Vert88t2

iTrader: (4)

I don't see it at all. But the car has an aem 10 channel peak and hold injection box installed so would that bypass any resistor for the injection? Or bypass the ecu??? I never felt with the aem peak and hold boxes before...

Vert88t2

iTrader: (4)

I checked the voltages earlier at the ecu and I either need a new meter or it just shows 0. With the key to the "on" position

satch

iTrader: (1)

3B is measured w/key to start as previously stated. And what did you use as a ground source? You can use one of the mounting bolts for ECU as a ground. Could you not stroll over to your battery and take a voltage reading from it as a method for testing the meter?

Vert88t2

iTrader: (4)

Do you measure both pin 21 and 3b with the key to start? I thought you were supposed to read it with the key off and then check it with the key on start... And yea that explains it I wasn't probing the ecu right... I wasn't grounding pin 3b or 21 I was puttin a lead off the meter on each... Duh me! I'll try that tomorrow

Vert88t2

iTrader: (4)

And what about the aem box? What effect will that have on my voltages to the ecu? And what about that resistor? It's not there at all

satch

iTrader: (1)

Not sure about the AEM box, but the pins I suggested you take a reading of have "nothing" to do w/this box you talk of. You might not have or need the Resistor Box though. It was installed from the factory for those cars w/low impedance injectors (before 1987.5). Resistors could be wired in line, thus there would be no need for the box. If you have high impedance injectors then you would not need the box either. If you pull the plug off of one of the secondary injectors then you could take an ohm reading. 2 to 3 ohms are low while 11 to 12 or so are high impedance.

satch

iTrader: (1)

This information was already explained in post #10. Please don't make me have to repeat myself.

And please don't ground the ECU pins. When you measure voltage, the Black meter lead goes to a ground ( one of the ECU bolts that holds it in place is your ground, is your ground, is your ground.....) And the Red meter lead goes to one ECU pin that you are trying to get a voltage reading from. Red lead to pin 2I w/key to on and the Black meter lead to one of the ECU bolts for ground. Cold engine and the reading should be between 2 to 3 volts. Fully warmed engine and it should read .4 volts. Pin 2I has a Green/White wire. Pin 3B is measured in the same way as far as the two meter leads are concerned and w/key to start it should register 8 volts or so. Pin 3B, found in the smallest of the three ECU plugs, should have a Black/Blue wire.

Vert88t2

iTrader: (4)

Hey come on now I appreciate the help but I did explain I'm new at this. I'm not trying to irritate anyone I just wanna fix my car. It's embarrassing enough that I can't do it on my own.

Thanx for the detailed explanation for checking the ecu pin voltages. I'm gonna try that tonight when I get home. I don't appreciate the help please don't be offended that I might not understand the first explanation. I'm just learning, a place where every expert here has been at one point in time.

Vert88t2

iTrader: (4)

Ok cool now is there only one resistor? Or one for primary and one for secondary? I know the car has low impedance injectors in it. But I have no resistor inline for them so that means I prolly should have one correct?

satch

iTrader: (1)

Each injector would have a resistor. But you have a system installed, the AEM box, that should match the impedance of the injectors used. Why the person who initially installed that would not address that is beyond me but I guess anything is possible. You would think that the box and injectors would be compatible w/each other as opposed to just the opposite, but who knows. And I'm not bothered by you being new to this at all, but it relates to more to typing one thing and you stating something else.

Vert88t2

iTrader: (4)

yea the guy I bought if from did mention something about thinking the injectors were high imp. When he realized they were low imp. I guess that's why he put in the aem box as opposed to installing the resistors? Who knows all I know is I have a nightmare to figure out! Lol. But it's worth it in the end... I'm gonna test those voltages tonight so I'll be back with more dumb questions!!!

satch

iTrader: (1)

I believe the AEM unit is for low impedance injectors so if you know the injectors are low impedance then there shouldn't be an issue w/this unit.

Vert88t2

iTrader: (4)

Ooook... So after measuring the voltages on pin 21 and 3b... I got 11.55V on pin 21 and 0.000V on pin 3b wtf?!?! Am I measuring the right wires?!?! Both of the wires are on the smallest ecu clip right? Do you have any pictures of the wires on the ecu clip or a diagram that would show where the right wires are located cause I gotta have this wrong

satch

iTrader: (1)

Those pins w/ the 2 in front of them are from the same plug. Those w/the 3 in front of them are another plug and those pins w/the 1 in front of them are from yet another plug. So there are 3 plugs in total at your ECU, the largest plug is plug #1. The medium sized plug is plug #2, and the smallest plug is #3. So pin 3B is in the smallest plug bottom row and far right position (aka bottom right corner and it should be Black/Blue). Pin 2I is in the second largest plug and is in the top row middle position (four pins to the right of 2I and four pins to left of 2I) and the wire is Green/White. And if you bothered to read post #32 it explained where pin 3b was. Deja vu?

ECU pinout: https://www.rx7club.com/2nd-generation-specific-1986-1992-17/88-rx7-wiring-diagram-968998/

Vert88t2

iTrader: (4)

Awesome thanx for that diagram! Now I get it! I just couldn't visually see where the pins were by explanation. I'm a picture person... I'm gonna try that now

Vert88t2

iTrader: (4)

Ok so now that I know where to probe it lol. Pin 21 shows .140 and pin 3b shows 12.47! But my engine is warm should I be doing this while cold? And also these voltages were taken with the key to the "on" position not the "start".

satch

iTrader: (1)

Are you suggesting that this info has not been covered already in "your" thread?

Vert88t2

iTrader: (4)

No. I'm not sayin you didn't tell me where I'm sayin I finally realized where you were talkin about... But now that I saw the ecu plug diagram I see what your telling me. Anyway what do you think about these voltage readings???

satch

iTrader: (1)

Post #10.

Vert88t2

iTrader: (4)

Ok I get it... I'll try better tomorrow with the way you said in post #10...

satch

iTrader: (1)

And since your contention is that the car does not start properly, it would make more sense to get a Thermosensor reading with the engine cold first and then when warm.

Vert88t2

iTrader: (4)

Yup gonna do this after work today. Now dumb question: I am removing the clips from the ecu to get these voltage readings. Is that right? Cause I seen you said to not ground the ecu. Is that what you ment by that is removing the clips to measure voltages?

satch

iTrader: (1)

No. You backprobe the ECU plug by sticking the Red meter lead into the back of plug of the slot where the wire you are testing the voltage of lies while the plug is plugged into the ECU and the Red metal lead of the meter wedges into the slot where the wire is so as to make a good connection. This is a voltage test and you are not grounding the ECU. So Red metal meter lead into the back of pin 2I and the Black meter lead touching one of the ECU mounting bolts.

Vert88t2

iTrader: (4)

Ok got it thanks!

Vert88t2

iTrader: (4)

Ok here's the update:
Pin 21, engine cold, key to "on": 4.98 volts
Pin 21, engine warmed, key to "on" 0.000 volts
Pin 3b, key to "start": 9.40 volts

Now all these voltages were read while car was not running. So my pin 21 volts are a lil high on cold and nothing while warm? What's your thoughts?