will wait before entering closed loop operation when the engine is restarted while still hot. This should be about 30 seconds. RPM to Enter Closed Loop – Any rpm above this point will activate closed loop.
68 Tuning a Race Engine : By far the best way to tune a high horsepower race engine is on the engine dyno. The dyno must provide certain feedback as to the brake specific fuel consumption (BSFC), and/or Air/Fuel Ratio to help initial tuning. Exhaust gas temperatures also provide helpful feedback.
69 1. Fuel Injection Type - In the engine parameters screen, Throttle Body Inj. must be selected for the fuel injection type. 2. TBI Switch – If a TBI system with progressive throttle linkage is used, the following two parameters must be set correctly or significant problems will occur.
70 Appendix 3 Tuning Troubleshooting Engine will not Start There are several different reasons why an engine will not start. - Make sure that the engine is receiving a RPM signal.
71 Engine Hesitates When the Throttle is Applied The following tuning will help alleviate hesitation when the throttle is applied. The flowchart (Figure 21) shows a graphical representation.
72 GOOD! START THE ENGINE THE NEXT MORNING TO RECHECK SETTINGS** DOES THE ENGINE STALL IN THE FIRST 2 SECONDS? YES INCREASE AFTERSTART ENRICHMENT 5% AT THAT ENGINE TEMP* ADD 5% MORE COOLANT TEMP ENRIC.
73 Appendix 4 GENERAL TROUBLESHOOTING Double check ALL wiring connections and system voltages BEFORE replacing components. If you suspect an ECU or component failure, check all other possible problems before replacing a component. CONDITION POSSIBLE CAUSE REMEDY 1.
74 Appendix 5 TESTING AND TROUBLESHOOTING ELECTRICAL COMPONENTS Testing Relays 1 - To test the relays, apply a 12 volt power source to terminal 85 and ground terminal 86. The relay should click. Using an ohm meter, check for low resistance across terminals 87 and 30.
75 3 - Check the voltage on the TPS with the throttle closed. It should be between approximately .3 and .8 volts. While watching the voltmeter, move the throttle lever from fully closed to fully open. The voltage should change smoothly from the idle voltage to 4.
76 Appendix 6 OXYGEN SENSOR EFFECT ON PERFORMANCE The oxygen sensor monitors the exhaust gases and outputs a voltage that corresponds to the air/fuel mixture.
77 Figure 57 O 2 Sensor Voltage Appendix 7 DESCRIPTION OF FUEL INJECTION SYSTEMS Combustion Principles and Air / Fuel Ratios During combustion of any substance a required surface to mass ratio and a correct amount of oxygen must be must be available. In internal combustion engines these requirements are controlled by the fuel management system.
78 80 82 84 86 88 90 92 94 96 98 100 A/F=14.7:1 A/F=12.6:1 A/F=15.4:1 Percent [%] FUEL AIR 93.5% AIR 6.5% FUEL 7.5% FUEL 6% FUEL 74% AIR 92.5% AIR Figure 58 Percent Air vs.
79 Emissions and Performance Internal combustion engines generate power by burning air and fuel mixtures. In gasoline fueled engines, the proportions of air and fuel (air/fuel ratio) are critical for optimum combustion. The quality of combustion is directly related to engine power output and its running characteristics.
80 The volumetric efficiency is a ratio that describes how efficiently the engine acts as an air pump for its size. The volumetric efficiency is calculated by the following equation: Volumetric effici.
81 (lambda sensor) oscillates between rich and lean within a defined operating window. As the O 2 sensor switches, the injector pulse width is adjusted by the ECU until the lambda sensor switches again to the opposite condition.
82 NOTE: If the application requires a static flow rate that falls in between two available injectors always use the next larger injector. For the example above if only 25 Ib.
83 Appendix 9 FUEL PUMPS Fuel pumps produce volume. Fuel pressure regulators make fuel pressure. It is important to understand this principle. An adjustable fuel pressure regulator can be used to raise or lower fuel pressure, if necessary. When doing this, one must ensure that the fuel pump can maintain the needed volume at higher pressures.
84 Appendix 10 WIRING DIAGRAMS Figure 61 : Commander 950 to Ford TFI Ignition Using Ford Computer Controlled Distributor, TFI Module. Figure 62 : Commander 950 to Aftermarket Ignition Using Ford Computer Controlled Distributor, TFI Module. Figure 63 : Commander 950 to GM HEI Using Mechanical and Vacuum Advance 4-Pin Module Distributor.
85 COMMANDER 950 TO AFTERMARKET IGNITION USING FORD COMPUTER-CONTROLLED DISTRIBUTOR, TFI MODULE (COMMANDER 950 CONTROLLING IGNITION TIMING) COMMANDER 950 BLUE/WHITE YELLOW/BLACK TAN/BLACK BLACK (16 AW.
