4AGZE Injectors Not Firing

Alex170984
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4AGZE Injectors Not Firing

Postby Alex170984 » Sat Feb 23, 2019 9:51 am

Hi all,

After my rebuild and trying to get the car running I have issues with fuel.

I have fuel pressure, fuel and a spark.

The car cranks but does not turn over.

I have measured the voltage on all 4 clips off of the injectors, all disconnected at the same time and found that 3 out of 4 have 12v on one side and 0 on the other. However, no1 has 12v on both sides.

Can this be the problem or another problem?

I am absolutely hopeless with electrics so please I will not be offended if you make your responces really simple!

Many thanks.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Sun Feb 24, 2019 6:00 am

Cranking the engine means its turning over

12v resides on one side of the injector and the ecu applies a signal low/ground to the other side and that's what fires the injector

Inside the ecu they use two transistors to switch the low/ground to the injector


Recheck check
Check grounds then retest


David
Last edited by Davegt27 on Wed Mar 13, 2019 12:18 am, edited 1 time in total.
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Re: 4AGZE Injectors Not Firing

Postby sirdeuce » Sun Feb 24, 2019 10:17 am

Check your grounds!
One shot, one kill.

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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Mon Feb 25, 2019 1:22 am

Could this be the ground in the ECU or a physical ground visible in the engine bay?

And the impossible is possible :(

I'm assuming that my ground is touching a live somewhere? Also, as 1 and 4 are linked, it is taking out no.4 as well?

2, 3 & 4 have 12v one side.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Mon Feb 25, 2019 1:46 am

Both,
there are several grounds on the GZE I can think of one on the intake, another on the removable panel near the coil



Also remember you have to push the clutch in when you try to start it
And you should get a slight tach bounce

Good luck
Last edited by Davegt27 on Tue Mar 12, 2019 1:13 pm, edited 1 time in total.
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Mon Feb 25, 2019 3:24 am

I cannot start the car with 3 injectors. It won't run. I've tried. It ran for a few seconds but I think because I flooded it.

Why press the clutch in?

I've checked the injector to ground, it gives me 12v. Both sides on no.1 injector give me 12v. The rest give me 12v and 0v.

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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Mon Feb 25, 2019 3:40 am

Is there a way of testing injectors 2, 3 & 4 to see if they are firing?

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Re: 4AGZE Injectors Not Firing

Postby davew7 » Mon Feb 25, 2019 4:02 am

The electrical signal to the injector is so short that most VOMs will not register the signal. Go to you local auto parts and ask for a noid light. They are only a few bucks, and will verify the injector signal. davew7

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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Tue Feb 26, 2019 12:40 am

If that earth does have 12v, is that the reason my injector won't fire?

At least if it is that wire it'll be fairly easy to trace back down the line even though the rail will have to come off.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Tue Feb 26, 2019 2:46 am

Yes the 12v on that one side is a big problem

When you unplug the injector that reads 12v on both sides is a easy step
And might eliminate one item (the injector)

Or a short at the injector plug
Now here is the problem
Because one transistor inside the ecu controls two injectors it is possible having 12v on
The wrong wire could short out the ecu's transistor

When I said disconnect that one plug and try to start would be a way to test that both transistors
Inside the ecu are still working
The car should run on 3 cyls

Hope this makes sense
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Tue Feb 26, 2019 3:54 am

Hi Dave,

The car doesn't run on on 3 I'm afraid to say. Tweaking the dizzy made no difference either. I didn't put my foot on the clutch though.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Tue Feb 26, 2019 12:47 pm

I just went out to my 88 5agze and the car wont even turn over without pushing the clutch in

there is a clutch interlock switch

I mentioned it because you said you just finished a rebuild (which means its been down for awhile) and sometimes people for get
its a real pain since you have to jump in the car to push the clutch in

HTH
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Re: 4AGZE Injectors Not Firing

Postby jondee86 » Tue Feb 26, 2019 12:48 pm

Here is the basic wiring schematic for the AW11 4AGZE injectors...

Image

As you can see, the injectors are wired in pairs, and it is impossible for only
one injector to have 12V on the downstream side if they are wired correctly.
If you have 12V downstream on only one injector, the downstream wires for
that pair of injectors must be separated, and one has been connected to 12V
by accident or mistake.

Trace the downstream wire from the problem injector and see where it goes :)

Cheers... jondee86

PS: Pressing the clutch when starting only applies if your car is fitted with a
switch on the clutch pedal to prevent the engine being started if the car is in
gear and clutch engaged.
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Tue Feb 26, 2019 1:06 pm

I have since cut off the first injector plug connector as there were only a few strands attached on the earth to the plug.

I've tested the wires again.

