Ok so my igniter went out and wired in MSD6AL and have spark
But the injectors wont fire and pins No10 and No20 have power. The grounds on the intake mani are there as well.

What else is needed for injectors to fire. As precautionary i took the extra third wire on dizzy and connected to harness and the IGF wire from old igniter plug from harness to the + side of IGN coil so it has a return power source for everytime it fires.

Any other input

Both sides of the injector have battery voltage when not firing. The ECU grounds the circuit to fire the injector. Most cases, the ground on the intake manifold (between 2nd and 3rd cylinders on top side of intake mani) is not good. Check that ground first. A quick way to test this is to directly ground this circuit at the ECU. If the injectors fire, then you have a grounding issue.

midwest86 wrote:Both sides of the injector have battery voltage when not firing. The ECU grounds the circuit to fire the injector. Most cases, the ground on the intake manifold (between 2nd and 3rd cylinders on top side of intake mani) is not good. Check that ground first. A quick way to test this is to directly ground this circuit at the ECU. If the injectors fire, then you have a grounding issue.

I pulled the harness and checked that ground so many times and was fine in that spot before.

How would one ground it directly at ECU?
And neither pin at the plugs had power but the pins at ECU did have power.

Also i thought only the left pins would have power and right pin grounds it out to fire

The injectors are wired in parallel.
The power supply comes down a single wire that splits into four before reaching
the injectors. After the injectors, the wires from two injectors splice together and
connect to Pin #10 and the other two splice together and connect to Pin #20.

Therefore, if you test with only one clip removed, you will always find 12V on
both pins of the clip. To test correctly you need to pull all four injectors clips, and
then test them one at a time. One pin on each clip should have 12V and the other
side should be dead... not have 12V or continuiity to ground.

The ECU only grounds the injectors when a transistor inside the ECU is switched
to ground. If you have continuity to ground on the ECU side of the injector clip, you
basically have a short to ground, and the injector will open and stay open as soon
as you turn the key ON.

As suggested, if you ground either pin#10 or Pin #20 with the ignition ON, you should
hear the injectors click to prove that the wiring is OK. Don´t leave the ground in
place for longer than it takes to make the injectors click, as they rely on fuel flow
for cooling.

Cheers... jondee86

Ok so with all pulled theres 12v on ECU side.

So it would be the brown grounds on intake mani thats the issue? i pulled it and checked the wires and they're fine and changed spot couple times and still nothing.

If you have 12V to ground on the ECU side with all four clips disconnected, then
there are really only two possibilities. One is that somehow you have managed to
get a 12V feed hooked into the injector wiring on the ECU side, or there is some
internal problem with the ECU that is putting 12V on Pins #10 and #20.

Check by pulling the 10-pin ECU plug, turning the key ON and testing to see if you
still have 12V on the ECU side wiring. If you do, see where the 12V is coming from
and remove the connection.

If you don´t have 12V on the ECU side wiring, with the 10-pin ECU plug still disconnected,
test the #10 and #20 ECU pins to see if they get 12V to ground when you turn the key
ON. If they do, then your ECU is funked

Cheers... jondee86

jondee86 wrote:If you have 12V to ground on the ECU side with all four clips disconnected, then
there are really only two possibilities. One is that somehow you have managed to
get a 12V feed hooked into the injector wiring on the ECU side, or there is some
internal problem with the ECU that is putting 12V on Pins #10 and #20.

Check by pulling the 10-pin ECU plug, turning the key ON and testing to see if you
still have 12V on the ECU side wiring. If you do, see where the 12V is coming from
and remove the connection.

If you don´t have 12V on the ECU side wiring, with the 10-pin ECU plug still disconnected,
test the #10 and #20 ECU pins to see if they get 12V to ground when you turn the key
ON. If they do, then your ECU is funked

Cheers... jondee86

Ok so pulled the 10 pin
At the ecu plug, No10 and No20 have 12v and with all injector clips removed, the yellow wire (left looking from wire side) has 12v as well.

But aren't they all supposed to have 12v and ecu controls ground, so my ecu isn't grounding it?
It's a power fc btw

Yes... in theory that´s how it works. With everything connected up and the ignition
turned ON, there is 12V at the #10 and #20 pins. When the ECU wants to activate the
injectors, it momentarily closes an electronic switch (transistor) and the 12V supply
is connected to ground for a few milliseconds.

