Installing the Holley Sniper EFI Kit

February 24, 2017 Mike Aguilar Fuel Delivery, Galleries, How-To and Tech Tips, News, Slideshow 1

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Installing the Holley SNIPER EFI Kit

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I’ve been a Holley fan since I could say the word “carburetor” correctly, so it’s no surprise when I say that one of my favorite manufacturers of electronic fuel injection systems is Holley. If you’ve been around long enough to read my article comparing fuel injection and carburetion, you know that for true hot rod looks and sound, I still prefer a high CFM carburetor over fuel injection.

However, Holley’s Sniper Self-Tuning TBI EFI unit kicks all my pro-carb arguments in the teeth. At first glance, it looks like a carb, and stomping on the pedal is going to give you that “secondaries opening WAAAAAAHHHHH!” that a nice four barrel carburetor gives. I took a look at one recently, and now I’m going to tell you about it and then show you how simple it is to install. Basically: If you can install a carb and crimp wires correctly, you can install the Sniper EFI.

Holley’s Sniper EFI Master Kit with Fuel comes with everything you see here.

What Is It?

When buying the Holley Sniper EFI kit, you’ve got two basic options. The first option is to just buy the injector body and the controller with the wiring harness and sensors. This runs in the area of $1000 and has everything you need for a basic install on almost any vehicle equipped with a four barrel carb. I recommend popping for the Master Kit, though. On top of the injector body, wiring, controller, and sensors, it contains stuff to upgrade your fuel system so you can produce power - new universal electric fuel pump, connectors, and filters. This is the way to go if you want to produce power.

The 7-Pin Harness

The injector body looks almost exactly like a carburetor at first glance. It comes in the old style brass satin finish, a shiny gloss finish or a black finish. There’s a three inch color touchscreen controller that mounts in the passenger compartment, where you can see and reach it to control the EFI functions. All told, installation should take you no more than two hours, less than that if you’ve got a friend to help you out.

Gather Tools and Prep for Installation

Refer to this image for assembling the EFI fuel hose to the -AN adapters. You’ll need to do this at both ends of the return line and the EFI side of the supply.

You’ll need plain and Phillips screwdrivers, as well as sockets, ratchets, extensions and wrenches. You’ll also want a pair of wire cutters and a good set of wire crimpers. Don’t use the crappy five dollars crimpers available at parts stores. Spend the extra five to ten bucks to get a quality set of crimpers. You’ll also need a drill and a stepper bit, and a hammer and a sharp brass punch will come in quite handy. Lastly, you’ll need something to test for the presence of voltage, such as a test light or meter.

First, Disconnect the Battery

Block the front wheels and jack up the rear of the car, being sure to use at least one jack stand for safety. Finally, drop and drain the fuel tank. There are usually two straps that secure the fuel tank. If it’s full, use a jack to lower it.

The Holley Sniper EFI Unit has two main wiring harnesses. One of these is a ten-wire harness and the other is a seven wire harness. The ten-wire harness controls advanced functions of the Sniper EFI and will not be used in this installation, but will be addressed in a later How-To piece.

Remove the Air Cleaner and Carburetor

Holley says you should install the fuel line, pump and filters first, but I prefer to start by removing the carb so that you have some leeway with the fuel line. Pull the air cleaner. Remove the fuel line from the fuel inlet on the carburetor and, if it’s a rubber line, pinch it off to keep it from leaking and to keep debris from entering the system. Next, remove and cap any vacuum lines, and then disconnect the transmission kickdown (if there is one) and the throttle cable and move it out of your way. Finally, remove the four nuts that secure the carburetor to the intake manifold and remove the carburetor.

Remove the Throttle and Kickdown

Mount the New Fuel Injection Unit

Make sure the mounting surface on the intake manifold is free of any debris and gasket remnants. Place the gasket over the mounting studs and then set the EFI unit over the studs. Install one washer and nut from the kit on the studs and tighten them in a crossing pattern. The kit also includes studs that you may need to use if the ones already installed aren’t long enough. Attach the throttle and kickdown cables to the EFI unit. You may need to transfer these from the carburetor.

Attach Throttle and Kickdown Cables

Note: The EFI unit must be installed with the pressure regulator on the passenger side and to the rear of the engine.

Connect the Vacuum Lines

Install the Pump and Filters

With the vehicle in the air, remove the fuel outlet line and drain the fuel into gas cans.

Note: If your vehicle already has a high volume/high pressure electric fuel pump, install the pre-filter before this pump and the post-filter after it.

