Moparts

Cutting off at idle

Posted By: bobbyb

Cutting off at idle - 10/07/22 08:47 PM

I’m having a issue that I can’t diagnose…my 69 Roadrunner with a 400/451 keeps cutting off at idle and in gear. Motor has 870 Holley, elec. fuel pump w/6lb of pressure, Mopar electronic ignition. Can’t seem to figure out the problem, hoping someone might have an idea, thanks.
Posted By: stumpy

Re: Cutting off at idle - 10/07/22 09:18 PM

What's your RPM at idle?
Posted By: bobbyb

Re: Cutting off at idle - 10/07/22 09:36 PM

1000 rpm, also it seems to occur after the car is hot and starts right up after it cuts off.
Posted By: TJP

Re: Cutting off at idle - 10/08/22 02:00 AM

Originally Posted by bobbyb
1000 rpm, also it seems to occur after the car is hot and starts right up after it cuts off.

I would guess electrical / ignition related.
Start with the easy stuff, Bulkhead connector, possible ballast on the edge of failing, GROUNDS between battery, engine, and body.
What type of ignition system? beer
Posted By: bobbyb

Re: Cutting off at idle - 10/08/22 02:47 AM

Mopar electronic ignition conversion, and already have changed module and ballasts resistor and also the coil, actually moved the coil mount to the inner fender thinking maybe it was getting hot.
Posted By: Cab_Burge

Re: Cutting off at idle - 10/08/22 05:54 AM

It sounds like you have a electrical "high joint" AKA high resistance open, when one part of the ignition feed circuit gets hot and expands and stops conducting at low RPM due to low voltage from the alternator. When you go to start it the 12V direct to the coil bypasses the ballast resistor and makes the motor start, when you rev it up the increased current jumps the high joint and allows th emotor to run until the RPM go down low enough to stop the current flow again.
1969 was a very bad year on Mopar cars electrical systems whiney shruggy
It will take some time and effort to find it and fix it but you can do it, don't quit.
I would start at the coil and work back through those two circuits, both the start and run feeds to the ballast resistor and then into the coil, remove all the slip fit connectors and clean and tighten them and then retests them, one at a time up wrench
The bulkhead connector can be a real challenge to clean ad tighten but it can be done by removing them one at a time from both sides of the bulkhead connector and look at them real hard and see if they slide off and on easy or hard. Clean and hard is better up work whistling grin
Are you still using the original mechanical voltage regulator and single field alternator?
If so check the voltage that it is running on when cold and again right before it shuts off when idling warm or hot..
I'm thinking it may be dying due to the volts dropping below the run voltage that ECU has to have too idle when warmed up scope up
Posted By: SomeCarGuy

Re: Cutting off at idle - 10/08/22 09:55 AM

I’ve had that exact issue before and it’s the ecu not having a good ground. Like cab said, resistance is getting higher at low rpm.

Two ways to attack. One is cleaning and sanding the mounting points on the back of the ecu and also the firewall so it has no paint or rust preventing the ground. Other thing to do is to run a dedicated ground to it. I prefer that method because it eliminates the problem for good as it can always corrode again and leave you stranded. As tjp said, grounds are always a good place to look.

As cab said wiring can be an Achilles heel on these things. Make sure you’re factory ground wire is in good shape. Adding a ground never hurts on these cars. Overall things just work better. Last 69 rr I had had the best electrics of any of my cars by the time I sold it. Extra grounds, bigger factory alt with dual fields, electronic regulator, fresh under hood harness from year one that included the late model stuff added like the regulator and ecu, cleaned bulkhead, added volt gauge and bypassed the amp gauge. Flawless.
Posted By: TJP

Re: Cutting off at idle - 10/08/22 04:27 PM

both Cab and SCG have excellent suggestions.

I will mention a few others that were "FUN" to find.
1. Freshly restored 72 Cuda with all new harnesses. it would die every time one closed the R door but start right back up and run fine until the door was closed again. Problem : When the Connector for the control module was molded, one of the female terminals was to deep in the connector and BARELY touching the pin on the module. closing the door would open the connection and the motor would die. The reason i mention this is it was a potential HIGH RESISTANCE connection.

