Holley 550-407, Installation Manual, Page: 14 / 54

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12V Switched
– Color = Red/White – Should be connected to a clean +12 volt power source. Power source should only be active when
the ignition is on. Make sure source has power when engine is cranking as well (check with voltmeter). Not all sources apply power when
the ignition switch is in “cranking” position. This wire is located approximately 7” from the ECU connectors.
DO NOT connect to a
“DIRTY” source like an ignition coil!
Refer to Figure 15.
12V Battery
– Color = Red – Should be connected directly to the battery. This powers the fuel pump and fuel injectors. This wire is
protected by a fuse in a sealed fuse holder. The fuse holder is located about 18
” from the ECU connector. A fuse is pre-installed (20A).
12V Fuel Pump
– Color = Green
- Used to directly power a fuel pump (+12 volt). Do not use this wire to power fuel pumps that require
over 15 Amps. For high current pumps, use this wire to trigger a separate relay and use larger gauge wire to feed the pump - 10 gauge is
recommended. The pump that include with
TERMINATOR™ systems draws less than 10 Amps and can be powered directly by this wire.
The fuel pump also requires a ground wire. Run a wire from the negative side of the fuel pump. Connect it to a solid chassis/frame
ground.
Chassis Ground
– Color = Black – Connect to a chassis ground point that has excellent connectivity with both the engine and battery.
This ground should not be connected at the same location as other grounds.
“Coil – ” – Color = Yellow – See section 13.0 below. This is an RPM input wire used for
some applications.
13.0 IGNITION/ENGINE SPEED INPUT
The most important signal for the ECU is the Engine Speed input. It is critical that this is configured and wired correctly or poor
performance will result.
There are 3 engine speed options on the
TERMINATOR™ systems. Each one is wired differently. If these are wired incorrectly, it is
easily possible to permanently damage the ECU so pay close attention to proper wiring. These options are described below and wiring
diagrams are supplied below the descriptions:
OPTION 1
) “Coil -” engine speed input – Use this if:

You are using a stock type mechanical advance distributor with a stock inductive ignition coil. Examples of this would be any
older style points distributor, a 1974-1981 GM large cap HEI.

Do NOT use this input if you are using an aftermarket Capacitive Discharge (CD) ignition system such as a MSD, Mallory, or
others. The ECU will be damaged if you connect to a capacitive discharge type ignition coil.
NOTE: Using this input, the EFI will NOT control the ignition timing of the engine. The timing will be based on the distributor initial,
mechanical, and vacuum advance, just like it did with a carburetor.
OPTION
2) “Tach Out” engine speed input
-

If you are using an aftermarket Capacitive Discharge (CD) ignition system such as a MSD, Mallory, or others, you need to
connect to the “Tach Out” connection or wire these systems provide. This is a 12 volt square wave output.
CAUTION! NEVER, NEVER connect any of the EFI wires to the coil on any CD type ignition system. The ECU will be permanently
damaged!
NOTE: Using this input, the EFI will NOT control the ignition timing of the engine. The timing will be based on the distributor initial,
mechanical, and vacuum advance, just like it did with a carburetor.
OPTION 3 )
“GM Small Cap HEI” Computer Controlled Distributor (Requires Holley Ignition Adapter PN 558-304) –

Small and Big Block Chevy engines can use a small cap GM HEI computer controlled distributor that was available on factory GM
vehicles f
rom the 1980’s through mid-1990’s. This distributor provides an engine speed signal to the EFI, as well as allowing the
EFI to control the ignition timing.
Figure 16 Distributor and Close Up of Distributor
OPTION 4 )
“Ford TFI” Computer Controlled Distributor (Requires Holley Ignition Adapter PN 558-305) –

Ford Sequentially Injected 5.0-5.8L engines from 1987-1995 used this distributor.