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Frustrating electrical issue (Video) - Need advice
Hey guys,
I have been trying to unlock an electrical issue in my FD for the last while and am really getting frustrated. I have uploaded a video that shows the problem:
Problem:
When I put my key to Acc or ON, the relays start clicking quickly and several systems do not come on (ex fuel pump prime) or flicker on/off quickly (ex. aftermarket gauges). The battery is charged and confirmed to be in good condition, I've also removed, cleaned and re-attached the ground by the main engine bay fuse box (it seemed to help the other day, btu the problem is back).
The voltage on my PFC commander is reading low and slowly rises when I go to key on, (starts at 6v then goes to 11v occasionally, this is with a charged 12.5v battery).
Suspected Cause:
This seems to be either a main relay problem or a ground problem that is affecting multiple systems (power not getting to main relay ground). I suspect it could also be high resistance in some wires.
Help required:
I need some help to confirm the correct root cause. Other than checking resistance across some random grounding points and wires. Honestly, I'm at a loss for what to check next.
1. Does this happen every time you turn the key on, or only sometimes?
2. Do you have a multimeter to measure voltage and resistance?
3. Have you used your multimeter to check the battery voltage when this happens? If you don't have a helper to turn the key for you, try taping the multimeter probes to the battery posts using masking tape.
If you've got some time and want to learn, find a copy of the electrical / wiring diagram. There should be a download link in the FAQ thread, one of the sticky threads in this section.
1. Does this happen every time you turn the key on, or only sometimes?
2. Do you have a multimeter to measure voltage and resistance?
3. Have you used your multimeter to check the battery voltage when this happens? If you don't have a helper to turn the key for you, try taping the multimeter probes to the battery posts using masking tape.
Thanks for the quick response, my answers below.
1) Not everytime but almost. It seems the problem gets worse with the car sitting for longer periods of time it then seems to disappear on it's own.
2) Yes, I've taken a number of voltage and resistance measurements. Mainly voltage at the fuse boxes and compared them to the battery, which are within 1 volt. I've also measured resistance between the battery negative and various grounds. Ultimately, I'm not following a system and looking for readings that might be off. If there is a system/process to follow, that would help me.
pull the plug off the back of the key barrel and hot wire it [ jump from + always on to acc or engine on to see if the problem go's away, and if it works pull the plastic thing off the back of the key barrel and pull it apart and clean the contacts and re grease it and maybe bend the arm just a little bit more to make more contact.
Yeah I would suspect the ignition switch. Don't know if it's still the case but Rock Auto had them for cheap and they were new Mazda parts in another brand's box.
Search around on the forum on the ignition switch.
You're getting a substantial voltage drop somewhere, that's typically the only thing that will make relays click, the gauges go nuts, etc.
Thanks guys - I've taken the switch out and will do the cleaning on it.
I couldn't find a working link to the old write-up on this (if I'm not mistaken, Dale it was your writeup!). I did find one on a miata forum, for anyone who needs it here is the link
Question:
While I'm at it, I do want to test if this was indeed the root cause, but am not sure which wires to jump (I looked at the wiring diagram). Does anyone know which ones I should bridge on the female connector?
The exterior terminals typically aren't the problem, it's inside the connector itself. I'm not certain if it can be taken apart easily to clean the internal contacts.
When you turn the key, it moves to different contacts to complete the circuit for that function.
So I cleaned up the ignition switch after finding a very good video on the process. The components seemed pretty clean but I didn't know what wires to try jumping to confirm that the ignition switch was not problematic for other reasons.
Ignition switch cleaning video (for anyone who would like to do this):
With key ON and relays clicking (like crazy), I measured the voltage at the fuse box and found it to be below 10V, although the battery terminals were reading a healthy 12.4V.
With this, I ran a new 4 gauge wire from the battery to the main fuse block under the hood (I removed the old one which I suspected was corroded). I tried again and had the exact same situation.
You're going to have to get the electrical diagram out and start going point by point to find where that voltage drop is happening. It could also be on the ground side with a ground that's loose or poor.
Do you have the battery in the stock location or is it relocated?
