Thanks Bewy, it's not the tach, as both tachs have same symptoms.
Tach reading high
- Thread starter 4spdragtop
- Start date
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Could the blk/yellow wire from ECU to coil cause this? Its hooked to same post on coil(-ve) as grey tach wire.
I checked for resistance and continuity, the blk/yellow wire appears fine.
Connections are good clean and tight.
I checked for resistance and continuity, the blk/yellow wire appears fine.
Connections are good clean and tight.
.
Steve, I've sorta been following along.
I haven't driven my car in a couple weeks. Out of town for work and way too hot. So, today I get in, fire it up and the damn tach is reading high
.
It shows idle around 2K when I know for a fact it's not over 800. On my drive I had it over 8k a couple of times
I haven't touched the car since the last time driving it. Beats the hell out of me...maybe a bug in the Chinesum crap tach. I'll pull the tach apart when I get time to see if the switch changed positions.
Good luck with yours!!!!
Steve, I've sorta been following along.
I haven't driven my car in a couple weeks. Out of town for work and way too hot. So, today I get in, fire it up and the damn tach is reading high
.It shows idle around 2K when I know for a fact it's not over 800. On my drive I had it over 8k a couple of times
I haven't touched the car since the last time driving it. Beats the hell out of me...maybe a bug in the Chinesum crap tach. I'll pull the tach apart when I get time to see if the switch changed positions.
Good luck with yours!!!!
Sorry to test of your troubles also. Its voodoo to me. I added a dedicated ground from ecu to batt-ve. I already had one from VR case to batt-ve.
I've already replaced coil. I have another ecu, but hate just swapping parts. No spare 70+ alternator...they want $120 for a Reman...
Latest video
I've already replaced coil. I have another ecu, but hate just swapping parts. No spare 70+ alternator...they want $120 for a Reman...
Latest video
.
Steve, I've sorta been following along.
I haven't driven my car in a couple weeks. Out of town for work and way too hot. So, today I get in, fire it up and the damn tach is reading high
It shows idle around 2K when I know for a fact it's not over 800. On my drive I had it over 8k a couple of times
I haven't touched the car since the last time driving it. Beats the hell out of me...maybe a bug in the Chinesum crap tach. I'll pull the tach apart when I get time to see if the switch changed positions.
Good luck with yours!!!!
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It just doesn't make sense. I think you're right...voodoo.
67Dart273
Well-Known Member
Steve I am out of logical suggestions. I would "dewire" the ignition, temporarily, and "hot wire" it to try and isolate. So clear back to the basics
1..Double check the tach ground wire
2..Check with voltmeter to be sure tack power is solid
3...Unbolt, clean and re-ground ignition module
4...Pull ECU connector and "work" it in/ out several times to scrub terminals. This is difficult because of the center screw. Some of them will come out
5...Then, disconnect the power to the ECU/ ballast and wire only that to a method of hot wiring, AKA maybe a temp switch taped and hanging in the bay, and connected to the start relay, or maybe even a good battery charger clamp, etc, so you KNOW the ignition is getting power.
Do you know how to check the alternator for ripple? Connect your voltmeter when set for AC not DC, to the alternator output stud and ground. Run car at high idle with and without a load. (lights, heater) Read AC voltage which should be very VERY low, the lower the better, and post that here.
1..Double check the tach ground wire
2..Check with voltmeter to be sure tack power is solid
3...Unbolt, clean and re-ground ignition module
4...Pull ECU connector and "work" it in/ out several times to scrub terminals. This is difficult because of the center screw. Some of them will come out
5...Then, disconnect the power to the ECU/ ballast and wire only that to a method of hot wiring, AKA maybe a temp switch taped and hanging in the bay, and connected to the start relay, or maybe even a good battery charger clamp, etc, so you KNOW the ignition is getting power.
Do you know how to check the alternator for ripple? Connect your voltmeter when set for AC not DC, to the alternator output stud and ground. Run car at high idle with and without a load. (lights, heater) Read AC voltage which should be very VERY low, the lower the better, and post that here.
Thanks Del, I tried to measure AC, at alt stud to gnd. Bounced all over whether load on it or not. Bounced from 0.6 to OL to 14.
For what it's worth, I had alt tested and its good. When I was working on it last night, I noticed I left VR unplugged and car started and idled "fine". Plugged it in and and noticeable idle rpm drop by approx 100 rpm. As well the alt stud to gnd increased with VR plugged in. Approx 12v unplugged and 14V plugged in. Had new spare VR, and swapped it, with same results.
AC voltage from alt stud to gnd was unreadable...all over the scale from 0.6v to OL.
