Awhile back I had my EGI fuse blow which left me stranded.

And I've been thinking about it here and there. Doing minor things like taping off broken wires etc.

But it keeps blowing.

It happened at the same time my speedo cable broke because the sleave end wiggled off (even though the lower gear half is still attached to the tranny) and was dragging on the ground.

On my first try, I replaced the fuse and tried to start it. I watch the tach bounce while it was about to start. Then I noticed that while the engine was still turning the tach was completely motionless which idicated to me that the fuse blew again...

So I was like okay, maybe I need to look harder at the grounds or other wires or something....But I can't find anything obvious. Then I decide to put another 30 A fuse in again, but this time, it blows immediately *POP*.

Now I'm really stumped.

So I was wondering after looking at the diagrams for the egi circuit. I'm not the very best when it comes to mazda's FSM wiring schematics. If anyone's got one with it color coded that would be nice.

#1 Can a cross in the CAS mate plug cause it to blow?
#2 Can a shitty stereo wire job trip it?
#3 Could the speedo cable have bounced around hitting wires on the tranny that would cause a problem like this?
#4 Could the Main fuse array have a cross?

I seached but I didn't really find anything helpful.

can anyone think of any wires in the engine bay that when crossed/shorted blows the egi but NOT the 15A engine?

 

The 30A EGI COMP fuse powers all of the EFI system except the injectors and coils. I can give you a list of the components it feeds if you want.

To answer your questions,

1. No
2. No
3. Highly unlikely
4. You mean a short? Possibly. Check it as per the FSM.

 

you don't have that green ECU code check connector or the TPS adjustment/test light connector jumpered to ground for some strange reason, do you? whatever it is, if you're blowing a 30 amp fuse that fast, it's a good solid short...

 

i had this same problem before..it turned out to be bad solenoids under the uim..try to check those if u can.

 

If you can't figure it out, take it to a shop that can.
Electrical problems (i.e. short) are a royal pain in the *** to troubleshoot, especially online.
We can go blue in the face trying to figure out what is wrong.


-Ted

 

****Then I decide to put another 30 A fuse in again, but this time, it blows immediately *POP*******

Explain that a bit. YOu mean that without the key being in the ON or Start position....the fuse just popped by putting it in the slot???

If it popped after you installed it and THEN turned the key to ON or Start.....then just remove all the plugs to the items powered by that fuse...then turn the key to ON and see if it pops. If it does not pop, then put one plug back on at a time til the thing pops. There's the problem child.

It powers all the solenoids on the rack..like the Blue, Orange, Grey, Brown, Green, Yellow plugs along with the two solenoids on the ACV and the BAC. So take all of them off and see what happens.

And the question comes to mind....what have you recently been messing with on the car?

 

****Then I decide to put another 30 A fuse in again, but this time, it blows immediately *POP*******

Explain that a bit. YOu mean that without the key being in the ON or Start position....the fuse just popped by putting it in the slot???

If it popped after you installed it and THEN turned the key to ON or Start.....then just remove all the plugs to the items powered by that fuse...then turn the key to ON and see if it pops. If it does not pop, then put one plug back on at a time til the thing pops. There's the problem child.

It powers all the solenoids on the rack..like the Blue, Orange, Grey, Brown, Green, Yellow plugs along with the two solenoids on the ACV and the BAC. So take all of them off and see what happens.

And the question comes to mind....what have you recently been messing with on the car?

 

I can't say that I'd do it like that though. I think the right way is to pull the plug on the MainRelay and then put a meter on the black/white wire and look at the ohms reading with everything disconnected and see if you have a direct short. Then put one plug back on at a time while reading the meter. You should be able to tell which plug/item is shorted that way.

But the fuse method will work. It just might cost you the price of three or four fuses before your done.

 

you're more right the first time, HAILERS- easiest way to find a short on a chassis grounded vehicle is to start isolating circuits- all the items you mentioned...if you have access to the wiring diagrams, you can "split" the circuit in the middle (whatever solenoid happens to be about half way down the circuit), then try the fuse- that will at least eliminate 50% of the components (one way or the other- whether the fuse blows or not)...then split the problem circuit in half again...it'll save you some fuses... reading for a short through a bunch of coils (solenoids) is a tricky thing- they won't show much resistance to begin with (especially with the meter's 9v power source), so you'll be fooled thinking that .2 ohms is a short...

 

Thanks guys.

Now that you mention it, maybe I forgot to turn the key to the off position, though I'm fairly certain that I did.
I'll measure for current when the car is in the off and on position when I start the trouble shooting process.

