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Old 03-08-2007, 04:40 PM   #1
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Default INJ fuse - at it again!!

Someone please shoot me.

The INJ fuse is blowing again, so I popped in my trusty fuseholder (fusible links are $2.99 a pop, and I went through 5 blade fuses this morning) and started to TRY and troubleshoot this. From what I can tell, the wire that goes to this circuit is the white wire, which then comes back out from the fuse and goes into some sort of relay, and then (I assume - I suck at electronics) out again. Everything I've read tells me this is some type of short. Is it possible there's something in the relay? I've found nothing in the wiring that looks like worn insulation or two wires rubbing or anything.

First pic - high-speed fuse holder visible, also note the aforementioned relay thingy:

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2nd pic - fuse box split open. note the white/green wire leaving the INJ fuse and going into the relay.

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Old 03-08-2007, 11:35 PM   #2
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i poped the 80main one the other day.when i grounded a wrench on the power to the alternator.yea i know im missing the lil rubber boot.that covers the exposed wire nut/bolt.
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Old 03-09-2007, 02:04 AM   #3
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http://www.madracki.com/miata/images/wiring/93diag.pdf

Figure 1 has the best diagram of that fuse block that i found so far. It is the white-grn wire and according to the diagram, that wire leads to three places: the Airbag control unit, The Main relay, and the Alternator. Hopefully this helps.


by the way, what is your suspension setup? I noticed that nut on the top and wondered.
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Old 03-10-2007, 12:31 AM   #4
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those are the FCM mounts, I like 'em.

I'm sorry, but reading that diagram I might as well be reading chinese (I suck at wiring). Do you think replacing the main relay could possibly cure this?
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Old 03-10-2007, 10:41 PM   #5
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I've spent MONTHS trying to fix my INJ fuse problem. It started after (or around the time) I installed my WBO2 sensor. So far I have:

- Pulled the fuel pump relays, etc and just use a switch to turn on the fuel pump.

- Reworked all the grounds under the dash.

- Moved my WBO2 grounds to the engine block.

- Removed the circuit opening relay wiring (I think this is part of it, can't say for sure right now since I am at work).


I recently got my car on the road again after 5 months of downtime. We will see if I am still blowing the fuse. Did you do anything electrically to the car to cause this? It could help diagnose the problem.
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Old 03-11-2007, 02:15 PM   #6
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Nope, the fuse blowing (this second time) didn't coincide with any underhood work other than putting in better turbo hardware. When it started the first time, I had just washed under the hood, and I credited opening the tape around the wires with fixing the problem (airing them out). This time it just started at random after I parked and came back to the car an hour later.
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Old 03-11-2007, 02:36 PM   #7
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Have you check the wire(s) to ground using an ohm meter with the fuse out?
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Old 03-11-2007, 06:11 PM   #8
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nope, I have a multi-meter still in its packaging too, what would I be looking for?
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Old 03-11-2007, 09:18 PM   #9
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check the output wire from the fuse box for short to ground.
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Old 03-11-2007, 09:45 PM   #10
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that sounds promising, which wire is that?
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Old 03-11-2007, 11:01 PM   #11
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do you have a an auxiliary fuel pump like the pierburg. if you do and your inj relay is blowing then its because you need another relay hooked to your auxiliary fuel pump.

Part# 50102
Fuel Pump Relay Kit

Designed specifically to prevent voltage drops at the pump and maintaining constant fuel pump pressure, and will prevent fuel pump amperage overloads from damaging the electrical system. It's a good idea to relay your fuel pump for the street and a must when you're racing. Kit comes complete with 30 AMP relay, relay base, 30 AMP circuit breaker, wire, mounting hardware and connectors.
http://www.painlessperformance.com/w...SearchField=21
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Old 03-12-2007, 12:30 AM   #12
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No additional fuel pump here.
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Old 03-20-2007, 04:53 PM   #13
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I give up. I hate wiring...
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Old 03-20-2007, 05:35 PM   #14
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How about the meth injection, where are you pulling the power for that?
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Old 03-20-2007, 06:21 PM   #15
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Quote:
Originally Posted by kotomile View Post
I give up. I hate wiring...
You selling the car?


If I had to fix something that was impossible to fix, I would run a wire from the battery, to a heavy AMP switch (get one at your FLAPS), to the fuel pump, to a fuse, then to ground. Take it completely off all the OEM wires. Yes, ugly, but you could drive the car until you finally figure out what the problem is. At least run a new ground wire for the thing and see if that fixes it.
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Old 03-20-2007, 06:44 PM   #16
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Quote:
Originally Posted by PAT! View Post
How about the meth injection, where are you pulling the power for that?
Straight from the battery.
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Old 03-20-2007, 06:47 PM   #17
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Quote:
Originally Posted by rmcelwee View Post
You selling the car?


If I had to fix something that was impossible to fix, I would run a wire from the battery, to a heavy AMP switch (get one at your FLAPS), to the fuel pump, to a fuse, then to ground. Take it completely off all the OEM wires. Yes, ugly, but you could drive the car until you finally figure out what the problem is. At least run a new ground wire for the thing and see if that fixes it.
No, I'm having it towed to Jacksonville so my mechanic brother-in-law can fix it and use it as a DD while he body-drops his truck. I'm leaving for Kuwait in 2 weeks so I won't need the car.

I think that would work if this fuse didn't control SO much, the INJ fuse is the fuse for the fuel pump, ECU, 02 sensor, alt, injectors etc.
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Old 03-20-2007, 08:08 PM   #18
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Get a testlight..... put the probe into one end where the fuse goes into.....and the alligator clip in the other......if there is short to ground the test light should alluminate. now start unpluging things related to the fuse's curcuit.

As soon as people stop downloading ****(our connection here is so slow) I'll take a look at the wiring diagram( it won't download now) so I can check out what is all on that circut....it'll give ya a place to start.
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Old 03-20-2007, 08:15 PM   #19
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Well, I began by unplugging things one-by-one and then checking by replacing the fuse and seeing if it blows when I crank the car.

By doing that, I know it's not:

Alternator
Injectors
02 sensor
fuel pump

what else..

meth injection
turbo timer

About the only thing I didn't check on that circuit was the bipes.

I know my inner fenders have been worn away on the inside.. is there any chance (if there are wires running through there) that the PF tire wore a hole in some insulation under the fender and is causing a short?
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Old 03-20-2007, 08:26 PM   #20
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hmmmm......it sounds really simular to a rx7 that I had to fix....Had a Apex'i AFC that had jacked up grounds on the ecu and caused the same fuse to pop. its worth checking out....
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