V8 and yes into the harness
V8 yes in the harnessWhat model is this? V8, 4cyl?
Where does it go? Into a harness?
1988 foxWhat year? Usually there is nothing else bolted to that battery/computer ground bolt from the factory. But I have quite a few foxes and if you tell me the year,I'll look.
Lol thanks anywaysThe one year I don't own. Lol. Sorry. I also don't have an 87.
That's the computer ground - check out the stripe color on the wires.What is the ground wire for. Its not the ecu cause if you look the wire bolted behind this one is for the ecu. Thanks
Not the computer ground. The computer ground is behind this wire in the pictureThat's the computer ground - check out the stripe color on the wires.
Grounds
This checklist applies to all Mustangs, not just the EFI equipped cars. Some of the wiring will be different on carb cars and carb conversions
Revised 26 –Oct -2016 to add fuel pump ground to the list.
Grounds are important to any electrical system, and especially to computer controlled engines. In an automobile, the ground is the return path for power to get back to the alternator and battery.
Make sure that all the ground places are clean and shiny bare metal: no paint, no corrosion.
1.) The main power ground is from engine block down by the oil filter to battery: it is the power ground for the starter & alternator.
2.) The secondary power ground is between the back of the intake manifold and the driver's side firewall. It is often missing or loose. It supplies ground for the alternator, A/C compressor clutch and other electrical accessories such as the gauges. The clue to a bad ground here is that the temp gauge goes up as you add electrical load such as heater, lights and A/C.
Any car that has a 3G or high output current alternator needs a 4 gauge ground wire running from the block to the chassis ground where the battery pigtail ground connects. The 3G has a 130 amp capacity, so you wire the power side with 4 gauge wire. It stands to reason that the ground side handles just as much current, so it needs to be 4 gauge too.
The picture shows the common ground point for the battery, computer, & extra 3G alternator ground wire as described above in paragraph 2. A screwdriver points to the bolt that is the common ground point.
The battery common ground is a 10 gauge pigtail with the computer ground attached to it.
Picture courtesy timewarped1972
Correct negative battery ground cable.
3.) The computer's main power ground (the one that comes from the battery ground wire) uses pins 40 & 60 for all the things it controls internally: it comes off the ground pigtail on the battery ground wire. Due to its proximity to the battery, it may become corroded by acid fumes from the battery.
In 86-90 model cars, it is a black cylinder about 2 1/2" long by 1" diameter with a black/lt green wire.
In 91-95 model cars it is a black cylinder about 2 1/2" long by 1" diameter with a black/white wire.
You'll find it up next to the starter solenoid where the wire goes into the wiring harness.
All the grounds listed in items 1,2 & 3 need to bolt to clean, shiny bare metal. A wire brush or some fine sandpaper is the best thing to use to clean the ground connections.
4.) All the sensors have a common separate signal ground. This includes the TPS, ACT, EGR, BAP, & VSS sensors. This ground is inside the computer and connects pin 46 to pins 40 & 60, which are the main computer grounds. If this internal computer ground gets damaged, you won't be able to dump codes and the car will have idle/stall/ performance problems
5.) The O2 sensor heaters have their own ground (HEGO ground) coming from the computer. This is different and separate from the O2 sensor ground. It is an orange wire with a ring terminal on it. It is located in the fuel injector wiring harness and comes out under the throttle body. It gets connected to a manifold or bolt on back of the cylinder head.
6.) The TFI module has 2 grounds: one for the foil shield around the wires and another for the module itself. The TFI module ground terminates inside the computer.
7.) The computer takes the shield ground for the TFI module and runs it from pin 20 to the chassis near the computer.
8.) Fuel pump ground the fuel pump has a ground pigtail the connects to the body under the gas tank. You have to drop the gas tank to see where it bolts to the body.
See http://assets.fluke.com/appnotes/automotive/beatbook.pdf for help troubleshooting voltage drops across connections and components. Be sure to have the maximum load on a circuit when testing voltage drops across connections. As current across a defective or weak connection, increases so does the voltage drop. A circuit or connection may check out good with no load or minimal load, but show up bad under maximum load conditions. .
Voltage drops should not exceed the following:
200 mV Wire or cable
300 mV Switch
100 mV Ground
0 mV to <50 mV Sensor Connections
0.0V bolt together connections
]
Extra grounds are like the reserve parachute for a sky diver. If the main one fails, there is always your reserve.
The best plan is to have all the grounds meet at one central spot and connect together there. That eliminates any voltage drops from grounds connected at different places. A voltage drop between the computer ground and the alternator power ground will effectively reduce the voltage available to the computer by the amount of the drop.
Not the computer ground. The computer ground is behind this wire in the picture
I will check when I get home. When I took the picture that night I looked it over and it looked like it was solid black. But I double check tonight. I say someone must have put a ground there for something.You jumped to conclusions and only provided a partial answer...
What is the stripe color on the two wires?
Both wires are solid black one is 16ga and the other is 12gaYou jumped to conclusions and only provided a partial answer...
What is the stripe color on the two wires?
Guess certain year foxbodys has two more grounds for something or was grounded in different locationsI think I found that pair of wires on my 89gt, it actually is grounded to the inner fender panel below the computer ground and runs into the main harness that enters the cabin. Don't know what it is for yet.
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