deadphoenix52

iTrader: (2)

i know nothing of electronics. but here goes.

i know the cars electrical system is very poorly designed. but im not sure how much is normal, and how much is an issue. for instance when i run any accessory at all, the volt gauge drops. i can hear the fuel pump power down. etc. turn signals, brakes, headlights. everything causes the power in the car to drop.

i plan on rebuilding the alternator, but i dont think that is my issue just yet. i also plan on attempting the archived relay DIY. the new one on the ignition switch. will this fix most or all of these electrical issues?

anything else i need to look out for? volt meter currently reads just under 14 at idle. and drop with every accessory. down to just over 12 at times

Nick

DivinDriver

iTrader: (15)

You most likely have a dirty connection somewhere that is resistively limiting your available amperage. The fact that it's happening without regard to where the draw is or the load's size, leans toward something either on ground or the main primary section of the system.

It could be an extremely weak alternator, but if it's keeping your battery charged routinely, more likely you have a loose or corroded ground point, battery cable, or primary-side connection.

Check the output connection of your alt first, it's the most-likely culprit. Work downstream from there.

deadphoenix52

iTrader: (2)

thanks, since the alternator is able to keep the battery charged, i dimissed it for the time being. ill start there. i left my haynes manual in lubbock. so im flying blind here.

hate electronics.

KansasCityREPU

iTrader: (9)

Since you have access to the internet, download the factory service manual and electrical manual here.

http://foxed.ca/foxed/index.php?page=rx7manual

deadphoenix52

iTrader: (2)

done. ive had the manuals. but i did download the wiring diagrams.

mazdaverx713b

iTrader: (91)

i would first start by checking your ground cable for splits, breakage, and for proper continuity. upgrading it to a larger size and custom make your own ground cable is always a good idea. the car's weak point is a poor grounding system. another thing of interest is upgrading your alternator to an S4 TII alternator.

deadphoenix52

iTrader: (2)

looks like the s4 alt is a direct swap which is nice. in my searching before i only found the 130 amp taurus one, and the buick one. but 80 amps should be plenty for the car. especially since i wont be running any crazy audio.

deadphoenix52

iTrader: (2)

bump.

could someone snap a picture of their starter motor wiring. mine is all facked up. im pretty sure this is causing some of my electrical issues. i just want to make sure that everything is correct before i continue

edit: what im interested in is the wire that is next to the black and yellow one that goes to the ignition switch. the bolt just to the right of it is used to ground something. and mine isnt connected to anything

deadphoenix52

iTrader: (2)

anyone?

74RX4

iTrader: (10)

Too difficult to get a good picture on the car, but here's an extra one I have.

deadphoenix52

iTrader: (2)

thanks. there is a wire coming off of the bolt below the 12v from battery in your pic. i THINK it may go to the blue/white wire thats close to all that. which i think is the hot start assist etc. but im not good at reading wiring diagrams.

thanks again, Nick

780rx7

In my '80, the fuel pump, brake lights, tail lights, fuel sending unit (basically all the rear electronics) ground to a single point inside the hatchback near the hatch release mechanism. There is a single wire coming from the drivers side at the rear of the hatch and attaches with an eyelet to a screw or mount bolt near the hatch mechanism. I had a loose ground connection there and everytime I used the headlights (taillights), hit the brakes or used the turn signals, there wasn't enough amperage to run the fuel pump and the car would die. It was a simple fix (after 3 hours of diagnostics and help from this forum). To diagnose, turn the key on to accessory, listen to the fuel pump and also wait for the fuel level to rise on the gas gauge. Then, depress the brake pedal and watch the gas guage to see if it starts to drop when the brake lights are activated. The sound of the fuel pump should drop as well if this is the issue. Not sure if your '81 has this same ground point, but it sounds like the same issue.

deadphoenix52

iTrader: (2)

thanks much for that. that sounds extrememly promising. ill be doing some work on the car this weekend anyway. ill check this out while im at it

-Nick

deadphoenix52

iTrader: (2)

the fuel pump sound drops but the gas gauge does not. so, im not sure what that means. i think my next step with this is to replace the alternator and battery cables. and go from there. im still gonna check this ground tho.

risingsunroof82

iTrader: (3)

this sounds like a potential problem i may have......

Jeezus

iTrader: (4)

Rewire the fuel pump with a relay and dedicated ground. I did this and there is more power through the lines.

Fuel pump cycles with the blinkers and stop lamps, with this there is more juice to go around.

