computer problem,ground wire related.

[nuttin but Z32]

hello, a while ago i had put the ground wire that goes on the back of the alternator on the chassis,and all the ground wires are connected in the right places this time,but,since i made a mistake with the ground wire from the alternator my car won't start.

i've been told that when i connected that wire to the chassis it messed up the computer,i know it did burned the relay fuse,but that is replaced now and my only problem could be the computer in the car.

could it possibly had messed up my computer?

car is a 91 NA
so far that is what i assume it's the only thing that is keeping my car from starting the swap
any help would be greatly appreciated.thanks!

[nissanfreak12]

Have you checked the ALL the fuses? It may have popped a few other ones with that happening.

What exactly is it doing. Is it cranking and not starting? Not cranking? Just completely dead like no lights come on at all?

Give us a little more insight.

As it comes to your thinking of the computer, Its very possible that could have happened, but thats what fuses for the most part do, is protect the computer and components. try the easy stuff first and work your way toward the comp.

[nuttin but Z32]

its cranking but not starting at all,as the fuses all of them on the engine bay are fine.
so far i have not checked the ones inside yet wich as of now i will first thing tomorrow morning.

[nissanfreak12]

If you still hve the factory alarm, try and disengage it, like with a clicker or unlocking the door, its possible it may have armed.

If all the fuses are fine, make sure your getting spark and fuel. Let us know about the fuses and if you do find anything.

[marty1mc]

Sorry, but I don't see how what you did caused any problem. The ground on the alternator is common with the block and chassis. I suspect you connect the Bat wire to ground?

[nuttin but Z32]

Well,my dad keeps telling me about when i put that alt ground to the chassis it burned the computer somehow.

[nissanfreak12]

Well,my dad keeps telling me about when i put that alt ground to the chassis it burned the computer somehow.

A ground is a ground, I thought you were talking about how you put a positive wire from the alternator to the ground. This would be logical for burning something. But if you just put the ground from the alt to the chassis, should not have harmed anything. Good catch Marty.

OP-is there anything else that was done about this time? Forget what your father said for a min, think anything that is different.

[marty1mc]

^Exactly. Ground shouldn't have done anything. The alternator even grounds through the mounting bolts to the motor.

What exactly (the exact part) was fried? If you grounded the battery terminal to ground, you probably fried the 100 amp fusible link.

Personally, I would stop concentrating on the alternator and work the basics of why the car isn't starting. I would look at fuel, air and spark.

First, pull codes. Make sure there aren't some odd codes (like injectors) causing the problem.

Next, pull the CAS and see if the injectors are firing and if the coil packs are creating spark. (If you are unsure how to do this, post back and I will lay out the procedure). If all of that is good, then check fuel pressure. Make sure the MAF is connected solid.

All of this assumes the car is cranking.

[nuttin but Z32]

I forgot all about how the codes work,i've been out of nico for a while.

A relay fuse burned down when that occured,but that relay is replaced now as for air,spark and fuel is all working properly.
Now,there are some vaccuumhoses that are missing,but since you can just crank up a car just to see if it starts then i don't see why not do it.

[nissanfreak12]

It sounds like you grounded a positive wire, you said you checked the relay fuse? Check the relays, all of them, its possible you melted the connection/plastic, even may have damaged some other relays that are around or even associated with the alternator in some way.

Even with the hoses disconnected, it should start, are you sure everything is connected?

Still a possibility the comp is toast, look in the section everything you need to know about the z32, this will let you know how to check for codes. This is what I would do before anything else, just so you are not running blind. This will give an idea where to start.

[nuttin but Z32]

ok so i got the code 13:engine coolant temp sensor.....
i know i seen it broke but it's just a sensor right?
is it a big deal or not big deal?

[marty1mc]

It's a big deal, fix it. The temperature sensor tells the computer the engine temp. and in turn affects fuel mixture, timing.

[nuttin but Z32]

ok easy fix....but does this mean that the ecu is not toasted?
if it's not,then it is like taking some weight off my shoulders
thank you all <3 NO h0m0 lol

[marty1mc]

Test the sensor, drop in water and look at the resistance with a meter. It should change, but use the FSM (http://www.300zx.co.uk/cgi-bin/manual.cgi) and find the section for testing it.

Second, do the basics. Pull the CAS, turn the ignition to on, turn the CAS and listen for the injectors to pulse. You can also check spark at the same time. If all of this is working, you ECU is probably fine.

Here is an online color wiring diagram as well...
http://www.ttxtz.com/tech/lee/

[nuttin but Z32]

Test the sensor, drop in water and look at the resistance with a meter. It should change, but use the FSM (http://www.300zx.co.uk/cgi-bin/manual.cgi) and find the section for testing it.

Second, do the basics. Pull the CAS, turn the ignition to on, turn the CAS and listen for the injectors to pulse. You can also check spark at the same time. If all of this is working, you ECU is probably fine.

Here is an online color wiring diagram as well...
http://www.ttxtz.com/tech/lee/

i can hear the injectors and fuel pumping into the engine,as for sparks ehhhhhh don't know about that yet.
as for i am doing all this by myself....
But even if the ecu is burnt,it will still give me codes?




thanks.

[marty1mc]

It can, as it is reporting errors in sensors, that doesn't mean the output section to the PTU (controls spark) is working. That said, I don't see anything you have done (based on what you have written) that would indicate you fried your ECU. That is why I am suggesting you look at the basics. Pull a coil pack, reconnect the connector, put a plug in it and ground the base of the plug, not the electrode. Turn the CAS or crank the motor and see if you get spark.

If you don't, work backwards. Check the corrosion on the connectors, PTU. Then check for 12v on the coil packs.

[nuttin but Z32]

yeah i will post pics soon as I am moving out of my parents and have a lot of unpacked stuff still.....
but i will show you what I've done with the car so far...













NOTE TO SELF: I'm running out of patience with this car.....

[junkyS13]

Did almost the same thing to my prelude years ago, didn't disconnected the Batt. before i started working and hit the body with the wire to the batt. It blow the MAIN fusible link. you may check the fusible link, its in the fuse box in front of the battery. also has a wire thats look like it is folded back to itself. I don't think your ecu is burned (thats way they put fuses in cars)


Kerry C.

[Sdavne]

I Want to check all my grounds this weekend, does anyone know where they all are or have a diagram, also does every Z have a factory alarm mine is a 90 and i have never heard it, and if so where is it located thanks

[NolimitZ32]

Not sure on the alarm. wiring harness layout is in FSM engine electrical section

[Ace2cool]

All USDM Z32's came equipped with factory alarms. JDM Z32's it was an option.

The alarm module is located in the passenger floorboard, to the upper-right of the ECU. It's secured by 2 bolts and is possible to remove with all other components intact. Just gotta figure out a creative way to fit a square peg in a round hole, figuratively speaking. It's also labeled "Theft Module", IIRC.