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ECU power??? Pins 71 & 82

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kiddsm95

15+ Year Contributor
154
0
Mar 23, 2007
Ann Arbor, Michigan
I initially thought that my MPI relay was going bad, but when I tested it I've verified that pin #6 (I think) is at 12V with the ignition off, then it is going low (0.86V with the ignition on...This is what it's supposed to do I believe. The MPI relay is sending power to pins 12 & 25, so I think I can claim that the relay is good.

The problem is that I'm not getting power on pins 71 & 82 with the ignition on or off. I believe that these pins are supposed to be "hot" all the time??? Looking at the schematic it points to the ignition switch, but if my ignition switch was bad wouldn't that mean that my dash lights shouldn't be working?

The car is getting fuel and spark, but I just can't get it to start. Is it the ignition switch or are there other components that would power pins 71 & 82?
 
71 and 82 are the Ignition Switch Pins.

One should get 12v when the key is turned on.

The other gets 12v when the key is turned to start. (Starter Cranking)


You will not get fuel and spark if there is not power to the first pin, the ecu thinks you turned the ignition off or have key in ACC position.



If your car won't turn over, check the Clutch Starter Safety Switch.
 
The problem is that I'm not getting power on pins 71 & 82 with the ignition on or off. I believe that these pins are supposed to be "hot" all the time??? Looking at the schematic it points to the ignition switch, but if my ignition switch was bad wouldn't that mean that my dash lights shouldn't be working?

Pin 71 is the signals from the ignition switch to tell the ECU your trying to start the car. It should only be hot while the ignition switch is in the START position.

Pin 82 is the one from the ignition switch when it's in the START or RUN position.

It your MPI relay is turning on the pin 82 must be getting 12v when the ignition is in START or RUN position. That's that triggers the ECU into turning the relay on.
 
Pin 71 is the signals from the ignition switch to tell the ECU your trying to start the car. It should only be hot while the ignition switch is in the START position.

I verified that I do have 12V on pin 82, so the MPI relay is good.
Pin 71 has no voltage with the ignition switch on. What exactly does pin 71 do, and can it prevent a dsm from starting? What sends power to pin 71?
 
I verified that I do have 12V on pin 82, so the MPI relay is good.
Pin 71 has no voltage with the ignition switch on. What exactly does pin 71 do, and can it prevent a dsm from starting? What sends power to pin 71?

It seems that I greatly overestimated your knowledge.

Let's try again.

Pin 71 is the signal from the ignition switch to tell the ECU your trying to start the car. It should only have 12v while the ignition switch is in the START position. The ECU get it after it's passed through the starter relay and is headed to the starter solenoid.

Pin 82 comes directly from the ignition switch. It's not connected to the MPI relay. When the ECU sees pin 82 have 12v on it, the ECU pulls pin 38 to ground (0v) and that turns on the MPI/MFI relay. You checked that the MPI relay was working and from that I was able to guess that pin 82 was getting 12v on it.
 
It seems that I greatly overestimated your knowledge.

Let's try again.

Pin 71 is the signal from the ignition switch to tell the ECU your trying to start the car. It should only have 12v while the ignition switch is in the START position. The ECU get it after it's passed through the starter relay and is headed to the starter solenoid.

Pin 82 comes directly from the ignition switch. It's not connected to the MPI relay. When the ECU sees pin 82 have 12v on it, the ECU pulls pin 38 to ground (0v) and that turns on the MPI/MFI relay. You checked that the MPI relay was working and from that I was able to guess that pin 82 was getting 12v on it.


Electronics definately is not my strong point. My car will crank, but it just will not start/run. I haven't measured the voltage on pin 38 yet to see what it was doing, but instead I measured pin 6 (blu/grn) on the MPI relay and found that it has 12V with the ign off and 0.86V with the ignition on. Is this equivalent to measuring pin 38 on the ECU?

Since my car cranks that mean pin 71 is getting power, and I've already verified pins 12, 25, 80 & 82 have power so does this mean the MPI relay and ignition switch are good? The car has fuel, spark and compression. The CAS and crank sensors are new, and the plugs are new (gapped to .030).

What else can keep a dsm from starting?
 
Swapped in 264/264 cams and crushed the original cam sensor when I was installing the intake cam gear, so decided to install a 1g CAS using the RRE/Magnus method. Couldn't get it started with the 1g CAS so I installed new original crank and cam sensors. Timing is lined up perfect everywhere, there is fuel, spark & compression.

Here's my other thread: http://www.dsmtuners.com/forums/cylinder-head-short-block/356483-cam-swap-h8-ecu-1g-cas-95-gs-t.html

I posted in ths section because I was under the assumption that I shorted something when installing the 1g CAS since I wasn't getting power on pin 71.

Eclipse has been down for about 3 weeks now, so any help is appreciated.
 
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