#2. Mis-wired ballast resistor when conversion was done. They had pulled the 12V signal for the Control module off the WRONG side of the ballast. Electronic components are finnicky. Sometime a 12v component will work at ~8 V and sometimes it won't. Why? numerous variables, temp, voltage, resistance and it's mood LOL

#3 Wire to pickup coil inside the distributor was broken internally. I assume it was from the vacuum advance moving and flexing the wire, BUT I have also found brand new wire with internal strands open inside the insulation. these can usually be detected by pulling opposite directions on the insulation. If a section seems weak or "stretchy" discard it.

#4 Bad crimps an on new harnesses. There are two parts to the crimp. The first crimps the copper wire. It should be tight with NO insulation inside the crimp. The second part is the strain relief which crimps on the insulation. it should be snug and prevent the insulation/wire from moving When inspecting flex the insulation where it enters the terminal. if it feels weak, it is likely breaking or broken internally.

#5 You've already replace d the ballast but i will mention it for others. The resistors will sometimes start to deteriorate internally causing intermittent issues like you experiencing

#6 Bad coil wire. They can be also broken internally or have had a bad connection on one end which has Burnt the conductor from arcing.

#7 as suggested make sure the male and female terminals fit snug for a good electrical connection.

#8 Any added terminals should be PULL tested to verify the integrity of the crimp.

#9 be aware that different terminals require different crimpers. Some are some what universal ( Home depot, harbor freight etc). Some should also be crimper a specific way. BUBBA doesn't adhere to theses ideas and believes a pair of pliers will work just fine or a hammer and punch on a battery lug tsk rolleyes musik


keep us posted beer
Posted By: bobbyb

Re: Cutting off at idle - 10/08/22 07:22 PM

Cab burge and some car guy, thanks for responding, what you’re both saying makes sense and I’ll pursue both. Just to let you know what I’ve got, I restored this car and just started driving it a year ago, a few hiccups along the way including this one, all the wiring was replaced, engine compartment and dash/instrument harnesses. Not saying they’re perfect, but letting you know. The alternator is high output dual field and voltage regulator is compatible with the conversion kit. With everything under the hood being new it’s just frustrating having this issue. By the time I figure this crap out the season will be over. Thanks
Posted By: bobbyb

Re: Cutting off at idle - 10/08/22 07:31 PM

Thanks tjp, sounds like you have had not so good experiences with new wire harnesses, as I mentioned earlier mine are new also but doesn’t mean they’re perfect, I’ve had a few issues with new products on my car in the last year.
Posted By: AARCONV

Re: Cutting off at idle - 10/08/22 07:40 PM

nothing there states you checked for spark or gas when it stalled..so when it stalled, what did you do? did it start back up, did it crank, did you wait for it to cool off, did you stick your head and look down the carb to see if gasoline is pumping in when you move the accelerator linkage, check for spark at the plug, at the coil? look for 12 volts on the positive side of the coil when it stalled? fuel pressure is good?
Posted By: moparx

Re: Cutting off at idle - 10/08/22 07:47 PM

and stay FAR AWAY from those cheapo, bolt on, "temporary" [oh YEAH ?] battery terminals ! panic
i hate those things with a passion, and if they are on a nicely restored vehicle, those things immediately make me question the rest of the vehicle.
there have been more problems caused by those things than i can count.
if you have those, get new cables before you do anything else !
just an old dumazz's opinion and 60yrs of playing with these toys.
your mileage will vary.
beer
Posted By: TJP

Re: Cutting off at idle - 10/09/22 03:13 AM

Originally Posted by AARCONV
nothing there states you checked for spark or gas when it stalled..so when it stalled, what did you do? did it start back up, did it crank, did you wait for it to cool off, did you stick your head and look down the carb to see if gasoline is pumping in when you move the accelerator linkage, check for spark at the plug, at the coil? look for 12 volts on the positive side of the coil when it stalled? fuel pressure is good?


in his second post he states
Quote
1000 rpm, also it seems to occur after the car is hot and starts right up after it cuts off.
wink
Posted By: TJP

Re: Cutting off at idle - 10/09/22 03:16 AM

Originally Posted by bobbyb
Thanks tjp, sounds like you have had not so good experiences with new wire harnesses, as I mentioned earlier mine are new also but doesn’t mean they’re perfect, I’ve had a few issues with new products on my car in the last year.

