Datsun 280zx won’t start

[Jimmyb]

On 2017-11-14 at 10:23 PM, Zed Head said:

Actually that is a common cause of wonderment, but, as Captain Obvious pointed out to me many moons ago, is normal, for a parallel circuit.  You're just measuring voltage on the other  pin through one of the other still connected injectors.  The voltage that you're measuring will have its path to ground through the transistor circuit in the ECU.  The grounds are ganged together at the transistor in the ECU.  That's why disconnecting the ECU breaks the parallel circuit.  I think that you can move on from that concern and go to the basics, like spark, and injector opening.

Have you verified spark, and tried to start it with starting fluid?  Starting fluid will tell you that you have spark, and compression, and that all of the important timing events are correct.  If it runs with starting fluid, you can focus on injector opening, or vacuum leaks, or similar.  If it doesn't run with starting fluid then all of those other important timing events are suspect.  It's a simple quick test that will get you much farther ahead than where you are now.  You can usually sit at the engine intake with the can of fluid and keep the engine running for a little while, just to hear how it runs.

 

On 2017-11-15 at 3:39 AM, Captain Obvious said:

As Zed Head mentioned, that is normal behavior. This is what the circuit looks like with the ECU installed:

If you pull the ECU out, it disconnects each injector from the others and you can test them individually.

 

On 2017-11-15 at 2:02 AM, JSM said:

So you know it will start on fluid and  you know the injectors are firing now, I'd go back and ensure you have pressure.  

I'd suggest if you have another pump, put it at the front of the car directly to the fuel rail from a gas can and then run the return line back to the same gas can to simulate a tank.  Eliminate the entire fuel system.

Put alligator clips on the wires to the pump and hook to the battery directly. 

Have a fire extinguisher by for safety. 

Similar to this (I removed the video)

 

Well that's.. I don't know, when I didn't thought I could be any more confused. But then I could be the ECU that's the cause of why it's not starting?

The ECU doesen't ground one of the pins properly? Are the ECU itself grounded through something? Like the chassi?

I might know of a guy that's restoring a 280z , not zx, with injection, maybe I can test his ECU if it's the same as mine.

To answer where I'm at:

- The car cranks

- I got spark, a good spark!

- I got fuel coming in and out of the rails (JSM, there are alligator clips on the wires to the pump diretcly from a battery as I'm not so sure 'bout the fuel pump relay)

- I've sprayed starting fluid over all the vacuum lines I could find while my girlfriend was cranking the engine and it did not react, so no mayor leaks there.

I mean, in my book this is a recipe for a working car, but no..

- The car fires up with starter fluid BUT it doesen't run, it immediately dies after firing. I can't make ut run if I keep spraying either. No compression? I'm doing a comp test hopefully this weekend.

- The injectors works, I've cleaned these in a ultrasonic wash and inside them with break cleaner and help from a battery + starter button to simulate the pulse until there was a beautiful mist coming out.

 

So here's my list of suspects and wonderments:

- The ECU, can I test this thing somehow? I know I can test the ECU connector to see if the cars wiring works but this is something I'm looking for help to do as my electrical skills are close to zero. But can I test the actual ECU?

- The injectors won't fire when they are in the car, I mean even with only 3 volts I could totally feel when the injectors were firing, but not now, not while they are back in the car.

- The metal relay (EFI relay I believe?)behind the plastic cover next to the battery. This relay seems to work with cables diretcly from the battery, it's clicking. But not when It's back in the car, totally silent when cranking.

 

So this is why I'm so hung up on the ECU, as the injectors do work, the EFI relay do work, but only with direct power from the battery and none of them are working when they are where they should be.

And again, thank you gous for taking a interest!

 

Ps.

I've read somehwhere that the tachometer has to be connected because they are a part of helping the ECU control the injectors, is this real or am I being fooled? Sounds wierd to me, but than again I'm grasping here.

I believe the tachometer is working properly but I'm giving this a look tonight after work.

Ds.

[JSM]

If it runs with fluid, I wouldn't be concerned about the tach.

