Electrical 1987 5.0l Wiring Question

[Cody D]

Hello, I've been trying to complete the wiring for a 302 swap that I've been working on and it hasn't been going well.

I have the wiring diagram and the ECU pinout diagram but I still am confused as to the purpose and need for a couple plugs in the engine bay.

There are two 8 pin plugs that have wires going into them from various parts of the car. Can someone explain to me the purpose of these plugs?

 

[wgreenlee4]

Are those the large plugs that attach to the wiring harness at the back of the lower manifold?

 

[Cody D]

I traced down the grey plug, one of the wires comes straight from the power relay after the ECU (I assume switched power), one of the wires goes to the distributor, and I believe two wires go to the A/C. So far I think that these plugs are for the connections from the engine/ECU to the dash. Could that be right?

 

[jrichker]

Are those the large plugs that attach to the wiring harness at the back of the lower manifold?

The connector pattern is wrong. The 10 pin connectors have 9 pins in a circle with one in the middle as shown below. See the graphic for the 10 pin connector circuit layout.

@Cody D, Keep looking...
@Mustang5L5 Mike can you help?

 

[Dan02gt]

Those look like the ones that go on the driver's side near the shock tower and connect various things on the driver's side of the car. I think the coil and AC would be 2 of them. Do you have the other harnesses they connect to? I could take pictures of my car if that would help.

 

[jrichker]

Those look like the ones that go on the driver's side near the shock tower and connect various things on the driver's side of the car. I think the coil and AC would be 2 of them. Do you have the other harnesses they connect to? I could take pictures of my car if that would help.

The 91 year was the first big change in the wiring harnesses and colors, so your good intentions are appreciated, but may not be much help.

Mustang wiring breaks out pretty much like this:

86- unique

87 shares many similarities with the 88-89, and some differences, most notable is the O2 sensor harness wiring which is unique to 87

88-89 major differences are in the Mass Air computer wiring. The 88 Cali Mass Air cars should be the same as the 89.

90 - unique - first year for air bags and has 2 additional plugs for the air bags. The 90 wiring harness parts with the exception of the engine fuel injection harness are mostly 90 only.

91 - wiring harness changed wire colors and fuel pump wiring changed

92-93 same wiring colors and fuel pump wiring as the 91, but the fuel pump relay has been moved from under the driver's seat to the engine bay under the Mass Air meter. It is easy to confuse the fuel pump relay with the A/C WOT relay, except that the wire colors are different. The fuel pump relay has pink/black, red, dark green/yellow and light blue/orange wires attached to it.

Any input as to differences or additions is welcome...

 

[Dan02gt]

jrichner

I know the harnesses are different through the different years. My car is a early build 91 and none of the wiring diagrams are 100% right for it. It has some colors that match to the '90 and some that match to the '91.

I guess I 'm not really sure what OP is asking. I was thinking he wanted to know where they physically go in the car.

Cody, Do you have the other part of the harnesses? If not I would try to find them.

 

[Mustang5L5]

I believe these are the two plugs in question

I will need to wait til I am in front of my car to ID where they run. As you can see, that's just a cropped photo I had on my phone.

 

[Mustang5L5]

So, the other harness snakes around the drivers side fender of my car. Short of pulling a bunch of stuff out, I'll describe how it runs.

It pokes out of the drivers side firewall below the hinge. The gray and black male plugs are about 6" away from where it comes through. About 12" away is where the tape out for the MC low fluid sensor is.

It then continues on under the coil. I lose it there.

So simple question. Is your MC low fluid sensor hooked up? If so follow it back and the two plugs you seek are 6" away

 

[Cody D]

Thanks for all the replies guys, for some reason I wasn't getting notifications (my fault) so I didn't think there were more replies.

I should have given more information, this is a swapped engine in an old BMW chasis, I don't have any other harness then the engine one. I made a mistake and when it was pulled apart I didn't verify the wires were labeled.

We've got almost everything hooked up and the car cranks like a champ. We had it run when we first turned it over for about 3 seconds then shut off, we had spark for a little bit, now we aren't getting spark or injector pulses so we think the distributor is pooched. I'm going to buy one Monday and swap it out, I swapped out the coil this morning and it didn't solve the issue.

If that doesn't fix it I'm seriously thinking about converting to carburetor, I know it's not efficient but I like the idea of simplifying everything in the build.

Any wiring that doesn't directly get the engine running isn't important to me, the plan was to build a fun hill climb car.

I'm so far over my head in this build it's almost funny, haha.

 

[Mustang5L5]

That's a cool build

 

[Cody D]

Thanks.

I have another question, if I'm not worried about day to day drive-ability what other negative side effect would I have with converting to a carburetor? I like the idea of simplifying my engine bay and simplifying future troubleshooting.