We've had a few, especially with M and H harnesses. Some mis-wires, bad crimps etc. Do keep us posted beer
Posted By: GomangoCuda

Re: Cutting off at idle - 10/09/22 02:05 PM

Does it gradually slow down and quit or is it instant like turning off the key?
Posted By: bobbyb

Re: Cutting off at idle - 10/11/22 12:55 AM

I can sit in the car and watch the tach and it’s holding steady at 1000rpms in gear, then it will have sort or a blip and drop to 950/900rpm and then it just shuts off, and like I said earlier it will start right back up again.
Posted By: TJP

Re: Cutting off at idle - 10/11/22 01:14 AM

Originally Posted by moparx
and stay FAR AWAY from those cheapo, bolt on, "temporary" [oh YEAH ?] battery terminals ! panic
i hate those things with a passion, and if they are on a nicely restored vehicle, those things immediately make me question the rest of the vehicle.
there have been more problems caused by those things than i can count.
if you have those, get new cables before you do anything else !
just an old dumazz's opinion and 60yrs of playing with these toys.
your mileage will vary.
beer


X 2 up
Posted By: Cab_Burge

Re: Cutting off at idle - 10/11/22 01:34 AM

Originally Posted by bobbyb
I can sit in the car and watch the tach and it’s holding steady at 1000rpms in gear, then it will have sort or a blip and drop to 950/900rpm and then it just shuts off, and like I said earlier it will start right back up again.
Do you know if the timing starts to retard when it slows down? IF not, check that out to see if the timing is not at full retard while idling and dies when it starts to retard more scope
Posted By: bobbyb

Re: Cutting off at idle - 10/13/22 12:22 AM

I’m going to look into your suggestion this weekend cab burge, thanks
Posted By: TJP

Re: Cutting off at idle - 10/13/22 01:55 AM

Originally Posted by Cab_Burge
Originally Posted by bobbyb
I can sit in the car and watch the tach and it’s holding steady at 1000rpms in gear, then it will have sort or a blip and drop to 950/900rpm and then it just shuts off, and like I said earlier it will start right back up again.
Do you know if the timing starts to retard when it slows down? IF not, check that out to see if the timing is not at full retard while idling and dies when it starts to retard more scope


A good suggestion, I always try o make sure the advance is fully out at no more than 200 RPM above hot Idle. beer
Posted By: Cab_Burge

Re: Cutting off at idle - 10/13/22 04:11 AM

I like to have all the mechanical advance in by 3000 RPM for both my drag racing and street and strip cars up
Posted By: TJP

Re: Cutting off at idle - 10/13/22 02:56 PM

Originally Posted by Cab_Burge
I like to have all the mechanical advance in by 3000 RPM for both my drag racing and street and strip cars up


I bring it in as fast as the motor will tolerate without detonation, 15-1800 RPM if possible wink beer
Posted By: terzmo

Re: Cutting off at idle - 10/13/22 05:10 PM

Believe it or don't but I just went through the exact problem with My 472 Hemi I changed carb..new fuel filter..new high flow fuel pump...cleaned all the paint off the orange box and fender to get a better ground..none fixed it. A friend told Me to check the alternator as He said it might not be putting out enough at low rpm. I checked the alt and it was good but noticed the belt was not as tight as it should be. I tightened the belt and have no stalling at idle any more. And that's the truth.
Posted By: TJP

Re: Cutting off at idle - 10/14/22 12:44 AM

Originally Posted by terzmo
Believe it or don't but I just went through the exact problem with My 472 Hemi I changed carb..new fuel filter..new high flow fuel pump...cleaned all the paint off the orange box and fender to get a better ground..none fixed it. A friend told Me to check the alternator as He said it might not be putting out enough at low rpm. I checked the alt and it was good but noticed the belt was not as tight as it should be. I tightened the belt and have no stalling at idle any more. And that's the truth.


