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Please help diagnose a loud buzzing

 
Old 04-16-2018, 03:32 PM
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Default Please help diagnose a loud buzzing

https://youtu.be/11EphHn26tY


So my Miata has been down for close to a year with the engine out. I resealed everything and finally got it into the car over the weekend.


Yesterday I got everything hooked up and was ready to start. My battery is super dead from being out for so long so I had it hooked to cables attached to my 3.

I had the key in the on position and everything seemed fine, and it was not connecting to tuner studio. So I turned the key back and was treated with a very loud buzzing noise. It sounded like it was coming from the driver side of the engine bay or the cluster/dash.


When I turned the key back to the on position it would stop. If I even pulled the key out it would still continue shortly or until I would remove the cables or terminal wires. If the key was put back to the on position, the noise would stop. While on the cables, various accessories seemed to be working. Radio and headlights appeared to function as normal.


I also noticed the fuel leaking from the injector seen in the video. It seemed to correlate with the noise but I could be very wrong. The injector would stop leaking, presumably after the pump primed.


I've also noticed that my trunk ground cable is showing famage where the exposed part bolts to the chassis.


As far as the leaky injector is concerned, I already have new o rings on the way.

Hopefully I've described enough to get some good ideas or a guru that has seen this before.

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Old 04-16-2018, 05:41 PM
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pretty sure that sound you're hearing is the injector just constantly cycling
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Old 04-16-2018, 05:44 PM
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Disconnect the injector seems pretty straightforward. Almost seems like it's trying to replicate a PWM signal - sure you didn't cross your idle air controller and injector wires?
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Old 04-16-2018, 05:51 PM
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Originally Posted by mj1176 View Post
pretty sure that sound you're hearing is the injector just constantly cycling
The injector is definitely making noise but it also seems like it's coming from elsewhere.

Originally Posted by gooflophaze View Post
Disconnect the injector seems pretty straightforward. Almost seems like it's trying to replicate a PWM signal - sure you didn't cross your idle air controller and injector wires?
Yes next time I'm at the car I'm going to disconnect the injector harness and probably pull the fuel pump fuse and see if the noise persists.
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Old 04-16-2018, 08:16 PM
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It's best to diagnose by eliminating variables. Fix injector leak, move on to the next thing if it's still clicking like that
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Old 04-18-2018, 09:29 PM
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So today I replaced the battery and cleaned a lot of grounds, making sure they had good contsct. I unplugged the circuit opening relay so no more fuel would come out, and tried again.


No more buzzing, and TunerStudio read my MS fine and I was able to recalibrate my TPS.

Tomorrow my new O rings should be here and I'm hoping once they are in and I plug the relay back in there's no more buzzing and it starts fine.


I noticed my coolant sensor in TS was bouncing from 0 to 180 consistently with the key in the On position but figured that could be due to it having no contact with water. I also emptied my coolant again replacing the cracked plastic and rubber isolators around the heater hoses with ones from an NB at the junkyard.
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Old 04-18-2018, 10:57 PM
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has nothing to do with contacting water and everything to do with still some outstanding bad wiring/electrical stuff
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Old 04-19-2018, 03:31 AM
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Ok I'll play with it later today. It worked fine prior to the engine being out, and I did install the Qmax reroute while the engine was out. From what I can find it looks like the two prong sensor that feeds the ECU grounds through one of the wires, but I'll check the clip and whatever else.

Here's a video of the bounce .

https://youtu.be/7v7mRBOnqkY

Again, car is off. Key in On position, and circuit opening relay unplugged.
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Old 04-19-2018, 12:08 PM
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The coolant sensor that feeds the ECU has it's signal and ground run through the fuel injector harness connector. If that is disconnected, it will cause some odd floating readings.

Did you bolt the ground at the back of the intake manifold back on? That is the ground for it.
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Old 04-19-2018, 01:51 PM
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Originally Posted by x_25 View Post
The coolant sensor that feeds the ECU has it's signal and ground run through the fuel injector harness connector. If that is disconnected, it will cause some odd floating readings.

Did you bolt the ground at the back of the intake manifold back on? That is the ground for it.
Ding ding ding. Was just coming to post that I am in fact an idiot.


Thought the temp sensor or harness was bad so I spent a long time getting to it around the QMax reroute but then I traced the wire and saw it fed into the injector harness. Plugged it in and it went right to 72 and held.
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