1976 280Z Wont Start

[NicholasKoenig]

22 hours ago, Dave WM said:

talking about the fuse links that connects from the battery post directly to the ECU.

If the headlights are dim and all the rest of the stuff like horn starter etc.. all exhibit low volt behavior, then I would suspect the battery, regardless of what the voltage tender says. You need to check the internal resistance of the battery, correct voltage means nothing CCA is what matters.

 

I took my battery to Autozone today to get it checked. They put it on their machine and it read 12.7 Volts and it said "Good Battery". I asked if this checked its CCA and the guy told me "It does what it does" lol. So I took the battery back to the car and connected it. Cranked the car over and my dmm said the battery was at around 10.5. According to what I read, this is above its cranking amps for 80F weather. 

I also went over and scuffed/cleaned every ground I could find, cleaned and checked every visible bullet connection, checked the battery cables and what not again. Doing this made the starter crank over a little faster. Still no spark after the coil, horn still sounds dull and low, exterior lights dim. 

I put the volt meter to the positive and negative cables that are connected to the starter and they read battery voltage. So power is def getting to the starter. One thing I noticed, I got a little play in the wires that connection the smaller cylinder above the starter (solenoid?). At one particular wiggle of the wire I even heard a "click" from something probably under the dash maybe. Couldnt replicate it. But the nut is tight and the connections are cleaned. Can the starter crank yet the solenoid be faulty? 

Hope this helps. Thanks!!

[Dave WM]

could be a high resistance joint at that connector. On mine the Positive lead of the starter is also where the wire that goes to the fuse links (and rest of the power supply for most everything else) is tapped. Since you are getting low voltages at the cars voltmeter and I presume at the fuse block (inside the car), I would start with just making up some new battery cables, esp if the ones you have are the least bit suspect. You can confirm a lot of stuff by reading the voltage at the fuse box with a load on like the ign key in the on position. If there is a high resistance somewhere there will be a voltage drop. Measure the voltage there with a multimeter. If its low then start working your way back to that starter connection. Another clue is with a heavy load like the headlights on the resistance will present with heat. So turn on the headlights, ign off, feel the connector at the starter, it should not be warm.

Some clarification is in order, there is a solenoid that electrically is a high current switch. one side is connected to the starter motor windings, the other to the battery thru a big wire, nothing in between.

there is also a smaller wire with a spade connector, this goes to the ign key, used to activate the switch and the engagement of the starter gear with the flywheel ring gear.

The wire harness has a large gauge wire white IIRC that shares the same connection to the solenoid as the big wire to the positive of the battery. This wire goes to the under hood fuse links via the wire harness.

The negative of the battery is connected to the starter physically and electrically by a mount bolt used to hold the starter to the transmission bell housing. All these wires need to be low resistance connections of a wire gauge suitable for providing the starter with the current needed to crank the engine without a significant voltage drop.

there are fuse links that are also separate from the fuse link boxes, they are the ones that feed the EFI directly from the battery terminals (not at the starter but at the battery post). they plug in and can have corrosion issues.

 

 

 

 

Edited August 22, 2017 by Dave WM

[NicholasKoenig]

On 8/22/2017 at 9:08 AM, Dave WM said:

The negative of the battery is connected to the starter physically and electrically by a mount bolt used to hold the starter to the transmission bell housing. All these wires need to be low resistance connections of a wire gauge suitable for providing the starter with the current needed to crank the engine without a significant voltage drop.

there are fuse links that are also separate from the fuse link boxes, they are the ones that feed the EFI directly from the battery terminals (not at the starter but at the battery post). they plug in and can have corrosion issues.

I got some detailed photos of the battery terminal wiring from Captain Obvious (who has helped me out so much in the past on the forum and in person!!). 

Based on your info and his, I have found that the two red wires that control the EFI were installed incorrectly to the terminals on my battery. In the process of taking the car apart and fixing general issues, I attempted to clean up the previous owners wiring mess and months ago probably assumed since that both EFI wires were red that theyd go to the positive. Now I know that isnt the case!! That said, I see that one red wires goes to the positive post and one to the negative. I know that of the two smaller red EFI wires, one is considerably thicker. And judging by some other photos of 280Z battery terminals on google, it appears the thicker red EFI wires go to the negative post. Can you help confirm this or tell me how to test which wire is which via dmm?

My new fuel relay (the combo one under the dash) arrived today and Im excited for that but want to connect the EFI wires correctly to the posts before putting that in. Im also going to check the fuse box in the passenger floor area again and go over each fuse. 

