Tach reading high

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Last time I used a test light was 1966...or was it 1965. Because they are pretty useless for most things.
When inductive ign triggers [ points or elec ], there is 200-300v of back EMF at the coil - terminal. That is normal & what has probably kept the light on.
 
yeah this is baffling it all sounds like its hould be fine

few things i might try in your position
1) undo clean and re do the earth strap from motor to body. and if you have bollt ends to your battery wires do the same there...expunge any greenness
2) undo clean up and re do with spikey washers, the mounting of the voltage regulator
3) undo and re do the mounting for the igition module
4) clean connectors at bulkhead and both ends of ballast
5)If you car has a lead from a 3rd connector at the stater motor. make sure it is connected and has not shorted to the exhaust, this is a 12 volt feed swicthed on by the starter motor and it runs to the igntion end of the ballast. starter has its fat wire to run the motor, and its swicthed wire to switch the starter motor on by the key, some have a 3rd wire which is your 12 volt feed to the igntion when the key is in start position.

funny tach signal keep king lead away from any control wireing and keep tacho green coil lead away from as much as possible

A short in the tach lead can result in the car not starting if that lead has shorted out to something at 8-12 volts (8-12 on both sides of coil results in zero voltage across coil and no spark) i'm thinking some power feed behind dash or on back of dash cluster

crazy tach issues are not uncommon when the tach is old and its capcitors have all dried up. bad tacho after a long lay up sometimes gets better as use tends to shock the ageing (but not shorted out or broken down) capacitors into functioning again...a bit like an old 1950s radio..hums badly when fist switched on but the hum slowly decrease with use as the capacitance of the aged capacitors increases slowly back towards what it should have been as they warm up. its like somthing inside the capcitor did a bit of ironing and straightend the withered conductor and insulator sheets out again.. :)


one other thing my car is 12 volt across the dash i have no 5 volt regulator
i know some US cars have 5 volt regulator for fuel gauge etc i don't know if this 5 volt feed is used for the tacho as well... if your regulator was busted your fuel gauge at least would be acting up... is it?

Dave
 
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Really? Thanks Tipps :thumbsup: SMH
Bewy said:
Last time I used a test light was 1966...or was it 1965. Because they are pretty useless for most things.
When inductive ign triggers [ points or elec ], there is 200-300v of back EMF at the coil - terminal. That is normal & what has probably kept the light on.
Click to expand...
 
Thanks Dave, frustrating as heck for all trying to help and myself.
I have done some of what you and others recommended.
1. Havent checked motor to body ground strap. I will chk, but it is a newer woven one. Battery connections are good, new -ve ground cable installed.
2. Both VR and ecu have been removed, cleaned connections and grounds. Already had toothed washers installed.
3. See above
4. Ballast connectors removed, they are good and clean. I did a visual on the BH connectors and they "look" good.
5. Havent looked at wiring at starter. Will chk.
I havent looked close under the dash, out of sheer dread lol. But I also think its under the hood somewhere.
I am going to test coil +ve in run and crank. When I checked with my test light and key on compared to crank, the brightness did not change. It should get brighter(full voltage) at crank/start.
A couple things I noticed when checking wiring,
1, the brown/white ecu wire that leads to distributor connector has a small "nick" right at connector. With car running, wiggling that wire didnt do anything, but an ohms check and continuity check, it appeared to fluctuate?( car off and ecu unplugged)
I will see about replacing it.

2, fusible link at starter relay that leads to alt stud is pretty warm. It may be too small of gauge, it is 18 ga, I'm going to replace with 14 ga. See pic with hand drawn schematic, I wrote 14 ga, but it's 18. Also on same stud at starter relay is a fusible link I installed when doing Mad Bypass. It MAY be on the small side as well, its 18 ga, but on my schematic its 16 ga. I will look at replacing it as well.
Another quirk when trying to start, coil -ve wasnt flickering with test light, but when checking coil +ve, after a second or 2 of cranking it fired up??....did grounding when checking coil +ve cause it to start??
Oh, fuel gauge is fine. I have modded dash harness, Mad Bypass, Ivr mounted for dash, triple gauges.
Thanks for input/advice.



