Cranks but won't start. Unplug ground at field spade on Alternator and it starts?

[340sFastback]

I put new alternator and voltage regulator on car about two weeks back. Everything worked great. Then last Friday stop to get gas on way to car show and car would crank but no start. I found if I let go of key real fast let it snap back into Run position I could get lucky and car would start. But no spark in Start position but starter would turn over engine. New alternator and voltage regulator worked fine up to this point.

So did some test: with neutral safety ungrounded, put key in Start position and measured 8 volts, battery had 12.5 volts. When I unplugged Ignition 1 from ballast resistor I got 12.3 volts at coil. After fooling around with car several days, ohm'ing circuits out not finding any wire problems I thought what if I unplug the Ignition 1 wire at voltage regulator and car fires up immediately? Then I thought what if I plug voltage regulator back in and remove ground wire on second spade at alternator and again car fires up immediately.

If I leave everything hooked up, put key in Run position, jump starter relay, send battery volts to coil, car fire immediately at which time I take battery to coil wire off. Charging system perfect, headlights bright no discharge, car runs fine everything seems to be working perfectly.

So its starting to look like there is some issue with two week old alternator bleeding voltage through ballast resistor, Ignition 1 to voltage regulator, and to field on alternator. Cause if I unground second spade on alternator car fires immediately because the 4 volts bleed from coil goes away. Or could there be some issues with voltage regulator?

Anyone ever seen anything like this before? Maybe @Mattax might know?

 

[Dana67Dart]

What car?
What year?
What modifications?

Post a photo of back side of alternator and of the voltage regulator



Everything worked as expected till you changed the alternator and voltage regulator.

Now starting is acting like you do not have voltage from IGN 2 while cranking.

Give us some more info and we can move forward

 

[340sFastback]

The alternator is a 1970 style with two spade field connectors. So I grounded one spade to housing of alternator. Voltage regulator is an original '69 style points type replacement part. Voltage regulator housing has zero ohms to negative side of battery.

 

[Dana67Dart]

What car?
What year?
What modifications?

Please answer these questions.

We can't help with a blindfold on

 

[340sFastback]

What car?
What year?
What modifications?

Post a photo of back side of alternator and of the voltage regulator



Everything worked as expected till you changed the alternator and voltage regulator.

Now starting is acting like you do not have voltage from IGN 2 while cranking.

Give us some more info and we can move forward

1969 Barracuda
All wiring is factory specs

New alternator and voltage regulator worked for two weeks then developed a no start issue.

Coil gets 8 volts when cranking. If I disconnect ground on spade connector on two week old alternator car gets full voltage at coil and fires immediately. I had local parts store order stock replacement alternator. What showed up was a two spade field alternator and I ground one spade to alternator body which worked flawless for two weeks. NAPA '69 stock replacement voltage regulator.

I get some pics tomorrow. But its a stock wiring stock replacement parts setup. I do have Unilite distributor been on there for 14 years and it gets power for Ignition 1 side of ballast resistor. Unilite igntion module and MSD High Vibration coil mounted in stock bracket on manifold.

Like I said in orginal post, new alternator and voltage regulator were fine for two weeks. Stopped to get gas all the sudden no start issue occurred.

 

[Mattax]

Background:

Cranks but doesn't start using the key. Starts when using a remote starter switch.

I have a 1966 Valiant, slant 6. When I try to start the car using the key, it cranks but will not start. If I hook up my remote starter switch with 1 lead connected to the starter relay & the other to battery +, it starts right up and keeps running. Any ideas? Thanks in advance.

www.forabodiesonly.com

Volts don't bleed.
Volts indicate loss of potential energy in the current path.

The ammeter - which you refered to - that there was no discharge indicating when the headlights were on with the engine running, presumably it showed discharge when starting and charge after starting. That's an example of current flow through a path. Once the battery is charged no current through that path.

So now lets take that to your missing 4 volts. Those volts when the current flowed through some resistance. OR they show the battery's energy level being drawn down by the starter.

