classiczoomzoom

car only shows 12 volts when trying to start unless i hook up a 50amp charger. here is what i have and what i have done

1985 12a carb.....stock

new battery
new starter
new wires both + and -

all leads have been cleaned and corrosion free.

Car will not start unless i hook up the 50amp charger

help please

jonvo4591

did you make sure your battery was fully charged at 12.6 volts?

Siraniko

iTrader: (13)

you need one more ground cable from motor to chassis provided that the alternator is good

classiczoomzoom

new battery is fully charged and I have made a second ground going to the one of the front shock bolts. What roll does a alternator take in a car during startup?

thanks

bliffle

Have you used a hydrometer to check the gravity of the electrolytic fluid in the battery cells?

Have you used a voltmeter to check the voltages around the starting circuit?

DivinDriver

iTrader: (15)

What does it do without the charger?

Click-click-click?

Slow turn but no start?

Something worth checking - - make sure your belts aren't over-tight, and that none of the stuff they run (pumps, alt, ac, etc) have seized up or are losing bearings. I had a alternator bearing seize up on me once (different car - V8 Camaro) and it left me stranded on the hollywood freeway at rush-hour. Engine wouldn't turn at all.

Too much mecnahical resistance could prevent the start from getting up enough speed without the additional current boost from the charger.

Kentetsu

25 year old cars that were built with aluminum battery cables, that's the problem. Once the aluminum starts corroding all you can do is replace the cables with new.

bliffle

Aluminum cables are a big problem in sub-zero temperatures. Anyhow, it's easy enough to test for excess voltage drops with a cheap multimeter from radio shack or home depot. Lot quicker than actually changing the cables.

Of course one good thing about changing cables is that you get rid of half the corrosion between the battery post and the cable clamp. In fact, if you get new cables AND new battery you get rid of ALL the corrosion.

But I'm too old and lazy so I just clean off the corrosion with that wire brush from the autostore. I'm also cheap, so the $4 brush looks like a better deal to me than $100 worth of cables and battery. In fact, sometimes I'm so cheap I just use an old piece of worn sandpaper castoff from some other project.

But I have to admire you young energetic rich guys for your enthusiasm about solving corrosion problems.

classiczoomzoom

Guess i forgot to say that i have new cables as well. almost everything is new except the engine. I have 12 volts at the battery and 12 at the starter. when i try and start it it start to turn and then at about 3k it slows down. then i have to wait 15 min and then i can start over again. yes the battery is new and the starter is new

[Chance]

I'm having major electrical problems as well... Good luck to you. Me and my '84 GS will be waiting for answers as well.

trochoid

iTrader: (6)

3k cranking rpm? That's a bit high. When an engine spins substantialy faster than normal when keying the starter, it's usually a sign of low compression. Since you've continued to try to start it with no success, there's a good chance the engine is flooded, leading to lower compression and faster spin up from the starter.

Deflood, clean/replace the plugs, squirt some enigine oil into the housings and try again.

blackdeath647

iTrader: (2)

i thought it should show 12 volts when starting? atleast mine does, starts at twelve then it'll drop to about 9/10 when cranking then it'll slowly go up to 13/14 once its running......is your car trying to start at all? does it just click, or does it turn the engine but no crank? if its clicking its gotta be a loose connection somewhere maybe corrossion, if its turning but no crank it could be your wires cap/rotor, or plugs.

classiczoomzoom

Yes it tries to start but only 2k. voltmeter shows 12 at battery and 12 at starter but only 10-11 at ignition switch

bliffle

So does the starter sound like it's spinning the motor with enthusiasm? Or is it grudging?

If the starter spins enthusiastically, then your problem is elsewhere so that it might cause the ignition voltage to drop so low that the spark is weak. Happens a lot to cars of all kinds in -30 degree weather.

You might have an iffy connection in the spark circuit, or there might be a short somewhere in the starter circuit (happened to me once when a mechanic who didn't understand electricity incorrectly hooked a 'mystery' wire to ground and the smallish short was not enough to stall the starter circuit but it killed the ignition circuit). That's one of the problems with "trial and error" approach.

Did you hook your voltmeter to the coil primaries and observe ignition starting voltages while cranking the engine?

Incidentally, I spotted a multimeter for $5 at the autostore this morning. Nice. It has a D'arsonval movement, which is nice for cars because you get a nice little ballistic averaging action that a digital doesn't do.

At that low price you can afford to have an extra, which is nice since sometimes you want two when testing a dynamic situation such as a coil primary circuit while attempting to start.

classiczoomzoom

Start with enthusiasm then it puchers down after 2 seconds. Starter is new by the way so is the wiring from the battery. Did a spark check earlier today and that sucker is a good hot blue color.

bliffle

2 seconds? That's much too fast in this weather.

Do you have a hydrometer for testing the electrolyte in the battery? I like the little $4 unit that looks like an eyedropper with 4 small tiny ***** floating in the cylinder. Draw a little fluid in, and if any less than 3-4 ***** float you have a discharged battery. Sometimes the electrolyte is low, too, and you have to add distilled water. I once had to add a whole quart to an old battery! All you need to add is the distilled water because the other chemicals are still in the battery: they have no way to escape short of breaking the battery. They can't evaporate like the water.

