Issue is with the car running the battery voltage jumps around wildly from 14v to 8v to 4V to 12V etc. Here's a link to a YouTube clip I made of it. I'e disconnected the alternator charging lead to make sure it wasn't a internal regulator problem. With the charging lead off the battery it still does the same thing..... all grounds are solid, and I'm at a loss. I just pulled the cap off the HEI and everything looks good. Tested the coil and the primary and secondary coils tested fine. Anyone have any ideas? I've replaced the battery and it made no difference. The wildly jumping volage is causing havoc with the fuel injection. It tests identical to a alternator with a bad voltage regulator but it does it with the Alternator put of the system
Have you started it with the alternator hooked up and disconnected the battery? Not sure if it is a good idea with the fuel injection but I think I would get the fi instructions out and see what it sez. Have the battery load tested, and maybe try a different meter.
I'e tried a different battery with the same results, I'd rather not chance damaging any of the FI electronics trying to run anything soley off the alternator.
It's not likely that the efi would even run on 4 volts. Try turning on the headlights, watch the volt meter and light brightness at the same time. My guess is that the voltage is higher and more stable than the meter says.
As much as a PITA as its gonna be, have you tried the voltage swing test on each individual fuse? I know youre getting steady volts at the FI end of things with a swing at the battery. Maybe even go as far as to lift one fuse at a time and recheck the swing. Are there any hidden anti theft devices or any other non OEM devices installed? Does the FI have any feed back stuff back into the system? A new battery would be the logical choice but since you switched to another its doubtful. Was that in fact a NEW battery? Stuhhrange coincidences happen on this old stuff! Just watched an alternator test back to back with your youtube and the guy touches the post with a tester and the GRD. clamp is loose as a goose. The guy proceeded with the test. ws
X2 on what Bill said. You're going to have to pull individual fuses or disconnect individual electric items (taillights, trunk light, stereo, etc.) one at a time until the voltage spikes disappear. That'll let you know what circuit to focus on. If you've got anything aftermarket (especially car alarms) start disconnecting there.
Yeah there' a utube video that shows the exact same voltage swings but the culprit was the alternator regulator, knowing ti rule that out I ran the tests with the alternator out of the system. All my connections are ROCK solid, I even went ad far as to change the fusible links and remove every ground and main starter feed to check them on the bench to make sure all my 0G connections were solid. Being a 12V tech I know how important good grounds and solid connections are
CAR doesn't have any antithefts of any kind. When I used the same multimeter on my daily driver and my wife's car it worked perfectly so that removes a faulty multimeter. The battery I put in was in fact a used known to be good battery.... I didn' want the just keep throwing money and parts at it without being sure. The FI wiring just consists of a constant 12V battery connection, a key on Ignition and tach signal from the distributer
What does it say if you measure right at the battery terminals? The DC voltage fluctuations you're seeing would almost be impossible at the battery because it acts as a regulator all by itself. The battery cannot instantaneously discharge and recharge at that rate. Since the battery acts as a regulator that is one reason you really don't want to dissconnect the battery while running. I'd put that meter on AC and see what you have going on. If it reads noteworthy amounts of AC then it points right at the alternator. Maybe possible ignition voltage leaking into the DC system? Make sure the alternator is completely disconnected, no wires whatsoever. I'd even disconnect the alt. belt for a short while to make sure nothing spurrious is coming out of the alternator.(probably the easiest thing to do) Maybe it is getting into the ground system through the case especially if you measure any kind of noteworthy AC on the 12V line. The odds of two bateries being bad is small. As you said the battery has been replaced so I'd look at the wiring getting the power to the harness where you're measuring at. Look for intermittent connections to the measurement point assuming you are not measuring the very same fluctuations at the battery. After that I like the idea of disconnecting fuses to see if any particular circuit is affecting the reading but I don't really see how they would be causing such major swings.
I am always metering the voltage directly off the battery, in the above video that is also directly off the battery terminals themselves. I'l have to get the car back together later as I removed the distributer cap and wires to check the resistance of the coil itself. I'l check for AC voltage once it's running again, as I had mentioned I did do the test with the Alternator completely put of the system.... but I guess you could be right about an internal short grounding out AC within the alternator I'm at the point where I'll try anything but nothing in the fusebox or fuses would be capable of drawing enough current to drop voltages that much. We'd be talking 100's of amps of draw, enough to turn which ever system was drawing it into a Mig Welder. Essentially catching lightning in a bottle Your right about the rate of discharge, for that to happen it would have to be a Giant capacitor....