Did you find and download a copy of the factory wiring diagram? The page that says B-1a / Engine Control System / Fuel Control System might be a good place to start. It's page 31 in my copy of the PDF. When the clicking and bad behavior is happening, try checking voltage at the 30A EGI fuse (under the hood) and at the 15A Engine fuse and 20A Fuel Pump fuse (in the cabin). The EGI fuse is basically bolted the battery positive terminal, but the Engine and Fuel Pump fuses get powered by some wires that run to and from the ignition switch. You should be able to measure the voltage on the fuses without removing them, most fuses have two small piece of metal on the top for probing with meters. Knowing the voltage for those three fuses should help track down if the problem is inside the ignition switch or something else.
As an additional piece of info, try to determine exactly which relays are clicking by removing them one at a time. Note that some relays might only get power when other relays are plugged in, for instance the EGI Main Relay provides power to the Air Pump relay.
Thanks a lot guys - I think I've found it and resolved the issue.
I had upgraded some wiring following a battery relocation by the previous owner. It seems I might have used a bit too much flux when I soldered on the ring terminals on the 0 gauge ground wires.
I've redone all the terminals I had soldered previously with compression terminals and have a nice 12.4v at the main fuses now.
The PFC seems to still be reading 12.0v but not sure if that is an issue with the PFC or if the stock ECU ground needs to be cleaned. Will dig into the wiring diagram to find the grounding location next.
Glad to hear you figured it out. Using solder on cars is a bad idea. The flux becomes corrosive and slowly eats the wire strands, and the heat weakens the wire strands so they are more likely to break from vibration. Just use a good crimper tool.
Nice find! Yeah, problems like this are 99% something that is not OEM.
You do typically see a little lower voltage at the PFC just from voltage drop. You could probably chase it down some but I wouldn't kill yourself.
Dale
This is exactly why im running a second battery for all my crazy add on stuff.
Related to this thread - do any of you know what else might cause the fuel pump not to turn on when the key is put in the acc position.
My situation - engine and engine harness are out. No ignition harness or igniter connected. The other symptoms that are known with this engine harness out issue are no-op for the sunroof, windows and wiper motor.
I do have the fuel relay mod that jumps the fuel pump to the battery, but the problem is when the key is turned to on, I have no acc 12v.
It won't. ACC will not run fuel pump, ON will. And it will only prime for a second or two, and that's the ECU telling it to prime. No ECU or harness and I think it won't do anything.
You can jumper the FP and GND connectors in the diag box under the hood to make the pump run with key On.
It won't. ACC will not run fuel pump, ON will. And it will only prime for a second or two, and that's the ECU telling it to prime. No ECU or harness and I think it won't do anything.
You can jumper the FP and GND connectors in the diag box under the hood to make the pump run with key On.
Dale
Ok thanks Dale. I was looking at the above schematic, apparently not close enough. I thought it was like some other cars where you turn the key to acc and you can hear the fuel pump prime. I did not know that the key had to be in the "on" position as if you are trying to start the car, unless I am misunderstanding that too.
From the schematic I get
OFF
ACC - (I thought this would give me 12v acc pwr)
IG2 / IG1 / ACC - (Is this the "ON" position your talking about)?
IG1 / ST - (when you turn the key to start the car and it falls back to the "ON" position).
So without the harness / ecu I wont get ACC 12v in general as well? <------- I think I just answered my own question with your answer Dale.
I will get general 12v acc, but the 12v line that I thought I was using for the fuel relay mod is not 12v acc because it will not work without the computer or engine harness.
So now I need to find a legitimate 12v acc source for my 2nd bat set-up.
What do you think Dale?
p.s. I dont want to booger up this thread, I just felt it was a related fuel pump operation issue.
Last edited by rotaryextreme; 03-08-21 at 06:19 PM.
Yep, the IG2/IG1/ACC is the "ON" position for the key. The ACC position is just the radio pretty much.
There are a number of threads on fuel pump rewiring, you can use the stock wiring and just use a better feed to the circuit opening relay to up voltage to the pump. If you're not using the stock wiring at all that's another story.
07-22-20, 05:26 PM