Dave999 said:
yeah this is baffling it all sounds like its hould be fine

few things i might try in your position
1) undo clean and re do the earth strap from motor to body. and if you have bollt ends to your battery wires do the same there...expunge any greenness
2) undo clean up and re do with spikey washers, the mounting of the voltage regulator
3) undo and re do the mounting for the igition module
4) clean connectors at bulkhead and both ends of ballast
5)If you car has a lead from a 3rd connector at the stater motor. make sure it is connected and has not shorted to the exhaust, this is a 12 volt feed swicthed on by the starter motor and it runs to the igntion end of the ballast. starter has its fat wire to run the motor, and its swicthed wire to switch the starter motor on by the key, some have a 3rd wire which is your 12 volt feed to the igntion when the key is in start position.

funny tach signal keep king lead away from any control wireing and keep tacho green coil lead away from as much as possible

A short in the tach lead can result in the car not starting if that lead has shorted out to something at 8-12 volts (8-12 on both sides of coil results in zero voltage across coil and no spark) i'm thinking some power feed behind dash or on back of dash cluster

crazy tach issues are not uncommon when the tach is old and its capcitors have all dried up. bad tacho after a long lay up sometimes gets better as use tends to shock the ageing (but not shorted out or broken down) capacitors into functioning again...a bit like an old 1950s radio..hums badly when fist switched on but the hum slowly decrease with use as the capacitance of the aged capacitors increases slowly back towards what it should have been as they warm up. its like somthing inside the capcitor did a bit of ironing and straightend the withered conductor and insulator sheets out again.. :)


one other thing my car is 12 volt across the dash i have no 5 volt regulator
i know some US cars have 5 volt regulator for fuel gauge etc i don't know if this 5 volt feed is used for the tacho as well... if your regulator was busted your fuel gauge at least would be acting up... is it?

Dave
Click to expand...

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your test lamp if it is a screw driver/probe based has a neon bulb

they glow if they see AC or DC....! hard to spot a problem... best used for just checking for power or no power.

the last time i had an ignition module fail the car just died at speed and then wouldn't start

i swapped in a brand new one and the car started but would not run properly

i limped it 20 miles to my destination at 20 mph and spent hours checking everything. carb stripped and cleaned rocker clearances checked dizzy out and checked advance mechanism checked

timeing light showed variation at any rpm above 1500
tacho was high tacho was low and tacho was ok for random periods dpending on how well or how rough it ran

basically my module was reacting to the trigger for every event but at a time it fancied. which wasn't when the spark was necessary i.e dwell all over the place, ok at idle , poor low rpm running but wrose under load and cross fireing plugs at higher rpm

at that point (about 4 hours later) i borrowed another module and all was well

i wonder if your ignition module has a fault


Dave
 
Thanks Dave, I've replaced coil and ecu. VR will be next. I replaced 18 ga fusible link with 14 ga. There is another 18ga one(from Mad Bypass) that I will change to 14ga.
Pretty sure test light is incandescent, but I'll dbl chk.
Haven't checked starter connections from below(on list) but did from up top with tug test and everything is tight and wrapped.
Dave999 said:
your test lamp if it is a screw driver/probe based has a neon bulb

they glow if they see AC or DC....! hard to spot a problem... best used for just checking for power or no power.

the last time i had an ignition module fail the car just died at speed and then wouldn't start

i swapped in a brand new one and the car started but would not run properly

i limped it 20 miles to my destination at 20 mph and spent hours checking everything. carb stripped and cleaned rocker clearances checked dizzy out and checked advance mechanism checked

timeing light showed variation at any rpm above 1500
tacho was high tacho was low and tacho was ok for random periods dpending on how well or how rough it ran

basically my module was reacting to the trigger for every event but at a time it fancied. which wasn't when the spark was necessary i.e dwell all over the place, ok at idle , poor low rpm running but wrose under load and cross fireing plugs at higher rpm

at that point (about 4 hours later) i borrowed another module and all was well

i wonder if your ignition module has a fault


Dave
Click to expand...
 