Disconnect Hoses

Remove the Tank

Once the tank is drained, remove the strap(s) securing it and lower it out of the vehicle.

Install the new fuel pump and filters as close as possible to the fuel tank. Make sure to put the pre-filter between the pump and tank. Also, be sure that the pump is below the bottom of the tank and that the directional arrows (inlet and outlet on all three) are properly oriented. Secure all three to the body or frame with the included brackets.

Mount the Pump

Mount the fuel pump somewhere close to the tank, preferably on the frame.

Use a pipe cutter to cut out a section of the hard pipe under the car, just in front of the axle. Use a pipe flaring tool to roll beads into both ends of the resulting lengths of pipe. Clamp a three inch section of fuel line between the pre-filter outlet and the inlet of the pump, then another between the pump outlet and the post filter outlet. Finally, clamp a short section of fuel line to the post-filter and hard line leading to the front of the vehicle.

Install Fuel Pump Block-Off Cover

Locate the mechanical fuel pump on your engine block. Using line wrenches (preferably), remove the hard line fuel connections at the pump and disconnect the low pressure line from the pump. Remove the line/hose between the pump and the old carburetor and as much of the line leading to the fuel tank as you can.

Remove the bolts/nuts securing the mechanical pump to the block and clean the gasket off. Apply a light film of sealant to the block-off cover and install it using the nuts/bolts that secured the mechanical pump in place.

Note: This isn’t a required step. All you have to do is bypass the mechanical pump, although removing it will help gain a horsepower or two due to decreased friction.

Make Fuel and Return Line Connections at the Fuel Tank

Route a section of fuel line from the inlet of the pre-filter to the outlet of the fuel pickup on the tank. Make sure you leave a little slack in the line, but not enough to kink the line when you put the tank back in place. Route a section of fuel line, from the area of the fuel tank pickup assembly, up to the EFI unit. Make sure you avoid pinch points, moving parts and heat sources. Use rubber-covered clamps to secure it every two feet or so to the body or frame of the vehicle.

Connect Pre-Filter and Pump

Remove the pickup/sending unit assembly. Look at the assembly to locate a spot where you can install the return line bulkhead fitting so it won’t interfere with the sending unit float. Use the brass punch to locate the hole and drill a 9/16 hole with the stepper bit. Use a file or rasp to deburr this hole completely. If your sending unit cover isn’t big enough to accommodate the bulkhead adapter, fill the tank with water, then drain and dry it and install the adapter through the side of the tank near the cover assembly. Be sure to keep the filings out of the tank.

Install Return Bung

Install the return line bung in the fuel tank. Rinse and dry the tank well before doing this.

Using the Stat-O Seals (rubberized washers) and nuts, install the return line bulkhead fitting in the pickup assembly. Install a barbed-to-AN adapter by first sliding the collar over the fuel line and then pressing the line onto the adapter all the way, and sliding the collar up until it slides into place next to the adapter. Connect a section of fuel line to the pickup assembly outlet. Reinstall the fuel tank and make the final fuel line connection to the pre-filter, being sure to leave about two percent slack for expansion, contraction, and movement. Be sure you use fuel injection hose and clamps.

Connect the Fuel Supply and Return Lines to the EFI Unit

Clamp an -AN fitting to the EFI side of the both supply and return lines (see image near beginning of article). Route the supply line up to the fuel inlet of the EFI Unit, being sure to avoid pinch points, heat sources, etc. There are three fuel inlets you can choose from on the EFI unit, one at each corner, except the passenger rear corner which has the regulator and return line. Attach the -AN fitting on the line to the inlet on the EFI unit. Route the return line to the passenger side of the EFI unit and connect its -AN fitting to the EFI unit outlet.

Use a Compression Fitting

NOTE: If you must make sharp 90 degree bends while installing the fuel line, you need to use 90 -AN fittings so as to not kink the fuel line. Kinking the fuel line will decrease the fuel volume flowing and decrease the line’s life expectancy. A “sharp 90 degree” is defined as any that causes the fuel line to bend in such a way that the ends of the bend are less than six inches apart.

Install the Oxygen Sensor

Route the oxygen sensor cable from the EFI harness to the rear as far as it will go. Connect it to the O2 sensor and locate a spot on an exhaust pipe to mount it, preferably after the merge. You need it installed so it “sniffs” the exhaust from at least one bank of cylinders, but preferably both, if possible.

