Hondata

When I got to start the car the fuel pump doesn't prime. I'll wait with the key in the run position for 2-7 minutes before the fuel pump finally primes itself and then the car runs fine and usually starts back up without having to wait at all. I've replaced all 8 capacitors and the transistor qm3 sta413a without any luck. Tstat ground is good and I've tried a known good main fuel relay. Ic7 terminal 32 is 5v with the ignition on and the fuel pump is not priming. If I sit with the key on long enough for the fuel pump to finally prime on its own I get a ground signal at ic7 terminal 32 and it goes right back to 5 volts after the fuel pump is done priming. I checked the voltage at transistor q10 and the terminal towards the vehicle harness has 5 volts at all times with the key in the run position. The middle terminal has no voltage with the key on until the pump starts to prime itself on its own. The furthest terminal from the vehicle harness has 5v with the key on until the fuel pump starts to prime and it goes to ground. Once the pump is done prime it goes back to 5 volts. As for rm7 the furthest left terminal(or closest to the vehicle harness) is always grounded no matter the key position. Counting from that terminal towards the right(away from the vehicle harness) the sixth terminal on rm7 shows no voltage until the fuel pump primes on its own and it jumps up to 0.7v then goes back to zero after the pump is done priming. The next terminal on rm7(the 7th terminal counting away from the vehicle harness) shows no voltage until the fuel pump begins to prime on its own. It's shows 5v until the pump is done priming and it goes back to 0v.

If the pump is not priming on its own and I myself ground ic7 at terminal number 32 the fuel pump will immediately kick on every time. I don't know where ic7 gets its signal from but it seems to like me grounding that terminal for it.

If that makes sense, any ideas?

Try your s300 in a different ECU. IF that works then you know that the old ECU was damaged and it is not usually worth the time trying to fix them.

True story I am having that same situation as we type!!! It's a headache however I wish I could repair and or find the problem!! If I find it I will post what it is...