I've done a ton of research - and yes, most of you are thinking, "dude, change out the main relay", but I don't think it's the master relay. I did put a new one in there anyway - and it acts the same.

It seems to be weather/temperature independent and it's getting spark which I verified. No codes, but the downstream o2 sensor - which has been in there for many years.

It's hard to get some good testing in there as it's an intermittent problem which usually clears up within a minute or two (and it's my girlfriend's car)

What I do know is that when it doesn't start, the fuel pump isn't priming. I'm starting to wonder if the ECU is intermittently NOT sending the ground signal to the relay to prime the fuel pump.

Once the car starts, it runs fine - never stalls and usually starts rights up again if recently shut off.

There's really no rhyme or reason to it though. We've had the car sit for 12 days after a trip and it starts right up and sometimes it won't start up after sitting overnight.

I haven't exhausted all my testing by any means, but wanted to get this out there and see if anyone else had a similar experience or has any suggestions.

At this point, I'm leaning towards some grounding issues, but just haven't had time to tear the car apart.

Also, Can anyone verify what signals the 3 wires to the fuel pump should be carrying at different times? (ignition / starting / running / off)

Thanks a bunch

 

Just wanted to follow up in the event someone else experiences anything similar.

After doing a little more research, I noticed that the problem was probably with the shift interlock system. The service manual I had was from an OBD1 Accord and it showed the interlock system as a separate component, but I couldn't find it in its stated location. I'm thinking it's integrated into the ECU in OBD2 vehicles.

I ended up just ordering another ECU off ebay. Threw it in, and all is good...

I did find a tech note stating there is/was a replacement for the 37820-P0H-L51 ECU, although I'm not sure if my problem was related to this. I am curious as to why there is a replacement though.

Link to tech note PDF if interested:
http://www.justanswer.com/uploads/Ho...46_A98-040.pdf