replaced power TR unit now car wont start
08-05-2011, 12:36 PM
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replaced power TR unit now car wont start
i replaced my power TR unit on a 1990 miata, when i was done it started right up. when i came back to the car it would no longer start. im running megasquirt pnp and i didnt disconnect the battery when replacing the power TR unit. i have spark and fuel, but the injectors are not firing. any ideas? im stomped
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08-05-2011, 01:49 PM
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The wiring of the fuel system is fairly simple:
+12 volts comes out of the Main Relay on the white/red wire when the key is on. The voltage then goes to the fuel injector harness (still red/white) and hits one side of each injector.
The other side of each injector goes back to the ECU- they're wired in pairs, so two wires, one yellow, the other yellow/black. The ECU closes those wires to ground, completing the current path through the injectors, when it wants them to fire.
We know the Main Relay is working, as the same white/red wire also supplies power to the ECU and several other things.
Look at the injector duration on the Megasquirt, either by logging it while you crank it or by setting one of the Megatune gauges to read Pulse Width 1. Is the MS even trying to squirt? Also, in MegaTune, do you see a believable coolant temperature reading when the system is on? It should read somewhere near ambient.
+12 volts comes out of the Main Relay on the white/red wire when the key is on. The voltage then goes to the fuel injector harness (still red/white) and hits one side of each injector.
The other side of each injector goes back to the ECU- they're wired in pairs, so two wires, one yellow, the other yellow/black. The ECU closes those wires to ground, completing the current path through the injectors, when it wants them to fire.
We know the Main Relay is working, as the same white/red wire also supplies power to the ECU and several other things.
Look at the injector duration on the Megasquirt, either by logging it while you crank it or by setting one of the Megatune gauges to read Pulse Width 1. Is the MS even trying to squirt? Also, in MegaTune, do you see a believable coolant temperature reading when the system is on? It should read somewhere near ambient.
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08-05-2011, 04:27 PM
#17
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I'd like to add that we accidentally put fuse in the ST connector a few weeks ago and blew the Q5 transistor, pman ordered a new one from diyautotune & I installed it last night so the fuel pump turns on now - data log coming in 30 minutes I'm gong over to his house with my netbook to log the cranking, we just went and got it connected and datalogged cranking so the info is coming shortly
Last edited by zvonkorp; 08-05-2011 at 05:55 PM.
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