You said, "- The metal relay (EFI relay I believe?)behind the plastic cover next to the battery. This relay seems to work with cables diretcly from the battery, it's clicking. But not when It's back in the car, totally silent when cranking. "

So the relay only clicks if you hardwire it out of the socket?  Have you verified that when you simply turn the switch to the "on" position the relay clicks? You need to check if power is making it to the relay itself I guess is my question.  With the key on, the relay should be on.  No other noise should be heard while cranking, unless for some reason it is cutting off which could be from a bad key switch.  I'm assuming it is because you have powers to your injectors.

Also try with a volt meter connected to the injectors and voltage is seen, crank the car and see if the voltage remains.

Also have you removed the connectors from the ECU and confirmed there is no corrosion on any of the connectors or ECU terminals?

Edited November 16, 2017 by JSM

[Zed Head]

The tachometer is a real issue that I've verified on two different EFI cars, a 76 and a 78.  So few people try to stat their engines with the tachometer out though, that nobody believes it and they all discount it, because, apparently, they don't understand why it would happen.  No offense to the non-believers, but it's true, it really is, you have to believe me... (read this in a pleading whiny voice) .  If you have a factory stock EFI car go remove the inline resistor and try to start the engine if you want to know, or generate some real knowledge refuting my claim.  Again, no offense, it is what it is.  Even worse, it only happens when everything is factory stock.  I have a GM HEI ignition module now and it starts fine with the tachometer disconnected.

BUT, JimmyB, you are way way ahead of thinking about things like that.  You haven't even done the most basic, usually the first, test of the EFI system - Confirm that Pin 18 (for the 280ZX's) of the ECU connector is electrically connected to the negative post of the coil.  That's what the ECU sees to know to open the injectors.

You're at the point where you need a multimeter or test light and need to go through the tests we always recommend in either the FSM.  It's possible that the ECU is bad but it's a lot easier to run a few simple tests first.  Go to the "Electrical System Inspection" section of the Engine Fuel and Emissions chapter of the FSM.  Ignore all of the ECCS and Analyzer test material, the simple tests are at the back of the chapter.  Sorry, but you're at that point.  The 280ZX wiring is different than the 280Z wiring but the basic functions are the same.  Page 80 is the first page.  See how they made a special place for the negative pin of the coil?  It's very important.

 

[Patcon]

So let me get this right. It will start with Ether but you can't keep it running with Ether? That would concern me if that's the case...

[Jimmyb]

10 hours ago, Zed Head said:

The tachometer is a real issue that I've verified on two different EFI cars, a 76 and a 78.  So few people try to stat their engines with the tachometer out though, that nobody believes it and they all discount it, because, apparently, they don't understand why it would happen.  No offense to the non-believers, but it's true, it really is, you have to believe me... (read this in a pleading whiny voice) .  If you have a factory stock EFI car go remove the inline resistor and try to start the engine if you want to know, or generate some real knowledge refuting my claim.  Again, no offense, it is what it is.  Even worse, it only happens when everything is factory stock.  I have a GM HEI ignition module now and it starts fine with the tachometer disconnected.

BUT, JimmyB, you are way way ahead of thinking about things like that.  You haven't even done the most basic, usually the first, test of the EFI system - Confirm that Pin 18 (for the 280ZX's) of the ECU connector is electrically connected to the negative post of the coil.  That's what the ECU sees to know to open the injectors.

You're at the point where you need a multimeter or test light and need to go through the tests we always recommend in either the FSM.  It's possible that the ECU is bad but it's a lot easier to run a few simple tests first.  Go to the "Electrical System Inspection" section of the Engine Fuel and Emissions chapter of the FSM.  Ignore all of the ECCS and Analyzer test material, the simple tests are at the back of the chapter.  Sorry, but you're at that point.  The 280ZX wiring is different than the 280Z wiring but the basic functions are the same.  Page 80 is the first page.  See how they made a special place for the negative pin of the coil?  It's very important.

 

I believe you.