We need to better understand the two locations where voltage to ground is being measured and the circumstance. If possible, also what the ammeter was showing.

 

[Dana67Dart]

Coil gets 8 volts when cranking

This suggests that IGN 2 is not able to provide the bypass it is designed to do.

What showed up was a two spade field alternator and I ground one spade to alternator body which worked flawless for two weeks.

Can't say for sure but...

99% of grounded field (round back) alternators are coming from the rebuilders as a isolated field (square back) with one terminal internally grounded. They clip off the spade terminal but leave enough of a terminal there that many have put field terminal on it and fried their voltage regulator.



Arrow points to trimmed terminal on the GROUNDED field terminal.

 

[Mattax]

Coil gets 8 volts when cranking.

This could be simply a weak battery.
Measure the voltage across the battery during cranking. If its below 9.5 Volts, its a weak battery. Try a slow recharge. It might come back.

Because battery's provide so much energy to the solenoid and starter, to test for power loss to the coil during start, clip one lead to the battery positive, and the other lead to the coil positive.
This will show voltage drop along the whole path to the coil. Because the points are opening and closing quickly, the meter's needle may fluctuate. A digital meter may be worse. Because of the pulsing nature of the current flow through the running coil, this is not a situation that lends itself to measuring for voltage drops.

 

[340sFastback]

This suggests that IGN 2 is not able to provide the bypass it is designed to do.



Can't say for sure but...

99% of grounded field (round back) alternators are coming from the rebuilders as a isolated field (square back) with one terminal internally grounded. They clip off the spade terminal but leave enough of a terminal there that many have put field terminal on it and fried their voltage regulator.



Arrow points to trimmed terminal on the GROUNDED field terminal.


View attachment 1716271029

I ran alternator with one spade grounded other hooked to field voltage regulator, reversed grounded other spade and hooked one that was grounded to field wire. This was done when everything was working two weeks back. So it looked to me that neither spade was grounded based on those tests.

 

[340sFastback]

This could be simply a weak battery.
Measure the voltage across the battery during cranking. If its below 9.5 Volts, its a weak battery. Try a slow recharge. It might come back.

Because battery's provide so much energy to the solenoid and starter, to test for power loss to the coil during start, clip one lead to the battery positive, and the other lead to the coil positive.
This will show voltage drop along the whole path to the coil. Because the points are opening and closing quickly, the meter's needle may fluctuate. A digital meter may be worse. Because of the pulsing nature of the current flow through the running coil, this is not a situation that lends itself to measuring for voltage drops.

Thanks. I have to check cranking voltage. It sounds like starter can spin the engine very fast. I see 12.5 volts at battery car off and around 14 volts when its running. Car can sit for days and starter still seems like spins engine fast. But let me check battery voltage when cranking.

 

[340sFastback]

This could be simply a weak battery.
Measure the voltage across the battery during cranking. If its below 9.5 Volts, its a weak battery. Try a slow recharge. It might come back.

Because battery's provide so much energy to the solenoid and starter, to test for power loss to the coil during start, clip one lead to the battery positive, and the other lead to the coil positive.
This will show voltage drop along the whole path to the coil. Because the points are opening and closing quickly, the meter's needle may fluctuate. A digital meter may be worse. Because of the pulsing nature of the current flow through the running coil, this is not a situation that lends itself to measuring for voltage drops.

Any thoughts on why car fires if I unground spade connector on alternator? Weak battery maybe?

 

[Mattax]

Not really. The starting voltage is worth checking so you have that as a reference. But a weak battery then should show major charging on the ammeter when the alternator is output is available at 14 Volts.

Yes some (alot?) of the replacement alternators draw a lot of field current but I've not had issues starting when using them. And the ballast resistor should further limit the field current during start.

One thought is to work back from the alternator.
So next test is starting with the field lead disconnected, at the field terminal on the back of the alternator. Effect should be the same as disconnecting the grounded brush from ground.
ANd it shoudl also be the same as disconnecting the field lead at the regulator.
The last thing in that circuit you could disconnected and still have the engine run after starting is the ign side of the regulator.

