76 280z Electrical Check List need advice on what to do next

[Blue_streak]

First off, I would like to thank everyone in the previouse thread i made that helped greatly with diagnosing and for the most part fixing my EFI issue. The thread can be found http://www.classiczcars.com/forums/fuel-injection-s30/52655-fuel-injector-replacements.html

Now on to my new issues and questions. After i replaced my fuel injectors i tested plug 1 on the ecu connector and did not read battery voltage. All the circuits for the injectors checked out ok but pin 1 was just not getting any power. From looking at the color wire diagrams available i was able to figure out that i had my coil wires reversed. Switched them around and still i was not getting battery voltage. Pouring over the diagrams again i noticed a connector under the dash that may of been the culprit, and sure enough when i found it and hooked it up pin 1 started getting voltage again. So it was at this point i tried to start the car, it started for 1 second and died, and i figure it was because the battery in it was dead. So a day on the charger, and battery went back in, tried to start it again and... NOTHING! In fact, now the tach wasn't even working now, and it was before. So i was really confused now, how could something that worked the day before not work and nothing had really changed. So i went back to the coil to see if maybe i missed something there, and then i noticed the ballast resistor(i think that right though i cant seem to find a clear answer on what its called) was really warm.

I got out my FSM and started going through all the tests and here are all my results.

1)Throttle Valve Switch:Idle Switch

Continuity

2)Throttle Valve Switch:Full Switch

Continuity

3)Airflow Meter

a)Pin 6 and Pin 8: 220 Ohms

b)Pin 7 and Pin 8: 194 Ohms

c)Pin 8 and Pin 9: 127 Ohms

4)Air Temp Sensor(Will Replace)

Not good

5)Fuel Pump Contacts

Continuity

6)Water Temp Sensor(Will Replace)

Not Good

7)EFI Relay: Fuel Pump Relay

Not Good

*This one does not make sense to me for reasons that can be seen at the end of this post

8)Air Regulator and Fuel Pump

Continuity

9)Ground Circuit

A,B,C,D All have continuity

Then i moved on to the Voltmeter Continuity Check

1)Revolution Trigger Signal

Battery Voltage

2)Power Line Circuit

Battery Voltage

3)Injector and Dropping Resistor

A,B,C,D,E,F All Battery Voltage

I was going to move on to the next set of tests when i accidentally turned the key to far in the ignition and the car started for 2 seconds before stalling, with out the ecu plugged in. After that happened i just moved on from those last tests and plugged the ecu back in hopped in the car and tried to start it. It started! For the first time in almost 2 years it fired up, only real issue is its running really rich but imagine this is due to the 2 temp sensors being gone.

I guess my main question is besides the obvious sensor replacements, whats my next step? Also how did it start with the efi relay testing bad and how did it run without the ecu plugged in? thanks

[Zed Head]

Without knowing which mystery wire you reconnected and where you found it under the dash there's no way to really know what you did. The car probably started on fuel from the cold start valve which is powered independently via the Start circuit, I believe.

You didn't show any test results so it's not clear what "tested bad" means for the EFI relay.

If it runs and you don't have any loose wires hanging around, you might as well get the sensor installed, let it run and tune it up. It won't run when warm without the coolant temp. sensor. BUT, it's not clear what "not good" means. Why don't you post some numbers? And make sure you didn't actually measure the thermotime switch. They look similar.

Making progress. Your AFM numbers are sketchy, they should be 180 and 100, not 220 and 127, but they're not far off from the 1.8 ratio. It might be okay, those numbers work for some people. If you have a lean condition you might be able to fix it with a potentiometer on the coolant sensor circuit.

[Blue_streak]

Tested bad, according to the FSM was meaning that continuity between pin 20 and body metal was non existent. The mystery wires i reconnected isn't to big of a mystery, its the wire that comes off the ecu connector that goes to slot 1. I didnt measure the thermo time switch these are tests that i only did through the ecu connector. Not good is just what the FSM was saying hence why i said it. Im actually not having a lean issue its running incredibly rich, i was thinking that maybe its over fueling because of the dead sensors. So ill replace those sensors and see what happens. I can find the coolant temp sensor but does anyone no the air temp sensor part number?