I'm sorry, I think I missunderstood you earlier when you mentioned the negative post of the coil. Maybe I read it to fast or maybe my English is'nt as good, I have a friend who knows a bit about electrics and who do knows how to work a multimeter properly that will help med out this weekend. I will suggest we do just as you say here, check the negative and follow the FSM. I'll keep you updated, thank you very much!

[Jimmyb]

6 hours ago, Patcon said:

So let me get this right. It will start with Ether but you can't keep it running with Ether? That would concern me if that's the case...

Yes, If Ether is starter fluid then yes.

And yes, it does concern me..

[Jimmyb]

Hi, so it was a late one last night again and the car still won't start.

Me and my friend followed the  Engine Fuel and Emissions chapter of the FSM. 

The first thing we tried were the #18 pin to the negative post on the coil as Zed Head recocmended and  that path is clean and useful..

So I colored that pin with a pink marker, and kept on going.

As you can see on the img that I uploaded:

1. Engine earth is great.

2. Throttle valve switch works

3. The EFI relay works (the green relay under the plastic cover next to the battery)

4. Air flow meter seems to work

So I really don't get it. Today I think I might leave the rails with injectors hanging loose just to confirm with my eyes that the injectors wont fire, now I'm desperate. I'm almost 100% sure that they don't but I have to see it. After ofcourse I try with a lamp connected to the injector clips, if the lamp wont work then ofcourse the injector hemselfs wont fire.

 

Any other tips?

Thanks,

/ Jimmy

 

Ps. I tried with another ECU last night, didn't do any good. This was a ECU from a -78 so the ground from ECU to the coil are on the #1 pin ( I think), so I cant exclude that there might be something wrong with my ECU just yet. Also my ECU connector is wierd, there's a cable that goes from yellow to blue, the same blue as the cable that later goes to the negative post on the coil, but that path is wotking so.. And there's a cable tie there so someone has probebly messed with this before. In Sweden a cable tie is called "Kattstrypare" wich directly translated means "Cat strangler", that won't help anyone out at all, but I thought I let you know anyway.

 

 

[Reptoid Overlords]

Mine has that as well. I am at work and don't have the FSM handy to find out what it is.

 

I've never looked into its purpose, but it is identical to the one in my car, so it most likely isn't an aftermarket installation.

 

Anti theft perhaps? Just a guess.

 

Also, I don't recall the fuel pump relay in the trunk, under the trunk floor mat being mentioned. It is identified as relay number 2 or 3, I believe. Again, no FSM handy.

 

 

 

 

[JSM]

That plug is what goes to the - coil. It's weird that it is external to the ECU. 

Have you verified fuel pressure yet?

[Patcon]

On 11/16/2017 at 6:02 PM, Patcon said:

So let me get this right. It will start with Ether but you can't keep it running with Ether? That would concern me if that's the case...

This to me seems like the first issue. If he can't keep it running with Ether (starting fluid) then it is not drawing enough fuel in or he is losing spark...

[Jimmyb]

1 hour ago, JSM said:

That plug is what goes to the - coil. It's weird that it is external to the ECU. 

Have you verified fuel pressure yet?

 

23 minutes ago, Patcon said:

This to me seems like the first issue. If he can't keep it running with Ether (starting fluid) then it is not drawing enough fuel in or he is losing spark...

We've done a continuity test and measured resistence between coil negative and pin #18 (0,1 ohm) AND we also applied signal with a cable fault locater/circuit tracer detector and resived the signal at pin #18, and yes it is the lonely cable beside the wiring connector.

Also finally got a nod light and just as we figured, the injectors don't get any power. The nod light works but not when put into the injector connector.

As far as the fuel pressure goes, there is a return line so how much pressure can it be? We have a good flow coming from the return line rail. The fuel pump have no voltage on the connector so the pump is connected directly to a battery.

I dont think its loosing spark but no its not getting enough fuel because the injector wont open. But it should still run on starter fluid even if the injector dont work right? Its only in the air and doesent the fluid burn up straight away?

[Mark Maras]

 Kind of a shot in the dark but the fact that it will start but not run leaves me wondering if this could be ignition switch related. There was a thread just a few weeks back that described the same symptom. It's quite common for them to fail in this way.