Jacob Butler

SOLVED: The wiring harness was the problem.

Greetings people of Zilvia. i have already searched through 500 threads and have had no luck. So i bought this 1990 nissan 240sx with 200k miles for my first car and it has never ran right once since i've had it. Idle is very inconsistent. But that is not the main issue. I was stuck in traffic on the freeway when the car just dies. When i try to start it cranks but nothing. Then it finally starts. I turn around and try to get home. Car dies again this time no luck. AAA comes to the rescue. Next day car starts like nothing happened. I pull out of the driveway and it dies. I ordered some new iacv connectors from wiring specialties and put those on. For the first time it had a steady idle. Then it stopped idling and i had to keep it alive. Then it died. So now it refuses to start, it will crank and crank but nothing. It has been sitting for over a month now cuz i have been trying to figure it out. No spark with spark plug grounded against the block. No spark coming out of ign coil. I know for a fact is has fuel because I smell it in the combustion chamber with the spark plug out.
New coil
New spark plugs
New plug wires
New dizzy
New cap and rotor
New ign control module
alternator tested to be good
charcoal canister is deleted and so is the fuel check valve
smog stuff next to the header is gone
has front end collision
has cxracing radiator with a beer can reservoir
has ricer pod filter
checked all fuses and relays i could find:
checked relay next to the battery
checked relay inside the car behind the radio
checked all fuses under driver side kick panel
check all fuses and relays in both fuse blocks
If anyone has any ideas it would be greatly appreciated, because at this point I have no idea what is wrong with this thing. I just wanted to get a second opinion.
Thanks!!

Jacob Butler

Update: I have taken the ecu apart and it looks brand new on the inside so I don't think that is part of the problem.

jedi03

sounds like fuel pump going out..maybe clogged filter...

Jacob Butler

But I'm getting fuel. Everytime I crank my car over I get different voltage at various connectors I test like dizzy, fuel injector, and ign coil. For example:
I test the voltage 11.83
Then I crank the car, no start.
Then I test again 13 volts.
Crank car, no start.
Then I test again 10 volts.
One time it was 60 and one time it was 1.3.
Thank you for the reply though.

Jacob Butler

I also tested the resistance across the pins on the ecu and some give an open loop, some give zero, and others give various resistance values. Not sure if thats right or not...

Jacob Butler

So the new multimeter I just got hasn't gotten around to reading 60v yet but the voltage still changes Everytime I turn the key off and on. Now the voltage just varies between 8 and 11 volts. Any ideas??

Sailor

Hey Jacob, can I suggest checking all of your grounds? If it does happen to be an electrical problem, they could be the culprit ( might as well clean them while your in there ).

Another suggestion, check for codes. Any more information such as what you have tested and what the ECU has thrown will help immensely

Jacob Butler

Thanks for your suggestions. I've just finished cleaning all the grounds I could find and the voltage no longer fluctuates at harness connectors. Instead, it just reads 1.3 volts at the connectors no matter how many times I turn the key on/off or crank the car. Also, I believe the ecu no longer gives codes if the battery has been disconnected. Any ideas?

Sailor

Check continuity from your ecu (the hub of wires not the ecu itself) to your ignition coils to check for broken connections. This might be a year ahead of yours but a link to the fill wiring diagram http://zilvia.net/f/showthread.php?t=650138
You are right about the ecu resetting itself, but I recommend checking for codes before you disconnect the harness. Try to start your car a couple of times. Take your ECU, turn the small dial on the side all the way to the right (diagnostics mode) , be sure to mark where it was initially. Do not start the car but put it in the on position (where you can hear the fuel pump prime) and read the red led. The first blinks are the first number of the code and will blink slowly, and a second series of blinks will be the second number ( for example a slow blink three times, followed by five fast blinks is the code 35 )

Jacob Butler

Ok thanks I will try that today. But it's not just the coil getting 1.3 volts. It seems to be everything is getting 1.3 like the fuel injectors and distributor are also getting 1.3. I will just test continuity for all of them.

