99 Miata with LS6
Thread Starter
Teching In
Joined: May 2003
Posts: 44
Likes: 0
From: Milwaukee, WI
99 Miata with LS6 Drove my LS6 swapped Miata last weekend about 35 miles when it shut off like it ran out of gas. When I got it home, I tested the fuel pump relay and it would send power for a couple seconds then stop, but the fuel pump would not run. Made sense that it would try to prime the pump and then stop.
after taking the pump out of the tank and finding a loose connection I put everything back together and tried to start the car when I heard sort of a pop either under the hood or dash. After that, no power to anything other than the door buzzer. Dash is completely dead.
I checked every fuse in the car along with the ones in the PSI harness fuse box. All are good. I even checked the main fuse and all of the big fuses under the hood with an ohm meter. No problems found.
Next steps? Check power at the starter and work up to the ignition and fuel pump relays in the PSI harness and see if there is power on the 30 prong on the relays. I realize with a swap there are many unknowns but what else should I be checking?
Is is it possible I shorted out the starter or the PCM somehow?
after taking the pump out of the tank and finding a loose connection I put everything back together and tried to start the car when I heard sort of a pop either under the hood or dash. After that, no power to anything other than the door buzzer. Dash is completely dead.
I checked every fuse in the car along with the ones in the PSI harness fuse box. All are good. I even checked the main fuse and all of the big fuses under the hood with an ohm meter. No problems found.
Next steps? Check power at the starter and work up to the ignition and fuel pump relays in the PSI harness and see if there is power on the 30 prong on the relays. I realize with a swap there are many unknowns but what else should I be checking?
Is is it possible I shorted out the starter or the PCM somehow?
There's a 100 amp breaker in the Miata box. It doesn't pull out. There is a 10 mm bolt on each side holding it in. Should be able to check power in and power out. It's powered directly off a small wire that you should have hooked to battery power. I've used about 10 PSI harnesses in Miata conversions with no problem. The amount of time the pump runs after start up is set in the pcm and is adjustable with HP Tuners. Sounds like you have something going to ground that shouldn't be and it sounds like it's in the pump circuit. I just run the hot wire from the PSI pump relay to the hot lead going to the pump. I tap it in at the stock Miata relay. Essential it takes the Mazda relay out of play but allows you to use the stock wiring from original relay to pump. The wire gauge is adequate for most any reasonable after market pump.
Thread Starter
Teching In
Joined: May 2003
Posts: 44
Likes: 0
From: Milwaukee, WI
There's a 100 amp breaker in the Miata box. It doesn't pull out. There is a 10 mm bolt on each side holding it in. Should be able to check power in and power out. It's powered directly off a small wire that you should have hooked to battery power. I've used about 10 PSI harnesses in Miata conversions with no problem. The amount of time the pump runs after start up is set in the pcm and is adjustable with HP Tuners. Sounds like you have something going to ground that shouldn't be and it sounds like it's in the pump circuit. I just run the hot wire from the PSI pump relay to the hot lead going to the pump. I tap it in at the stock Miata relay. Essential it takes the Mazda relay out of play but allows you to use the stock wiring from original relay to pump. The wire gauge is adequate for most any reasonable after market pump.
I had originally run the fuel pump wire from the relay in the PSI harness to the stock fuel pump (red/blue) feed wire. Some on the V8 Miata Facebook page suggested the pump had burned out due to the fact that I didn’t replace the fuel pump wiring with larger gauge wire. I have now run a 14 gauge wire from the PSI relay to the fuel pump, however that larger wire does not go all the way into the tank to the pump. I spliced it in right before the stock plug on top of the tank.
When speaking with Flyin Miata, they said that they don’t upgrade the wiring on their builds which leads me to believe that it is not necessary.
Staging Lane
Joined: Apr 2017
Posts: 87
Likes: 0
From: Tulsa, Oklahoma
You might want to rethink your entire fuel pump wiring loop.
I asked the question on t V8Miata forum while doing my build and got enough feedback to make me decide to use entirely new wiring.
https://www.v8miata.net/v8-miata-wir...00-miata-3139/
In a nutshell you are using this big long existing loop that goes from the rear of the car at the battery up to the right front of the engine bay, thru a big main breaker, then over to the wad of wires around the steering column, thru a relay, along the left side of the car to the fuel tank and then into the tank to power the fuel pump. If you trace the path the electrical path is around 15 feet long.
In order to remove the possibility of having the exact trouble you are having I ran a new heavier gauge wire directly from the fuel pump to the battery with a dedicated fuse and relay and about 4 feet of wire.
My build is documented here and about half way thru I show how the fuel pump wiring was done.
https://www.v8miata.net/general-moto...d-getrag-3104/
Hope this helps.
I asked the question on t V8Miata forum while doing my build and got enough feedback to make me decide to use entirely new wiring.
https://www.v8miata.net/v8-miata-wir...00-miata-3139/
In a nutshell you are using this big long existing loop that goes from the rear of the car at the battery up to the right front of the engine bay, thru a big main breaker, then over to the wad of wires around the steering column, thru a relay, along the left side of the car to the fuel tank and then into the tank to power the fuel pump. If you trace the path the electrical path is around 15 feet long.
In order to remove the possibility of having the exact trouble you are having I ran a new heavier gauge wire directly from the fuel pump to the battery with a dedicated fuse and relay and about 4 feet of wire.
My build is documented here and about half way thru I show how the fuel pump wiring was done.
https://www.v8miata.net/general-moto...d-getrag-3104/
Hope this helps.
Thread Starter
Teching In
Joined: May 2003
Posts: 44
Likes: 0
From: Milwaukee, WI
You might want to rethink your entire fuel pump wiring loop.
I asked the question on t V8Miata forum while doing my build and got enough feedback to make me decide to use entirely new wiring.
https://www.v8miata.net/v8-miata-wir...00-miata-3139/
In a nutshell you are using this big long existing loop that goes from the rear of the car at the battery up to the right front of the engine bay, thru a big main breaker, then over to the wad of wires around the steering column, thru a relay, along the left side of the car to the fuel tank and then into the tank to power the fuel pump. If you trace the path the electrical path is around 15 feet long.
In order to remove the possibility of having the exact trouble you are having I ran a new heavier gauge wire directly from the fuel pump to the battery with a dedicated fuse and relay and about 4 feet of wire.
My build is documented here and about half way thru I show how the fuel pump wiring was done.
https://www.v8miata.net/general-moto...d-getrag-3104/
Hope this helps.
I asked the question on t V8Miata forum while doing my build and got enough feedback to make me decide to use entirely new wiring.
https://www.v8miata.net/v8-miata-wir...00-miata-3139/
In a nutshell you are using this big long existing loop that goes from the rear of the car at the battery up to the right front of the engine bay, thru a big main breaker, then over to the wad of wires around the steering column, thru a relay, along the left side of the car to the fuel tank and then into the tank to power the fuel pump. If you trace the path the electrical path is around 15 feet long.
In order to remove the possibility of having the exact trouble you are having I ran a new heavier gauge wire directly from the fuel pump to the battery with a dedicated fuse and relay and about 4 feet of wire.
My build is documented here and about half way thru I show how the fuel pump wiring was done.
https://www.v8miata.net/general-moto...d-getrag-3104/
Hope this helps.
Got to my new pump today from Flyin Miata and installed it. Car fired right up. Going to pursue getting the failed pump warrantied since Deatschwerks has a 3 year no fault warranty.
Thanks to everyone who responded for the help!