I have 12v on all power leads on all 4 injectors. I have dropping voltage to 0 on all 4 earths. Injector 1 had 12v straight away on injector 1 earth lead before I cut that connector off!

I have fiddled around with the connection in the ecu to make the pins closer together.

I've got new injector plugs coming so after I've connected the wires together I'll retest the voltage.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Tue Feb 26, 2019 2:32 pm

thanks Jondee

as far as I know all MR2's have a switch on the clutch my 85 had it as well as my 88,89 SC MR2's have it


we usually save the wiring stuff until after we do the basic check
for example unplugging the connector eliminates the injector then you test for power and ground

after that you unplug the connector at the ECU and test again
you just eliminated all components and it would be time to dig into the wire harness and look for a short

HTHs
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Sun Mar 10, 2019 4:46 pm

jondee86 wrote:Here is the basic wiring schematic for the AW11 4AGZE injectors...

Image

As you can see, the injectors are wired in pairs, and it is impossible for only
one injector to have 12V on the downstream side if they are wired correctly.
If you have 12V downstream on only one injector, the downstream wires for
that pair of injectors must be separated, and one has been connected to 12V
by accident or mistake.

Trace the downstream wire from the problem injector and see where it goes :)

Cheers... jondee86

PS: Pressing the clutch when starting only applies if your car is fitted with a
switch on the clutch pedal to prevent the engine being started if the car is in
gear and clutch engaged.


Hi Jondee,

This is really weird how the wires could somehow become wired incorrectly, as the car ran fine before and I had no issues with the wiring loom prior to the engine rebuild. I have not altered the fuel rail loom and I wouldn't have had any reason to either.

What injectors are wired in pairs? I thought it was 1&4 and 2&3?

I don't really get what you say about having 12v downstream...sorry I really don't understand electricals.

I don't think the AW11 MR2 has a switch on the clutch pedal.

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Re: 4AGZE Injectors Not Firing

Postby jondee86 » Sun Mar 10, 2019 10:16 pm

In electrical wiring diagrams electricity is thought of as flowing from the
higher potential 12V positive terminal to the lower potential ground terminal.
Thus the "downstream" side of an item with some resistance will be the side
that is closest to the negative or ground terminal.

I have coloured the 12V side of the injector wiring red and the zero or ground
side freen. One pair of injectors is connected with dotted wires and the other
pair with solid wires. You can see that each pair is connected together on the
downstream side, so if one clip has 12V on the downstream side, the other clip
must have 12V also... provided they are wired correctly.

When you are testing for voltage on the injector clips you must remember to
have all four clips off the injectors. If you test one clip while the other one of
the pair is still has the clip on the injector, YOU WILL GET 12V on both pins :)

Cheers... jondee86
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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Mon Mar 11, 2019 2:55 pm

I think an important question is does you car turn over when you try to start it (does the starter motor spin)

Image
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Mon Mar 11, 2019 4:19 pm

Hi Dave,

Yes it does.

I've had it running when it's been flooded by the cold injector.

If the resistor pack was not giving the full amount of voltage, would this affect all the injectors?

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Tue Mar 12, 2019 3:24 am

If the resistor pack was not giving the full amount of voltage, would this affect all the injectors?

yes should be 9v to 14 v according to the book
the diagram I posted above shows the switch for the clutch

the below shows the pin out for the ECU

Image

I will check my car later today I think I told you some wrong info
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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Wed Mar 13, 2019 12:29 am

is this a SC'ed MR2 or a car that has been converted to SC?
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Wed Mar 13, 2019 4:37 am

Hi Dave,

This is on a converted AW11, but I did cover over 2000 miles in 2017 before I decided to rebuild the engine.

This is a problem that has occurred whilst the loom has come off.

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Re: 4AGZE Injectors Not Firing

Postby Davegt27 » Wed Mar 13, 2019 7:51 pm

Well looks like you narrowed down the problem

There are all kinds of ways to do a conversion like yours
From modifying a NA hardness to using SC/GZE harness
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Thu Mar 14, 2019 3:07 pm

Hi Dave,

My engine came with the 4AGZE harness. Nothing had been modified to make it work.

I'm guessing one of the wires in the conduit has broken down. I'll get the rail off at the weekend so I can get to the mass of wires underneath.

Is there a earth point somewhere under all that lot?

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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Thu Mar 14, 2019 3:15 pm

jondee86 wrote:In electrical wiring diagrams electricity is thought of as flowing from the
higher potential 12V positive terminal to the lower potential ground terminal.
Thus the "downstream" side of an item with some resistance will be the side
that is closest to the negative or ground terminal.

I have coloured the 12V side of the injector wiring red and the zero or ground
side freen. One pair of injectors is connected with dotted wires and the other
pair with solid wires. You can see that each pair is connected together on the
downstream side, so if one clip has 12V on the downstream side, the other clip
must have 12V also... provided they are wired correctly.