Sometimes you have to check voltages around the starter circuit, so, to facilitate singlehanded debugging without an assistant, I usually drill a tiny hole about 1/16" diameter and 1/8 deep in the center of each battery post, and thread in a small sheet metal screw or a small machine screw (like #4) leaving the head and about 1/16" of thread above the post. That way I can clip on an alligator clip from my voltmeter and observe as I crank the engine.

So I attach alligators to the negative screw and a solid ground, like one of the screws on the shock tower, prop the meter on the windshield, crank the engine and observe the voltage, which should be zero, of course, but in this imperfect world it will probably be some small value like 1/2 volt. Anything over 1 volt is definetly a problem with the negative cable or the connection at the battery or to the ground.

Then I repeat the experiment with the clips attached to the screw on the positive post and ground. This should read about 12.0-12.6 volts before you twist the key, and shouldn't drop below about 10v. when you crank the engine.

There are other things to test , but this is a good start. Like, you go under the car and attach to the two big screws on the solenoid and check that while cranking.

Rx-7Doctor

iTrader: (13)

Need to have more information.

What led up to the no start condition?

When you stated it won't start unless you hook the booster up. Will it stay running and does it run normal?

classiczoomzoom

I got the car last year and the guy was selling because it died. I tested the basics out and found that the problem was probably carb related. i picked it up for 400 bucks. i had it running before winter and it ran fine on its own without any other power source. The car sat "covered in snow" all winter and now i have time to get it working. before winter i found antifreeze on the plugs and steam from the intake manifold. I picked up a carb rebuild kit and a new intake gasket and o-rings. Now it doesn't start but i don't have antifreeze on my plugs. the plugs get wet and my floats are filled up. Think that gets you up to date.

blackdeath647

iTrader: (2)

have you checked cap and rotor? i know it sounds stupid but just making sure you have checked all the basics...

classiczoomzoom

I put in a new one last year but i check it this morning and found deep grooves in the
caps terminals. must have put it on wrong making the rotter slice into it. will pick one in town tomorrow. I'm also going to get a new set of battery cables. maybe the ones i have are to cheap. of coarse still not getting 12 volts on the gage.

bliffle

Sounds like you found it.

Panel voltage gauges are kinda numerically unreliable. Each of my FB gauges reads differently. Gotta use a real voltmeter.

During the winter you probably got a lot of condensation in a number of places including inside the distributor (which will short the high-voltage secondary) and the fuel tank (which will put water in the fuel). Usually somr alcohol will soak up the water in the tank and burn it thru the engine.

classiczoomzoom

UPDATE

i was able to fix the voltage problem. the crappy cables i got last year were not copper core so they corroded. the new ones i got are bad ***, hooked them up and boom. 12volts reading inside the dash.

now here is the next weird thing that poped up....my stinking fuel pump stopped working, i figured i must have screwed something up when i was down there with the starter. correct me if i'm wrong but the wire is the brR.

still think i got a good deal on the rx7. got it for 400 bucks and it had new tires and new snow tires also on there own rims. i have put about 120 bucks into and i think if all goes well once the fuel pump is operational i can drive it. next upgrade aside from getting a stereo is exhaust and maybe a carb.

classiczoomzoom

Almost done

OK, looks like my fuel pump is pooched. tested the voltage and it's there. should i get the stock pump or does anyone recommend something better?

Thanks everyone

trochoid

iTrader: (6)

Please explain/detail the location of the BrR wire. The wires going to the starter are a large black battery cable, a BY wire from the ignition switch and an LW wire that goes back to the hot start relay. The fuel pump has 2 wires. An LW for power and a B for ground, both of which come through the grommet in the bottom of driver's side bin. I have yet to find a BrR wire in the harness. Over time, wire colors fade. Take your BrR wire and scrape off the top coating to see if perhaps it has faded and is a different color than you posted.

If the engine is cranking at 2-3k rpm, there is definitely something wrong. Cranking speed should be in the 200-400 rpm range. Compression testing is baselined at at 250 rpm. If your cranking rpm is that high, then either your tach is way off or you have no compresion. Even with the plugs removed, I doubt the starter could spin the engine at 2k.

Since you said the plugs are wet, they may not be firing when they need too, clean and dry them. Check the engine fuse under the dash, that one is for the fuel pump. Also go through the usual fuel supply checks, the fuel filter, the filter screens that surround the banjo bolts in the fuel return/supply lines on the top of the carb. The fuel pump can be tested seperately by running battery power to it directly. If it works that way but not through the4 switch, the fuel pump relay may be bad.

If the fuel pump is bad, a stock replacement is the easiet but it's not cheap. Other options would be a Carter 4070 or any aftermarket pump that puts out 60-70 gph. It will require rerouting fuel lines and a low pressure fuel pressure regulator and gauge capable of holding the fuel pressure in the 2-4 psi range.

classiczoomzoom

The color of the wire i said earlier was wrong i re-checked it. it seems that my rpm gauge is acting up it bounces around that is why i thought it was 2k. Like i said it looks like im going to replace the fuel pump. i tested it and it definitely is bad.

i found a bunch of replacement pumps at napa for about 60 bucks. you said to find one that puts out 60-70 gph these only put out 30. isn't that enough if not napa should update there stuff since they say it is compatible. thanks again for your help