snitm

The diagrams in the service manual stop short of _really_ detailing where fuse #2 is in relation to the fuel pump. Best I can tell is it looks like, when key is ON, IG1 provides +12V to the main relay (5 in diagram, or BLK/YEL wire) -- but only if fuse #2 is in place. And IG1 powers the fuel pump only if the ECU's A15 is grounded (1 in diagram, or GRN/YEL wire) -- which closes the portion of the main relay to complete the circuit between IG1 and the fuel pump (out 4 in diagram, or YEL/GRN wire).

SO all said, I'm left not understanding why fuse #2 isn't blowing instead of fuse #46. But that is me just not understanding electricity well enough.

If I could get the main relay's connector apart I could try taking the YEL/GRN wire out of the picture.. would isolate the short to be down that wire to the fuel pump. Sadly, that main relay's connector is tough to access and there is very little play in the connecting wires.. I'm concerned about screwing it up.

I did open up my original fuse blowing main relay. My untrained eye isn't seeing any obvious compromising issues in the PCB's solder joints, etc.

I am waiting on the correct s2000 replacement (39400-S1F-003), but have been using a stop-gap main relay from Autozone that is for del sol, civic, odessey, crv (Autozone generic replacement for 39400-S10-003). Fuse 46 reliably blows with it too. I'm going to do isolated testing on it as documented in the service manual -- supply 12V and ground and verify continuity in 2 different paths (verifies relay closes as expected, opening up the appropriate pathways).

snitm

I did isolated testing of the Autozone relay and it doesn't work at all. Whereas my original one, that is now noisy, does at least result in the relay closing and continuity as expected (as detailed on points 15 and 16 on service manual page 11-104).

snitm

Early result with the correct Fuel Pump Main Relay is: Fuse 46 still blows (with fuel pump disconnected).

My struggle is _real_.

snitm

I got the s2000 Electrical Troubleshooting manual today and focused on the power to ECU (6 in the above diagram).

Here is the referenced "Circuit D04":



I reconnected the Fuel Pump Main Relay and disconnected C102. I jumped ground to ECU Connector A15 and Fuel Pump Main Relay's ground ("3" as shown above) -- doing so made the Fuel Pump power up. And fuse 46 did _not_ blow.

So now I _know_ the issue is below C102. I had no idea the injectors and IACV were directly powered by this circuit.

My hunt for the short now moves into the engine bay to chase the IACV and injector wires.

snitm

FIXED IT! There was a short on the 12V wire to the Idle Air Control Valve, ran new wire rather than try to find the short within the main engine harness..

Kyle

Good job! Electrical gremlins seem to be the bane of most enthusiasts. Luckily you're handy with a meter, testlight, etc....Most people toss up their hands at blown fuses....electrical issues are simple in theory usually but hard to locate and isolate.

snitm

Thanks, nice to be able to avoid seeking professional help from the local car electrical specialist.

flanders

Great that you seem to have found the problem.
It might be a good idea to locate the actual short and make sure no other wires are damaged, not fun but keep it in mind

snitm

I'm going to leave well enough alone because I think there is considerable risk of damaging other wires in the main harness trying to hunt for the actual short.

The location where the IACV and IAT wires branch out of the main harness looks very flimsy. Could be something there. Regardless, if it ain't broke I'm not fixing it.. and hopefully by splitting the IACV 12V out to a different wire I'll reduce potential for issues by discontinuing running that 12V through the main harness.