I am glad you found a solution wink But electrically, it does not make sense. If the alternator output was low, the battery should have supplied adequate current/ voltage to compensate for the low alternator output. The exception being the battery is very weak or there is a problem elsewhere in the circuit. In that case the Alternator could back feed the circuit to mask the root cause beer
Posted By: Cab_Burge

Re: Cutting off at idle - 10/14/22 01:24 AM

Batteries store current, they cannot make it after they are activated the first time scope work up
They can recover when in decent shape, but they cannot recharge themselves beyond their float voltage shruggy
Posted By: terzmo

Re: Cutting off at idle - 10/14/22 10:30 AM

Originally Posted by TJP
Originally Posted by terzmo
Believe it or don't but I just went through the exact problem with My 472 Hemi I changed carb..new fuel filter..new high flow fuel pump...cleaned all the paint off the orange box and fender to get a better ground..none fixed it. A friend told Me to check the alternator as He said it might not be putting out enough at low rpm. I checked the alt and it was good but noticed the belt was not as tight as it should be. I tightened the belt and have no stalling at idle any more. And that's the truth.


I am glad you found a solution wink But electrically, it does not make sense. If the alternator output was low, the battery should have supplied adequate current/ voltage to compensate for the low alternator output. The exception being the battery is very weak or there is a problem elsewhere in the circuit. In that case the Alternator could back feed the circuit to mask the root cause beer


I worked this issue along with an established Mopar Guy of over 50 years,( his time of experience, not how long I worked the problem,lol) even He said He learns something every day. The car would not stall when warming up...take it out on the road immediately after startup and it ran normal. Once warmed up at operating temp, it would idle at a light for a short time and stall if too long waiting. IF put in neutral and run at high idle,1300rpm, it would not stall. So after tightening the belt I "assume" it was slipping at low idle enough to drop voltage at the box. It would not stall when warming up as it had a higher idle speed while warming up. Makes sense or not, I have had the car out several times and it runs and idles great.
Posted By: bobbyb

Re: Cutting off at idle - 10/14/22 01:05 PM

I’m all out for ideas, that’s why I’m here and will definitely check it out.
Posted By: TJP

Re: Cutting off at idle - 10/14/22 05:06 PM

Originally Posted by bobbyb
I’m all out for ideas, that’s why I’m here and will definitely check it out.

have you checked the gap between the pick up coil and reluctor tips As I recall the gap s/be ~ .006-8" and checked with a brass feeler gauge. The two should be parallel to each other as well with no chipping of the tips.
One could also try another pickup coil.
Might also check for excess play in the shaft.
I have also in the past run a small braided ground strap from the control box to the engine to make sure the box, egine and distributor are grounded to each other.
Really stupid question, Your distributor clamp is tight, Correct?
Posted By: bobbyb

Re: Cutting off at idle - 10/14/22 06:15 PM

I’ll check “everything” you mentioned TJP
Posted By: terzmo

Re: Cutting off at idle - 10/14/22 06:39 PM

Check not only the belt but get the alt checked. On another note of craziness...At the mopar shop a mechanic was switching from mopar electronics to MSD. Car started for a second then shut off. (512 motor)..Car would crank but no start. All wiring/ground were correct. Solution was the diode in the alternator went bad. Replaced alternator and car runs fine. Also as a side note..runs 6.80's in 8th. Figure that.

Also...Chrome alternator pulley's, like mine, tend to slip a bit more than stock pulley's.
Posted By: TJP

Re: Cutting off at idle - 10/15/22 03:18 AM

I just had a thought,
Hook up a temporary red light to the input side of the ballast which also feeds the control module. Place the light inside the car so it is clearly visible when the car dies. if the light goes out your part of the way there. If not go to the control module and check it's 12 V signal, then onto the coil. IF all of the above maintain power your remaining components are the coil itself or the signal between the distributor pickup coil and module or the module and the negative side of the coil. Keep us posted beer
Posted By: Sunroofcuda

Re: Cutting off at idle - 10/15/22 04:51 PM

Bobby, start it & with it running & hood open, jiggle the wires that connect to the ballast resistor. If you see a spark & the engine quits, you have a bad $3.00 ballast resistor. Went through this on my old '71 Hemi Charger - took two weeks to find the problem, & I found it by luck!
Posted By: bobbyb

Re: Cutting off at idle - 10/21/22 06:41 PM

Terzmo, I believe we might have had the same problem. I did a few things to the car 2 weeks ago and no luck, yesterday I tightened up my alternator belt and test drove it today and it didn’t stall, I’m going to take it out tomorrow for another test drive to be sure, but I think we found my problem! Thank you, that’s why I posted my problem thinking someone might have had the same issues. Thanks again!
Posted By: bobbyb

Re: Cutting off at idle - 10/22/22 12:06 AM

I’d like to thank everybody else for their input also, thanks guys! Hope this isn’t premature but I think it’s fixed.
Posted By: TJP

