ntomsheck

iTrader: (1)

Hey guys. First, I wanna start off by saying this isn't on a thirdgen. However, this is the largest collection of automotive-knowledgeable people I know, so I figured I'd post the question here in addition to the car's proper forum. I wont say what the car is, but it's a 74 and it's carburetted, and the manufacturer rhymes with 'flotsun'. It's a customers car that I'm trying to get running, after sitting for 20+ years.

With a battery charger connected, I can turn the car on run, and the tach shows 1800rpm + (it moves around, but it's always above 1800rpm). The ampere gauge (yes ampere, not voltage) barely moves when I turn the ign to run, even though the charger is on 200amp START. If I stick a spark plug in the coil wire and hold it against the manifold, I get a constant, very hot spark. The car has a transistor-ignition module mounted on the wheel well, with points-elimination sensor (factory) mounted inside the distributor. The alternator is not currently hooked up, but from what I can tell in the wiring diagrams, this car has an external voltage reg. Any ideas? I'm stumped.
The car will have a chevy 350 in it, once the car runs and proves that it's a good base to start with.

Rolling Thunder

Ok not sure how much help I can really be as I havnt not worked with that particular brand but hey ill bite its an old car how bad could it be lol. First If you have any schematics you could send me it would be of great assistance to me to help you get to the bottom of things. now im not totally sure what your questions are but ill answer to the best of my ability and just let me know if im off base or missing the point.

First the tach. Without a good schematic I'm not sure what sort of a signal it requires to work. It may be that that is why its getting stuck above 1800 RPMs is due to a lack of a signal telling it to do otherwise. Could be a bad gauge or whatever drives the tach may be faulty but again for that I would really need some sort of a schematic to piece together what it should be doing and what it needs to work.

Second the amp gauge. This doesn't surprise me. See voltage, current and resistance are all related. Setting your charger to 200 amps start means that the charger will try to provide up to 200 amps. You'll notice that if it was hooked up to nothing and set it 200 amps START no current will be flowing. This is because having it connected to nothing is essentially infinite resistance which would require theoretically an infinitely high voltage to force 200 amps through that resistance (that is just air). Now because it would be a bad thing to apply an infinitely large voltage to your battery/electrical system the output voltage is limited so its not even possible for the charger to force current to flow in a situation like that. Now looking at the car with the voltage limited and virtually no electrical devices drawing current (meaning a high resistance) there isnt much current that can be drawn from the charger. The electrical system will accept only what it will draw. Further more depending on how the gauge is wired and how your charger is hooked up will determine if that draw is even measured. However your probably lucky it didnt draw 200 amps through the gauge as that would likely kill it.

Spark plug. When you say a constant spark do you mean actually a constant spark like a arc welder or constant in terms of just not intermittent repetitive spark as you would expect to find when cranking?

As far as the voltage regulator not really sure what your asking here?

ntomsheck

iTrader: (1)

For constant spark, I mean just not intermittent. It actually looks to be about the amount of spark you would see at 1800+ RPMS. The tach is a single wire driven off the coil, and I actually think the tach is working just fine, but something is telling that coil to fire off constantly.

You explanation would make sense for the amp gauge, however, when I turn the car to run, it actually goes backwards into the negative (I just noticed this).

For the voltage regulator, I was saying that since the alternator doesn't have a voltage regulator, it shouldn't matter if it's hooked up or not; there seems to be one hidden in the car somewhere, at least according to the diagrams. The voltage regulator should hamper any crazy interference from the charger (but I've been wrong before).

Rolling Thunder

Ok well I may have a guess as to whats going on here. My take is you dont have a battery in the car your just doing testing off the battery charger? The issues may be that electrical noise generated by the charger is triggering a false spark. See the voltage regulator regulated the voltage by controlling the output of the alternator. Since there is no alternator its essentially doing nothing but existing. However it was never the regulators job to deal with electrical noise like voltage spikes. That job is done by the battery as the battery essentially acts like an infinitely large capacitor shorting out voltage spikes (charging the battery) and providing current if the voltage dips to maintain the correct voltage. Without the battery in place your electrical system just gets the raw output of the charger unfiltered. Being the the output of the charger is probably not going to be a nice clean voltage this could be causing false triggers. That ignition module is looking for voltage variations (and is very sensitive) and could easily be mistaking the noisy output of the charger for a signal to fire the coil. I would try putting in a good battery hooking the charger to the battery and then trying it again. I wouldn't be surprised if that cleared it up.

Also yes a negative deflection is correct. Im assuming youve got the battery charger hooked up to the +/- battery cables. What it means is the car net current draw is being drawn from the battery resulting in a negative reading as its discharging the battery. If you were to put the positive lead of your charger to the output of the alternator (the white/red wire) your reading would be positive instead as the net current draw was coming from the alternator which would be charging the battery.

Also thanks for the schematics.

ntomsheck

iTrader: (1)

Hmmm, you're the second person to recommend replacing the battery. I didn't know a battery charger's output was that dirty haha. I'm sure there's another one laying around somewhere. Where the car is parked, the owner has 4 or 5 other lawn ornaments (read: non-running cars). I'll reply back with the details; I should be going there tonight.

Rolling Thunder

Well its not that the output of the charger is that bad. Surly its not perfect but its not that bad. The issue is the ignition module is looking for a relatively small signal so even a relatively small imperfection of the chargers output could be seen by the ignition module as a signal to fire the coil. Its just very sensitive like that.

One thing though I wouldnt recommend trying to borrow a battery from one of the other lawn ornaments. Thing is if there anything like the lawn ornaments im familiar with their batteries arnt really well maintained. If it was truely dead as it very well probably is and you go to hook your 200 amp charger to it the battery is pretty much going to short out the charger drawing most of the 200 amps to try and charge which as im sure you could guess would probably not have a happy ending. You could try to put a trickle charge on the battery to charge it up first but that will take a long time and if the batteries no good it may not even work even then. What i recommend instead is taking jumper cables and jumping from your running car's battery to the positive and negative battery cables of your project and not use the charger. This will have the desired result and probably be a lot less of a hassle.

ntomsheck

iTrader: (1)

Ah that makes sense. I would be picky about the battery haha - I wouldn't grab it from the silverado or buick that's been sitting out there for a year. A 72 charger just had it's engine removed, maybe I can sneak their battery out of the garage hahaha. That, or the cadillac. Somehow, a mid 2000's cadillac escalade made it's way to this guys house. It looks like it was hit by a semi, but it has the 6.0 vortech LQ9 in it, which I might nab. However, no one seems to want to explain where this cadillac came from... I digress; I should be going out there today, I'll report back after a few tests.

ntomsheck

iTrader: (1)

Went out there today, and snuck the battery from the charger to the car. With the ignition on, almost everything works. Just a few burned out lights in the gauges. The tach is down to zero where it should be, the electronic fuel pump even ran. Fortunately I didn't hook the fuel lines up yet, as orange/brown 20 year old gas poured out. Needless to say, a few trips to the hardware store, and a few more parts put on, and we had it popping with some ether. There was a little bit of carb backfire though, so I've gotta recheck my plug wires and check the timing again. Regardless, thank you for your help - turns out it was just the battery.

Rolling Thunder

I'm glad to hear it worked out and was resolved so easily. Don't worry though I'm sure some other issue will turn up that wont be so easily solved haha. Well best of luck with the rest of the car glad I could help.