2.3L ('83-'97) Help diagnosing bad Ecu

[Shotrod69]

I have a 2.3 93 ranger 2wd.
It has new plugs, wires, coils, fpr, and injectors.
I have tested injector connections, power has 12v going to it and ground has 60 something ohms. I don’t remember the prefix.
With old injectors it still ran rich, would have to drain and fill oil after 350~ miles due to fuel in oil. I assumed it was a stuck injector(s)/bad fpr. I replaced injector with junk yard ones from wrecked ranger. It ran better after doing this. Not by much and plugs 1/4 were getting fouled and plugs 2/3 were staying wet.

after installing new injectors I started the truck. Letting it run for about 30 seconds. It ran very well. So I shut the truck off and buttoned things up. When I went to drive away from the shop it spit and sputtered then died. I assumed I didn’t give it enough gas when I let the clutch out. Not the issue.

now it will barely run for 30 seconds. And after 2 attempts to get it to run for less then a minute, there will be ~1” of fuel on the dipstick. When I was trying to leave the shop I hadn’t checked that. So one of the tests I was trying to do I pulled the fuel pump relay. With less the 5 minutes of driving it had enough fuel in the oil to run and drive on it.

I’ve attached pictures of the ecu board. It doesn’t look like the capacitors are leaking, but in all honesty I know jack squat when it comes to circuits.

 

[RonD]

The 2 capacitors looked OK, but while its obvious when they fail it's not obvious as they fail, lol

You mentioned the FPR, but did you replace it or test it?

You will need to redo your test on injector connectors
Electricity needs a "circuit", a Circle
There is no 12volts(positive) unless there is a 0 volt(negative) for the current to Flow in a circle, a circuit
You can hook a light bulb up to 12v but nothing happens until you also hook it up to a Ground/Negative/0 volt terminal

Unplug all 4 injector connectors
Computer connected
Key on
Use test light or Volt meter on each injector's 2 wire connector, should be 0 volts seen, not 12v or -12v, 0volt, there is no circuit, no circle, no ground

Each injector gets 12v on the red wire with key on
But has NO ground from the computer UNTIL the engine starts to spin, until crank sensor starts to send a timing pulse
So key on
Engine not spinning
Means 0 volts at injector because there is no ground
If there is a Ground from computer, then injectors open and flood the engine

1993 should be Batch fire, which means on a 4cyl engine 2 injectors share 1 ground wire from the computer, so if that 1 wire is shorted to ground then 2 injectors open with key on
If computer "driver" for that 1 wire is bad then 2 injectors open with key on

So after the test if you find 2 injectors shorted to ground, then unplug computer connector and retest those 2 if ground is still there then its a wire issue, if ground is gone then its a computer issue, replace computer, its not repairable
60 ohms would mean partial short to ground
0 ohms is a dead short
50,000+ ohms is no ground, or N/C(no connection)

 

[Shotrod69]

The 2 capacitors looked OK, but while its obvious when they fail it's not obvious as they fail, lol

You mentioned the FPR, but did you replace it or test it?

You will need to redo your test on injector connectors
Electricity needs a "circuit", a Circle
There is no 12volts(positive) unless there is a 0 volt(negative) for the current to Flow in a circle, a circuit
You can hook a light bulb up to 12v but nothing happens until you also hook it up to a Ground/Negative/0 volt terminal

Unplug all 4 injector connectors
Computer connected
Key on
Use test light or Volt meter on each injector's 2 wire connector, should be 0 volts seen, not 12v or -12v, 0volt, there is no circuit, no circle, no ground

Each injector gets 12v on the red wire with key on
But has NO ground from the computer UNTIL the engine starts to spin, until crank sensor starts to send a timing pulse
So key on
Engine not spinning
Means 0 volts at injector because there is no ground
If there is a Ground from computer, then injectors open and flood the engine

1993 should be Batch fire, which means on a 4cyl engine 2 injectors share 1 ground wire from the computer, so if that 1 wire is shorted to ground then 2 injectors open with key on
If computer "driver" for that 1 wire is bad then 2 injectors open with key on

So after the test if you find 2 injectors shorted to ground, then unplug computer connector and retest those 2 if ground is still there then its a wire issue, if ground is gone then its a computer issue, replace computer, its not repairable
60 ohms would mean partial short to ground
0 ohms is a dead short
50,000+ ohms is no ground, or N/C(no connection)

new fpr x2
Injector test was red wire to engine ground that got 12v
Injector test for non-red wire to batt pos or inj pos was 60 or 60k ohms. I don’t remember which, but I’m pretty sure it was 60k ohms.
I would’ve tested while cranking to see what happened but I was by myself.
I will check if removing the computer changes anything in the ground wire

 

[RonD]

You test "the other" wire on an injector, unplugged from injector, to battery Negative, should be HIGH ohms
Then turn key on and test again, should still be HIGH ohms, in the thousands, or N/C, no connection at all