When you are testing for voltage on the injector clips you must remember to
have all four clips off the injectors. If you test one clip while the other one of
the pair is still has the clip on the injector, YOU WILL GET 12V on both pins :)

Cheers... jondee86


Hi jondee,

When I got 12v on both connectors on no1, all the clips had been removed.

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Re: 4AGZE Injectors Not Firing

Postby jondee86 » Thu Mar 14, 2019 5:44 pm

There is only one possible explanation for this seemingly impossible result.
And that is (and you did mention this) that a strand of frayed wire had made
a bridge between the 12V pin and the ECU (zero volts) pin. If this happened
then you would indeed measure 12V on both pins.

When you have refreshed the wiring with new clips and connections, you need
to test again and make sure that there is only 12V on one pin.

After that you can look to see why the injectors are not firing :)

Cheers... jondee86
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Re: 4AGZE Injectors Not Firing

Postby UNLIMITED 86 » Fri Mar 15, 2019 12:54 am

I see many good suggestions have been made but you dont even acknowledge doing/trying any of them, or provide results.

Since you're 'hopeless' with electrical (your words), chances are you're overlooking the problem, which likely has a very simple solution (like a loose ground connection).

When troubleshooting, always eliminate the basics first. 99% of the time, you will fund it's not going to be an exotic or complex cause. In other words, its more likely you have a slightly loose ground connection than it is for a strand or 2 from one wire to break through 2 layers of insulation and cause a short.
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Re: 4AGZE Injectors Not Firing

Postby Alex170984 » Sat Mar 16, 2019 3:20 pm

Hi Unlimited86,

I have acknowledged the suggestions and advice.

I've recently had twins, 15 days ago to precise so my time on here and my car now, is very limited.

I have tried all of the suggestions and I have come back to the same problem, of having 12v on my earth on injector no1.

I have tested the output of the resistor pack, I have disconnected all injector clips and tested the voltage individually as per Jondee's advice, all of which come back to the same problem. I have tested the ohms at the ECU side, I have tested the ohms on the injectors. I do not have a clutch switch, so that is irrelevant.

I know the issue will be very simple indeed, however, an earth will not cause the issue I have with my injector no.1 earth reading 12v. Bearing in mind the loom is 30 years old and I don't know how many times it had been on and off the car before I bought the entire engine so I do not know the integrity of the loom condition.

I am now trying to find the time to disassemble my fuel rail, injectors, air intake and wiring loom, so I can strip back the conduit and find the wire that is indeed causing me the problems I am experiencing.

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Re: 4AGZE Injectors Not Firing

Postby jondee86 » Sun Mar 17, 2019 1:28 am

Hey... congratulations on the new additions :) Your first job is helping your
lady take care of the twins... fixing the car can wait a little while !!

Cheers... jondee86
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Re: 4AGZE Injectors Not Firing

Postby UNLIMITED 86 » Sun Mar 17, 2019 9:28 pm

Alex170984 wrote:Hi Unlimited86,

I have acknowledged the suggestions and advice.

I have tried all of the suggestions and I have come back to the same problem, of having 12v on my earth on injector no1.

I have tested the output of the resistor pack, I have disconnected all injector clips and tested the voltage individually as per Jondee's advice, all of which come back to the same problem. I have tested the ohms at the ECU side, I have tested the ohms on the injectors. I do not have a clutch switch, so that is irrelevant.

I know the issue will be very simple indeed, however, an earth will not cause the issue I have with my injector no.1 earth reading 12v. Bearing in mind the loom is 30 years old and I don't know how many times it had been on and off the car before I bought the entire engine so I do not know the integrity of the loom condition.


Yes but have you verified all of your ground wires are secured? This should always Step 1 when dealing with issues related to the 'Angry Pixies.' And I dont mean just looking at them; you need to put a wrench on every single one and verify they are adequately secure. Finger tight wont cut it!!!

And it's obvious (now) that the clutch switch is irrelevant; however, the question kept getting asked cuz you weren't clear in the original post and didnt acknowledge the question/provide clarification for sometime afterwards.

Also, we all have harness that are 30+ years old so its irrelevant. Ive owned my current car since around 2006 and have had the harness off multiple times without any issues other than a few broken connectors (which still work BTW). If all you did was remove the harness to rebuild the engine and it's all-of-a-sudden having this issue after you reinstalled it, then I can almost guarantee it's something you overlooked.

But if you want to go through all the work to tear things apart, I cant stop you. Just don't get frustrated when you don't find the problem and remember that you learn more from failure than you will from success.

Either way, good luck and congrats on the twinsies!
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