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Electrical & Idle problems with 1985 Rx-7 12A

Old 09-12-15, 09:55 AM
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CA Electrical & Idle problems with 1985 Rx-7 12A

Sorry for lengthy post, but i really appreciate any insight/feedback!

1985 Mazda Rx-7 12A. Was sitting for around 8 years and I dont know any of the history on the car.

I got it to start up so I know it runs. I just went through the car and did a basic tune-up (new battery, spark plugs, wires, oil, oil filter, fuel filter, air filter, fresh gas, new belts, flushed radiator, bleed brake lines and put new master cylinder.

Ive been thinking on changing the cap/rotor and coil next, thoughts? Does this car also have ignitors or are coils the same thing?



Problems:

Wont idle, dies as soon as i let off gas

The RPM gauge works but is sometimes jumpy and doesnt go up smooth. Also the warning buzzer goes off even when its only showing 3000-4000 rpm on the gauge (and it only sounds about that rpm, it dosent sound like its redlining at 7000rpm...but i could be wrong, im new to Rotary engines and how they operate)

I have it jacked up and took rear tires off and shifted through the gears easily getting it to register 50-60MPH on the dash...but rpm stayed around 3-4k and warning buzzer came on at that RPM so I would shift at that point.

MPH and odometer work, but just about all other gauges do not work (temp gauge doesnt work, oil pressure gauge doesnt work, fuel gauge doesnt work)

Battery dash light is on, but very dimly...you can barely make it out during the day. Like its not getting enough voltage or something. (I tested alternator and tests good at 13v+).

EXH dash light is on, lit very dimly as well (exhaust overheating system?)

When the car is off and i turn the key on none of the dashlights light up. Everything remains black until i actually start the car, at which point the battery and Exhs lights come on dimly.

The lights and headbeams work perfect, and the highbeam dash light looks bright and is working. The adjuster to change dimness of the dash panel works fine when the lights are on...but doesnt change the brightness of the Battery/Exs warning lights.

When i put the emergency brake on the Battery/Exhs warning light gets brighter and is easier to make out.

The emergency hazard lights work and lights show up on dash, but neither turn signal work or flash on dash.

The horn doesnt work

Radio turns on and works

The air system works including heat

When I push brake peddle the brake lights dont come on. But when i turn headlights on they light up as normal.

---

I checked the fuse box under the steering wheel to the side of clutch pedal and all fuses are fine.

So what could be going on here? Im guessing multiple problems...or could one bad sensor/gauge/wire be shorting everything out?

Possible bad coil/ignitor the reason why it wont idle? Or just gunked up carb? What about the RPM issue though

Why would battery light be on if alternator is putting out good and the battery is new? Coil/ignitor problem, bad voltage?

Whole dash panel bad and need to be replaced?

Im hoping I can salvage this car and im not getting myself into a real mess! The car is complete and would be a shame to not get it road-worthy again.


Thanks for any advice or input!

I might post take a video so you can hear/see whats going on.

EDIT: Here is a link to the video I just took so you can hear/see what it is doing. There is some sort of buzzing noise coming from the engine/under hood. Maybe just the fanbelt or a vacumn leak maybe? Also you can see how weird the RPM gauge is acting. The video cut off early but basically the warning buzzer for 7000rpm goes off when its showing about 2000-3000rpm on the dash...or sometimes sooner. The rpm gauge isnt really working. Maybe bad ignitors? I was going to switch them but it looks like the only way to take off the inner ignitor is to remove the alternator?

VIDEO: http://sendvid.com/4h1464es
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Old 09-12-15, 10:16 AM
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the warning buzzer can be adjusted that's probably why its going off at 4k RPM.

fuses might look alright but can be busted check with a test light or multimeter and see wich ones arnt working.

the person probably couldn't get it to idle and thats why its sat for 8 years if its been sitting for that long id say the carb would need a freshen up, change the fuel lines and maybe check the fuel tank for dirt/rust.
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Old 09-12-15, 10:41 AM
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Originally Posted by The1Sun View Post
Ive been thinking on changing the cap/rotor and coil next, thoughts? Does this car also have ignitors or are coils the same thing?
i would change the cap and rotor, best to start fresh. it does have ignitors on the distributor, and then separate coils. the coils are bulletproof, but you may have a bad/dying ignitor, more below.


The RPM gauge works but is sometimes jumpy and doesnt go up smooth. Also the warning buzzer goes off even when its only showing 3000-4000 rpm on the gauge (and it only sounds about that rpm, it dosent sound like its redlining at 7000rpm...but i could be wrong, im new to Rotary engines and how they operate)
the tach, and redline buzzer are driven from the - side of the coil, just like any other car. if its jumpy, this means that its not working correctly. i suspect that if you put a timing light on the trailing side, it wouldn't flash consistently, which points to a bad ignitor, although it may just be a bad connection, so best to check/clean all the connections on the coils first.

