V1 Nukers City Goblin - 2009 SS/TC number 2 build

[ctuinstra]

I’ve been following this trying to absorb knowledge for when my time comes and this fuse problem is a good puzzle. I don’t have a donor or wiring diagram, but I have a question that I hope helps. What does the INJ fuse power? Coil packs only doesn’t seem like the circuit would be named INJ. Only turning the ignition on without trying to start also doesn’t make sense for the fuse to blow. Are the injectors powered by that circuit or a fuel pump? They would get power with just key on. Maybe a short in that part of the circuit.

The INJ fuse powers only the coils. I know, it doesn't seem intuitive, it made me look a couple of times. When the powertrain relay energizes, it applies power to the coils, engine running or not. If the coils or the circuit is shorted to ground, it will blow it as soon and the relay is engaged. The two diagrams I've posted are basically all there is to that circuit. The coils receive power and then also receive a separate signal to fire the spark plug.

 

[ctuinstra]

Also, what I haven't mentioned is that while thenuker and I were talking, he ohm'ed out the circuit with the one coil unplugged and the short was no longer there. Then he measure between the power and ground terminals of the coil while it was out and it was shorted. This is proof positive the coil is bad. When he replaced it, it did not blow the fuse until after the engine was running.

 

[ctuinstra]

One more thought that I just had, it didn't blow the fuse until sometime after it was running. Have you checked the output of the alternator? I wonder if the voltage regulator is bad and running too high??? Just a thought of something else to check.

 

[TheNuker]

Okay guys @ctuinstra @Rttoys @Briann1177 @Brian74 @Lonny

so I measured voltage on the purple wire on the suspect line, it has between 6 and 11volts on it. The other 3 I measured at the plug side orange, light blue, green all measure no voltage.

I reattached the purple wire and read it from the plug side and it’s the same. I reverified the other 3 plugs have zero voltage. So........ back to the ECU? As that is where the voltage has to be coming from right?

Thanks guys,
Nuker-

 

[ctuinstra]

Okay guys @ctuinstra @Rttoys @Briann1177 @Brian74 @Lonny

so I measured voltage on the purple wire on the suspect line, it has between 6 and 11volts on it. The other 3 I measured at the plug side orange, light blue, green all measure no voltage.

I reattached the purple wire and read it from the plug side and it’s the same. I reverified the other 3 plugs have zero voltage. So........ back to the ECU? As that is where the voltage has to be coming from right?

Thanks guys,
Nuker-

If you got something different on the purple wire to the coil that is going bad than what is going to the other three wires, it sure seems like it would be the ECU. They should all be reading the same with just the ignition on. That purple wire should just pulse the coil when needing to fire the plug. What I don't know is if it is active low or active high; I would assume it active high since all of the others are low all the time. From what you are telling me, I vote for the ECU.

 

[Rttoys]

You should have battery voltage on the first wire of every coil and ground on the next one. the next 2 I’m not 100% sure on.

so if you unplug all coils and plug in one at a time, when you get to the “problem” one does it blow? Can you plug that coil into another connector and it still blows Or not blow?

 

[Rttoys]

There’s a lot going on in these last few pages, so I’m trying to keep up, but we need to keep it simple. I’m not a fan of ecm/bcm being bad. It happens, but I like to make sure before it’s condemned.

 

[Rttoys]

I’m still in the short to ground camp. I would be all over the wiring harness trying to find a wire hitting ground.

 

[ctuinstra]

I’m still in the short to ground camp. I would be all over the wiring harness trying to find a wire hitting ground.

He measured the fused line to ground. The only time it was shorted to ground is when the bad coil was in the circuit.

 

[ctuinstra]

There’s a lot going on in these last few pages, so I’m trying to keep up, but we need to keep it simple. I’m not a fan of ecm/bcm being bad. It happens, but I like to make sure before it’s condemned.

We have been all over the simple stuff. I was not a fan of the ECM, but after the last post is pretty clear there is something going on with it.

 

[Rttoys]

We have been all over the simple stuff. I was not a fan of the ECM, but after the last post is pretty clear there is something going on with it.

I understand. I just hate replacing the ecm/bcm, because I always get hosed on it. I like to be **** sure before I replace one and it’ll be the last thing I tell anyone to replace.

 

[Briann1177]

I reattached the purple wire and read it from the plug side and it’s the same. I reverified the other 3 plugs have zero voltage. So........ back to the ECU? As that is where the voltage has to be coming from right?

Thanks guys,
Nuker-

Boy, was I wrong. Purple wire is pin 55 on the big ECM connector, right?

 

[TheNuker]

Okay as a round up.

The 4 grounds (black) all show 0 volts
The 4 hots (pink/black) all show 12.xx volts
The 4 browns all show 0 volts
The 4 grounds (black) have solid continuity between the plug and both the head,block, and several ground spots I tested with.
The 3 different colored wires Orange, Light Blue and Green show zero volts with ignition power turned on when fuel pump kicks on.
The 1 different colored (Suspect problem) purple wire is bouncing around 5.5-11.5v with ignition turned on.

With ignition turned off all wires show zero volts.

I have not tried to move the problem plug onto a different coilpack yet because the coilpacks are expensive haha.

Without the (suspected bad) coilpack wire connected the fuse will not blow.

Once the coilpack is blown the fuse will pop(after you replace it) as soon as you turn the key to the second power click the same as when the fuel pump kicks on. This will happen with just the 1 (bad) coilpack connected.

I have confirmed on the donor engine harness along with my new harness that these purple wires are in the exact same ECU plug spot row 2 7 down.

I have solid continuity between the cut purple wire at the ECU and the plug side.

Tomorrow I will plug in the coilpacks plug in the cylinder next to the (problem) coilpack and confirm its fine.

Let me know if I've missed any tests, But so far the only major variation is that my purple is HOT and none of the others are.

Is anyone else with an LNF able to test for voltage on their 4 coilpack different colored wires?

Thank you guys!
Nuker-

 

[SmsDetroit]

Been doing some digging while following this thread. From what I can find that fuse powers the coils And the injectors. I don’t think it would hurt to unplug the injector and test it to see if it’s shorted. Sounds like all the wiring for the coil checks out. Maybe it’s on the injector side.

 

[TheNuker]

Boy, was I wrong. Purple wire is pin 55 on the big ECM connector, right?

Hey Brian, Here is the wire

Nuker-

 

[Briann1177]

That looks correct. I guess a new ECU will be the way forward.

 

[TheNuker]

Ordered a new ECU from amazon, so I can return it if the same problem. Smart thinkin huh!

Also ordered full version of HP tuners with 2 credits so I can move my zzp tune over.

Nuker-

 

[TheNuker]

I received all my stage 2 powder coating back today! Really like this color!

Nuker-

 

[TheNuker]

Well its looking like as long as this new ECM fixes the problem, I should have all parts to test drive by tuesday!

Nuker-


PSA its super hard to find a lot of the lighter weight wheels for our cars right now! And sticky tires.

 

[Waterdriver]

Depending on your bolt pattern, check Goodwin Racing. I think they just got a shipment in.

Miata NA/NB 1990-2005 Wheels | Mazda Performance Parts

Street, Autocross and Track Performance for your Mazda, Fiat 124, Toyota-Subaru BRZ/FRS/86.

www.good-win-racing.com