92 4.0 swap wont run

4x4ranger97 · Jun 26, 2014

Im new to the forums so bare with me. Me and my buddy have been workin on his 1988 Ranger 2.9l to a 92 4.0l swap. We cant get it to start up, and I can usually get a engine start up. The fuel pump is good on it, all the grounds are good. The old ignition coil was getting 3.9 volts, I had an extra one from my 97 4.0 that was getting 12.3 volts on my truck, but got 3.9 on his. but if you put the volt meter straight to the wire for the coil plug in it got around 12 volts. We tried grounding out the grey/yellow wire like yall said in another thread but it didn't do anything. Any suggestions?

SenorNoob · Jun 27, 2014

First: Howdy and welcome to TRS!

Second: HUH?

RangerSVT · Jun 28, 2014

The ignition coil gets its signal from the ECU (ground side), which is a pulsed signal. The power side is 12 volts from an ignition source. Make sure you have 12 volts power when the key is turned on (hot in run and start), not hot all times. If you get 12 volts when key is on, but not when cranking, either your ignition source is dead when in crank mode, or your relay could be faulty....

SVT

RonD · Jun 28, 2014

Yes, there are 4 wires on the Coil pack connector, one will/should have battery voltage(12v) when key is on, this comes from the EEC Relay
EEC relay should click when key is turned on, it powers Fuel Pump Relay(not fuel pump), it powers fuel injectors, it powers computer(EEC, PCM), EDIS-6 module and Coil

The other 3 wires on the coil connector are grounds to fire each coil, there are 3 separate coils in the coil pack, these are only grounds when EDIS-6 module grounds them so no real way to test them live.

The EDIS-6 module doesn't know you are trying to start the engine from key position, it uses a CKP(crank position) sensor for that.
When the crank shaft starts to turn the CKP sensor sends a pulse to the EDIS-6 module, the EDIS-6 reads this pulse and then starts spark.
CKP sensors has 2 wires and is located behind main pulley passenger side, make sure that is hooked up.

'92 4.0l EDIS-6 module is located on the radiator support, could be under battery or on my '94 is is on the FRONT side of the rad support.
It is usually black and has EDIS-6 label on it

Acgallen · Feb 16, 2024

RonD said:
Yes, there are 4 wires on the Coil pack connector, one will/should have battery voltage(12v) when key is on, this comes from the EEC Relay
EEC relay should click when key is turned on, it powers Fuel Pump Relay(not fuel pump), it powers fuel injectors, it powers computer(EEC, PCM), EDIS-6 module and Coil

The other 3 wires on the coil connector are grounds to fire each coil, there are 3 separate coils in the coil pack, these are only grounds when EDIS-6 module grounds them so no real way to test them live.

The EDIS-6 module doesn't know you are trying to start the engine from key position, it uses a CKP(crank position) sensor for that.
When the crank shaft starts to turn the CKP sensor sends a pulse to the EDIS-6 module, the EDIS-6 reads this pulse and then starts spark.
CKP sensors has 2 wires and is located behind main pulley passenger side, make sure that is hooked up.

'92 4.0l EDIS-6 module is located on the radiator support, could be under battery or on my '94 is is on the FRONT side of the rad support.
It is usually black and has EDIS-6 label on it

I believe this is what i have going on, not getting a click of a relay, and no fuel/spark. I swapped my 4.0 into an 85 bronco, how would the relay know when the key is turned? I have the normal red/Lt Blue wire that tells the solenoid when to crank, but what would be responsible for telling the engine harness when key is on?

RonD · Feb 16, 2024

There is a PCM(EEC) Relay in the engine bay, it powers all the engine electrics, computer, spark and injectors, also powers fuel pump relay(not the pump)

In a 1988 Ranger there will be 2, maybe 3 relays on the inner fender by the Starter Relay(solenoid)
Brown relay is the EEC Relay
Green Relay is the Fuel pump relay
Black relay is the WOT relay only found if there was Factory AC

These relays can even be UNDER the engine bay fuse box, like this: https://ww2-secure.justanswer.com/uploads/BR/brimax/2012-11-18_231834_89_ranger_fuel_pump_relay.gif
But I think that started in 1989

EEC relay gets 12volts from a red/light green wire when Key is in RUN(on), also in START
This activates the relay with key on
EEC relay in 1988 may have a 20/30amp fuse in engine bay fuse box OR a fusible Link hooked up to Starter relay post with the battery positive cable, at the EEC relay end that would be a Yellow wire
This is the 12volts that powers the engine electrics when EEC relay is on

Acgallen · Feb 17, 2024

RonD said:
There is a PCM(EEC) Relay in the engine bay, it powers all the engine electrics, computer, spark and injectors, also powers fuel pump relay(not the pump)

In a 1988 Ranger there will be 2, maybe 3 relays on the inner fender by the Starter Relay(solenoid)
Brown relay is the EEC Relay
Green Relay is the Fuel pump relay
Black relay is the WOT relay only found if there was Factory AC

These relays can even be UNDER the engine bay fuse box, like this: https://ww2-secure.justanswer.com/uploads/BR/brimax/2012-11-18_231834_89_ranger_fuel_pump_relay.gif
But I think that started in 1989

EEC relay gets 12volts from a red/light green wire when Key is in RUN(on), also in START
This activates the relay with key on
EEC relay in 1988 may have a 20/30amp fuse in engine bay fuse box OR a fusible Link hooked up to Starter relay post with the battery positive cable, at the EEC relay end that would be a Yellow wire
This is the 12volts that powers the engine electrics when EEC relay is on

Thank you lots Ron! I will do some probing and see where my power is stopping. I added the fuze box from the 92 harness, so i think my relay is bad.