[EuroDat]

I been a little silent the last week. we lost two collegues at work and it shock us up a bit.

Reading your last post, I had a similar problem with the air temperature sensor in the AFM. I ended up replaceing the sensor. Its NLA so you will need to find a work around. Here is my thread on how I solved it. http://www.classiczcars.com/forums/fuel-injection-s30/51993-faulty-air-temperature-sensor.html

Zed Head came across a possibility, by accident, when he was removing his water temp sensor. You could experiment with the old one and if you can get it apart ok, by two new ones. They cost around $25 from Nissan P/N: 22630-N4200 SENSOR WAT :: Nissan Parts, NISMO and Nissan Accessories - Courtesyparts.com

Your 2 second idle run was probably caused by fuel still in the inlet manifold. The ignition works independant from the ECU. After it burnt that fuel it went back to your not starting/running problem.

Chas

[Zed Head]

Tested bad, according to the FSM was meaning that continuity between pin 20 and body metal was non existent. The mystery wires i reconnected isn't to big of a mystery, its the wire that comes off the ecu connector that goes to slot 1.

That's one weakness of the way the FSM is written. They have a set of quick tests, then a set of more detailed tests. But with a meter at the ECU connector you can just go directly to the full test.

You might just have bad connections, not bad relays or sensors.

The coolant sensor harness has two bullet connectors in-line, on the top of the intake manifold, that could be disconnected. You can either find and trace the wires or go directly to the sensor and measure resistance across the two pins. I would just go directly to the sensor myself. It's cramped but you can get in there.

You can also measure the air temperature circuit at the AFM before you try to replace it. Eurodat had to fabricate a way to use anther sensor in his AFM. It would take some work but may not be necessary in your case.

Odds are good that your parts are fine it's just the wires that need work. Best to confirm, once you start wrenching things tend to get broken.

Sorry to hear about your colleagues Chas. It wasn't tied to MH17 was it? Things are getting strange in the world.

Edited July 27, 2014 by Zed Head
Got my N.G.'s mixed up.

[Blue_streak]

Ok, so i tested the air temp sensor it self in the AFM, it was 20 Celsius in the garage and the sensor tested as 2520 ohms. So ill look at the wiring next.

[Zed Head]

Not clear how you could get readings on the other pins but not the air temp. sensor. The wires are all run into the harness at the same spot. Odd.

The coolant sensor will have a much bigger effect.

[Blue_streak]

That was my thought, I noticed the ground wire off the afm was not attached, but I don't thing that would stop anything. Oh well, I figure ill test continuity between the afm connector and the ecu and go from there. Grabbed the coolant sensor plugs from my spare engine and they have continuity, so on my way to testing the sensor I'll test the wiring currently on there . Thanks for all the help, honestly I means a lot. I've been trying to get this thing road worthy for a long time.

[Zed Head]

Actually, the ground wires are very important and often overlooked. The black wire on the AFM body seems redundant but who knows. If the air temp sensor grounds through the AFM body and the AFM body doesn't have good conductivity through the mounting bolts then that wire becomes important.

The EFI harness and ECU also ground through the second, smaller, black wire at the negative post.

All of the electrical connections are potential failure points on these old cars. Blue just linked to a good resource in this thread - http://www.classiczcars.com/forums/open-s130-zx-discussions/52710-help-please.html#post460982

[Blue_streak]

Ok, so i found that the wires to my water temp sensor where broken. Fixed them up and the ecu can see it again. Only issue now is the sensor is in the 52000 ohms range, by the table in the efi bible im pretty sure that means its gone bad. Will be replacing that one.

[Zed Head]

Don't forget to check directly at the sensor. Mentioned in case you're still at the ECU.

They're not too expensive though so the money spent is almost worth the clean pins on the sensor, by themselves.

[Blue_streak]

Checked the coolant sensor at the sensor, ya 51560 ohms is what it settled at . So that's bad, on the plus side though that ground wire off the afm made all the difference ecu can see it again and it's reading perfectly

Edited July 30, 2014 by Blue_streak