low voltage no start
 

So after over 3 weeks of driving the car with the new motor, I've came upon a new and very confusing problem .

Here is some supporting information.
-ms3x
-car was involved in front end crash a few months ago. It fixed now.. And I never experienced any electrical prolems.
- car ran perfect for 3 weeks
- a week ago I installed cops, but the car has been driven hard since then with no problems.
-after the motor swap l noticed my ac was not working. my compressor was not kicking on. Checked 12 volts with meter to show that I was indeed not getting 12v to it. Suspecting a bad relay (the one near the headlights) we took it out and tested to see if it would "click" when 12v was applied to it..it did, so I moved it to the I'll take care of it later section.

Now three weeks and 800 miles later. I drove the car on the car on highway for about 55 minuets. After parking the car for a few hours, I came back, and put the key in the on position.. First thing I noticed was the driver side fan turned on..which was only suposed to happen when the car was at 180 degrees. I tried to start the car, but the motor would just turn over.. I heard no fuel pump or any attempt at spark.

Note: 5-8 mins before parking the car.. I went to a gas station, turned the car off. Got gas, and turned it back on fine afterwards.

So here's where the trouble shooting starts

-plugged in my pc. "Not connected"..
-tested communication. Failed
-ran detect. Low voltage error
-got multimeter out and tested the power in on the harness. Read 4 ish volts
-visually checked all fuses. All liked good
-disconnected tps, maf, high idle control. Ecu power supply went from 4 to 6v
-attempted to remove cas. Volts went negative !? Put all acc back
-friend shows up with his ecu, same problem. Tow Car home..

-checked fuses under the dash. With fuses still in. All read 12volts.
-checked fuses under hood by removing each one and checking power and receiving poles. All power poles read 12v. All but the " head" fuse, which read 12v in the power pole and 4 on the receiving end. Put all fuses back
-got the 4 volts on the receving end of the "head" fuse to go away by removing the "retractor" fuse (maybe there is\was a probem with the headlight harness from the accident? Or is it a coincedance ?) Checked the ecu..still reading 4volts. Put all fuses back
- now suspecting the relay from my compressor has something to do with it.. I unplugged it and tested ecu. Same 4 volts. Plugged it back


So now I'm stuck.. I have no idea what to do and I'm out of a daily driver.
Any recomendations?

Tomorrow I! Going to try to unplug the main harness plug that goes to the injectors\cas and coils. I'm going to test ecu and see if the brings my volts up. If it does not.. I'll unplug everything and try to weed out the draw or resistance. Also, I did not check the "fuel injector" relay\fuse.. I dont really know how. I also noticed it was slightly warm to the touch.

I hate asking for help like this.. But I'm all out of expertise and ideas

Voltage on the load side of your fuse blocks (I assume this is what you mean by "receiving pole") implies bad grounds. You might want to start there.

The retractor circuit and headlight circuit are both supposed to be grounded at the same spot on the fender, this might explain the changes in readings when you pull the fuse.

Yep, I mean load side. Thanks!

I'm going to search for this ground near the fender.

Update:

-Removed all harness plugs..Cas, coil pack, injectors, tps, ICV, coolant temp.. everything that can be undone has been undone..

Still reading 4v at the ecu

After a bit of thinking.. I've come to the conclusion that if the ecu source is reading almost 12v with the ecu disconnected.. and 4 with just the bottom plug (ms) connected, It should limit my search to everything that is connected to the MS plug.. which is

-MAIN 28 +12V (almost 12v when not connected)
-MAIN 37 Fuel pump (Removed FP relay under dash)
-MAIN 20 Air temp (MAF unplugged)
-MAIN 23 OEM NB (Havent touched)
-Grounds
-MAIN 21 Coolant (Unplugged)
-MAIN 22 TPS (Unplugged)
-MAIN 26 5V Reference
-MAIN 24 Crank IN

Still getting same shit.. low voltage.

After hitting walls. I went back to the main fuse box... With all of them in, I started taking them out one by one and measuring volts again.

Whats odd is,

When I took out the "cooling fan" fuse, the ecu Volts went to zero.. which is not supposed to happen. Right?

I placed the "cooling fan" fuse back in and then took out the "FUEL INJ" fuse out. Thinking this fuse has ties into the main fuse, i was expecting to get a zero reading on the ecu.. Nope, got the same 4 volts... which is also strange.

So I'm thinking there is a strange short somewhere in the headlight/fan harness that's causing this crazy drain. I don't understand how this can be possible since I literally, have the fan and headlight relay harness completely undone and out of the car.


Any help would be appreciated.. even crazy talk is welcome.

Please god.. :bowdown:

Long shot.. but have you tried swapping out the INJ relay for a known good one?

Yes. :giggle:

INJ Relay was the problem..

Note to self: even if the relay "clicks"... does not mean its still good.

Contacts within the relay can be burned or carbon covered and make a bad connection. I'm glad you found it.