Thanks
Steve
AC voltage from alt stud to gnd was unreadable...all over the scale from 0.6v to OL.
Thanks
Steve
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67Dart273
Well-Known Member
Steve maybe there is a large drop in the charge path from the alternator to the battery. Clip the meter to battery positive, and the alternator stud. Run the car and turn on loads like lights, heater, whatever, and run engine on fast idle. This will give you an idea of the drop in that line. I don't know why the ripple reading is so ???
The ripple reading you mentioned is the NEW alternator?
The ripple reading you mentioned is the NEW alternator?
Thanks Del the alternator is "newish ". No noises and elec shop gave it a clean bill of health.
Here is a quick video I did last night, I shut car off before symptoms arose again.
With VR plugged in, it "loads" the engine so to speak. RPM drops and alt stud voltage goes up as does the battery running voltage. This is with no load applied.
Once I reinstall alt I will chk/test from batt +ve to alt stud.
Not sure why my AC test from alt stud to ground was wonky? I dont necessarily have the greatest meters??
AC or DC voltage being measured from batt +ve to alt stud?
Here is a quick video I did last night, I shut car off before symptoms arose again.
With VR plugged in, it "loads" the engine so to speak. RPM drops and alt stud voltage goes up as does the battery running voltage. This is with no load applied.
Once I reinstall alt I will chk/test from batt +ve to alt stud.
Not sure why my AC test from alt stud to ground was wonky? I dont necessarily have the greatest meters??
AC or DC voltage being measured from batt +ve to alt stud?
I measured DC from alt stud to batt +ve, 0.25V DC for the most part, BUT it does bounce to 14V.
I measured from alt stud to gnd, and now got steady 14.3v with no load.
Turned lights heater on and got 15.25V.
I measured from alt stud to gnd, and now got steady 14.3v with no load.
Turned lights heater on and got 15.25V.
67Dart273
Well-Known Member
Let me be clear. You are saying that you connected to alternator stud and battery, and it did sometimes bounce to 14? THAT MIGHT BE A PROBLEM. You may have an intermittent open in that path. You have a thermometer gun? (laser thermometer?) See if you can find a hot spot in the harness
Also try a wiggle test. With the thing running high idle, and a good load, IE headlights, heater, etc, wiggle the harness near the alternator and the bulkhead and see if your meter reacts
If you have an intermittent in the charge line, THAT would also explain your erratic AC ripple measurement
Also try a wiggle test. With the thing running high idle, and a good load, IE headlights, heater, etc, wiggle the harness near the alternator and the bulkhead and see if your meter reacts
If you have an intermittent in the charge line, THAT would also explain your erratic AC ripple measurement
Yes Del, for the most part the voltage from alt stud to batt +ve is 0.25v but will fluctuate a little.
Voltage from alt stud to gnd is steady 14.3, no load.
I unhooked/connected/mounted ecu and vr and wires. Same symptoms.
1/2 hr ago car stalls out after tach starts bouncing. Tried a restart, no go. Swapped ecu, still no start/spark.
Hooked timing light clamp on coil wire leading to distributor to chk for spark, and none.
Voltage from alt stud to gnd is steady 14.3, no load.
I unhooked/connected/mounted ecu and vr and wires. Same symptoms.
1/2 hr ago car stalls out after tach starts bouncing. Tried a restart, no go. Swapped ecu, still no start/spark.
Hooked timing light clamp on coil wire leading to distributor to chk for spark, and none.
Pretty sure its correct, -ve to tach and to blk/yellow to ecu. Blue wire to coil +ve.
Thanks Matt, I'll dbl chk but I'm pretty sure it's good.
67Dart273
Well-Known Member
I admit I am about out of ideas. Any radio amateurs in your area? One that knows how to use an oscilloscope?
you might consider investing in a 4 pin GM HEI module, and build you an emergency ignition, you can use that to substitute for your "regular" one. Mine is a coil on the box, module inside, alligator clips for power and ground, and the distributor pickup cable.
Notice the blue "ground" symbol on one of the mounting holes. Look at the back of the module. There is a plastic locating tit you have to cut/ file off so it "lays" flat and you have to mount it flat on something (flat sheet of aluminum) so it has some "heat sink." DO NOT try to run it "in air" you need something for a "sink."
NOTICE the way the distributor is hooked up, showing the "bare" terminal on the dist. connector. This changes the timing if wrong.