You almost did this

I thought what if I unplug the Ignition 1 wire at voltage regulator and car fires up immediately?

That will verify the problem relates to the field circuit. So do it. Then go to the other side. If its in the alternator, I can't quite picture what the isssue is, but you ]'ll have narrowed it down to that. Then its your call whetehr to return or open it up.

 

[67Dart273]

I would pull that alternator off where you can SEE it and do some checking. Maybe the so called insulated terminal is not. Maybe the insulator is broke, or it is (should not be) grounded, or maybe the field windings are shorted/ partially shorted.

It may be that voltage drop in some splice/ connection or even the bulkhead connector terminals where IGN1 passes through are corroded and the alternator (if it is the problem) is causing a big drop

None of this makes sense.

Is this breaker points? With the points accidently open, key on, coil + will read same as battery because there is no coil current

With points "accidently" closed, key in run, coil + should read (varies) 5 ish to 10 ish volts. The VR/ alternator field circuit comes off the same "run" buss (IGN1) so if you are getting proper coil voltage in "run" then not likely the alternator is AFU.

Cranking, coil plus should be close to "same as battery." that is a simple circuit, one wire. It goes from ign2--usually brown--through the bulkhead--to the coil + side of the ballast, and it is what gives the coil "full battery" when starting.

You may be getting fooled by bad connections somewhere, AKA as mentioned, the bulhead connector, etc

 

[340sFastback]

I have ohm'ed the Ignition 1 and Ignition 2 circuits from ignition key plug to coil. They were zero ohms. Positive battery cable to ignition key bat terminal zero ohms. Alternator to starter relay post zero ohms. New ignition switch tested before install: zero ohms when key in run and start on applicable terminals and open circuits on applicable terminals. Zero ohms from voltage regulator and alternator to neg battery. Two week old ballast resistor .8 ohms.

Once car is running amp meter shows strong charge, lights are bright, car runs perfect. After driving a while amp meter stays on slight charge lights off. So charging systems seems to be working perfectly when car is running. Only symptom is no spark when cranking due to low voltage at coil.

Car started perfectly for two weeks after new alternator and voltage regulator were installed. Even drove around with AC on for two hours in 100 degree heat charging systems was good and strong. Stopped for gas last friday, no spark when cranking engine over issue ever since. Starter seems to turn the motor over fast and no signs of starter weakness or dying off while cranking engine. Mini starter been on there for 20 years or so.

 

[340sFastback]

Pictures

 

[340sFastback]

Looks like battery is 7 years old. And car was apart for a year for full floor replacement recently and I don't think I took best care of battery during that time....

 

[67Dart273]

Then I would concentrate on the IGN2 bypass circuit. Once again did you hook your meter to coil + and crank engine, what do you get for voltage when cranking?

Using an ohmeter to troubleshoot in this way GENERALLY is poor practice, WHY?

Because if you DO have a poor connection, switch, etc, someplace, they are often not stable in resistance. Under load they heat, and the resistance goes up. Troubleshoot first with voltage loss, looking for voltage drop along the path

 

[340sFastback]

Then I would concentrate on the IGN2 bypass circuit. Once again did you hook your meter to coil + and crank engine, what do you get for voltage when cranking?

Using an ohmeter to troubleshoot in this way GENERALLY is poor practice, WHY?

Because if you DO have a poor connection, switch, etc, someplace, they are often not stable in resistance. Under load they heat, and the resistance goes up. Troubleshoot first with voltage loss, looking for voltage drop along the path

Yep I agree with ALL of the above....

 

[340sFastback]

Voltage readings:

Battery at rest - 12.5 volts (battery is 7 years old)
Battery when cranking - 10.5 volts
Voltage at + side of coil when cranking: 8.5 volts (does not start)
Battery to + side of coil voltage drop from battery when cranking: 1.8 volts (does not start)
Battery to + side of coil voltage drop from battery when cranking, ground at alternator disconnected: 1.6 volts (starts)

Note the 8.5 volts does not match the 1.8 or so voltage drop. But I wrote the numbers down as I went and thats what my notes say.

