4.0 swap wiring issue

[ratney]

In the process of putting a 4.0 in my 84 b2, I think I must have wired something wrong my injector plug with the key on has both wires testing hot any ideas?

 

[RonD]

What year is the 4.0l?

The red wires on the injectors get power when the EEC Relay closes, when key is on.
So I would test those with key on and key off.

Non-Red wires should be connected to the EEC(PCM) as the control to open injectors, these are grounds when activated.

Depending on the year the injectors could be batch fire or sequential fire.
Batch fire(EFI) would only have 2 "control wires" at the EEC, it fires 3 injectors at the same time.
Sequential fire(SEFI) would have 6 wires to the EEC, one for each injector, I think 1994 was the first year SEFI was used in the Ranger 4.0l

Unplug the EEC connector and see if the non-red wire voltage goes away, if not then there is an issue in the wiring harness.

 

[ratney]

Its out of a 93 explorer. I'll check it this afternoon. Thanks

 

[RonD]

And how are you testing?
With connector off the injector?
With a volt meter or 12v test light?

An injector is just a relay or coil type device, 1 wire wrapped around a core, when power is passed thru the wire it becomes an electro-magnet and pulls open the needle valve to let pressurized fuel in.
So if tested with connector on injector and there is 12v coming in on 1 wire there will be some voltage on the other wire if measured to separate ground, that's just the voltage in the wound up wire, injector coil won't pull open needle valve until the "other wire" is a ground.

 

[ratney]

I tested with wire off and both were hot with a test light when key was on. With key off there was no juice in either.

 

[ratney]

OK Ron I disconnected my EEC and still getting 12vts on both wires with plug off

 

[adsm08]

Unhook the battery and test continuity between the two pins. If it reads low resistance unplug the injector harness from the main harness and try again.

 

[ratney]

If I unplug all injectors, then the red tests hot and the white and tan don't. If I plug one back on they all go back to hot on that side

 

[adsm08]

DURR! Can't believe I missed that one.

You are seeing the power coming out the other side of the other injectors on that bank. You should still be able to see the switched ground if you hook up a dumb light and crank the engine.

I suppose the next step would be to check continuity of the white/tan wire back to the computer.

 

[RonD]

Yes, I said that in Post #4.

The injectors should read about 14 OHMs , so low resistance, if you test voltage with injectors connected you will see voltage on both wires.

 

[ratney]

With all wires off injectors and connector unplugged 0 ohms with any injector plugged in 25 ohms unplugged with connector plugged in 28.8 and 16.6 ohms across pins

 

[RonD]

Injectors are 16.6 ohms on there own, that is within "good" range, I believe range is 11-18ohms.

Never tested the wiring so can't say on that.

I think the '93 explorer 4.0l used Batch fire, I know the '93 Rangers did.
'94 was the first year in the Ranger 4.0l that had SEFI, sequential injectors, so each fired separately just before spark plug fired.

Batch fired systems on a V6 fired 3 injectors at the same time, I believe it was bank fired so drivers side passenger side would alternate.