Dave999 said:
your test lamp if it is a screw driver/probe based has a neon bulb

they glow if they see AC or DC....! hard to spot a problem... best used for just checking for power or no power


Dave
Click to expand...
12 Test lamps are not neon. A Neon lamp requires much higher voltage to fire the neon. 12V test lamps are either a common incandescent lamp, or an LED setup
 
So "measured" spark from coil to distributor. Approx 1/2". IMO weak. Anymore and spark was very weak/erratic.
A couple times now I've noticed with test light and voltmeter that when measuring coil +ve to batt gnd that I only get approx 6-7 Volts when cranking
Should be full 12ish??
So measured from ballast resistor, run side, key on 10V, cranking approx 6V
Now measuring ballast at start circuit, key on 7.1V(its lower??), cranking approx5-6, again lower then run side?
Tests were done to batt -ve.
Am I messing up the tests?
 
Measuring cranking back at the ballast can be misleading, because ignition power DURING CRANK comes to the coil + (and should be very close to battery voltage, then BACKFEEDS through the ballast, to the junction of the "run" line, and backfeeds into the box to give the box power. NOTE again, this is only for cranking.

So yeh, "key side" of ballast can be fairly low during cranking. Remember, the key "run" power goes dead during cranking

If you are sure that the crank voltage went low at coil +, you either have a bad terminal in the bulkhead connector, a loose terminal in the ignition switch connector, a bad contact in the switch, or some other intermittent bad connection. DON'T FORGET THE BATTERY FEED INTO THE KEY as well!!!
 
Thanks Del, I did Mad Bypass, so should be no bh connections? The connection is now the red/black soldered together I believe.
I'll definitely look at switch connections again.
67Dart273 said:
Measuring cranking back at the ballast can be misleading, because ignition power DURING CRANK comes to the coil + (and should be very close to battery voltage, then BACKFEEDS through the ballast, to the junction of the "run" line, and backfeeds into the box to give the box power. NOTE again, this is only for cranking.

So yeh, "key side" of ballast can be fairly low during cranking. Remember, the key "run" power goes dead during cranking

If you are sure that the crank voltage went low at coil +, you either have a bad terminal in the bulkhead connector, a loose terminal in the ignition switch connector, a bad contact in the switch, or some other intermittent bad connection. DON'T FORGET THE BATTERY FEED INTO THE KEY as well!!!
Click to expand...
 
Spark length is not a good indicator of spark quality.
A good spark will be white/bluish in colour & have a 'crack' sound.
A poor spark will be yellow-ish.
 
Well the only thing MAD does is hopefully get you good solid power "that far." But the ignition switch connector and switch could still be iffy, and none of the other wiring in the bulkhead connector were redone by the MAD deal, so the "run" wire and the bypass circuit (either) could be iffy in the connector.

I would not think that the bypass circuit during start would be related to your original problem tho
 
4spdragtop said:
I thought all was good, swapped in new SMP UC12 coil. Steady rpm reading, started to dial in carb and timing with tach and vac gauge. Grabbed vac gauge and tach, jumped in car to chk readings in gear and I noticed the tach started to jump again...ffs. I "thought " I heard a "tick" (electrical??) Under the hood, but I was in drivers seat. I shut car off, tried to restart, no spark. Pulled new coil and specs are good/same as outta the box.
Could alternator be causing this? Dist gapped at .08. Double checked va didnt interfere with reluctor under vacuum.
With dist out, spun shaft while hooked to continuity tester and it beeped.

SMP readings 1.9 ohms and 10.7 ohms. A little higher than cold, which is
normal I believe?
2 prong ballast resistor measured 0.7 ohms, unhooked.
Click to expand...

There should be more resistance than that on the distributor pick-up. Scale your ohm meter up a notch or 2 from full continuity beep. There is a spec for it, I don't have handy. Test without spinning and at differnt reluctor points
 
Solarguy said:
There should be more resistance than that on the distributor pick-up. Scale your ohm meter up a notch or 2 from full continuity beep. There is a spec for it, I don't have handy. Test without spinning and at differnt reluctor points
Click to expand...
I don't see where he mentioned the resistance of the distributor pickup. THERE IS CONSIDERABLE DISAGREEMENT on what is acceptable reading. I believe that the readings have gotten even "wider" now with many imported parts

As long as the thing runs correctly, I'd forget about the dist. pickup
 
Appreciate the help/suggestions guys. I've got a buddy coming over to hopefully help with this. For all the cranking tests, I've been using my DIY remote starter. OEM 67 switch is in place and I put it key in run and then use underhood remote. Could that skew readings?
Baffles me why I'm not getting 12v at coil +ve while cranking? I've unhooked remote start button and will use oem key switch for tests.
Solarguy said:
There should be more resistance than that on the distributor pick-up. Scale your ohm meter up a notch or 2 from full continuity beep. There is a spec for it, I don't have handy. Test without spinning and at differnt reluctor points
Click to expand...

