EFI Wiring Tips: Proper Ground And Voltage

By: Dan S | 05/06/2014 < Back to Motor Life Home

When installing a Holley or any EFI system to your vehicle, it's imperative to have a proper ground and voltage for the system. The internals of an ECU contain delicate microprocessors and many other components that rely on clean, sound power and ground. Here are some tips from Holley's EFI program engineer Doug Flynn on how to get the proper ground and voltage connections for your EFI system. 

1) Always Connect Directly To The Battery: 
The best place to connect the main power and ground for the ECU is the vehicle’s battery. By connecting the EFI’s main power and ground this way, allows the battery to act as a capacitor which filters the power going into the ECU. The most important part of the wiring process is making sure the proper power and ground supplies for the ECU are clean. If you connect the main power from somewhere else on the vehicle, you run the probability of getting poor ground or “dirty power” into the ECU. This can cause improper ECU operation and worst case scenario can damage the ECU.

2) Connect Using The Proper Battery Terminal Posts:
Batteries are either top post style or side post style. If you have a side post style battery, go to an auto parts store and pick up some adaptors that install the battery cables into the sides of the battery. These will provide a stud to properly mount the ECU power and ground.If you have top post style battery, simply connect the ECU’s power to the positive terminal of the battery and connect the ground to the negative terminal battery. 

3) Run More Than One Ground Wire: 
Running proper grounds from the battery to the engine block, frame and body, is just as important as running the ECU’s main power directly from the battery. Connect the main battery ground to the stock location on the alternator bracket with a star washer and make sure the surface is clean. Run a ground cable from the block to the frame and a ground cable from the body back to the battery. 

4) Use The Correct Gauge Wire: 
It is recommended to use at least a 1 gauge wire from the battery to the block and the block to the chassis and at least 10 gauge wire from the body back to the battery.

5) Use A Volt Meter To Find An Ignition Power Source: 
When wiring fuel injection, you’ll need to find a switched ignition power source. Some people use an old fashioned test-light to find the connecting voltage. The problem with test lights is that they tell you where power is, but not how much is actually available. The better option is to use a volt meter. This will tell you exactly how much voltage you have at a particular source. When putting fuel injection into an older vehicle, it’s common to run into degraded and deteriorated wiring. A volt meter will show you where you have a good, reliable source of 12 volt power that will ensure a smooth running and dependable fuel injection system. 

If you follow these basic tips, you'll eliminate any issues with power and ground for your EFI system, and get more reliable performance for optimum tuning and increased power output. For more information on Holley's bolt-on Terminator EFI systems. By Taylor Vlahos, DS Media

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