86 COMMANDER 950 TO GM HEI USING MECHANICAL AND VACUUM ADVANCE 4-PIN MODULE DISTRIBUTOR (COMMANDER 950 “NOT” CONTROLLING IGNITION TIMING) COMMANDER 950 INSTALL SUITABLE WIRE TERMINALS WITH PLASTIC.
87 COMMANDER 950 TO AFTERMARKET IGNITION USING GM HEI WITH MECHANICAL AND VACUUM ADVANCE 4-PIN MODULE DISTRIBUTOR (COMMANDER 950 “NOT” CONTROLLING IGNITION TIMING) COMMANDER 950 YELLOW/BLACK DISTR.
88 COMMANDER 950 TO GM HEI IGNITION USING COMPUTER-CONTROLLED DISTRIBUTOR, 7-PIN MODULE (COMMANDER 950 CONTROLLING IGNITION TIMING) COMMANDER 950 BLUE/WHITE YELLOW/BLACK TAN/BLACK BLACK (16 AWG) DISTR.
89 COMMANDER 950 TO GM HEI IGNITION USING COMPUTER-CONTROLLED DISTRIBUTOR, EXTERNAL COIL (COMMANDER 950 CONTROLLING TIMING) COMMANDER 950 QUICK DISCONNECT BY-PASSES COMMANDER 950 TIMING BLUE/WHITE YEL.
90 COMMANDER 950 TO AFTERMARKET IGNITION USING A GM 7-PIN STYLE DISTRIBUTOR AND EXTERNAL COIL (COMMANDER 950 CONTROLLING IGNITION TIMING) COMMANDER 950 QUICK DISCONNECT BY-PASSES COMMANDER 950 TIMING .
91 COMMANDER 950 TO AFTERMARKET IGNITION USING MAGNETIC PICK-UP DISTRIBUTOR (COMMANDER 950 “NOT” CONTROLLING IGNITION TIMING) COMMANDER 950 YELLOW/BLACK GROUND CASE TO ENGINE BLOCK 5 TACHOMETER 0 .
92 COMMANDER 950 TO AFTERMARKET IGNITION USING MAGNETIC PICK-UP CRANK TRIGGER (COMMANDER 950 CONTROLLING IGNITION TIMING) HEAVY RED (+) WHITE BROWN SWITCH ORANGE (+) AND BLACK (-) RED (+) SWITCHED POW.
93 COMMANDER 950 TO AFTERMARKET IGNITION USING HALL EFFECT PICK-UP CRANK TRIGGER (COMMANDER 950 CONTROLLING IGNITION TIMING) HEAVY RED (+) WHITE BROWN SWITCH ORANGE (+) AND BLACK (-) RED (+) SWITCHED .
94 D8 NOSenable NOS1 ECU GND NOT USED NOT USED Injector A Injector B Injector D Injector C D16 D14 D15 D11 D12 D13 D9 D10 B2 NOT USED ECU GND Analog GND EST / SPOUT Bypass Analog GND IPU (-) Park / Ne.
95 D8 NOSenable NOS1 ECU GND NOT USED NOT USED Injector A Injector B Injector D Injector C D16 D14 D15 D11 D12 D13 D9 D10 B2 NOT USED ECU GND Analog GND EST / SPOUT Bypass Analog GND IPU (-) Park / Ne.
96 Points Out Purple/Yellow Analog GND ECU GND Injector C Injector D Injector B Injector A NOT USED NOT USED Analog GND Bypass EST / SPOUT NOS1 NOSenable O2 Sensor signal MAT singnal Battery TPS signa.
97 C6 Bypass NOT USED Injector D Injector C Injector B Injector A O2 Sensor signal Analog GND NOT USED ECU GND NOSenable NOS1 +5 Volt ref NOT USED Analog GND EST / SPOUT Analog GND ECU GND Battery Coo.
98 Holley Performance Products 1801 Russellville Road, P.O. Box 10360 Bowling Green, KY 42102-7360 Technical Service : 1-270-781-9741 Fax: 1-270-781-9772 Email: support@holley.
An important point after buying a device Holley 950 (or even before the purchase) is to read its user manual. We should do this for several simple reasons:
If you have not bought Holley 950 yet, this is a good time to familiarize yourself with the basic data on the product. First of all view first pages of the manual, you can find above. You should find there the most important technical data Holley 950 - thus you can check whether the hardware meets your expectations. When delving into next pages of the user manual, Holley 950 you will learn all the available features of the product, as well as information on its operation. The information that you get Holley 950 will certainly help you make a decision on the purchase.
If you already are a holder of Holley 950, but have not read the manual yet, you should do it for the reasons described above. You will learn then if you properly used the available features, and whether you have not made any mistakes, which can shorten the lifetime Holley 950.
However, one of the most important roles played by the user manual is to help in solving problems with Holley 950. Almost always you will find there Troubleshooting, which are the most frequently occurring failures and malfunctions of the device Holley 950 along with tips on how to solve them. Even if you fail to solve the problem, the manual will show you a further procedure – contact to the customer service center or the nearest service center