67Dart273 said:
I don't see where he mentioned the resistance of the distributor pickup. THERE IS CONSIDERABLE DISAGREEMENT on what is acceptable reading. I believe that the readings have gotten even "wider" now with many imported parts

As long as the thing runs correctly, I'd forget about the dist. pickup
Click to expand...
 
Correct, p/u coil readings vary. For Mopars 140 to a few hundred ohms. Wire thickness & overall winding length will affect the reading.
 
You will not get 12 v at the coil while cranking. That is normal. Battery voltage drops while starter is cranking. So expect about 10.5 v at the coil while cranking & that could vary a little.
 
Well, looks like part of the issue is at the ignition switch. When I unplugged the ignition switch connector and wiggled large red wire I got voltage fluctuation. I'll pull DS bucket, ac diffuser and triple gauges. Problem is probably the splice. Next day off I'll try to limber up and get under there. Instead of soldering the wires together, I may try individual ring terminals with a nut bolt thru them.
Anyone know any midgets?
 
Do not know any personally, but I did see one on Judge Judy a few years back. His name was Mr. Long & it tagged my warped sense of humour.....
 
Steve, what I was gettin at when I asked about a dwell meter was have you tried another tach? Dwell meters all usually have a tach function. Just to make sure yours is not giving you a false reading. There are also tach guns similar to IR temp guns that are really affordable and handy too. Just a thought.
 
Thanks Rob, both oem dash tach and aftermarket tach were flickering, so I figured it was something besides the tachs. One(of many) issues was that I was using my DIY remote starter instead of key switch, which IMO was throwing tests off. With a buddy over, looks like we tracked it back to an ign sw wiring....again...
RustyRatRod said:
Steve, what I was gettin at when I asked about a dwell meter was have you tried another tach? Dwell meters all usually have a tach function. Just to make sure yours is not giving you a false reading. There are also tach guns similar to IR temp guns that are really affordable and handy too. Just a thought.
Click to expand...
 
Sparkys.....not sure if I'm thinking right here.
For troubleshooting such as this tach issue while engine running, shouldn't we be able to override the ignition switch "on" position with a remote start jumped from +Bat to Ign 1 of the ballast?
He engages the remote start switch when the tach starts floating.
 
4spdragtop said:
Well, looks like part of the issue is at the ignition switch. When I unplugged the ignition switch connector and wiggled large red wire I got voltage fluctuation. I'll pull DS bucket, ac diffuser and triple gauges. Problem is probably the splice. Next day off I'll try to limber up and get under there. Instead of soldering the wires together, I may try individual ring terminals with a nut bolt thru them.
Anyone know any midgets?
Click to expand...
We're called "Little People" :(
 
Daves69 said:
Sparkys.....not sure if I'm thinking right here.
For troubleshooting such as this tach issue while engine running, shouldn't we be able to override the ignition switch "on" position with a remote start jumped from +Bat to Ign 1 of the ballast?
He engages the remote start switch when the tach starts floating.
Click to expand...
I thought I suggested, maybe not. YES I would have hot wired it for testing a long time ago. Hot wire tach direct to a good solid battery source, and hot wire key side of ballast to a solid battery source.

Key/ start/ coil power. I've preached this a thousand times. Key IGN1 "run" power GOES DEAD in cranking. Voltage to the ignition for starting ONLY comes from the ballast bypass circuit, ign2, "brown," hot ONLY in start. It is NOT the same as the start wire to the relay, but works the same. It sends hot full 12V to the coil + for starting. HOW DOES THE ECU get power. During cranking, the coil + terminal, getting hot power from the key, feeds BACKWARDS through the ballast resistor and feeds "some" voltage to the ECU. It is a stupid design, but I admit, it always worked.
 
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