Weird No Start Condition - 260Z

[Patcon]

Is it possible it could have gotten 180° out somehow?

[SteveJ]

19 minutes ago, Zed Head said:

How about something got jarred when you removed the distributor cap?  The reluctor wheel or the magnet or stator.  Those ZX distributors are kind of fragile when they get older.   There were some good sparks there, so the make-break circuit seems to work.  Looks like a trigger problem.

Well, maybe that will show up in further diagnostics, but I agree with you about the trigger problem. The spark looks great WHEN IT HAPPENS!   It's a rebuilt distributor installed within the last 5 years or so. You never know what they replaced during the rebuild. I have another distributor I can throw in if needed.

@Patcon I don't think that is possible in this case. The problem started without pulling the distributor or rotor. Only the cap was removed without pulling wires and put back in place. 

[SteveJ]

And I went down to the car to check the stator. In the 260Z, it moves around with not much force. I'm going to swap it with another ZX distributor I have on hand.

Thanks for your help, guys.

[SteveJ]

So I swapped out the distributor. The spark is stronger and more consistent, but still no start. It started to catch when I was dumping a lot of starting fluid into the throttle bodies while holding the throttle open, so now I'm suspecting a lack of fuel. I'm going to see about the diagnostics on the GM TBI system.

[Zed Head]

It would be interesting to see more about that system in general.  Is it from an 80's GM car?  Is it heavily modified?  I don't know a lot about TBI, except from exploring injector styles in the wrecking yard and digging in to an occasional GM TBI system.  Only the mechanicals though, no electronics.

[SteveJ]

There is plenty online on the GM TBI. One site had the pinouts for the ECU and different threads on diagnosing "no pulse" conditions. It gives me a place to start.

[SteveJ]

Follow up: It is running now.

As I mentioned previously, I found some good diagnostics on the TBI.

I checked for 12VDC at the injectors - Good.

I unplugged the TPS to clear codes in case the ECU locked in that it was flooded.

I tried using an ohmmeter to look for a grounding pulse on the injector with the meter...As I cranked, it sounded like the engine wanted to fire, so I kept cranking until it fired.

The engine ran briefly on one injector, dying soon after I stopped cranking. I plugged in the rear injector lead and tried again. No start.

I unplugged the rear injector again and got the engine to run briefly, but it died again when I plugged the rear injector lead back in.

I unplugged the front injector lead and got the engine to run. I played with the throttle to keep it running while I plugged in the front injector lead, and it kept running with both injectors. My stress level dropped significantly.

I should probably invest in a noid light kit.

Anyway, I attached a document I created that has the images of the pinouts for the ECU and some of the diagnostics I was trying when I got the car to run. @Zed Head, I thought it might pique your curiosity.

TBI Diagnostics.docx

[Zed Head]

11 minutes ago, SteveJ said:

Follow up: It is running now.

But why?  I haven't looked through the Doc yet.  I wonder if it's an OBD-1 or -II system.  Trouble codes.

[SteveJ]

I didn't try to pull the codes because I didn't want to break out my ancient laptop. It's an ODB-I system that runs at a blazing 140 baud. What I speculate is that when I was trying to start without the coil wire connected this morning, the TPS triggered a flooded signal in the ECU. The car started to fire AFTER I unplugged the TPS with the key in ON. I think that cleared the code for that problem. (My rambling in the previous post doesn't emphasize this point.)

Typically when I start the car, as soon as I hear it fire, I give it a little gas. This time I was outside the car, looking at the engine bay, so I wasn't adding fuel after firing.

Now, the key is for me to try starting the car tomorrow and see if it behaves. I need to fine-tune the timing with the replacement distributor anyway.

[Zed Head]

9 minutes ago, SteveJ said:

I didn't try to pull the codes because I didn't want to break out my ancient laptop. It's an ODB-I system that runs at a blazing 140 baud.

ODB?  Ol' Dirty Bastard?  Wu Tang.

I think OBD-I uses flashing lights on the ECU.  Watch and count.  Anyway, hope it was just an odd occurrence.

[SteveJ]

Yep, I'm getting tired after fighting that problem all day.

OBD-I does use the flashing lights after you put the paper clip in the right terminals of the ECU. There is software that allows a PC to read the codes, too, without having to count blinks. Unfortunately that software barely runs right on Windows 7, and you can forget about using it on a later computer. I still have a couple of Windows 7 laptops around, though. I'm not sure how good their batteries are. I can datalog with this setup, too, and even get Affordable Fuel Injection to create a new map.

At least I have some idea of what happened, and I know more about diagnosing the system. That should make future issues less problematic...I hope.

[Racer X]

1 hour ago, SteveJ said:

Unfortunately that software barely runs right on Windows 7, and you can forget about using it on a later computer.

Have you tried using Windows Virtual PC?

I found it useful to run some OEM (GM, Ford Service Bay, International trucks) service manuals from the 1990's that run from CDs, and refused to load and run on Windows 7 Pro.