Is the fuse box with the #10 fuse the engine bay fuse box or the box under the dash?

Is the fuel pump still not priming and the car not starting?

Does the starter motor crank the engine?

Plug everything back in, and have an assistant turn the key to crank the engine. Measure the voltage from the blk/wht wire at the starter to a good ground (like - battery post). Let me know the voltage.

 

Do you have any way to determine what is wrong with the ECU and why it went from working on back-up to not working at all? Thanks for your consideration.

 

I'm trying to figure out if the electrical portion of your ignition switch is bad, a bad ECU, or bad wiring/connector.

My apologies for the repeated questions. The thread is getting long and I'm not understanding some of your responses. My goal is for you to not waste money replacing a working part.

Hopefully this is the last recommended test. With everything (main relay, ignition switch, etc), back probe the green/black wire on the main fuel relay. Use a wire to connect that back probe to a good ground. Essentially you are grounding that green/black wire with a jumper wire. Try starting the car and let us know what happens.

 

The fuel pumph primed but did not stop. Again, a crank no start

 

The grn/blk wire test is different, because you just verified the ignition switch is sending enough voltage to prime the fuel pump on the blu/red wire. You already proved the fuel pump can run, when you jumped power directly to the pump.

I think you need an ECU. I think you already tested for power and ground to the ECU and didn't find something wrong. I also remember you saying the car ran on back-up. What does that mean? Just want to make sure you don't have a loose pin at the ECU or corrosion on the connection.

To save money, try to find a u-pull-it yard close by. Places like LKQ list what vehicles they have on site and you can call to get prices. car-part.com searches junkyards that subscribe to their service for parts where you can sort by price or distance. You may find a cheap ECU near you. I think car-part calls is computer box engine. Ebay is an alternative.

You need to make sure the OEM part number on the donor ECU is a valid part number for your vehicle's ECU. OEM parts sites like hondapartsnow.com will give the OEM part number for your vehicle.

 

a solid LED with no blinking, The book says BU for back up. And to my understanding it means the computer is either dead or about to go dead. I was driving in FS mode (fail-safe mode) because the car would not drop below 750 RPMs

 

Ok, backup mode means limp mode to me.

No programming when swapping an 89 accord ECU. Just make sure you verify the OEM part numbers match.

It may be possible that you have a bad solder joint or maybe a bad capacitor on your ECU circuit board. You may want to remove the ECU and open the box to inspect the circuitry? You can watch some youtube videos on bad solder joints for accord ECU to get an idea of what you are looking for. Not sure if you have a soldering iron that you can attempt to repair. I've seen services on ebay to repair ECUs that may save you money as well.

 

I inspected the solder and it all looks good. there are 3 red/blue wires going to the ECU and one of them had electrical tape, so i ripped the tape further and found this weird wiring

Is that an additional ground, to screw the unit back in, or can it float there? All the wires are neat in the connectors and there are **********no missing or corroded tabs/spines**********

 

Technically the bolt is an extra ground, but the wiring to the ECU should have grounds and not cause an issue.

 

Turns out that someone somewhere down the line installed an American ECU in a Japanese model.