Carb to EFI (Looking for suggestions/advice)

[85GT-TTOP]

Here is my situation. I have a 1985 5 speed Carb GT. I want to swap over to EFI. I have a complete 1990 running parts car. I have everything, complete wiring harnesses, computer, fuel rails, intake, mass air meter, distributor, fuel tank, fuel lines....everything. What obstacles are in my future should I decide to tackle this swap? I am guessing the dash gauges won't be plug and play? Thanks for any info you may have.

Chris

[wraithracing]

Starting with a running complete parts car is often the best option for an EFI conversion. All the miscellaneous items will drive you crazy and cost you a lot more than you ever expect.

All of your gauges will work with the EFI setup with the exception of the fuel gauge. The 87-93 fuel sending unit uses a different Ohms setup than the earlier cars. The best option is to purchase an EFI fuel sending for the 84-86 cars here: http://www.foxresto.com/SVO-GT-Turbo...-p/4883010.htm

That unit will work just fine with your stock fuel gauge and will bolt right into the tank. Other than that, most of the swap is pretty straight forward as your post suggests. You will most likely want to make sure you tag everything as you disassemble the 1990 so you know where everything goes and how it connects. My advise is take A LOT of pictures and video if possible to help you as you begin the swap and reassembly. If this is your first swap, I would also recommend to keep modifications to a minimum and get the swap completed and running. Once you know everything functions and works properly then it's much easier to make changes and modifications. There will be a few issues along the way, but nothing insurmountable. Just take your time and label everything WELL! take pictures, and keep the parts organized.

If you have the room and the ability, you might consider stripping out the 85 to prepare for the swap and then you can simply move many of the parts over as you remove them from the 90 parts car. Items such as the fuel tank, fuel lines, vent lines, etc. take up a huge amount of room and are easy to damage when just sitting around. The wiring is generally the most tedious task, but again take pictures and or video of the removal as that will help. You may also want to clean up the harness and remove any additional wiring not needed for your conversion, but that is a personal choice.

Best of luck and let us know how we can help!

Trey

[ZephyrEFI]

An '86 dash harness would speed things up considerably!

Just remember when you get frustrated, it's a LOT easier to swap Mustang to Mustang than it is to swap Mustang to Zephyr. Stuff like the gas tank? It just FITS! No cobbling whatsoever!

[k98dave]

Sounds like you did your home work which always a smart move. The mechanical part (fuel/return lines) etc should be straight forward. Did your fuel tank come compete with the pump?
The wiring can be a little more complicated, did you also get the body harness that runs back to the tank?

[85GT-TTOP]

Dave, I have everything. The 90 is a running driving car and is in my driveway as we speak. My biggest concern is having to splice wires for the gauges to work. I am very mechanically inclined and have built many mustangs. Its just tracing wires is not my cup of tea. Are the door harnesses the same between 85 and 90? Both cars have power windows and locks. I have the 85 somewhat stripped interior wise already so that will help. Would an 86 dash harness be plug and play with all the other 90 wiring? Would there be an issue with the 86 dash harness and 90 due to speed density vs mass air? Sorry for so many questions I just like to be prepared. You can see the other mustang I just finished over on corral under member build up forum titled "1990 Un Cola convertible build" to get a feel for my skill level. I would link it but not sure if I am supposed to. Thanks everyone so far. The information is very helpful.

[85GT-TTOP]

Also having my 90 convertible as a reference for everything will help I'm sure.

[wraithracing]

It's been awhile since I have done this swap, but I don't think you are going to have many issues with your gauges. The engine harness is somewhat standard alone, although I am sure there are a couple of things that connect between the two. The gauge sensors and sending units are separate from the ECU sensor, so that should not cause you an issue there IIRC. I could be wrong, but I will find out too in the near future as I will be doing the EFI swap to my 82 GT.

The 87-93 door harness is different than the 86 and earlier due to the changes in the interior door panel. You can make them work, but there's little benefit IMHO unless you are swapping to the later 87-93 door panels and switches.

As you stated the 86 harness is a SD and the 90 is a MAF. If you had both, then I would use the one you like better and modify as needed. Before I bought an 86 harness though, I would buy a retrofit EFI harness and save all the trouble of swapping harnesses, but I know that is more money and may not fit the budget. Although if you hate wiring as much as I do, then you might consider it for you own sanity!

Trey

[85GT-TTOP]

I'm getting a little confused. I will have all mass air wiring and parts from the 90. My question is how will the 86 dash harness match up to the 90 engine wiring. Will I need to modify the 86 dash harness in any way? All the 90 mass air stuff should be fine as it all is coming out of the same car.

Thanks

[Dean_T]

In my opinion if you already have a complete running '90 V8 Mustang, getting an '86 dash wiring harness won't gain you much - it's just as easy to modify your existing harness or make an adapter harness like I did to my '84 as to figure out which connectors on the '86 harness has the wires to match what the SEFI harness has.

The following thread is what I did and I also mapped out some of the connector plugs on various years SEFI wiring harnesses. I need to update the pin-out pictures and add more years.

You probably will have an easier time with adapting to the newer dual exhaust since your '85 had dual cat back exhaust unlike my single lung '84.

Good luck!

http://vb.foureyedpride.com/showthre...or-Destruction

[85GT-TTOP]

That is very helpful. Thank you very much.