Re: Cutting off at idle - 10/22/22 01:19 AM

Originally Posted by Cab_Burge
Batteries store current, they cannot make it after they are activated the first time scope work up
They can recover when in decent shape, but they cannot recharge themselves beyond their float voltage shruggy
Sorry i didn't see this earlier frown
I'll agree but still not understanding why the battery was not able to supply the needed current unless it was weak. I'm ASSuming we are only talking about a few amps to run an ignition system.
The car stalls because of a slipping alternator belt. But immediately after stalling, the battery has now has enough Current to engage the starter and power the ignition system until the alternator spins fast enough to replenish the battery? Doesn't make sense and sounds realcrazy to me ?
Please feel free to educate me shruggy beer
Posted By: Cab_Burge

Re: Cutting off at idle - 10/22/22 05:48 AM

The alternator regulator will make the alternator charge more when the engine first starts due to the drain on the battery from the starter turning the engine over and making it start, with the belt tight the alternator will put out over 12.75 VDC idling, it may only put out less than the minimum voltage the ECU has as it cut off voltage at idle with the motor warmed up with a loose belt work shruggy
A quick check with a decent voltmeter will tell you if that is the case or not shruggy scope
Posted By: TJP

Re: Cutting off at idle - 10/22/22 04:14 PM

Originally Posted by Cab_Burge
The alternator regulator will make the alternator charge more when the engine first starts due to the drain on th ebattery from the starter turning the engine over and making it start, with the belt tight the alternator will put out over 12.75 VDC idling, it may only put out less than the minimum voltage the ECU has as it cut off voltage at idle with the motor warmed up with a loose belt work shruggy
A quick check with a decent voltmeter will tell you if that is the case or not shruggy scope


The part I am having trouble with is why the battery which should be at ~ 12.4- 12.6 won't keep the car running, but will start it powering both the starter and ignition, during which time the static V will drop to 11 or so volts due to the amps drawn by the starter.
I am not disagreeing or wanting to start an peeing contest but rather understand how low alternator output at idle makes the motor die but start right back up with less available V and I from the battery than was available when it died confused shruggy beer

If their are other large draws on the system BOOM BOOM STEREO, 50+ Amp fans and A/C Then it might make a bit more sense. Way back when, one would toggle switch the field connection off at the drag strip to take the drag off the motor wink
thanks for trying to make a hard headed pollock understand the above beer
Posted By: Cab_Burge

Re: Cutting off at idle - 10/22/22 05:31 PM

I added a 100 amp Power Master alternator to my last pump gas car, I disconnected and bypass the amp meter and installed a Volt meter. That alternator put out 14.5 volts constantly, not sure how many amps it put out though when idling after starting or 20 minutes later going down the road shruggy
I can remember more than one early (pre 1968) Mopar showing negative amps (discharging) on the stock amp meter when idling (less than 800 RPM in gear) at night with the lights on due to having a stock Mopar small output alternator shock shruggy
Posted By: Sniper

Re: Cutting off at idle - 10/22/22 07:04 PM

Originally Posted by TJP



The part I am having trouble with is why the battery which should be at ~ 12.4- 12.6 won't keep the car running, but will start it powering both the starter and ignition, during which time the static V will drop to 11 or so volts due to the amps drawn by the starter.
I am not disagreeing or wanting to start an peeing contest but rather understand how low alternator output at idle makes the motor die but start right back up with less available V and I from the battery than was available when it died


Ballast resistor is bypassed in start so you will have more voltage to the ECU in start than in run.

In a normally working system you have about 9v to the ECU in run, when the ballast resistor is bypassed you get full battery voltage, even if it battery voltage drops to 11v in start that is more than the ECU gets in run.
Posted By: TJP

Re: Cutting off at idle - 10/23/22 02:14 AM

Originally Posted by Sniper
Originally Posted by TJP



The part I am having trouble with is why the battery which should be at ~ 12.4- 12.6 won't keep the car running, but will start it powering both the starter and ignition, during which time the static V will drop to 11 or so volts due to the amps drawn by the starter.
I am not disagreeing or wanting to start an peeing contest but rather understand how low alternator output at idle makes the motor die but start right back up with less available V and I from the battery than was available when it died


Ballast resistor is bypassed in start so you will have more voltage to the ECU in start than in run.

