No injector pulse

[Captain Obvious]

Don't get hung up on the composition or the exact value just for a test. In other words, just to test "Dead" or "Not dead" on your ECU, it doesn't have to be wire wound. It also doesn't have to be exactly 15 Ohms.

Just for a test, any resistor between say, 10 and 20 Ohms regardless of composition should work just to see if there are other problems.

BTW - There's another identical resistor in there, closer to the big wiring harness connector. How's that one look? I'm trying to come up with situations that would have fried your resistor and one of them is reversed polarity to the ECU like maybe having jumper cables connected backwards? If that were to happen, there would be damage elsewhere on the board, including the other 15 Ohm wirewound.

Do you see signs of heat anywhere else inside the ECU?

[Captain Obvious]

Forget about the reverse polarity stuff... I took a refresher look at my notes and reverse polarity shouldn't fry that resistor. Haven't looked deeply enough to guarantee that something else might fry, but those two wirewound 15 Ohm resistors should be OK.

Actually, there's something to check... There are two spherical glob shaped zener diodes with red stripes on them. One of them is visible in your pic (ZD101). There's another one near the other wirewound resistor (ZD201). Measure the resistances of those two zeners in both directions when you get a chance. Use a low Ohms scale.

With that resistor fried, it's possible that ZD201 (the one NOT visible in your pic) took a hit.

And after that... I'm not going to get into component level troubleshooting of the board. It's going to be impossible on-line.

[77Datz]

Thanks for all the tips, captain obvious. (<--no joke, but awesome pun) I'll have to test more components in the computer too, I tested most if the diodes and they were fine. I should be getting the new resistor tomorrow and I'll solder a new one in and try to repair the board as best as I can and I'll see if it'll start. I know a lot about small electronics like this, because my Dad taught me how to solder when I was 6 and I've always been around it as he worked as a lead technician at a company that makes computer chips. I just didn't think I'd be doing this type of thing to a car.

If it doesn't start, I'll be totally stuck. I just can't seem to figure out exactly why it wont start and stay running, I thought it was a fuel issue, I never thought it to be electrical.

[Captain Obvious]

Haha! They call me Captain Obvious! :laugh:

I'm not holding out lots of hope that simply replacing that resistor is going to fix it. I don't know what happened that fried that resistor, but it clearly wasn't pretty. I'd be very surprised if the damage was isolated to simply that resistor, but it doesn't hurt to try. After replacing that resistor (and verifying that there aren't signs of heat elsewhere), you can do a very basic "reality check" on the ECU on the bench without having to install it in the car:

Connect ground to pin 5

Connect a FUSED 12V supply to pin 10. The fuse should be 2A or smaller.

The ECU should draw less than 1 Amp. If it draws more than that and pops the fuse, then there's still something wrong inside.

If you are at all unclear on how to do the above, then don't try...

BTW, it's not a computer. There are no programmable devices inside. It's all analog.

[SteveJ]

Ah, but it is a computer. It's an analog computer. Analog computer - Wikipedia, the free encyclopedia

[77Datz]

Good news everyone! I replaced the resistor this morning and she started right up! Shes running a little rough, timing needs to be adjusted and I have to drain the old gas and put some new in, she needs an oil and coolant change as well but for now, I finally got it running!

[Captain Obvious]

Excellent! That's awesome! I'm surprised (but very pleased) that the damage was confined to that resistor. I'll take another look at my notes this evening and see if I can come up with any theories as to what could have caused that. I don't remember off the top of my head what part of the ECU that resistor is associated with.

Keep that other ECU on the shelf in case there are any issues in the future. It's good insurance.

So how's this for a small club to belong to... Has anyone else here ever done successful component level troubleshooting inside a 280Z ECU? Anyone?

[Captain Obvious]

Ah, but it is a computer. It's an analog computer.

Haha! Yeah, and so are two resistors used as a voltage divider

[77Datz]

I was amazed when it started up and didn't die right away like it had been doing for the past two weeks. I haven't heard about anyone else doing this kind of troubleshooting and repairing, especially when it comes to an ECU. The 280z ECU is complicated, but yet still simple enough to repair with some basic electronic know-how.

Now the fun can start, next up on my to-do list is fluid changes, some extensive cleaning, new tires and a little bit of body work and I can get her on the road.