85 - Stock fuel pump power
86 - Ground
87 - New fuel pump power
30 - Fused power to battery (20A should do)

Don't use 87A.

deadphoenix52

iTrader: (2)

k here goes.

i was driving home from work and braked unnecessarily hard for no reason. then all of a sudden my tach goes haywire. the volt meter jumps up to 14/15 my fuel pump sounds like its on steroids. the kicker is, any time i activated any accessory at all, tails, headlights, brakes, literally anything. everything went immediately back to normal. tach worked, fuel pump sounds normal, volt meter drops etc.

i get home and discover that the little battery cable that connects to the ignition switch came out. i dont have a battery tie down and the battery slid during the braking. which yanked it out.

this tells me two things

1. my alternator works
2. i'm retarded

because the original diagnosis of a bad main ground was correct. i was too damn lazy to go get new cables and had hoped it was something just loose somewhere. the reason everything went haywire is because of the ground. the reason everything returned to normal i think, is because the car was able to use the ground point of whatever accessory i was running.

yes? no?

im getting some new cables today or tomorrow. also, just in case, where does the alternator ground to? the battery? cuz idk.

deadphoenix52

iTrader: (2)

new cables on. problem is much much better. still present. the pump etc can be heard powering down, but not nearly to degree as before. and the car doesnt want to stall anymore.

finally got a multimeter. voltage at idle was around 14.2. with the headlights dropped to 13.8 and did not return. so the rest of my problem im attributing to a weak alternator.

unless anyone has any other suggestions? thats really the only thing i can think of at this point

deadphoenix52

iTrader: (2)

ok. so today i replaced the worn alternator. along with everything else in this thread, this sums up to, new alternator, new battery cables, new starter motor.

the problem is still present. im all out of ideas here. I checked for the ground near the hatch release and couldnt find it. going to look again in a bit.

battery voltage is 12.5 with the car off, and 14.06 now with the car running. i double checked the alternator, turn on some lights and things, and this time the battery voltage remained at 14. so my issue is somewhere else. has to be a ground, but i have no idea where to begin. its still in the main system due to any accessory at all causing the issue. ignition switch? maybe i need some new fusible links?

i remember when the little cable that goes to the positive terminal on the battery was disconnected, the voltage shot up, and the problem seemed fixed apart from everything not working right thats hooked up to that.

also noteworthy, is that the voltmeter in the car reads slightly lower than the actual voltage, assuming its correct, i should trace that as well?

any help is greatly appreciated

-Nick

82FanTC

iTrader: (9)

I have the same issue. Don't have fusable links anymore, have fuel pump hooked up to a isolated relay, S4TII Alt, new battery cables. Still can hear the fuel pump surge with the brake lights and turn signals and get weaker when I turn the lights on. I gave up....I suggest moving on unless it gives you a good excuse to go out to the garage to play :-)

deadphoenix52

iTrader: (2)

my next step is to replace the fusible link fuse box thing. everything in the car goes through there. and a weak connection there would affect everything else on the car.

also, the electronics got a jump when that little wire got disconnected.

wheres that relay DIY when this doesnt work lol (in the archives i know)

-Nick

DerrickS

You should clean the ignition switch. I just did this couple weeks ago because my car was having issues with starting and then immediately shutting back off. I took the switch apart and cleaned it and the problem was fixed. Much better starting now.

I still have issues with the voltage getting low. The problem that you are already aware of is that the electrical systems suck in these cars. No relays, so all the current runs through the switches. This is not good practice, but to make matters worse, mazda really skimped on the design of the contacts. Now, 25-30 years later, all the these switches and accessories have high resistance and really tax the charging system.

You've done the big stuff, which is good. Ideally you'd go through it all and make sure every switch was in great working order (high beams, anyone?) but that's a bit difficult. You might just up the current capability of the alt which will help with voltage drops. The down side is that you could have a high resistance connection/switch somewhere that can't take the current draw and over heat, but your probably fine.

That being said, I wish I was seeing 14 v on my gauge. I always see 13 or so, and mostly between 12 and 13. Battery stays charged though, so I'm working on it at a slow pace.

deadphoenix52

iTrader: (2)

this is the state of things now



i got the highbeams fixed and im going to clean everything else down there as well. the ignition switch was on my list.

a good cleaning will have to do until i get around to actually adding the relays etc etc.

deadphoenix52

iTrader: (2)

on an unrelated note, where is the red/yellow for the door jamb?

when i open my pasengers side door all the interior lights and chimes come on, not so for the drivers side, and i cant find the wire

clykins

iTrader: (1)

I would take the grounds off clean them off really well, both the connector and the unpainted surface it is bolted to. The two I would look at are the one from the negative battery cable on the driver's side strut tower and the one at the end of the negative battery cable mounted on the rear housing. While you're at it I would clean off the battery posts too. Let is know if you figure this out. Good luck.