Wiring grounds

[jtbonds13]

I just got an 89 EB Bronco II for 500 this weekend. I wasnt expecting no problems from a truck that cost 500. It looks like the PO didnt think ground wires were required so he either cut them or just left them unbolted. What are all the location that grounds are bolted to?

 

[RonD]

You need a large gauge ground wire from battery to block for the starter motor, this is usually the "big" black wire from the battery.
Then a ground "strap", usually, from engine to Firewall.
Some battery cables come with a smaller black wire that will run to frame rail or radiator support panel, or you can/should run a ground wire from engine to frame.

The engine/trans are often isolated from the frame by rubber mounts, as are some body parts like the cab.
So engine, firewall, body panel, and frame should cover you.


Some times the power distribution boxes will have dedicated ground wires or a ground wire that connects to the same location as a smaller wire coming from the battery.

Here are some electrical diagrams.
http://www.therangerstation.com/tech_library/EDiagrams/index.htm

 

[jtbonds13]

Thank you thats exactly what I was looking for. Also on the wiring diagram I can't seem to find the IAT and ECT. I am getting codes from thoes two sensors and I want to check the wiring.

 

[RonD]

The IAT is also called the Air Charge Temperature(ACT) Sensor, both the ECT and the "Air Charge Temperature Sensor" wiring are in diagram 3 of 3 for 3.0/4.0 engines, 2 of 3 on the 2.9l engine.

I believe both of the sensors themselves can be tested with an OHM meter, engine cold and then engine warm tests.

 

[jtbonds13]

Where does the solid organe wire for pin 49 bolt too. Its just hanging out.

 

[RonD]

Not sure if this will help but I found this:

When the 2.9 Liter engine had been around for awhile, I began noticing a recurring problem, particularly on Rangers and Bronco II units with automatic transmissions. There is an orange ground wire that leads from Powertrain Control Module (PCM) pin 49 to the back of the passenger side cylinder head. It should be clamped between the dipstick tube bracket and the head. The circuit inside the PCM depends very heavily on this ground in order to properly read the Oxygen Sensor Signal, and some technicians would forget to reconnect that ground when reinstalling the transmission. Black smoke problems and odd O2 sensor voltages were common with ground loose or disconnected.

 

[jtbonds13]

Thanks that helps a lot.