datz

i wanna checkout the ecu to see if that mighttake part in small problems. i got the values per FSM and it pictures backprobing the wires,but geez there like ~1" of space to do that.
this is my first time, so does anyone have any suggestions to do it another way?

hiroichi1515

iTrader: (17)

Honestly, I think the easiest way to test an ecu is to throw another one in. Especially if its an N/a. Those ecus seem to be a dime a dozen. I have like like 6 s4 n/a ecus.

datz

get this, when i bought the car, got down to the ecu, some guy plugedanother in and just set it next to the bolted down one. wtf
i know thats easiest but before i spend ~50 bucks i wanna test the ones i got since i have very little if any info on them/ the car.

FirstRotaryExp

iTrader: (3)

if the car runs strong then teh ecu is fine. Generally speaking, the rx7 ecu's tend to be quite happy for 20+ years unless some idiot down the road ran teh battery wires backwards or jumped it with reversed cables.

Noxi

iTrader: (4)

To test an ECU as old as ours can be slightly annoying swapping it out with another that you know works just right can be the easiest way to save time.

Back probing and a DVOM (multi meter) and reading voltage I believe is way to test them

Most the times ecu's are fine and dont fry, I have only ran into 1 that was bad from a BMW due to some one using an Arc welder and frying the system by hitting ground wire w/o removing the ECU

HAILERS

Unbolt the ECU from its mount. T

Tilt it up so you can access the wires.

Compare your readings to the FUEL AND EMISSIONS readings. It's not just the ECU that you looking at, your looking also at the INPUTS from the sensors. So you can now tell if the sensors are sending the right inputs along with the right ECU outputs.

This takes all of thirty minutes at no cost. Done

datz

yup it toast. but checking most of the pin outputs i never got a correct value.
i would think some parts could be fried and not others, cause the car starts/runs/drives/ect.
ie the 3Zpin(rear secondary injector) with the ign ON the FSM says ~12v but it shows ~1v
3Qpinj(BAC) ign ON, FSM says ~8v but it reads ~1v

calpatriot

THose low output readings may not be caused by the ECU. It is also possible that those circuits are grounded (somewhere in the wiring harness). If that is true, a new ECU will not help. Before you go buy an ECU, try this: disconnect the offending circuits at both ends (pull the plug on the ECU, and at the sensor). Use the ohms setting on your DVM, and check the resistance from each circuit on the wiring harness to ground, and to each other. It should be infinite. If that is ok, connect the sensor back up, but not the ECU. Check the resistance at the terminals of the ECU connector on the wiring harness. See that the values are consistent with the FSM values for the BAC and for the injector. If those are ok, then it is likely the ECU.

datz

im horrible when it comes to electronics but i get the basics. sorry to re-iderrate, your sayin disconnect the sensor plug and the ecu plug, ground one end, and check resistance, but there is 1 pin for most sensors and like 2-6 wires in the sensor connector.and when you say "to each other" ? ?

HAILERS

If you check any of the injectors at the ECU plug and don't get batt voltage.......then that injector plug is off the injector. Take the ECU plug off that has that injector wire and just read the PLUG wire with the key ON. The voltage comes FROM the fuel injector TO the ECU on that plug. So if batt voltage isn't there and is at the other injector plugs, then that injector plug is off the injector.

ECU wiring is read from LEFT to RIGHT in a UP/DOWN fashion. So make sure your on the right wire in the plug before continuing. Injector wire colors are green/red, green/white, green/black and light green.

A faulty BAC might give you slight starting problems (goes full open when the key is HELD to START) and might cause the idle to drop unacceptabely low when a load is put on the car at idle (like headlights turned on or heater turned on). Other than that it won't cause driving problems. Some BAC problems can be traced back to it's electrical plug having a pin in the connector "pushed back" and not making contact and a worse case scenario would be its transistor gone **** up inside the ECU. It's a TIP 120 NPN transistor that can be bought at radio shack for ? buck fifty. You solder it in after removing the old one.

datz

page 22 pictures the injectors grounded on one side and receiving "power" from connection THROUGH the ecu, and injectors cant make electricity so they need electricity from somewhere to work, correct?

satch

iTrader: (1)

There is a wire which comes from the main relay that feeds power to the coils and the injectors. When the wire at the ECU, which is connected to the injector sends a ground signal to the injector the injector fires.

HAILERS

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No. Read post #12 just above this. Power goes from the Main Relay.........through the front harness............front harness connects to the Emissions harness..........power goes into the given injector........passes thru the injectors coil.............travels back thru the Emissions harness to the ECU.........where the ECU pulses a gnd on that wire to make the fuel injector open/close.

Much like post #12 above said.

3Z should be a light green/red wire and is for the rear secondary injector. IF you don't have any voltage on this wire, then the plug is off the rear secondary injector. There is no connector in between that injector and the ECU pin 3Z. Remove the plug and check the wire in the plug with key ON. No voltage means the injector plug is off. Done did falled off. Or has a pin pushed back in the injector connector...........or a poor splice of the injector pigtail.