In a normally working system you have about 9v to the ECU in run, when the ballast resistor is bypassed you get full battery voltage, even if it battery voltage drops to 11v in start that is more than the ECU gets in run.


Every schematic I've seen has the ecu pin 1 getting full voltage in the run position with either a single or dual ballast ?
Posted By: Sniper

Re: Cutting off at idle - 10/23/22 02:32 AM

Originally Posted by TJP
Originally Posted by Sniper
Originally Posted by TJP



The part I am having trouble with is why the battery which should be at ~ 12.4- 12.6 won't keep the car running, but will start it powering both the starter and ignition, during which time the static V will drop to 11 or so volts due to the amps drawn by the starter.
I am not disagreeing or wanting to start an peeing contest but rather understand how low alternator output at idle makes the motor die but start right back up with less available V and I from the battery than was available when it died


Ballast resistor is bypassed in start so you will have more voltage to the ECU in start than in run.

In a normally working system you have about 9v to the ECU in run, when the ballast resistor is bypassed you get full battery voltage, even if it battery voltage drops to 11v in start that is more than the ECU gets in run.


Every schematic I've seen has the ecu pin 1 getting full voltage in the run position with either a single or dual ballast ?



You are right, I meant to the coil + not the ECU. The coil will, at some point went the supply voltage drops too low, not produce enough juice to reliably spark the plugs.
Posted By: TJP

Re: Cutting off at idle - 10/23/22 04:10 PM

Originally Posted by Sniper
Originally Posted by TJP


Every schematic I've seen has the ecu pin 1 getting full voltage in the run position with either a single or dual ballast ?



You are right, I meant to the coil + not the ECU. The coil will, at some point went the supply voltage drops too low, not produce enough juice to reliably spark the plugs.


Just wanted to clarify for others as well as make sure I wasn't losing it LOL up

I had a customer years ago with a car that would randomly not start. He had taken it to several different shops and a customer recommended bring it to me. They had wired the pin 1 to the wrong side of the ballast blush. A 12V component depending on it's mood will sometimes function on the lower voltage and other times not. Temperature and a number of other factors will cause this.
When I was in Final test at intel there were parts that would consistently pass as a bin 1 @125c and drop to a bin2 at 127c, 3 degrees F made the difference. Others would flat fail at the higher temps beer
Posted By: terzmo

Re: Cutting off at idle - 10/24/22 01:05 PM

Originally Posted by bobbyb
I’d like to thank everybody else for their input also, thanks guys! Hope this isn’t premature but I think it’s fixed.


I am so happy for you that you found the problem. This issue had me so upset with the car all this season that I didn't even care to drive it. I lost an entire cruising season because of it. Also glad it is confirmed that this was a genuine issue and genuine fix. Ever since I tightened the belt,the car doesn't stall when warmed up. Good cruising to You. as a side note..My life-long mopar guru still shakes his head about the fix and now I can tell him there was another just like mine. Lol.
Posted By: TJP

Re: Cutting off at idle - 10/24/22 03:14 PM

Originally Posted by terzmo
Originally Posted by bobbyb
I’d like to thank everybody else for their input also, thanks guys! Hope this isn’t premature but I think it’s fixed.


I am so happy for you that you found the problem. This issue had me so upset with the car all this season that I didn't even care to drive it. I lost an entire cruising season because of it. Also glad it is confirmed that this was a genuine issue and genuine fix. Ever since I tightened the belt, the car doesn't stall when warmed up. Good cruising to You. as a side note..My life-long mopar guru still shakes his head about the fix and now I can tell him there was another just like mine. Lol.


Tell your guru there is another dissident that agrees with him wink I will repeat my earlier comment, share it with him and I'll bet he agrees with te following statement thumbs

Quote
I am glad you found a solution wink . But electrically, it does not make sense. If the alternator output was low, the battery should have supplied adequate current/ voltage to compensate for the low alternator output. The exception being the battery is very weak which is unlikely as it starts right back up, or there is a problem elsewhere in the circuit. In that case the Alternator could back feed the circuit to mask the root cause beer

Posted By: terzmo

Re: Cutting off at idle - 10/24/22 03:27 PM

Loosen the belt on your alternator after it's warmed up..see what happens
Posted By: moparx

