ECU Issue - Fuel Pump Circuit Fried

[vrracr]

My 2001 has had several issues over the past year and after having everything finally addressed, the car wouldn't start. Fuel pump would not kick on so it was replaced...still the issue existed. Then next step was to check all of the wiring and everything seemed okay. So I took out the ECU and sent it to a company in California. They tested it and informed me today that the fuel pump circuit is toast and that it is not repairable so they will be sending it back to me. How it happened is unknown but at least now we can go back and trace the wiring related to the fuel system only and see if there is a looming issue there.

I wanted to know if any of you have experience this and where a good source for a replacement ECU would be.

 

[Old Guy]

The processor in the ECU energizes a transistor in the ECU which completes a ground path (the transistor will be in what is called an open collector configuration) that energizes the fuel pump relay (which happens to be a part of the main FI relay). If by some freak accident, you happen to apply 12 v directly to the open collector of that transistor with no load / resistance between 12 v and the collector, you will definitely toast the transistor when the processor initiates an 'on' condition to the transistor. However, that kind of damage should be repairable (replace the transistor). If the output port on the processor is toast then, yes the ECU is also pretty much toast. I would quiz the repair shop as to which part of the fuel pump circuit is dead because the circuit is pretty simple

You could go with an aftermarket ECU (AEM ...); but, I expect that sourcing an OEM replacement from Honda or from someone who has replaced their OEM ECU with an aftermarket ECU will be the low cost solution.

 

[vrracr]

I received the ECU back today. In the box was a receipt from SIA in Illinois who tested the ECU. Looks like I was given incorrect info by the middle man I sent the ECU to. The receipt states that SIA does not have the parts to repair the fuel pump circuitry. It does not mention that it is not repairable. So I supposed this is somewhat good news.

Now I need to find a vendor who can source the part needed or still look for a replacement ECU.

 

[vrracr]

The processor in the ECU energizes a transistor in the ECU which completes a ground path (the transistor will be in what is called an open collector configuration) that energizes the fuel pump relay (which happens to be a part of the main FI relay). If by some freak accident, you happen to apply 12 v directly to the open collector of that transistor with no load / resistance between 12 v and the collector, you will definitely toast the transistor when the processor initiates an 'on' condition to the transistor. However, that kind of damage should be repairable (replace the transistor). If the output port on the processor is toast then, yes the ECU is also pretty much toast. I would quiz the repair shop as to which part of the fuel pump circuit is dead because the circuit is pretty simple

You could go with an aftermarket ECU (AEM ...); but, I expect that sourcing an OEM replacement from Honda or from someone who has replaced their OEM ECU with an aftermarket ECU will be the low cost solution.

Thank you for your response, by the way.

 

[drew]

If the ECU otherwise works: You might consider wiring up the fuel pump to a Key On powered relay, or at least in place of the ECU output. At least as a work around so you may drive your car.

Possibly a little unsafe if you get into a major collision, which can be alleviated with an inertia switch. EEC 90's style.

 

[Old Guy]

If the ECU otherwise works: You might consider wiring up the fuel pump to a Key On powered relay, or at least in place of the ECU output. At least as a work around so you may drive your car.

Possibly a little unsafe if you get into a major collision, which can be alleviated with an inertia switch. EEC 90's style.

Its probably a bit late to the party; but, that test would certainly allow you to confirm that the 'rest' of the ECU works (if you can get the engine to run). If the engine won't run, then it would be something more fatal than just the fuel pump control.

 

[drew]

I've seen an Integra pull the same stunt (dead ECU fuel pump output) and the owner just used a manual fuel pump switch; cheap, easy and built-in theft deterrent. A manual switch is NOT advised because of the human operator.

In this case, there might be another ECU output to scavenge, with a diode and feed into the Main Relay (? verify). A small 12v relay should do the trick and only cost a few dollars, you might be able to just integrate this into your ECU board/casing too. Indeed you might be able to feed the MR Key On power supply back in the ECU MR input with a simple wire jump.

Plenty of kludge options to go around


I prefer to make "tee connectors" from salvaged connectors rather than cut the original wiring harness. The NSX Mitsumi connectors are used on other Honda's of the same years....go to your local pick a part.



Please verify where the ECU output is delivered. I have not consulted the wiring diagram for this post, last time I messed with the MR was a decade ago. Finding a used ~2001 ECU might take a very long time, as there are not a lot of cars made.