Funny, I have a similar problem.

• the fuel pump turns on when jumped at the pump with power using factory gnd.
• the FP relay works in my daily driver
• the FP does not turn on when jumped at the diagnostic box

Am I chasing wires at this point or a bad GND? I really hope I make it to the track tomorrow. How do I check to see which side of the relay is working properly?

http://www.y8spec.com/miata_tech/wiring%20all.pdf
P12

 

So if I jump power, and the fuel pump turns on, then MS is working properly (GND to fuel pump)?

Both relays appear to be working. I can hear the relay click under the dash and I can run the relay under the hood in my daily with success. All fuses are good.

 

I'm starting to question the computer. I have continuity on all wires, and this is the last thing I have not checked. The violet wire coming out of the plug should switch to GND, right?

 

The ECU violet wire should supply 12 volts when the fuel pump is on. The coil this activates on the circuit opening relay grounds via a black wire.

The light green wire should turn the relay on when grounded, but the MSPNP does not control this wire. The wire this circuit would get 12 volts from is white with a red stripe and gets power from the main relay. This is the setup that is tested at the diagnostic box.

 

I have a DIYPNP and I'm concerned that if for any reason anyone was to replace the ST SIG fuse I'd have a dead ECU.

What's the best method of providing some protection here? install a relay or diode inside the DIYPPNP on the 1C pin?

Btw, where is the Section B-2 diagram in the mazda manual? I can't find it.

 

Bummer about this design. Just fell prey to it when the guys in the shop replaced the ST Sign fuse while tracking the fuel pump not working. I should've remembered and told them, or taped over it.

Convinced me to go back to stock, which I dd, in Iowa (I'm from SF, CA). Not that the MSPnP isn't a good product, but when traveling cross-country it's just something else I had to worry about. And to be honest, I don't like to play around as much as required. It was fun and educational, just not for me.

 

cool story bro. it's a .20c part you need to replace.

The ST_SIGN fuse sends power to the fuel pump relay to activate it for ~2seconds with key ON. The MSPNP acitavates the pump in the same way. The problem is when the fuse stays in place, it overloads the driver in the MSPNP, heats up, and burns out.

There are other methods in order to activate the 90-93 fuel pump (I've used 4 different way myself) but this method is the most PNP way.

there's nothing inheretly dangerous about their method, you just need to make sure the fuse stays out. the car will run without that fuse when the stock ecu is also in place. even if you blow the component inside the MS, jumping FP an dGND in the diagnositics box will have you running again.