Re: Cutting off at idle - 10/24/22 07:03 PM

Originally Posted by terzmo
Loosen the belt on your alternator after it's warmed up..see what happens



that would be a good A-B-A test.
beer
Posted By: terzmo

Re: Cutting off at idle - 10/24/22 08:23 PM

Originally Posted by terzmo
Loosen the belt on your alternator after it's warmed up..see what happens


Loosen the belt..run it on the street until it hits temp..and just drive normal..stop and idle at lights or pull into a spot,go to reverse, back up ...those were most of the times it quit
Posted By: TJP

Re: Cutting off at idle - 10/25/22 02:14 AM

Originally Posted by terzmo
Originally Posted by terzmo
Loosen the belt on your alternator after it's warmed up..see what happens


Loosen the belt..run it on the street until it hits temp..and just drive normal..stop and idle at lights or pull into a spot,go to reverse, back up ...those were most of the times it quit


With a good battery, the alternator field windings can be disconnected and the vehicle should still run, UNLESS there is a problem between the battery and the alternator that the alternator is back feeding. Current follows the path of least resistance. 68 years old, 30 years in engineering and 25 years owning a classic car restoration and repair business. Brush up on electronics 101A and Mopar charging ignition circuits. I'm done
beer wave
Posted By: SomeCarGuy

Re: Cutting off at idle - 10/28/22 03:17 AM

I’m not seeing a loose belt solving this. Band aid.
Posted By: TJP

Re: Cutting off at idle - 10/28/22 04:43 PM

Originally Posted by SomeCarGuy
I’m not seeing a loose belt solving this. Band aid.

whistling up bow
Posted By: terzmo

Re: Cutting off at idle - 10/29/22 12:31 PM

still no stalling after several cruises with it and put into described situations purposely to get it to quit and runs excellent. Believe it or not.
Posted By: TJP

Re: Cutting off at idle - 10/29/22 04:26 PM

Originally Posted by terzmo
still no stalling after several cruises with it and put into described situations purposely to get it to quit and runs excellent. Believe it or not.

What we are trying to get across is that if the battery is in good condition and fully charged, the car should run off the battery alone (for a short time) unless there is a connection issue in the wiring between the battery and alternator.

The alternator will back feed the connection issue masking it until it can no longer do so. At that point it will either stop running altogether or caus a melted harness / fire.

Disconnect your alternator field terminal and see if the issue returns. It should as the alternator will no longer be charging.
IF so, run a 10G jumper from the Alternators battery post to the battery. this will prove what we are trying to tell you as the jumper will now back feed from the battery. beer
Posted By: NachoRT74

Re: Cutting off at idle - 11/02/22 03:26 PM

my opinions:

-Stock alts still being new back on the days where unneficent at iddle. In most cases you disconect the batt with engine running and engine will stall. Alt don't provide enough juice at iddle.
-If you add to this a low tension on alt belt... increases the problem
-then, add to this years of sulfating, oxidation, loosen contacts, damages on wiring (and ammeter itself) between batt and the main power splice which is located between ammeter and alt.

we have the perfect storm to an ignition system failure ( along with the rest of the car electrocity ) with everything of this working together.

sure if you have an alt able to source the complete car electrical system at iddle, you barelly will notice any problem if some, between batt and main splice, because alt will be feeding the main splice without any reading on ammeter... straight to all the devices




Posted By: TJP

Re: Cutting off at idle - 11/02/22 04:27 PM

Originally Posted by NachoRT74
my opinions:

-Stock alts still being new back on the days where unneficent at iddle. In most cases you disconect the batt with engine running and engine will stall. Alt don't provide enough juice at iddle.
-If you add to this a low tension on alt belt... increases the problem
-then, add to this years of sulfating, oxidation, loosen contacts, damages on wiring (and ammeter itself) between batt and the main power splice which is located between ammeter and alt.

we have the perfect storm to an ignition system failure ( along with the rest of the car electrocity ) with everything of this working together.

sure if you have an alt able to source the complete car electrical system at iddle, you barelly will notice any problem if some, between batt and main splice, because alt will be feeding the main splice without any reading on ammeter... straight to all the devices

Nacho,
I'm glad you joined in as your electrical knowledge seems superior to most, myself likely included wink
if I understand your statements correctly,
1. The charging systems back in the day were adequate but marginal by today's standards. iagree
2. If the engine stalls when the battery is disconnected the alternator is not charging enough, or the output is being lost in poor connections etc.
3. But with the battery connected, if the alternator output is low, the battery should supply the needed power to keep the engine running unless
a. the battery is weak
b. there are bad connections between the battery and loads causing voltage drops which in turn causes the ignition system to fail.
4. If "b" is the case, the real problem is the bad connections between the battery and loads.