[Dave WM]

On mine the thicker wire went to the positive terminal thru a fuse link wire connected in series with the positive lead of the battery.

Since there is some confusion here I would HIGHLY recommend you disconnect the wires, unhook the battery and do some continuity testing from the wire ends. Example remove the 36 pin connector, disconnect the battery and test what you think is the neg lead to the various EFI connector pins designated as neg, there are several  (not the ecu) to confirm continuity.

NEVER test the ECU pins themselves, only the connector that is attached to the harness and only with the battery disconnected and the key off.

the positive should trace to the ign relay, pull out the relay and confirm continuity at the socket back to what you think is the positive lead (larger wire) in the harness near the battery.

 

Edited August 23, 2017 by Dave WM

[NicholasKoenig]

Thanks to new found knowledge given by you I have the efi wired to what I believe is correct. I also checked the grounding again. (Battery terminal to block then chassis etc) and its grounded. 

I swapped in an old ECU and cranked it- nothing. 

Swapped the newer ECU in and we have fuel pressure at the rail again AND spark at the plugs. Pretty sure I also heard the injector clack too. But still didn't fire up. 

Its dark out now so I can't really do much. I want to go over the AFM again. Any other ideas now that things are improving? 

EDIT: 

lights still dim and horn is still dull and low. 

Edited August 24, 2017 by NicholasKoenig

[JSM]

If your getting spark now, spray some starting fluid and see if she kicks over. If she does you injectors aren't likely firing or they may be clogged. Doubtful on the clog, but maybe. Hasn't been sitting that long. 

[NicholasKoenig]

50 minutes ago, JSM said:

If your getting spark now, spray some starting fluid and see if she kicks over. If she does you injectors aren't likely firing or they may be clogged. Doubtful on the clog, but maybe. Hasn't been sitting that long. 

I'll see if I can try that tomorrow.

If they are clogged, could I soak them in like fuel injection cleaner or something? 

[JSM]

If they are clogged with the fresh gas sitting in them they may work free. My 280zx sat forever (10 years) and they worked free finally within 30 min. I was using starter fluid and I think running the motor on it alone helped the injectors pulse more and free up. At least that is my best guess. 

Or take them out and make one of these to pulse them and run carb cleaner through them. Honestly, I don't think that is your issue.  I would do this as a last resort as it's a PITB!

Edited August 24, 2017 by JSM

[Dave WM]

I still don't like hearing about dim headlights.

Test the battery with a voltmeter while cranking should not go below 10v are the terminals getting hot?

time to break out the FSM and start checking voltages. My guess is either the injectors are clogged which has been covered above OR they are not getting a signal to fire. A noid light would be next to test for that.

[JSM]

1 hour ago, Dave WM said:

I still don't like hearing about dim headlights.

Test the battery with a voltmeter while cranking should not go below 10v are the terminals getting hot?

time to break out the FSM and start checking voltages. My guess is either the injectors are clogged which has been covered above OR they are not getting a signal to fire. A noid light would be next to test for that.

Or an old good working injector works well too.  You can hold it in your hand and feel it actuate.

[Captain Obvious]

Here's the pics I sent to Nick. A couple shots of my battery and cables. I'm using VW cables and I really like them.

Here's the battery end of the cables. The two smaller connections power the EFI system:

Here's the rest of the battery wiring. Unfortunately I had to use some of the yellow crimp connectors to put things together. I'll clean them out of there someday, but since it works (but is unsightly), it's lower on the priority list:

Here I'm holding up the EFI fusible link:

And here's where the positive cable connects to the starter solenoid. I'm holding a rubber insulating boot out of the way. Note the smaller white wire coming off the same terminal. The battery cable is on last hiding the smaller ring terminal of the white wire behind it. This white wire is how the rest of the car (minus the EFI) get's power:

I'm not sure if it's something that changed with years, but I wouldn't make any assumption about the polarity of the EFI wires based on wire size. On my 77, I believe both wires are the same gauge, so I just wouldn't be comfortable without making measurements between the battery end and the ECU connector end.

So cranking and getting spark is an improvement! 

[Dave WM]

yea, that's why I wanted him to confirm everything with power off by checking continuity, but must be right now.

agree a working injector could be used for a noid, that is a closer load test etc..

I have used mech stethoscope, but unless you have listened for it before you may not have the "ear" calibration needed