Alternator spade resistance tests:

Spade that I ground to alternator body: 5.9 ohms
Alternator field with alternator ungrounded at other spade: 3.3 ohms
Old round back alternator, single spade connection: 31 ohms

Note: I have Edelbrock heads so not able to pull field wire off of spade on alternator unless alternator is unbolted due to no clearance no room to reach connector. And to unbolt alternator have to remove AC belt idler bracket, loosen water pump bolts, coolant runs all of the floor ect so unless I wanna go all out haven't removed alternator yet.

 

[67Dart273]

"Spade that I ground to alternator body: 5.9 ohms"

No understand LOL. You ungrounded it? Is anything connected to the opposite field connector?

" Alternator field with alternator ungrounded at other spade: 3.3 ohms"

You are going field to field? This is about right. The fields vary as to battery current draw, there is a procedure in section 8 to check that. Some newer/ heavier alternators draw more current. I could be wrong, 4-6amps? So Ohms law is I (current in amps)= E(volts) / R (resistance) So 12V divided by 3.3 is somewhere around 4A so that should be OK

You want to make sure with both field terminals isolated from ground, that both field terminals measure open (infinity) to ground (the case)

 

[67Dart273]

Try this. monitor coil + to ground. Turn key to run, and then disconnect the alternator field. Note voltage rise. Then reconnect, and disconnect the push on terminal at the voltage regulator. Should be same effect

Now move your meter to the opposite end of the ballast resistor and again note key in "run" voltage, and again disconnect alternator field and note drop if any.

This is getting to be a puzzle

IT also may be that the battery is just plain too weak. You need min. of 10.5V or higher at coil when cranking

Have you rigged a spark gap and looked at spark during this problem?

What you want is a METAL (copper/ steel) core wire to replace the coil secondary wire. This can even be low voltage wire if you "hang" it in the air during testing. "Rig" this to a test gap if you can get it out to 3/8-- 1/2" or so. When cranking, spark should be nice, not snappy BLUE and at least 3/8 to 1/2"

 

[340sFastback]

Took new alternator off. 6 ohms spade to spade. Each spade is open circuit to alternator housing.

Swapped old alternator back on no difference. Old alternator is a known working unit.

Bought new battery at rest 12.5 volts. During crank 11 volts. Car starts if I unplug Ignition 1 from voltage regulator. Voltage regulator hooked up sounds like no spark engine just spins.

Start engine hook voltage regulator to Ignition 1 amp meter shows charging even with lights on. Let it run amp meter shows reduced charging. Does not discharge lights on.

 

[Mattax]

6 ohms spade to spade.

Probably within spec. Slip ring to slip ring the rotor resistance should be 3 to 4 ohms at room temperature. The carbon brushes work well as a conductor when spinning but can show a lot of resistance when measured with a meter like that. But at least we know it's not open.

Each spade is open circuit to alternator housing.

Good. So no short there.

Bought new battery at rest 12.5 volts. During crank 11 volts.

Good.

Swapped old alternator back on no difference. Old alternator is a known working unit.

Assuming the old alternator has a grounded brush holder, that would eliminate something related to the grounding wire used with the insulated brushes.

Car starts if I unplug Ignition 1 from voltage regulator.

And in a previous test it started when the grounding wire was disconnected.

So that seems to narrow it down to the section of the circuit. Maybe there's a short or partial short somewhere in there.
Next places to disconnect during starting are each end of the field wire (R3), at the VR, and then at the alternator.

 

[Mattax]

What regulator is that?
It looks like it might be a type that was used with certain special option alternators.

 

[Dana67Dart]

Without rereading the entire post ..

Have you verified that you have cranking g voltage to the plus side of the coil during cranking?

The IGN 1 is not active during cranking. And is a make before break type contact that gets power a spit second before the IGN 2 looses power.

If no IGN 2 getting to the coil it will never fire.