ecu usage

[bennettracing]

Guys,

I'm in the process of swapping my 2.3/A4LD to a carbed 302/t5 combo. My question is, I'm trying to make everything as clean as possible, will it be possible to completely remove the ECU and engine wiring harnesses? My concerns are with using original gauges and such. Can anyone tell me the reasons why I shouldn't remove it alltogether?

Thanks,

Kyle

 

[jrichker]

The EFI wiring harness contans the wiring for the temp gauge, oil pressure gauge, A/C clutch and probably several other things I have forgotten about.

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 http://www.veryuseful.com/mustang/tech/engine/

Do not use an EFI in tank fuel pump with a carb. You will never get the pressure/flow regulated properly. Either go full EFI or use a tank/fuel pump/fuel lines out of an 84 or earlier Stang. Fabricating your own setup is possible but there are some snags to overcome.

If you try to use your current tank, you will need to pull the fuel pump out and fabricate a pickup tube & strainer sock to replace the fuel pump. Or you can have a sump fabricated and welded onto you existing tank. Many welding shops will not weld fuel tanks because of the dangers involved if the tank isn't purged properly.

You will need an external electric fuel pump unless you change the timing cover for one with the mechanical fuel pump mount on it. You will need to add a relay & switch and wire in the existing inertia switch for an external low pressure electric fuel pump.

You will need to run some new fuel feed lines or braided hose. The 3/8" aluminum tubing works well, but you will need a flaring tool and bending springs to fabricate the lines. Braided hose is easy to run and route, but is much more expensive. It is about $3.50-$4.00 a foot plus the end fittings, which are $3-$4 each. Fabricating hose assembles can be difficult, but anyplace that makes hydraulic hoses can do it for you for an extra charge. See http://www.amazonhose.com for more information.

You will need a new distributor and duraspark box or equalivent system. The distributor will need a steel gear to match your roller camshaft.

Keep in mind that carbs are great for the strip but not for the street. If there are emissions requirements in your area, a carb'd car will not pass. If these are not concerns for you, then go ahead with your carb engine swap. Since a convertible is not typically an all out strip car, but a weekend cruser, the EFI would seem to be a better arrangment.

If you are not proficent with electrical wiring, your converstion to carb job will be more complicated than you might like. Learn to read electrical schematics, because you will need that skill to do the job right.

AutoZone wiring diagrams

http://www.autozone.com/servlet/UiB..._us/0900823d/80/16/71/3c/0900823d8016713c.jsp for 79-88 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/19/59/5a/0900823d8019595a.jsp for 89-93 model Mustangs

http://www.autozone.com/servlet/UiB..._us/0900823d/80/1d/db/3c/0900823d801ddb3c.jsp for 94-98 model Mustangs

 

[bennettracing]

Electronics are my specialty, my question was is there any way to bypass the ECU and still have proper usage of factory gauges? Are the gauges ECU controlled, or is the ECU simply a jumper point for them? Obviously the ECU will need several of these signals, but does it modify the incoming signal that goes out to the gauge itself?

It appears (please correct me if I'm wrong) that either plug #39 (or even possibly #27 as a carrier) goes indirectly to the factory gauges. Could I utilize my individual sensor wires to directly interface with gauges? (bypass the ECU harness entirely)

Thanks a bunch, great info, it will be saved for future reference.

Kyle

 

[jrichker]

The gauges are separate and independent from the computer. If you want to run
the signal wires directly to the gauges, that would work OK.

The 90 model engine & body wiring are different from all the other Mustangs
because of the air bags and instrument wiring. The diagrams posted earlier are
generally typical of Mustangs made between 87-93, but are definitely not specific
to the 90 model.

Copied From bbunt302

Just for reference, here's a list of all the compatible years:

89 harness should work for 86-89 as long as you're using mass air.
90 harness will only work in a 90. (B/c of air bags and dual dash connectors)
91 through early 92 harnesses should be compatible (single dash connector, fuel
pump relay under driver's seat)
Late 92 through 93 harnesses should be compatible (single dash connector, fuel
pump relay under the hood)

Computers from 89-92 are all the same. Look for the A9L sticker on the back cover
for a 5 speed that matches your requirements. Example: E9ZF 12A650 AA" with
the A9L code.

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 http://www.veryuseful.com/mustang/tech/engine/

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

http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif

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