I did something stupid. I swapped a 1994 2.3 with a 1999 2.5

[Mike4390]

I have an almost perfect 1994 Ranger body, just needs paint, Absolutely no rust, primer under bed even is perfect. Engine blew. Friend gave me a 1999 Mazda excellent running rust bucket. I am not automotive inclined so I thought I could just swap engines.... Wiring is 60 pin to 106 pin. ooops. Engine installed already. Fuel tank replaced with 99 pump assembly and fuel line with no return. I have engine wiring harness from the 1994 and the 1999. I swapped engine and trans. I added a sensor to exhaust as earlier didn't have one. All was good, then I attempted to figure out front body harness. Now I am in no man's land. Some say it can be done others say no. Engine is same I believe so can I use the engine wiring harness from the 1994 and replace the engine harness on the 99? I am not sure I could find a used engine form a 1994 to even rebuild locally. If it can be rewired is anyone willing to take me step by step through the process? Its a lot to ask. My other option is take it to junkyard as I am poor and was trying to be proactive to get this going before my 1999 Expedition with 300000 miles dies... I have traced where each wire goes and labeled on both power distribution boxes but It leaves me lost as how to go forward. I have no auto experience... another stupid move lol

 

[Ranger850]

Probably going to need the FSM for each truck and do a cross reference.
@19Walt93 or @RonD may be able to help, but you're going to want to get familiar with the "tech library" and the "Articles/Resources" sections located at the top of this page.

 

[RonD]

You need to use the 1999 2.5l Computer and engine wiring harness...................period

Beside fuel pressure issue, the 1994 had separate spark system and hall effect crank sensor
1999 has spark system in the computer and needs a VR crank sensor, there is no "wiring work around" for these which is why you need the 1999 computer and its engine wiring harness

But the 1999 engine wiring harness should be plug and play on the 2.5l engine, and then plug it into 1999 computer
Computer just needs 12volts and Ground, same as 1994 computer, so wires are there in the main harness

There are only 2 relays involved with engine and computer
PCM relay in engine fuse box
Fuel pump relay, in engine fuse box
Used in 1994 and 1999

As the wire colors can change year to year there can be no "step by step wiring" for this swap unless someone else has done this exact swap(1994/1999) and documented it

But assuming 1999 2.5l computer and engine wiring harness there are probably less than 10 wires that need to be spliced

Manual or automatic transmission?

 

[Mike4390]

I have the FSM for each truck, Just ignorant on procedure

 

[Mike4390]

How do I add a VR crank sensor to my 1999 2.5 or is it already there? Its a manual trans

 

[Mike4390]

Ok I spoke to soon. I found the VR crank sensor. I used engine wiring harness and it hooks to battery and then to power distribution box. I get no response from key in start position. I get power to the fuses in PDBox. There is power to pcm. Am I missing something? Would someone be willing to tell me what 10 wires need to be spliced? I will find color changes and match them up. I am just frustrated with my inexperience.

 

[RonD]

PCM/EEC relay in 1994 engine fuse box has 4 wires
Like all relays there are 2 activation wires(12v and ground) and 2 "power wires" 12v IN and 12v OUT, high amp side

PCM relay activation side has ground all the time, turning key on gives it 12v so it closes
12v IN wire has its own fuse always has power
12v OUT wire runs to PCM 12v in wires, should be 2, but it also sends 12v to the fuel injectors and most engine solenoids

Fuel pump relay is a little different in that its activation side gets 12v from PCM relay when its on, but has no ground
The PCM has a wire that grounds the fuel pump relay, pin 80 on PCM, I show light blue/orange wire
It only grounds it(activates fuel pump) for 2 seconds with key on, then grounds it full time once engine starts

10 was not a magic number, lol, just saying there won't be that many wires to splice in the harness

Look in the 1999 FSM at the PCM relay
And in the 1994 FSM

 

[Mike4390]

I understood there could be more or less than 10 wires. My ignition key doesn't react with relay because I believe the relay is in engine fuse box. Should I splice the b/r wire that used to go to sidewall solenoid to the solenoid in the engine fuse box?

 

[RonD]

All engine system relays are in engine bay fuse box, all 2 of them, lol

Only relays in cab are for lights, power windows, door locks, ect............nothing to do with engine

Don't have an FSM for either, what I do have doesn't show brown/red wire for either relay

 

[RonD]

If you mean Red/blue wire on Starter relay on engine bay inner fender, that's just for activating starter motor, separate system from engine wiring
Should be left as is

 

[Mike4390]

I wont be using the relay on fender with new power distribution box will I? I thought blue/red wire from key will be directed to relay in Power dist box.

I have a yellow with green stripe wire going from the starter relay in the 1999 power distribution box and I dont know where it goes and its disconnected. any one know?

 

[RonD]

If you are using the 1999 engine fuse box then no, starter relay was in the engine fuse box

And it did use a Tan/red wire to activate that relay, so brown/red
Its from the Clutch pedal switch, but a Pink wire on the clutch switch in 1994(or red/blue), changes color at the firewall connector I believe
So if 1994 firewall connector then you would splice the tan/red(1999) to the red/blue(1994)
And starter should activate with key turned to START, 2.5l doesn't have PATS(it disabled starter relay)

1994
Ignition switch-----(red/blue)------clutch switch-----(pink)-----//------(red/blue)---------------starter relay

1999
ignition switch----(red/blue)---fuse 24----(white/pink)---clutch switch----(pink)----//---tan/red---starter relay

// = firewall

A fuse was added in 1999 but not really needed

 

[Mike4390]

Many thanks Ron, If the tan/red wire goes to starter solenoid and then another tan/red goes through 42 pin connector to starter relay? what other wires go to relay in power dist box?

 

[RonD]

Starter Solenoid is on the starter motor in 1999(well 1994 as well, lol)

So in 1994 there is a red/blue on inner fender starter relay
That wire would be spliced to the tan/red wire going to starter relay in 1999 engine fuse box

1999 then has a Yellow/blue wire that runs from that starter relay(in fuse box) to the starter motor solenoid, "S" terminal, small one

 

[Mike4390]

coming out of the relay in the power dist box on 1999 is as we spoke a yellow wire with power at all times with key on, then a yellow with blue stripe to starter solenoid on starter. I have a small black wire coming out of rely. Can I assume its a ground? Where would it normally be grounded in the power dist box? or could it be something else? I have no anti theft so its ground?