Just checked. Yellow wire is receiving 12 v with key turned but the red/green is only reading 9v. Would that be a grounding issue or something else?

RobbieD · Feb 17, 2024

Acgallen said:
Just checked. Yellow wire is receiving 12 v with key turned but the red/green is only reading 9v. Would that be a grounding issue or something else?

Probably a ground issue. Where is your meter's negative lead when testing?

If meter ground to battery negative post, target wire reads 12V; but if the meter ground is to the engine block and target wire reads much less (like 9V), that would indicate a poor ground path between the battery and engine.

The battery negative post must a good ground path (thick wire/cable) to a minimum of three things: engine, body and frame.

Acgallen · Feb 17, 2024

Acgallen said:
Thank you lots Ron! I will do some probing and see where my power is stopping. I added the fuze box from the 92 harness, so i think my relay is bad.

RobbieD said:
Probably a ground issue. Where is your meter's negative lead when testing?

If meter ground to battery negative post, target wire reads 12V; but if the meter ground is to the engine block and target wire reads much less (like 9V), that would indicate a poor ground path between the battery and engine.

The battery negative post must a good ground path (thick wire/cable) to a minimum of three things: engine, body and frame.

i have all 3 properly grounded together. I just checked the ecm ground and that was good too. I can meter anywhere on my grounds and still get 12.1 v. I have 12v at the fuze, but reading the relay, yellow has 12v, red/green has 9.5v and the black wire is nothing. I also tried jumping yellow to red and still got nothing. Since this is a swap, i only have the fuel pump, eec and ignition fuses . With the key out, green/red still reads 9.5 v

RobbieD · Feb 17, 2024

Acgallen said:
I swapped my 4.0 into an 85 bronco

I had to go back and reread the whole post; the 10 year jump makes it confusing. So this is a 1985 Bronco II, and you're dealing with '85 wiring, right? And the truck originally had a 2.8 motor?

Are your voltage readings on the red/lt green wire with ignition key in "run" or "start"? Some of the earlier trucks have a resistor to drop the voltage in "run".

It sounds like you've looked at the grounds, so we'll rule that out for now.

Acgallen said:
With the key out, green/red still reads 9.5 v

Shouldn't be. Take a look at the ignition switch, the electrical part behind the steering column trim covers, and make sure that the switch is not separating where it's crimped together. While you there, meter the power going into the switch, and coming out of the switch in the different key positions.

Acgallen · Feb 17, 2024

RobbieD said:
I had to go back and reread the whole post; the 10 year jump makes it confusing. So this is a 1985 Bronco II, and you're dealing with '85 wiring, right? And the truck originally had a 2.8 motor?

Are your voltage readings on the red/lt green wire with ignition key in "run" or "start"? Some of the earlier trucks have a resistor to drop the voltage in "run".

It sounds like you've looked at the grounds, so we'll rule that out for now.

Shouldn't be. Take a look at the ignition switch, the electrical part behind the steering column trim covers, and make sure that the switch is not separating where it's crimped together. While you there, meter the power going into the switch, and coming out of the switch in the different key positions.

This is an 85 bronco (2.8) with a 92 4.0 wiring harness in it. Only 85' left is the cab wiring and a few plugs. I am testing the truck in "run" or key turn before actually cranking. I have hooked up my ignition switch wire (Red/Lt Blue) bypassing the safety protocols directly wiring to solenoid. Is that the wire i should be probing? Or should there be a red/green wire on the column that needs to be hooked up to the engine harness? I pulled the fuse to the EEC relay and it read battery voltage when probed. Not sure how, but i think im losing voltage between the fuse and relay.

Let it also be known, the engine cranks well and i have wired a manual switched fuel pump in. So i know fuel is at the rail, just not being injected. There was also no spark at the coil and obviously spark plugs

RobbieD · Feb 17, 2024

Red/Lt Blue should be the "start" wire only. For powering the ignition circuit I would be looking for the Red/Lt Green, at the ignition switch, which shows 12V in "run" and "start".

SenorNoob · Feb 17, 2024

Acgallen said:
Let it also be known, the engine cranks well and i have wired a manual switched fuel pump in. So i know fuel is at the rail, just not being injected. There was also no spark at the coil and obviously spark plugs

Sound like you never got ignition power after the ECU relay. Is there 12v at the ECU Pin1? Also gotta have power on the Red wire after the ECU relay.

Also maybe a dumb question but is the EDIS plugged in? I missed it the first time I tried to start mine after swap.

Acgallen · Feb 17, 2024

SenorNoob said:
Sound like you never got ignition power after the ECU relay. Is there 12v at the ECU Pin1? Also gotta have power on the Red wire after the ECU relay.

Also maybe a dumb question but is the EDIS plugged in? I missed it the first time I tried to start mine after swap.

I do have EDIS connected. The ECU relay at least in my case was 2 red/green wires, 2 yellow/black, and a black/green single wire. The red/green is supposed to trigger the relay during the key cycle, and im not 100% sure but i think it needs 12v to trigger the relay. Im only reading 9v at the plug with the key turned.

Acgallen · Feb 17, 2024

RobbieD said:
Red/Lt Blue should be the "start" wire only. For powering the ignition circuit I would be looking for the Red/Lt Green, at the ignition switch, which shows 12V in "run" and "start".

On the drivers side of the engine harness, there is a male grey 8 pin plug with that red/green wire. Should that be spliced into the column wiring?

92 4.0 swap wont run

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