I run my car with an HEI, and I also made an "emergency" module, with an HEI module in a box, and a coil. All you need is green clip to ground, yellow to 12V, hook up coil wire to distributor, and off you go
![[img]](https://www.forabodiesonly.com/mopar/attachments/hwlcfa-jpg.1715236943/[img])
you might consider investing in a 4 pin GM HEI module, and build you an emergency ignition, you can use that to substitute for your "regular" one. Mine is a coil on the box, module inside, alligator clips for power and ground, and the distributor pickup cable.
Notice the blue "ground" symbol on one of the mounting holes. Look at the back of the module. There is a plastic locating tit you have to cut/ file off so it "lays" flat and you have to mount it flat on something (flat sheet of aluminum) so it has some "heat sink." DO NOT try to run it "in air" you need something for a "sink."
NOTICE the way the distributor is hooked up, showing the "bare" terminal on the dist. connector. This changes the timing if wrong.
I run my car with an HEI, and I also made an "emergency" module, with an HEI module in a box, and a coil. All you need is green clip to ground, yellow to 12V, hook up coil wire to distributor, and off you go
So I ran it again and wiggled jiggled everything with no issues.
I had a temp gun and shot the pi$$ outta everything lol. Back of alt where shaft spins is over 100*, fld connectors are 90*.
Blue coil wire is 90 * right near coil, but 6" down its 80*. Its a solid length of wire but way longer than it needs to be.
10* heat difference? Coil was 85.
I'll look into the HEI Del, thanks for the layout/explanation.
I had a temp gun and shot the pi$$ outta everything lol. Back of alt where shaft spins is over 100*, fld connectors are 90*.
Blue coil wire is 90 * right near coil, but 6" down its 80*. Its a solid length of wire but way longer than it needs to be.
10* heat difference? Coil was 85.
I'll look into the HEI Del, thanks for the layout/explanation.
I admit I am about out of ideas. Any radio amateurs in your area? One that knows how to use an oscilloscope?
you might consider investing in a 4 pin GM HEI module, and build you an emergency ignition, you can use that to substitute for your "regular" one. Mine is a coil on the box, module inside, alligator clips for power and ground, and the distributor pickup cable.
View attachment 1716139072
Notice the blue "ground" symbol on one of the mounting holes. Look at the back of the module. There is a plastic locating tit you have to cut/ file off so it "lays" flat and you have to mount it flat on something (flat sheet of aluminum) so it has some "heat sink." DO NOT try to run it "in air" you need something for a "sink."
NOTICE the way the distributor is hooked up, showing the "bare" terminal on the dist. connector. This changes the timing if wrong.
I run my car with an HEI, and I also made an "emergency" module, with an HEI module in a box, and a coil. All you need is green clip to ground, yellow to 12V, hook up coil wire to distributor, and off you go
View attachment 1716139073
Not surprised idle rpm dropped 100 rpm. When the alt was properly connected later, it puts a load on the engine, hence the rpm drop. That is why it is silly to use a larger amperage alt than the car's electrical accessories require.
Forgive me for not back reading....I hate it, lol......but have you attached something else such as a dwell meter with a tach to compare to the tach in the car and rule it out?
I hate back reading too Rob, lol. No dwell meter attached (dont have).
Watching/learning this video,
Watching/learning this video,
Ok, so armed myself with a new Multimeter and test light(incandescent bulb)
Key on, NOT RUNNING
11.83V battery
Coil +ve 7.14V
Coil -ve 2.10V
RUNNING at idle
13.92V battery
14.2 V DC alt stud to gnd
0.135 V AC at idle, alt stud to batt +ve.
Stalled at 28 min mark, LEFT KEY ON
Coil +ve 7.05V
Coil -ve 1.90V
All seems normal?
Hooked new test light to coil -ve and gnd. Dim as it should be, but did NOT flicker.
Another quirk(in my mind) when measuring coil +ve voltage when it was grounded with test light, and cranked the light was bright , and almost started when grounding positive side?
I tap tested the dist connector on ECU side and distributor sparked.
Key on, NOT RUNNING
11.83V battery
Coil +ve 7.14V
Coil -ve 2.10V
RUNNING at idle
13.92V battery
14.2 V DC alt stud to gnd
0.135 V AC at idle, alt stud to batt +ve.
Stalled at 28 min mark, LEFT KEY ON
Coil +ve 7.05V
Coil -ve 1.90V
All seems normal?
Hooked new test light to coil -ve and gnd. Dim as it should be, but did NOT flicker.
Another quirk(in my mind) when measuring coil +ve voltage when it was grounded with test light, and cranked the light was bright , and almost started when grounding positive side?
I tap tested the dist connector on ECU side and distributor sparked.
Thanks Del, after car stalled and checking coil -ve to gnd with test light cranking, it should flicker/pulse right?
It was not.
It was not.
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