I´m no electronics engineer, but I don´t think a transistor that switches to ground
should show 12V on the input pin when there is nothing connected. And if all he clips
are off the injectors, and the 10-pin plug is out of the ECU, there definitely should not
be 12V showing at the wiring plug.

If there is, then you are picking up 12V from somewhere, and if this is feeding into
the ECU side injector harness, it could stop the injector from opening even if the ECU
is switching the transistor to ground correctly. I´m not up with the PowerFC but AFAIK
it is a programmable drop-in replacement for the factory 4AGE ECU, and I would
expect the ground switching for the injectors to work the same.

Cheers... jondee86

I checked the harness plug for the power when it was pulled, not the actual ecu pin. Should I have done that?

Yes. If ALL the clips are off the injectors, AND the 10-pin ECU plug is pulled, there
should be no way for there to be 12V anywhere in the injector harness wiring when
you turn the key ON. This is the first test.

With the 10-pin plug out of the ECU, test the ECU pins to see if they have 12V on
them when the key is ON. This is the second test.

I´m pretty sure your grounds will be good. What you have to discover is whether
the ECU is actually switching the 12V to ground or not. The fact that someone shot
a big dose of 12V up a ground wire may well have upset something in the ECU, so
that it no longer switches the injectors.

Cheers... jondee86

Ok I will check again when home.
But doesn't the yellow wire get power from the 2pin connector at end of harness and blue ones come from where?
Since ecu controls ground it wouldn't be providing power to #10,20 but only grounding?

With the 10 pin ecu plug disconnected and all the injector plugs removed you should still get 12v to one side of the injectors through the resistor box right.... that is what feeds 12v to the injectors right?

I’m very curious cause My injectors arent pulsing. I just sent my ecu out for a bench test and repair. Hopefully it wasn’t a waste of time and money. Thanks jondee

ThunderBolt wrote:With the 10 pin ecu plug disconnected and all the injector plugs removed you
should still get 12v to one side of the injectors through the resistor box right....
that is what feeds 12v to the injectors right?

Yes, you are right about that In the case in question I am pretty sure that we were
troubleshooting the wiring from the injectors to the ECU, so once the clips were off
the injectors, voltage on the power supply side was irrelevant.

As to why injectors don't pulse, there are a few possibilities..
- the ECU is not getting the correct information from sensors.
- there is no power supply to the injectors (you have that covered).
- the ECU ground wires are not not connected to a suitable ground.
- the switching transistor in the ECU is blown/not working.

If you can get the engine to fire up on starting fluid, that will at least confirm that the
ignition is working and that the necessary sensor inputs are present. Note that injector
pulses are in the order of a few milliseconds and usually can't be detected with an
analog meter. You need a "noid light" that uses a flashing LED to show pulses.

Cheers... jondee86

-car runs on starting fluid.
-injectors flow tested at RC engineering.
-tried aw11 and Ae86 ECUs.
-continuity is good on E01,E02,E1
-injector ohm is 14.2 so resistor wires are tied together.
-getting 12v on No.10 and No.20 (10 pin plug)
-diagnostic codes 7,11 (TPS)
-redtop swap running original 85 gts harness.. I didn’t do the swap I just rebuilt motor.
-AC/PS delete.
-checked inlet,trans,engine to frame grounds.

must be something I forgot to hook up but I was thinking buying a refurbished distributor. I tried grounding pins 10 and 20 but couldn’t hear the injectors clicking! Doing this by myself so maybe I just couldn’t hear it. Y’all mind if I post some pics and maybe something stands out.

ThunderBolt wrote:-injector ohm is 14.2 so resistor wires are tied together.

Can you clarify exactly what you did here? Normally there is one wire into the
resistor pack and two wires out. Which wires are tied?

Y’all mind if I post some pics and maybe something stands out.

Help yourself You need to upload your images to a hosting site and then post
a link back here using the IMG tags.

Cheers... jondee86

All three are wired together in a twist cap.

Should be fine then. I'm wondering why you don't get some fuel related action
from your engine. Usually, even if the main injectors are not firing, the cold start
injector supplies enough gas to get the car to fire up on closed throttle. Only runs
for a couple of seconds and then dies as the cold start injector only fires when the
engine is cranking.