Raising the output of the alternator will "mask" or hide these connection issues as the alternator is "backfeeding' the voltage drops.
So, I maintain the real problem is the bad connections not the alternator's output.

I have driven several 60-70's mopars home with a non-working alternator years ago. Maybe 20-30 miles at most with no other loads on the system.
To summarize:
The batteries main purpose is to start the vehicle and provide power when the alternator output is low a for a period of time. The amount time depends on the load, condition and capacity of the battery.

If the above is true, the real issue the OP is facing is bad connections somewhere between the battery and alternator.

To confirm this one could run a heavy gauge wire between the battery and alternator output stud. this would allow the battery to backfeed the bad connections.

Posted By: NachoRT74

Re: Cutting off at idle - 11/03/22 12:00 AM

In my opinion, it was marginal still for those days standards. But is just my opinion. If you are driving around the country, you will barely keep the car at idle so the charging deficit will be marginal, but on big cities will be mostly at idle between traffic lights, loosing load from batt being discharged constantly. I guess back in the days with less heavy traffic conditions we can say that could be considered as a “standard” stage? Dunno

Yes, you are 95% correct on the interpretation of my words. As many of you know, english is not my mother language so sometimes it CAN be hard to my explain what I’m trying to say.

About the wire between alt and batt, that will VIRTUALLY bypass the amm but, also provides an extra path for the load coming/going through all the network. If some problem is present on wiring you are not fixing but hiding it.

Alternator output has been always a problem anyway, from factory.

With a damaged charging system ( damaged alt, belt or alt wire ) sure you should keep the load demand as low as posible because:
-Ignition system will need the best load and voltage rate capacity as posible.
-Ammeter will be safer, same as all the wiring between Batt and main splice.

The OP can be confronting several issues at the same time, but yes, still with an inoperative alt ( for WHATEVER reason ) the batt should supply the power to still keep running the engine. So it could be a problem between batt and main splice ( ammeter included ) down the under dash harness tape which spreads the power to everywhere.

And is not about voltage really, since voltage can still run through a hair, but amperage, which needs to get a good path to supply the requested power. Of course, a damaged path causing resistance will affect both, voltage and amperage, and both are always in a straight relationship, but a good amount of amperage being supplied, will affect less the voltage rate.

Energy is based on watts… increasing voltage or amperage on a steady resistance. Electric devices sucks amperage to provide watts based on a steady voltage rate and resistance.

Increasing voltage will require less amperes to produce watts.

Amperes are sucked in by the devices not pushed in by the source, to keep their energy/work capacity,

Resistance will produce amperes restriction and poor work capacity.

Etc…
Posted By: AARCONV

Re: Cutting off at idle - 11/03/22 01:41 AM

Try this test
https://youtu.be/9_6OFD2wpMw
Posted By: TJP

Re: Cutting off at idle - 11/03/22 01:41 AM

Originally Posted by NachoRT74
In my opinion, it was marginal still for those days standards. AGREED smile

About the wire between alt and batt, that will VIRTUALLY bypass the amm but, also provides an extra path for the load coming/going through all the network. If some problem is present on wiring you are not fixing but hiding it. AGREED

The OP can be confronting several issues at the same time, but yes, still with an inoperative alt ( for WHATEVER reason ) the batt should supply the power to still keep running the engine.

So it could be a problem between batt and main splice ( ammeter included ) down the under dash harness tape which spreads the power to everywhere.

thank you for responding bow bow up

My suggestion to run a jumper from the battery to Alternator was to prove the real issue was between the battery and alternator feed and that the car should stay running even with low or no output from the alternator for reasonable periods of time>

If the OP is wanting to verify,
Disconnecting the field wire(s) will shut the alternator down and should cause the vehicle to die that would prove what we are saying.
if the vehicle does stop running, running the suggested jumper from the battery would PROVE that the connection issue is being hidden by the alternator.
thank you again beer
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