Drill a 9/16 inch hole in the exhaust between ten and 45 degrees off the horizontal (this keeps condensate from damaging the sensor). Thread the O2 sensor into the bung and, placing the gasket between the bung and exhaust pipe, hold the bung against the pipe. Wrap the clamps around the bung and ensure the sensor is centered, then tighten the clamps to ensure no exhaust leaks. More recommendable would be to weld the bung to the pipe if you know how and have the equipment.

Install the Coolant Temperature Sensor

Wrap the coolant temperature sensor with Teflon tape or coat the threads with thread sealant of some sort. Locate a suitable spot in the water jacket to install the coolant temp sensor and route the two sensor connector to this location. Remove any plug or sensor from the temp sensor mounting location and install the temp sensor. Connect the harness to the sensor. If you have a temperature gauge, you’ll need to locate the sensor for it elsewhere, as the EFI coolant sensor should be mounted in the intake water jacket for optimal performance.

Route the Wiring for the Touchscreen Control Pad

The touchscreen control pad isn’t an absolute necessity once the EFI is programmed and the vehicle is running, but it does allow you to do data logging and it does look cool in the passenger compartment. Route the harness for it through the bulkhead using a grommet, one of which is supplied in the kit and requires a two inch hole in the bulkhead. The touchscreen should be installed where it is visible and can be safely reached while driving.

Make Ignition and Tachometer Wiring Connections

Connect the seven pin harness to the seven pin connector from the EFI unit and route it towards the battery. Using your test light or meter, locate a power source that is on with the key in both the “Run” and “Start” positions. Connect the pink wire to this source using either a solderless butt splice or by soldering and covering with adhesive heatshrink tubing.

Connect the Tach Lead

Locate the yellow wire in the seven wire harness and route it to the negative side of the coil. Trim the excess. Strip and install a ring terminal from the kit and bolt it to the coil’s negative side. The green and purple wires are only used if you have a Capacitive Discharge ignition box, such as an MSD 6AL. If so, the yellow wire will not be used.

Wire the Fuel Pump

Note: If your vehicle has a high volume/high pressure electric pump, you don’t need to worry about this section except to disconnect it and connect the power wires to the new pump.

Locate the blue wire in the harness and route it towards the fuel pump. Unless you already have an electric fuel pump, you will also need to route a black wire for ground to the pump. Terminate the wires using ring terminals from the kit (heat sealing them with a lighter or heat gun) and connect them to the pump terminals. You can lower the vehicle off the stands now.

Make Battery Connections

Route the black and red wires to the battery negative and positive terminals. Trim them to remove excess length and strip the ends. Install a suitable ring terminal, heat seal it to the red wire and bolt it to the battery positive. If you have a ground wire from the fuel pump, strip it and terminate it and the black wire from the harness in a suitable ring terminal, also heat sealing it, and then connect it to the battery negative cable end.

Mount the Relays

There are two 40-amp relays in the seven-pin harness. One is for main power and the other one, with the blue wire for the fuel pump, is obviously for the fuel pump. These need to be mounted to the inner fenderwells near the battery with self-tapping screws.

Dual Sync Distributor Diagram

Use this diagram if you have a Holley Dual Sync Distributor and external ignition box.

Programming the EFI ECU for Your Engine

Configuring the ECU begins with entering the Config Wizard on the touchscreen.

Once all wiring and fuel connections have been made and the throttle and kickdown cables are connected, it’s time to program the EFI’s ECU for your engine. Turn the key to “Run” and select “Wizards” and the EFI model number you’re installing.

Starting Setup

You will need to enter the following information:

• Number of cylinders
• Engine displacement in cubic inches
• Set target idle (usually around750- 800 RPM)
• Type of cam (Street, strip)
• Power adders being used
• Type of ignition being used

Engine Setup

Start the engine, let if idle for a minute or two, then rev it a few times. I would clean up most of my tools while I let the engine run so the ECU can learn idle parameters.

All Done!

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About Mike Aguilar 388 Articles

Mike's love of cars began in the early 1970's when his father started taking him to his Chevron service station. He's done pretty much everything in the automotive aftermarket from gas station island attendant, parts counter, mechanic, and new and used sales. Mike also has experience in the amateur ranks of many of racing's sanctioning bodies.

1 Comment on Installing the Holley Sniper EFI Kit

bryanmcdougall April 1, 2018 at 11:50 am

Has anyone installed a Holly Sniper EFI on an 85 C4 corvette

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