EEC testing

[F300k]

88 bronco2 started truck ran about min, backfired, wouldnt start. i thought it was fuel relay because didnt hear them when i turned the key replaced, still didnt work. i jumped aruond relay pumps worked, wouldnt start no spark. is there away to test eec befor i go buy one? thank you Frank

 

[RonD]

Best thing to do is to use a OBD I scanner to see if EEC is responding, or use the "jumper method" to see if EEC will respond.

The Fuel Pump relay gets its 12v power from the EEC relay, this doesn't turn on the fuel pump relay.
The EEC relay is turned on when the key is in Run or Start position, EEC relay supplies 12v to Fuel injectors and ignition module, along with fuel pump relay.
EEC relay is next to Fuel Pump relay.

The EEC(PCM) uses Grounds to control most systems, not 12v power.
So the fuel pump relay has 12v with key on, but no ground, the EEC connects the ground for 2 seconds when key is first turned on, activating the fuel pumps, then disconnects the ground.

Near the EEC module there will be several Ground points for the EEC, if these are loose or corroded then EEC has no ground to connect to the fuel pump relay.

I would test fuel pump relay socket with key OFF
You should have 1 slot with 12v, that's the power for the fuel pump from a fuse, Black/yellow wire.
Turn key ON, another slot should now have 12v, this is power for the relay from the EEC relay, Red wire.
If no 12v on second slot then check EEC relay.

The Light Blue/orange wire should be the ground wire from the EEC, connect test light to + on battery and to this wire, turn key ON, light should come on for 2 seconds.

The dark green/yellow wire sends the fused 12v power to the inertia switch and then fuel pumps.