I am a retired Foreign Car Mechanic that has dealt with all kinds of stuff since 1970. I recently was asked to get a 1980 Z car running. I have made good progress in narrowing down the issues, so here's the story and what I got.

This car was the victim of reversed jumper cables about 4 years ago and has never run since. Now with fresh gas, good battery and plenty of spark I find that the fuel injectors get battery voltage with the key on. Needless to say, after a brief moment of running it floods out. With the injectors unplugged, it holds pressure as it should and no leaks from the system.

I think it fried the ECM, and I think it is a California edition, so I need to get the part number and go shopping.

It did fry a fuseable link but other than that all systems are go. I had considered the head temp sensor, but I don't think it would cause the injectors to go into full voltage without even turning the starter.

Any way to confirm my diagnoses before buying an ECM would be great.

This is my first post with you guys and have high hopes that you can help.
Jon in Colorado

 

They always run full voltage so long as the key is on. As for the flooding It either has to be the CHT or the AFM. Might want to check the O2 as well.

Best way to check is to download the EFI bible and run the volt ohm check on the system though the harness, if everything is pass the it has to be the ECU.

http://xenons130.com/files/1980%20EFI%20Bible.pdf

And welcome to ZDriver! I hope you get this Z going!

Its pretty hard to fry the ECU Unless the key was turned on when the jumpers where backwards, even tho the fuseable links should have kept is somewhat safe.

 

THere are error codes/flashing lights for the ECU IIRC... might be worth checking that out as well if you think there is an issue with the ECU.

I'd check the AFM and the connector to the AFM.

Head temp sensor should be pretty easy to check with a multi meter...

 

OK Guys, I left out one important factor. The injectors all have 12 vts but they also have a full ground. I assume this system works like the Bosch units that use an intermediate ground to fire the injectors and the fact that these all have a full circuit (hot and ground) with the key on makes me think the ECM is the issue. I will follow the link suggested and see what else I can find out, but cannot image that a defective AFM would allow for so much gas to be dumped into the engine without even having the starter engaged.

 

One more thing, the key WAS on as they attempted to start it with reverse polarity. So. . .

 

Yikes... Ya the ECU is probably toasted then...

 

Thanks Guys, Now I just have to pass the great news to the owner. Any suggestions on availability of an ECM for a 1980 California born z Car??

 

Ebay or occasionally one will show up here. You just need an N/A ECU/ECM, weather it came from a 5 speed or automatic doesnt matter. Salvage yards, etc. etc.

 

Actually for that one is has to be the right year Cali model I think. Sense that changed a lot with different things.

 

Whats the difference?

 

In a 1980? Cali has no air temp sensor but has an O2, Fed has an air temp sensor and no O2.

But between manual and auto doesn't matter.