And another thing that HAILERS brought up. I didn't really mess with anything on the emissons rack as of late. I just rebuilt this motor and put in about a month ago.

However now when I think about it, before I had the new motor in there I busted one of the solenoids on the rack. One of the nippled ends broke. So then I was kinda bummed and got one of the solenoids off of a rack that was from an 87 gxl (this ones a 91) and put it on. Now it didn't really screw with the motor that ran off of it before the rebuild back then.....But like Ted said, Electrical is *demon* like..... So maybe that solenoid from the 87 onto the 91 is the wrong resistence or something and has finally decided to rear its ugly head?

Anyway,

I like the suggestion of circuit deduction that Hailers and Wayne mention.

I'll start with the main Fuse array first and then work my way up from there as per their/your instructions.

It just really pisses me off beuse I have a chevy 350 I'm supposed to be dropping into my Toyota PU...But before I rebuild it I need to get this problem solved.

One last thing that happened was that my radaitor cap was really crappy before I replaced it. It sprayed hot collent all over the engine bay a couple of days before all this trouble...So maybe all the solenoids are bad? Whatever. I'm just really gald that the Fuse is blowing instead of my ECU....And no, there's no jumpered tps or error checker.....Thankful also its a solid short then an elusive cloaked wiggle-wire one.

All this info is really helpful!

Thanks again to everyone here.

 

I ran into this situation this weekend with a bud's t2. Luckily I found the problem pretty fast. It was just a short. The aws plug had melted and grounded out on the downpipe.

 

There's more powered by that fuse than just the three solenoid valves on the vac rack. You also need to check the two solenoid valves on the AVC, the BAC valve, the ASV, the AWS valve, the boost control solenoid valve and the OMP.

Unplug them all, turn the ignition on, and start plugging them back in until the fuse blows.
Nope, they're all the same.

 

if you have some contact cleaner or brake care, remove the connectors you can get too (or that the coolant could get to- why didn't you tell us that in the first place?) and spray 'em down real good...if you have coolant pooled in a plug, just disconnecting it to isolate the solenoid is not gonna work- you'll still have the short, and you'll think it's further "up" the circuit...spray 'em all down good, reinstall the fuse, see what ya get...

 

Well it seemed to have run fine for two days prior so, I kinda didn't think it was related. But thought it noteworthy all the sudden because it might have somthing to do with it just in case.

Here's the update.

So now I got the key in the on position. I followed all your directions and started putting plugging stuff back in.

Well, here's what happend.......LOL

Nothing.

The fuse didn't blow at all.

He heh heh ehehehehe. Ummmmm yeah....Actually I am not surprised because this is an rx7 we're dealing with here.

BUT, when I plugged back in the black plug on the ACV it went *click*...and I looked to see if the fuse blew but it wasn't. So I thought to myself, maybe I heard the clip snaping back into place or something.....No, it's definately a *click* for that plug...No other noises for any of the other stuff.

So what do you guys think? I'm gona try to start it without the ACV plugged in.....But not so sure I'm on the right track. The thing about shorts is, I want to make absolutely sure I nail it. I don't think Isaacs gonna drive by next I get stranded.

 

Neither of the solenoids in the acv should have pulled in if the car was not running.

The Port Air solenoid won't pull in after 20,000 miles and the Split Air should not pull in unless your in FIFTH gear.

I'd find out which solenoid went click. If it's the aft solenoid.....then I'd make sure the car is not in fifth gear. If it's not in fifth, and clicks.....that's wrong and there is something wrong with the OVER THE TOP SWITCH. That said, the fuse should not have popped just becauce a ground was put on that solenoid (ground put on by the path from the over the top switch, or fifth gear, your choice of words).

If the fwd solenoid clidked.....look at your odometer. If it is b/t 100,000 and 120,000 miles, then that is acceptable for it to click. It's a built in flaw in the second gen.

Since the fuse did not blow when all was put back together........try leaving the key to ON and going to each solenoid, acv etc and wiggling the wiring and try to make the wires short out.

As a last thought....leave the plug off the fwd solenoid on the acv. Leaving it off does no harm in any way what so ever.

I'd certainly shake the harness because if it did it several times already...it's gonna do it again when your not wanting it to.

 

Thanks again HAILERS.

Will follow up. I started it and ran it, no fuse blew so I'm going to look at it more indepth with the new info you provided.

But in the mean time I somehow magically candy-landed my water pump again.

Its so awesome. I have a streak of king midas ***... my RX7 doesn't turn to gold, only ****.

LOL. Whatever, fuck it, I'm getting my 350 drop kit this week, so I'll get to that later.

Thanks again.