Cannot get injector pulse - passes EFI bible tests!

[MrChefur]

Hey everyone! I'm starting a new thread since my "help me!" thread got too long and isn't getting any attention now.

Long story short, I'm not getting pulses to my injectors. I've been working on this problem for 2 weeks and I can't seem to get it. The car ran before I tore it down to replace oil control rings 4 months ago, so it's not likely a component failed. I'm thinking I put something together wrong.

If I disconnect the ECU connector and ground each injector's pins, they audibly fire. If I manually fire them a few times the car will start afterwards for a few seconds from the leftover fuel, so I know it's not a fuel pump or clogged injector issue. The car will start from starting fluid. My noid light also doesn't show any pulses.

Here's the results of the EFI Bible tests:

• 1-9(a-d): Control Unit Ground Circuit #1: continuity from pins 5, 16, 17, and 35 to ground. Pass
• 2-(1): Ignition Coil Trigger Input Circuit: pin 1 to ground reads 12.5v. Pass
• 2-(2): Control Unit Power Input Circuit: pin 10 to ground reads 12.5v. Pass
• 2-3(a-f): Injectors. All read battery voltage. Pass
• Pin 1 to ignition coil negative reads continuity
• Tachometer jumps while cranking

I also tested my dropping resistors and they both pass the FSM tests.

What could be causing this? I am at my wit's end here. Thanks for reading.

[Zed Head]

16 minutes ago, MrChefur said:

The car will start from starting fluid. My noid light also doesn't show any pulses.

Does it stay running after it starts?  Not clear.   

Just trying to get a feel for the problem.  The thing about the early Datsun EFI systems is that the Start functions are kind of separate from the Run functions.

You didn't say year of car either.  Forgot from your other thread.

[MrChefur]

Just now, Zed Head said:

Does it stay running after it starts?  Not clear.   

Just trying to get a feel for the problem.  The thing about the early Datsun EFI systems is that the Start functions are kind of separate from the Run functions.

You didn't say year of car either.  Forgot from your other thread.

Sorry, missed a few details. No it doesn't stay running, just burns what's left and dies.
It's a 1978.
Here's my previous thread:
http://www.classiczcars.com/topic/58265-rebuilt-engine-idle-problems-running-rich/

[Zed Head]

27 minutes ago, MrChefur said:

• Pin 1 to ignition coil negative reads continuity
• Tachometer jumps while cranking

I'm just going to start over without reading the other thread.  

Your tests so far have shown that you have spark, and timing is essentially correct, and the injectors are powered.  Have you checked the ground circuit for the ECU?  The EFI system has a dedicated ground circuit to the battery's negative post.  Grounds are often overlooked.  In all of your tests you have supplied the ground yourself, but the ECU might not have a good ground, for the injector-open circuit.  No ground - no current - no injector opening.

The Bible has a set of ground check tests.

[MrChefur]

1 minute ago, Zed Head said:

Have you checked the ground circuit for the ECU?  The EFI system has a dedicated ground circuit to the battery's negative post.  Grounds are often overlooked.  In all of your tests you have supplied the ground yourself, but the ECU might not have a good ground, for the injector-open circuit.  No ground - no current - no injector opening.

The Bible has a set of ground check tests.

Is that not the tests 1-9(a-d)? They're labeled as control unit ground circuits, that's from the Bible.

[240260280]

Is fusible link to EFI system connected at bat +pos terminal?

Is intake manifold grounded to cable in EFI harness?

[MrChefur]

8 hours ago, 240260280 said:

Is fusible link to EFI system connected at bat +pos terminal?

Is intake manifold grounded to cable in EFI harness?

The intake manifold is grounded. I'm not certain about the fusible link though. My car has a 2 spade connector on a wire coming from the positive terminal to 2 fusible links and into the harness. I checked continuity and it seemed like it's working properly, but I cleaned the connections just to be sure.

[S30Driver]

Does the EFI relay click when you turn the ignition key to on?

[Zed Head]

14 hours ago, MrChefur said:

If I disconnect the ECU connector and ground each injector's pins, they audibly fire. If I manually fire them a few times the car will start afterwards for a few seconds from the leftover fuel, so I know it's not a fuel pump or clogged injector issue. ...    The car will start from starting fluid. My noid light also doesn't show any pulses.

Here's the results of the EFI Bible tests:

• 1-9(a-d): Control Unit Ground Circuit #1: continuity from pins 5, 16, 17, and 35 to ground. Pass
• 2-(1): Ignition Coil Trigger Input Circuit: pin 1 to ground reads 12.5v. Pass
• 2-(2): Control Unit Power Input Circuit: pin 10 to ground reads 12.5v. Pass
• 2-3(a-f): Injectors. All read battery voltage. Pass
• Pin 1 to ignition coil negative reads continuity
• Tachometer jumps while cranking

I missed the ground circuit test mention.

The fact that your injectors don't seem to be opening seems to be the key.  You've tested everything else.  That means the ECU isn't triggering the transistors to ground the injector circuit.  Maybe.

I don't see any coolant temperature sensor resistance readings.  If that circuit is shorted out, the ECU will supply less fuel because it thinks the engine is super-hot.  Maybe the noid light pulses are so short that you can't see them.

If that circuit is right then a problem with the voltage pulse on Pin 1 seems possible.  I've mentioned several times over the years how I've had engines that wouldn't start when the tachometer was out.  Not your case since your tachometer is in and seems to be working but it shows that the Pin 1 voltage quality is important.

[MrChefur]

2 hours ago, S30Driver said:

Does the EFI relay click when you turn the ignition key to on?

Yeah, it clicks pretty loud. I suspected it before so I made an improvised relay with some switches, but got the same result.

2 hours ago, Zed Head said:

I missed the ground circuit test mention.

The fact that your injectors don't seem to be opening seems to be the key.  You've tested everything else.  That means the ECU isn't triggering the transistors to ground the injector circuit.  Maybe.

I don't see any coolant temperature sensor resistance readings.  If that circuit is shorted out, the ECU will supply less fuel because it thinks the engine is super-hot.  Maybe the noid light pulses are so short that you can't see them.

If that circuit is right then a problem with the voltage pulse on Pin 1 seems possible.  I've mentioned several times over the years how I've had engines that wouldn't start when the tachometer was out.  Not your case since your tachometer is in and seems to be working but it shows that the Pin 1 voltage quality is important.

I'll be sure to check the coolant temp sensor readings later tonight. If memory serves, they came back fine, but since I didn't write it down I'll have to check again.

How would I determine the quality of the pin 1 voltage?

[Zed Head]

25 minutes ago, MrChefur said:

How would I determine the quality of the pin 1 voltage?

I don't know.  All I know is that I've had ECU problems, and tachometer problems, both due to changing one of the components on that branched circuit.  You might double check the blue wire connection at the ignition coil, clean it well.  The Pin 1 circuit.  Maybe you have continuity, but the resistance is too high.

Do you have the factory stock ignition system or something else?  I think that people have reported the MSD system, and/or Crane, doesn't work with the 280Z EFI.

Here's an example from MSA's site - http://www.thezstore.com/page/TZS/PROD/12-4005

[MrChefur]

4 hours ago, Zed Head said:

Do you have the factory stock ignition system or something else?  I think that people have reported the MSD system, and/or Crane, doesn't work with the 280Z EFI.

Stock type ignition system with an aftermarket coil. I don't think that's my issue though, seeing as it ran before my teardown and gives good spark.

I also got a new ignition relay in today which changed nothing.