MPH and odometer work, but just about all other gauges do not work (temp gauge doesnt work, oil pressure gauge doesnt work, fuel gauge doesnt work)
the speedometer is mechanical, but all the other gauges are driven from the Meter fuse in the fuse box. since the tach sometimes works, the meter fuse is not blown, but there may be a bad/dirty connection in there.

Battery dash light is on, but very dimly...you can barely make it out during the day. Like its not getting enough voltage or something. (I tested alternator and tests good at 13v+).

EXH dash light is on, lit very dimly as well (exhaust overheating system?)

The adjuster to change dimness of the dash panel works fine when the lights are on...but doesnt change the brightness of the Battery/Exs warning lights.
the dimmer won't change the warning light brightness, however if some of them being dimly on is a clue that there is something amiss, probably a bad ground somewhere.


When I push brake peddle the brake lights dont come on. But when i turn headlights on they light up as normal.
the brake lights are powered by the same fuse that does the lights, and then there is a brake light switch, possible switch is dirty/unplugged, or i've even seen the brake light wire plugged into the clutch switch...


in summary, i'm not sure what is wrong, but since the car has been sitting for so long i'd suspect there are dirty/corroded switches/fuses/relays. i would unplug and plug back in all the fuses, and then cycle all the switches a bunch of times, i think i would also do the same for everything on the coils. new cap and rotor. if there is an aftermarket alarm in the car, pull it out and put it back to stock

i would also play with the idle mixture, its just part of a normal tune up.
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Old 09-12-15, 11:36 AM
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I wouldn't run through the gears without wheels on. It's possible the drum/rotor could go flying off.
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Old 09-12-15, 11:46 AM
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Originally Posted by j9fd3s View Post
the tach, and redline buzzer are driven from the - side of the coil, just like any other car. if its jumpy, this means that its not working correctly. i suspect that if you put a timing light on the trailing side, it wouldn't flash consistently, which points to a bad ignitor, although it may just be a bad connection, so best to check/clean all the connections on the coils first.


i would unplug and plug back in all the fuses, and then cycle all the switches a bunch of times, i think i would also do the same for everything on the coils. new cap and rotor.

up.
Just to clarify, you mention "coils" and then "ignitors". From my understanding they are 2 separate things right? The car has 2 coils mounted on side by headlights, and 2 ignitors mounted on the distributor.

So when you say "which points to a bad ignitor, although it may just be a bad connection, so best to check/clean all the connections on the coils first."

You mean check the connections on the ignitors right? And not the coils
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Old 09-12-15, 12:03 PM
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Originally Posted by The1Sun View Post
Just to clarify, you mention "coils" and then "ignitors". From my understanding they are 2 separate things right? The car has 2 coils mounted on side by headlights, and 2 ignitors mounted on the distributor.

So when you say "which points to a bad ignitor, although it may just be a bad connection, so best to check/clean all the connections on the coils first."

You mean check the connections on the ignitors right? And not the coils
yep, 2 separate things. i would clean both connections,
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Old 09-13-15, 10:14 AM
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Originally Posted by j9fd3s View Post
yep, 2 separate things. i would clean both connections,
My idle issues were fuel pressure related. Check your fuel pumps output, if less than normal, check fuel lines especially at the tank. Sitting for eight years can clog up your fuel tanks strainer. Other idle related issues were distributors guts being out of alignment and carb needing overhaul. These are pretty easy to do, kind of fun too.
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Old 09-18-15, 07:13 PM
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UPDATE:

So I'm making good progress! I figured out the main problem with the tach and all of the gauges not working. It turns out it was one of the fuses that had a loose connection. The metal prongs where the fuse plugs into was completely loose so the fuse wasnt making any contact. I fixed that and now everything is working (except the fuel gauge, which is probably a stuck float and im hoping will fix itself with a couple tanks of fresh gas and maybe some MMO).

But the tach is working perfect, the oil gauge, the temp gauge, voltage gauge. The battery warning light and the EXHS warning light both went out and all the dashlights are working as normal now. Turn signals and everything. Its amazing what one little fuse can do haha.

The idle problem I sort-of fixed by adjusting the idle screw, it now idles surging slightly between about 700-1000 rpm. But at least now it doesnt die and I can keep it running. Im going to try and drive it a bit once I get some tires on it and see if the idle clears up with some fresh gas going through it. Otherwise im thinking I might have to do a carb rebuild.

But I've definitely made some good progress and im excited to take this baby out for a test drive soon.
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