Has anybody attempted to repair their ECU?

[sscanf]

I just made the temp sensor tweak to my 1976 280Z and its improved my cold performance to the point where I was able to replace my ball valve with an ebay Aux Air unit (from a Porsche by the way). I can now start it cold and not have to pop the hood or feather the accelerator for any reason. Very happy about that.

Still messing with the settings on the pot (all I had on hand was a 5K pot so its a little touchy - it seems to be running nicely at 10% of the range - presumably about 500 ohms). Anyway, this has me wondering if anyone has attempted to fix the source of the problem on the ECU. I found a photo of the boards and I see two fat resistors on that board (1 Watt maybe). I'm tempted to pull the board and replace them and have a look over the board for any hot spots or unhappy looking electrolytics. Has anyone on the list tried this before? Any success?

Thanks,

Dan

[alternativez]

Once resolved an exasperating no-start problem on my '85 BMW 635, finally determining the problem to be inside the ecu. By that time I was fearless or desperate, so I judiciously reflowed solder in suspected circuits. Worked in my case. Hope this is relevant. Good luck!

[Zed Head]

It's not really clear what causes the "lean mixture" problem. Electronic component drift or a system tuned to 1970's gasoline have been suggested. But the coolant circuit resistance mod seems to work to get back to normal. That seems to be the "fix", it's just a question of where you put the resistance.

The ECU is very primitive so the best fix you could probably come up with would be a smaller resistor on the coolant circuit, inside the metal ECU box. Same solution, just a different appearance.

There is a list out there of what the various components inside the ECU do. I think that the coolant sensor is one. So once you knew the resistance change you needed to make it might be fairly simple to swap a resistor. I could probably dig up the thread.

[FastWoman]

Dan, it wouldn't surprise me if the lean drift is from loss of capacitance as caps dry out. If you think about it, that would result in a shorter time constant, faster ramp, shorter pulse, less fuel. I'll be interested to hear what results you achieve (if you attempt a fix).

[Zed Head]

Here's that list I was thinking of. cygnusx1 posts it every now and then on various forums. Post #26, although the whole thread is generally relevant to what you're thinking of.

http://www.classiczcars.com/forums/fuel-injection-s30/44688-280z-fuel-injection-good-system.html

[Captain Obvious]

I've poked around a little with the board, but nothing significant. I didn't find anything that looked even remotely unhappy. One thing I can tell you is that I've not seen any electrolytics used at all. So I'm not sure I'm buying the "drying out" theories. Granted, I've been inside a whoppingly huge number of "two" though, so take that with a grain of salt.

I remember the big resistors of which you speak, and IIRC they are just input protection for some of the sensors. Low value and low current. If you're really curious, let me know and I'll refresh my memory.

Troubleshooting to fix long term drift? Not me!! Not without Robert Bosch on speed dial!

[sscanf]

I have worked on lots of boards from around this era (as a hobbyist only). They are generally pretty easy to work on and often, but not always, tell a story just by looking at them. Most of my experience is with raster and vector video game monitors of the early to mid 80's. They are full of electrolytic caps that dry out and need replacement (recall the last time you played pacman on a washed out monitor vs a crisp and beautiful monitor) - its the caps. They fail gradually over time and things drift.

Transistors and diodes of the era don't really fade away though, they just work or they don't.

I also work on old radios (as in 30's - 70's) . The heat in these things can also cause resistors to drift but these are almost always in places where heat is a problem - and its the high value resistors that are more prone to drift. They also have the same problem with electrolytic caps and the technology used in the 40's and 50's requires a shotgun approach to restoring tube radios - replace every electrolytic cap because, if it hasn't failed yet, it will soon (and often will take something else with it). Tubes (the transistors and diodes of the era), on the other hand, are vacuum packed and will work today the same they did that last time the radio was turned on.

So, based on all that and what I see above, I'm guessing that there's not much I can do though I am sort of surprised to hear that there are no electrolytic caps on those boards. What are those big red things? Maybe Bosch made their own caps an put them in those funky cases? There is talk above of schematics and parts lists - are there any out there?

That much said, I hate to remove the brain from my nicely running car and hack at it. Anyone have a busted one they would consider donating or selling cheap?

Dan

Edited June 11, 2014 by sscanf

[240260280z]

Maybe try to take these two items and run with them for us. We are all interested:

http://www.team.net/TR8/tr8cca/wedgelab/injection/us_tr7/tr7ecu.htm

http://www.classiczcars.com/forums/fuel-injection-s30/44688-280z-fuel-injection-good-system.html#post384761

Some initial goals (useful to all of us for tuning) to figure out would be:

1. How to independently vary A/F at idle

2. How to independently vary A/F at WOT

3. How to independently vary A/F at cruise

[Captain Obvious]

What are the big red things? Same as the small red things. Film caps, probably polyester. Just higher value or voltage, or both.

Good luck with the poking around and let us know if you see anything suspicious!

On edit, forgot to mention... I'm surprised as well about the lack of electrolytics. I fully expected to find at least a few in a power supply section or something, but I really don't think so. Credit to the designers!

Also, video game repair? Cool! That's one of the things that got me through college. Classes during the day, game repair in the evenings. Always had to earn the next semesters tuition!!

Edited June 12, 2014 by Captain Obvious

[sscanf]

OK. I just bought and ECU from a 1977 in "Untested" condition on ebay for $27.50! I'll let you all know how it goes.

[240260280z]

Good luck! Looking forward to your findings!

Most importantly: Have Geek Fun brother!

[Captain Obvious]

Absolutely! And if there's anything I can do to help, I'd be happy to!