Electrical Issue: Thinking perhaps a bad ground at this point?
 

1984 RX7 12A Carbureted , Rebuilt approx. 3-4 years ago

Ok,

So one day, I go to roll down both windows (power windows) at the same time and the car slowly loses rpm and stalls. I start to play around and notice when I put any electrical load on it, headlights, brake lights, A/C (A/C is more like an instant kill switch), it stalls.

While it is stalling I can see the Voltage gauge, which usually stays around a steady 14, drop as well, especially if I hold the power window button down after the window is all the way down/up.

Everything else seems to be functioning normally from what I can tell, oil pressure is good, fuel pressure is right on, temperature is good.

So I take the alternator in (mind you this it the original alternator from 1984), and have it tested. It passes all tests. Then I take the battery in, it had a low charge, but passed all tests and they recharged it for me.

So I do some reading, and I read about the voltage regulator which is in the alternator, so since it was the original alternator I figured it couldn’t hurt to replace it. I got a new one, and stepped up the amps as well, getting a 60 amp one instead of the original 52 amp.

Now I can press the brake pedal to turn on the brake lights and it is fine. But say if I do a combination, like headlights + brake lights , it will slowly stall again. The battery is only a 2-3 years old, and I drive this car a few days a year only during the summer.

I followed all the grounds I could fine from the top of the engine, wire brushed them down to shiny again and put them back on, as well as the terminals on the battery and the connectors to the terminals. I am at a loss at the moment. Would appreciate any help I could get.

On a side note, I noticed something new around the same time and I am not sure if it is related or not.

So I go to drive it down the road, I noticed a hesitation when I hit the gas, a drop in the rpms, then it seems to catch and take off. My dad and I had been messing around with a tuning issue with the spark plugs and moved the timing. So I figured that we had backed it down to slow and that would cause the lag. So I stepped it up, and now there is still the hesitation, some times the car stalls (doesn’t recover from the drop in the rpms), and the exhaust glows red. So from what I had red that means the timing is up to high, so I backed it down again trying to have a happy medium, no glowing exhaust, but the lag is still there. Hope this gives you guys something to chew on, and if you need any questions answered I’ll check the post daily. Thanks again for any insight you may have.

Your weird hesitation thing is most likely carb related. Set timing with a timing light. The original wiring is aluminum so it corrodes. Best bet is to replace the main ground wire with some copper wiring along with replacing the main starter power wire along with upgrading the main power wire from alternator to battery. This should help the voltage drop issue.

I have a similar problem (i.e. engine stall). It dose not involve the windows. The car sometimes stalls during deceleration with the throttle released approaching a stop. Every day after approximately 3.5Km the engine will loose boost (as if no gas) then gets going again. It will then stall when stopping at the next set of traffic lights or when the clutch is in on other occasions. At idle speed it runs without a problem ! I have had the electrics checked (all OK), had Cat changed, new ECU (2nd hand) but still have the same problem.

Is there a thread that shows where all the grounds are?

http://rx7.foxed.ca Download the wiring diagram for your car.

Replace fuel filter, check plugs, if you have fuel injection (not sure exact model you have) could be dirty/leaky injectors.* Tell us what kind of car you have and we can help more.

Hey guys

So I have two issues currently:

1. When I roll down the power windows, turn on the headlamps, or/turn on the AC, the car drops revs until it dies and the battery guage drops from 15 to roughly 10-12 range. Anyone seen this? Radio does not affect the car whatsoever.

2. The car starts fine, warms up fine, the choke pulls back in when its warmed up, but when I go to press the gas the car stalls. If you slam the guess it will drop to almost dead, but then catch back up and rev. If I play with the throttle and make sure the revs stay up I can drive it around.

Any help would be appreciated.

Thanks,
Benz

Sorry,

Also, I replaced the altenator last month (purchased it through a mazda dealership but I'll check to see if it fits your requested spec).

thanks

Good grief, nobody goes to the dealership for hard parts!:lol: Unless you're getting a killer mechanic deal, you're getting fleeced! If they gave you a stock alternator back, then you're prolly going to have the same problem because it's your ancient, oxidized wiring harness that's putting up the electrical resistance fight for the poor 52 or 55A alternator. A lot of people simply run an 8 ga wire right from the alternator directly to the battery positive to get around most of that problem.

:cool:

I'll give it a try, thanks!

Mar3,

Quick question, what is AP in relation to:

"AP on the carb ain't doing the job no more"

Thanks,
Benz

AP is short for Accelerator Pump. Its a part on the carb, NOT to be confused with a fuel pump.

Edit: What your accelerator pump does is when you are at idle and first hit throttle it spuirts a shot of fuel into carb so it doesnt go lean right off the bat until the vaccuum sucks fuel out. This could be your problem with your stalling and whatnot when you first push the gas.

Does anyone have a picture of the accelator pump on a 12A carburated engine?

Yes, but I can't post it because I'm at work...I'll put it up tonight...heck, I'll just take a pic of the one in my car and post that so I don't have to dig for it.:lol:


:cool:

edit: sent to work, here they are...

https://www.rx7club.com/attachment.p...1&d=1247232446

Where

• 1 - the alternator
• 2 - air cleaner
• 3 - bracket and throttle cable attached to carb
• 4 - Oil filler cap, aftermarket Al one
• 5 -Emissions solenoid pack
• 6 - Spark plug wires on distributor cap
• 7 - fuel hose

...the AP housing is outlined in both pics...

https://www.rx7club.com/attachment.p...1&d=1247232446

Mario III

Thanks Mario, that saves me tons of researching time. I'll check it out this weekend. I'm going to start with the AP, and if that the stall issue, move right on to replacing the altenator and terminal wires to see if I can get that fixed.

That's what this New Member's tech section is all about. It's for those of us that don't like saying "Go search through the FAQ's, man!!"...:crackup:

Some of us never tire of supplying what we know or helping others out with arcane rotary knowledge. Good luck on the carb work and keep us updated! Just remember, though, without us being able to actually lay hands on the car or have it in our garages with all of our tools, this thread represents our best GUESSES at your problem, ok? ;)

:cool:

Mario,

Can you adjust the ap? I bought a haynes manual after looking through the forums and I still can't figure out if you can or can't. If you can, can you give me a brief overview. I just don't know where I should start. Oh, and I appreciate all "guesses."

Thanks,
Benz

Yes, it can be adjusted. If you look at the AP there is a rod looking deal that hooks to it with a nut on it. If you turn the nut clockwise (in) the AP will shoot more fuel, and vice versa. If adjusting it way in or way out doesnt seem to affect anything then there is another problem. Really though take your time adjusting the AP. Really, you should not turn it more than 2 full rotations either way (before testing) and when you just need to fine tune it then go in 1/2 or even 1/4 turns.

Well battery died before I got to try adjusting the Accelerator pump. On hold till I get a new one.

Spend the money now and get an Optima...you'll also need a "universal" battery hold down kit since the factory battery hold-down bracket won't work with the Optima...you'll still be able to use the factory holes and tray, though.

:cool: