What to do about 91 harness in a non mustang application.

[BK_CAULEY]

What to do about 91 harness in a non efi mustang application.

want to use an old 91 harness i have to put a EFI 302 in a 81 mustang. and my question is what do i need to do to accomplish this. i see people running them in classics all the time, but whta are they doing to connect power to the ECU.

As far as i know (depending on year of harness) the brown 8 pin connector or black/grey that plugs up to the dash harness on the drivers side sends the power to the ECU and coil and so forth. so how are people using them in older applications to use a stock harness and ECU?

If im not making myself clear please let me know.

Im using these as guides but am stumped.
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

it looks like pin 30 is gonna be a bit of trouble.

 

[BK_CAULEY]

so no one has ever seen or heard of anyone using a 5.0 harness in classic or anything?

 

[jrichker]

Pin 30 is the safety circuit that prevents the key On Engine Running diagnostic from running if the car is in gear or the clutch is not depressed. It checks to see that the transmission is in Neutral or the clutch depressed (T5, T56, Tremec 3550 & TKO)). This prevents the diagnostics from being run when the car is driven. Key On Engine Running test mode takes the throttle control away from the driver for several tests. This could prove hazardous if the computer was jumpered into test mode and then driven.

 

[BK_CAULEY]

sp how do i get power to the ecu to do it then? doesnt it recieve power through the dash harness.

 

[jrichker]

Diagram courtesy of Tmoss & Stang&2birds

See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring Mustang FAQ - Engine Information Everyone should bookmark this site.


Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif

Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif

Complete computer, actuator & sensor wiring diagram for94-95 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/94-95_5.0_EEC_Wiring_Diagram.gif

Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg

HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif

TFI module differences & pinout
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif

Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif

AutoZone wiring diagrams

For 79-88 model Mustangs
AutoZone.com | Vehicle Selection - Year

For 89-93 model Mustangs
AutoZone.com | Vehicle Selection - Year

For 94-98 model Mustangs
AutoZone.com | Vehicle Selection - Year

For 1999-2005 model Mustangs
AutoZone.com | Vehicle Selection - Year

 

[Teddyzee]

Posted in error, cannot delete.

 

[BK_CAULEY]

Posted in error, cannot delete.

haha, thanks for the reply in the other thread though.

 

[BK_CAULEY]

Manual transmission setups source ground for the "in-neutral" signal from the SIGRTN ground circuit..... and automatic transmission setups source ground for the "in-neutral" signal from the starter solenoid-to-fenderwell ground.

i dont recall any grounds from the starter solenoid? can you be a little more specific. im trying to get this mess straightened out here.

so if i have an a9p where do i send the pin 30 wire to? i got that if i have an a9l i can just loop it to pin 46 and call it a day. and does the connector #39 have to be hooked up in any kind of way? its just dangling there and im not sure of it.

 

[liljoe07]

What is it that your trying to do?

What Transmission are you going to be running?

What ECM are you using?

 

[liljoe07]

Connector 39 needs to be hooked up, if not the VSS and 02 and Fuel pump wont operate

 

[BK_CAULEY]

It will be going into a 84 carbed car. im trying to convert it to efi. and using a a9p. and i will be using a t-5. i figured it was going to the fuel pump. im not worried about that that going to be wired seperate anyways. im not worried about the VSS either. 02's yea... so what do i need to do about it. i dont see a plug for it on the 84. so what do i need to connect from it and to where?

 

[liljoe07]

This is going to be an adventure.

With the T-5 all you need to do is ground PIN 30. This will make the ECM think its in Neutral. No problems there....It doesnt harm anything.

As far as the VSS....you need it, or else you wind up with some stalling. So it will need to be wired in by hand, same for the 02's. You can run power to the O2's by hand, but it needs to be on a 12v switch source. The actual signal wire for the 02 will need an 02 harness from a manual car, that way it just plugs into the ECM main harness.

How far along on this swap are you?

 

[BK_CAULEY]

i have a o2 harness and actually have it plugged up to the main harness. and from seeing the diagram bellow i need to hook the grey/yellow wire to a hot in run position. no problem there.

so lets get this straight. pin 30 with an a9p ground to body. CHECK

gry/ylw hot in run CHECK

now lets tackle this VSS issue. should i just go to the pick and pull and get a trans harness from a donor car? that would be easy enough.

 

[liljoe07]

i have a o2 harness and actually have it plugged up to the main harness. and from seeing the diagram bellow i need to hook the grey/yellow wire to a hot in run position. no problem there.

so lets get this straight. pin 30 with an a9p ground to body. CHECK

gry/ylw hot in run CHECK

now lets tackle this VSS issue. should i just go to the pick and pull and get a trans harness from a donor car? that would be easy enough.

1- Check

2- Check

Yes that would be the best bet for the VSS.

The VSS sends a Signal to the ECM

anything under 6mph and whatever your base idle is it will use

anything over 6mph and the ECM uses other things like Timing and the IAC to control idle. Like when coming to a stop with the clutch in, the RPMS wont drop so fast that it stalls. The RPMS will hang somewhere about 1100rpms till your under 6mph then it will idle normal.

 

[liljoe07]

Do you know what if the harness you got was from a auto or manual car? It makes a difference

EDIT: Scratch that, I was thinking A9L ECM, its late, Im Tired.

 

[liljoe07]

But your also going to have to get voltage to the ECM relay and start voltage to the TFI

 

[63bird390]

vss

i never used one in my 68 mustang in over 2 years and i have no problems idleing. and the car pulls very strong way better than the old carbed engine. ive always been a big block guy but the little 302 has surprised me.

 

[BK_CAULEY]

does the trans harness plug into plug 39? i think i got this figured out now.

 

[liljoe07]

The trans harness comes in to the inside of the car from the driverside of the trans tunnel. From there I forget where it runs. Ill have to go look.

 

[liljoe07]

You better be a pretty cool guy, since I just pulled my seat up to find where the Trans harness runs.

Once it comes through the trans tunnel, it goes under the driver seat and up in the dash. Follows the lower dash rail over the green plug. Granted it does split off and go to the Clutch Switch.