Jacob Butler

Alright so I tried to get the codes off the ecu when I realized there's no power going to the ecu because the lights would not come on at all. Also the car is no longer getting fuel either because the fuel pump does not prime anymore. I tested to see if the ecu had 12v coming out of it's connections. One out of all of them read 12v. All the others were all over the place reading 7v, 9v, and others would read open loop. As far as the continuity test went, first I tested with one lead on the fuel injector. I got open loop for all holes. Then I tested for the coil. I got 0.3 ohms at one of the holes and 15 ohms at a different one. Neither of which matched up to the ones in the wiring diagram.
Any more ideas?
Otherwise I think I am going to get a different harness because the one I have is pretty hacked up already.

Jacob Butler

Alright, new harness is in and the car is now getting spark. The car started on starting fluid. But now the fuel injectors are not getting 12v, instead voltage constantly fluctuates. ??? Only idea I have left to do is remove harness again and take off all the electrical tape and looms to follow the fuel injector wires back to ecu. But I wanted to see if anybody else had an idea before I do that. Ecu is now getting power so I checked it's codes.
Code 13(coolant temp sensor) not sure why
Code 41(air temp sensor) pod filter

Jacob Butler

Tps also does not have 12v

Sailor

The 12v to the injectors happened after you tried starting the car? Can you hear them clicking when you try to start it?

Tps is mostly a variable resistor and will send a value based on where the throttle is located. So not finding 12v is ok, measuring the resistance might be a better option for this. Unless your measuring directly from the plug, in which case could be a variety of voltages 5v 12v

I'm going to recommend trying to fix, then clear, those codes. Check your service manual for all the grounds and make sure tehy are clean and tightly fastened

Jacob Butler

The fluctuating voltage at the injectors happens anytime i turn the key to the on position. I do not hear them clicking. They seem to be doing exactly what my ign coil was doing with the fluctuating voltage. I fixed the ign coil voltage issue by switching to a new harness. Its almost like the wires that control spark were messed up on my old harness and the wires for the fuel is messed up on this one. So its normal for the tps voltage to be fluctuating all over the place with the key on just like the injector connectors do? Also im getting code 41 because the stock air filter is long gone so the connector for the air temp sensor is just hanging there. I have no idea why it is giving a code 13 for coolant temp sensor. The car showed no signs of having a bad cts when it ran, and the did start while spraying starting fluid.

Jacob Butler

I have taken the new harness out of the car and performed the continuity test that you told me to do to the old harness. Here are the results.
tps:black wire read 0.1 ohms. the orange/brown with green stripe wire read an open loop.
fuel injector 1: red wire read 0.2 ohms, orange/brown wire with black stripe did not exist in the loom down towards the ecu so i tested all the wires. when i tested a white with black stripe wire it read 0.4 ohms.
fuel injector 2: red wire read 0.2 ohms, orange/brown with black stripe read open loop, even on that white with black stripe wire.
fuel injector 3:red wire read 0.2 ohms, green with black stripe wire read 0.2 ohms.
fuel injector 4: red wire read 0.2 ohms, green with black stripe wire read open loop.
should i just go ahead and undo all the tape on this harness and see whats causing this???
edit: nevermind, i am just an idiot and i got the colors mixed up. all 4 injectors and tps measured fine. the harness is not the problem.

Jacob Butler

12v is getting to and from the fuse box, along with other random voltage values. But all that leaves is the ecu right?

Jacob Butler

Alrighty so I've replaced the coolant temp sensor for the ecu and saw no change. Then I went to clear the code because I know the so sensor is good and I know the harness is good. I turned the screw all the way to the right on the ecu until the lights flashed to mode 4. Then I turned it back. Ok then I turned the ignition off and back on the check the codes. Except the codes did not clear. What gives??? Also I know the coolant temp sensor for the gauge is good so that can't be it.

Jacob Butler

well the pos starts now. 1 problem fixed a million left, thanks for all the suggestions guys. I really appreciate it. I ordered a new ecu and with it installed the car had to spark. I put the old ecu in and it starts. I believe when i put the new harness in i overtightened the bolt for the ecu. So really the harness was the problem. Also i got the cts code to clear aswell.