I take it that you have checked that the pump runs and gas is getting to the fuel
rail. That's it... I'm out of ideas now

Cheers... jondee86

I do get fuel related action through the cold start injector(it fires up then dies after a few seconds). I can't get the injectors to manually click through grounding the #10,20 pins. What is the order of operations on manually pulsing the injectors?

Cheers jonde86 you are keeping my ae86 drive alive. any input is much appreciated and I am trying things daily to get her alive again. you ever in Las Vegas NV hit me up buddy if you run out of ideas I completely understand.

Just poke them with 12V. I use a couple of those little test wires with aligator clips
on the end. Connect one pin to 12V and tap the wire connected to the other pin on
the negative terminal. You should be able to feel the solenoid react and hear a
click. I check mine on the bench before installation as it's easier that way.

Don't leave 12V on the injector as they use the gasoline for cooling and will
overheat if left connected with no gas flow. If they were flow tested they should
be clean and not gummed up.

Cheers... jondee86

Just a thought here. If this is a USDM car the crank angle goes through the igniter before it gets to the ECU and just the TDC signal goes directly to the ECU. You would get spark as the MSD is triggered by the distributor but doesn't shoot a signal to the ECU. I believe if you got an igniter back in place it would be fine. Don't forget the transformer for the tach signal.
The JDM distributor sends all the signals to the ECU and the ECU fires the igniter. The USDM is kinda weird as the TDC signal goes to the ECU and the other 4 pulses go through the igniter first, for some reason, maybe amplification????, before going through the ECU. Then the ECU gets to send a signal to the ignitor. Yeah I just repeated myself.

I looked at his for a while to see if I could adapt a USDM igniter to JDM ECU. I ended up finding a JDM ignitor and gave up on that project. I had it worked out but never applied my theory.

So tonight went well with the corolla... well kinda.

I verified I am getting pulse to my injectors, I was using my Noid thingy incorrectly. I adjusted my TPS and my code 7,11 is gone now!!! But it still isn’t starting I checked the following tonight.

- resistance checked out ok on my distributor.
- manually pulsed injectors.
- no engine code present.
- set tps
- adjusted FPR from 50 down to 40 psi at the rail.
- 12v present on B,B1 and Batt. Pins

My battery is getting showing 11.8v so it’s getting worn out but I hook jumper cables up when I try to start the car. It runs for a few seconds off the cold start but that all I’m getting. I smell exhaust it wants to run.

So what signals does the ecu need to get this thing running.

my EFI main relay is bad so I bridged it. could that be messing something up? ordering another one tonight...

The EFI Main Relay is the one you pull when you want to make sure the engine
won't run. It controls the power supply to the ECU. There should also be a 15A
EFI fuse in the underhood fusebox... check that one as well.

Cheers... jondee86

Checked the AFM like the service manual said and the resistance between pins was really off spec so I ordered a remanufactured AFM. Also got me a new EFI main relay and battery. Man I hope this works. I’ll keep y’all posted hopefully this helps someone out with similar issues.

Installed a new battery and a remanufactured air flow meter and she started up.

Congratulations Just out of curiosity, did you try cranking it with the
new EFI relay before you installed the new AFM ?

Cheers... jondee86

this all very similar to my problem!

Here is the internal circuit diagram for the AFM...



The basic function of the AFM is to tell the ECU how much air is entering
the angine by monitoring how far the flap opens. When the flap opens it
moves a slider over a carbon track creating a variable voltage input for
the ECU. This signal is used by the ECU to control the fuel injector timing.

There are two other functions built into the AFM. The first is the THA or
inlet air temperature sensor and the second is the FC aka IDL or fuel control
switch. The FC switch contacts are closed when the flap opens due to the
air drawn in when the engine is cranking. This creates a ground path that
allows current to flow thru the COR which in turn sends power to the fuel
pump. As long as the flap stays open, the fuel pump will get power.

If the FC switch does not close or if the ground path from the AFM to the
chassis is broken, the engine will not receive fuel once you let go of the
key, and the engine will die. The cold start injector circuit is independent
of the ECU and the cold start injector will squirt only while the engine is
cranking. The engine will fire for a couple of seconds and then die if the
FC has not supplied a ground for the COR.

Cheers... jondee86

I did not try to crank it after installing just the efi main relay. I swapped both parts then started the engine.