I have a EM1 with a B18C5 engine w/OBD1 w/Hondata S300. Back in October the car would not start. The fuel pump would not activate. I figured it has to be the main relay. So I buy an aftermarket main relay and still nothing. I end up buying an OEM Honda main relay, and still nothing. So I ship the ECU out to be repaired, and the guy finds a problem and fixes it. He also replaced all the capacitors. He bench tests the entire ECU and ships it back. I reload the file and the car starts. The next day the same thing, fuel pump not activating. The ECU is not triggering the main relay. So I send the ECU back to the same repair shop, and he says there is nothing wrong with the ECU that he bench tested it 3 times and it checks out okay. He even put it in his car for a week and no issues. I get the ECU back, reload the file and the car starts. The car sat for about a month. I go out to start the car and same thing, no fuel pump. I take the trim panel off and see the Hondata flashing red with the key in the "on" position. I then plug in the laptop to the ECU and do absolutely nothing and wait a few minutes and the light turns green and the fuel pump turns on and car starts. I shut the car off 5 times to see if it does it again and everything seems okay. Now I'm afraid to drive it that I will get stranded somewhere. Does anyone know what could be causing this?
Thanks

 

It's a guess but.... I'm going to say it's still the ECU.
Capacitors are not the only thing for fuel prime issue.

Another possibility is IC17 and QM3 (STA413A Transistor).
Both of those needs to be working order. They do present intermittent issue when they are going bad.
These ECUs are like 30+ years old now. Kind of norm to have these issues.

EDIT: BTW, I've replaced both for my ECU... I also did have intermittent issue. If I just kept turning the key on and off a lot of times, it would eventually prime. At least that was my symptom.

 

What version S300 do you have (what color is the Hondata board) ?

 

The color is white.

 

Do you also have an S300?

 

STA413A most likely.

Even if the s300 wasn't making a good connection, the ecu would go into limp home mode and still prime, as far as I remember.

STA413A causes intermittent issues like described. Good luck

 

It definitely sounds like the STA413A is the problem. I wonder why this wasn't picked up during the bench testing. Now I have to find a good repair shop to replace it.
Thanks

 

no s300, but i’m using an emulator. CobraRTP.
btw, i would just get both replaced if i were you. not like IC17 is expensive and not worth doing it twice.

 

Parts are on order. Thanks.

 

Update:

I finally received the STA413A, and went to install the new transistor and heated up the old solder to remove the old one and guess what? The copper rails lifted up off the board. I just don't understand how the repair shop couldn't find all these things wrong with it. So after all that I had to order a new ECU. I was tired of throwing good money after bad at this old ECU. Waiting for the new ECU to arrive. Hopefully this fixes the problem once and for all.

 

You can replace the copper traces with small bits of wires. Just run them where the traces ran. Perfectly acceptable way to mitigate e-waste

 

As @theYBLEGAL mentioned above, you can repair that by running wire.

This is not exactly same but, I've had capacitor blow up on my door lock module which completely destroyed portion of my PCB trace.
You just have to scrape off the PCB coating and solder in the wire trace.

 

That's pretty clean repair work there. Soldering it to the trace itself, before it splits to both joints. Very nice.

You could even run wires directly the joints and problem also solved.

 

Update: The new ECU/S300, and new jumper harness are in and everything is back to normal. Car runs great.