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Old 10-22-2010, 02:47 PM   #1
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Default ecu/ fuel problems HELP!!

i shut my car off the other day and a few hours later i went to get in and go and it wouldnt start due to no fuel. it had a bell engineering turbo kit with a bipes acu on it attached to the ecu wiring. since then i have done a series of tests and cant get anything to read right. i removed the bipes acu and reconnected the factory white wire to the ecu that bipes requires you to splice. i then tested to see if the relay on the passenger side firewall clicks and it does. then i checked power to the fuel pump and injectors and it doesnt get power to either. i replaced the fuel pump relay but still nothing. am i on the right track to believing that the ECU is bad? i have ordered a megasquirt and it should be here tomorrow but until then i was just trying to rule out any other possibilities of failure??? as i am pretty mechanically inclined but relatively new to the miata scene so any help you guys could throw in would be greatly appreciated. thanks
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Old 10-22-2010, 03:01 PM   #2
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Run 12v across two posts of the relay and test for continuity across the other two. I have had relays that click and are still bad. If you replaced the fuel pump relay check to see if you have fuel now, you might have burned out your coil packs and have no spark(this happened to me on my 94).
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Old 10-22-2010, 03:15 PM   #3
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the fuel pump and the fuel pump relay are new however im still getting now power to the pump or injectors. ill run that test on the relay on the firewall this evening.
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Old 10-22-2010, 04:27 PM   #4
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You have a new main EFI relay, the one above the passenger front fender? That was the one that was bad on my car.
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Old 10-29-2010, 04:40 AM   #5
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It would help if we knew what year of car you had, as the wiring differs.

As a generalization, there are two different relays that we are concerned with. Th fuel pump relay (circuit opening relay) controls the fuel pump, and is triggered either by a switch contact in the VAF sensor (90-'93) or a signal from the ECU ('94+). This one is inside the car, under the dash near the steering column.

Note that in any year, this relay will NOT be energized unless you are cranking on the starter or the engine is running. (This is a safety feature.) You can force it on by opening the diagnostic box under the hood and installing a jumper between "F/P" and "GND".

The "Main Relay" (under hood, in box) supplies power to the ECU, injectors, most sensors, etc. This guy simply switches on when they key is on, and its output is a white wire with a red stripe. You'll find that circuit going all over the place under the hood.

I'm not sure what you mean by "the relay on the passenger side firewall", unless you live in the UK / AUS / JP, and the passenger side is thus on the left as viewed from the perspective of the seated driver.
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