 

[Mustang5L5]

Negative side effect is you no longer have the cool factor of saying you swapped in an different EFI engine into a car that it never came in and made it run well.

Nothing wrong with carbs. A different skill set in tuning, that's all.


Not cheap, but there are standalone harnesses for the 302 when used in engine swaps. Might be cheaper than carb and manifold.

http://www.americanmuscle.com/frpp-efi-harness-8693.html


Or you could trace some wiring diagrams and see what those are for. I want to say low brake fluid sensor and AC clutch are some of them.

 

[a91what]

If you just need the car to run...

Engine harness with injectors, ect sensor, IAT sensor, plug for the tfi(distributor plug)... then you need the coil wiring... map sensor and bap sensor and o2 sensors.

 

[jrichker]

Thanks.

I have another question, if I'm not worried about day to day drive-ability what other negative side effect would I have with converting to a carburetor? I like the idea of simplifying my engine bay and simplifying future troubleshooting.

The EFi system in the fox body cars isn't hard to troubleshoot, it will usually tell you what is wrong. Even an fossil like me (I'm 71) can learn how to do it.

 

[General karthief]

I don't know what a 'hill climb' car is/does but I do have a cartoon mind so I can picture several scenarios, now you can run a carb with float bowls that center pivot or side pivot bowls or whatever they are called but keep in mind an efi engine theoretically can continue to function upside down and adapt to most any climate, I also know a guy that rock climbs and uses efi because of the extreme angles he encounters.
Something to think about.
And thats my uneducated opinion.

 

[Cody D]

Negative side effect is you no longer have the cool factor of saying you swapped in an different EFI engine into a car that it never came in and made it run well.

Nothing wrong with carbs. A different skill set in tuning, that's all.


Not cheap, but there are standalone harnesses for the 302 when used in engine swaps. Might be cheaper than carb and manifold.

http://www.americanmuscle.com/frpp-efi-harness-8693.html

Or you could trace some wiring diagrams and see what those are for. I want to say low brake fluid sensor and AC clutch are some of them.

Haha, that's a good point, the cool factor is important. Thanks for the link. We have traced the wiring so many times this past week, as I'm sure you know 1987 is the worst year to find a wiring diagram for and once I did find one some things still didn't appear to match perfectly.

If you just need the car to run...

Engine harness with injectors, ect sensor, IAT sensor, plug for the tfi(distributor plug)... then you need the coil wiring... map sensor and bap sensor and o2 sensors.

That's a lot of help, thanks. Thursday and Friday when we were troubleshooting we kept coming back to the thought that our wiring and connections were good but the ECU, Coil or Distributor had gone.

The EFi system in the fox body cars isn't hard to troubleshoot, it will usually tell you what is wrong. Even an fossil like me (I'm 71) can learn how to do it.

That's why I went with the old 302, I figured it's a simple design with relatively inexpensive parts.

I don't know what a 'hill climb' car is/does but I do have a cartoon mind so I can picture several scenarios, now you can run a carb with float bowls that center pivot or side pivot bowls or whatever they are called but keep in mind an efi engine theoretically can continue to function upside down and adapt to most any climate, I also know a guy that rock climbs and uses efi because of the extreme angles he encounters.
Something to think about.
And thats my uneducated opinion.

This is hill climb racing:
View: https://www.youtube.com/watch?v=ZbK74e_P0Eg


So today I woke up early, ran to the nearest city and bought a brand new distributor, put it in and the car fired up immediately. What a glorious sound. Thanks so much for everyones help, I'm new to the Mustang scene but I'm not accustomed to this much help from some forums, haha.

Video of the BMW E302 firing up:
View: https://www.youtube.com/watch?v=Ep36ZruCG4M

 

[General karthief]

Aaand another satisfied customer!
Now when you get that b'stang on the road and into competition make sure you add us to the 'thanks to' list on the trunk lid,
I'll spell it for you:
K-a-r-t-h-i-e-f

 

[Mustang5L5]

as I'm sure you know 1987 is the worst year to find a wiring diagram for and once I did find one some things still didn't appear to match perfectly.

Probably a little late for this....but...

http://www.ebay.com/itm/1987-Ford-M...ash=item3f786eb91a:g:af8AAOSwuxFY1Wat&vxp=mtr

 

[Cody D]

Aaand another satisfied customer!
Now when you get that b'stang on the road and into competition make sure you add us to the 'thanks to' list on the trunk lid,
I'll spell it for you:
K-a-r-t-h-i-e-f

That sounds like a good idea for the BMustang.

Probably a little late for this....but...

That would have been nice actually.