You sound pretty well versed on DCV's. Just another YT vid I grabbed. Looks like yer gonna gafta think outside the box on this one. Make a bad connection on the diode trio? This guy is using the spade connector stuff but CAL-HAWK??? Its chinaman stuff! Perservere... sometimes its an FM (freekin' mystery!) ws
Very possible. When I get the car back together and running later I'll test for AC voltage entering the system. Believe me I'd happily throw a new alternator on and be done with it
Someone please correct me as I must be doing something wrong. When I tested the battery for AC volts with the car running I got 30v+ All the ripple tests I found online say it should measure .05?
It is weird but when I came to this last post there seemed to be more information but once the video loaded it went away. Well that explains why your DC voltmeter was going crazy. Did you rev it up a bit to see if the AC would go up? It was trying to turn the AC readings into something that resembled DC readings. If the car isn't too hot disconnect the alternator belt to take it out of the equation completely. Start it up and see what you get DC and AC wise. It won't hurt to idle it for a minute or less without a water pump. Just keep it short. Once the belt is disconnected the alternator can't be producing any kind of voltage. A couple of bad diodes would cause 30V AC on the circuit but you're saying that the main output wire from the alternator is disconnected. I'd remove any wires that are going to the alternator. At that point if you are still getting AC then something else is producing it. I'd look into the ignition system at that point. I just wanted to add that years ago you could buy a kit to disconnect the regulator from an alternator and then you could run something like a 110V AC/DC drill at a higher idle. As long as the tool was rated as AC/DC. An alternator can easily run a 100W light bulb once it is disconnected from the battery and regulator. Not really good for the diode cluster because of their voltage rating.
The above video was WITH the alternator charging lead on. That's exactly what I did last night, I ran it with the alternator belt off. The DC voltage readings were stable so I removed the Alternator and I'm going to take it to get checked out today. I'm going to run it again later this morning just to make sure as even when the voltage was jumping around before it would be constant at times. Just want to make sure that it didn't just happen to be one of those times. The thing I find strange was I was having the same issue before even with thing the alternator charging lead off. Which means that IF it is the alternator then it must be grounding out in the case somewhere, I still had the belt spinning it so the that's the only path it could take. Can anyone confirm that the AC reading isn't normal? When I checked online for Alternator ripple tests the AC voltage wasnt supposed to be anywhere near that
Went to a custom Alternator shop and they spun it up for me. 14.6V at 125 Amps, no Diode issues or AC leakage, perfect condition
I can assure you that 30VAC on the 12V line is wrong. The .05V is more like it. If you checked the voltage on the +12V line with an oscilloscope you'd see the 12VDC and on top of that would be 30VAC floating around. If you disconnected the belt and the AC went away then something is wrong with the alternator(the Alt Shop just couldn't check for it) or something is passing through it. Maybe electronic ignition although I don't know how that would work? Unfortunately it looks like trying another alternator is your only choice. You could always open up the alternator to have a look to see if one of the windings is touching the case. Can you borrow another alternator for a test?
I only tested for DC with the alternator removed and it was constant. I couldnt run it long obviously, but while I did the DC voltage was fine and not jumping around. I didnt check for AC, but can when I'm home later. From out I've found online the AC voltage reading could just be nonsensical.... I picked up some 10A diodes and was going to try one in line at the Distributer 12V and the Ignition Trigger wire to see if it stopped any potential back feeding. NoLift, seeing how it seems to be just a back and forth between us do you mind checking online for a AC ripple test. From what I've found I believe I'm doing it properly but anything is possible. Unfotunestly getting my hands on another alternator to test isn't possible
AC ripple Test. Although I know my meter is fine I went out and bought another multimeter.... needed a spare anyways
I just did the same test on my daily driver with the new meter and got 0.3 V AC which is inline with things found online. I'l test when I get back home but I fear the autoranging feature on my other meter wasn't working and it was actually 0.3 not 30.... but when I tested an outlet in my garage with the same meter on AC I got 124v. Which made me think the 30v reading was accurate. See what the new meter says
