Stalls with electrical loads

-

goldduster360

Well-Known Member
Joined
Jan 23, 2009
Messages
326
Reaction score
41
At my wits end with this car. It stalls sometimes just by turning on the headlights. It will stall when thrown in reverse and will stall when the fan setting is on high. I have done the following:

Checked engine vacuum at idle-19"
Swapped Carbs with a known good one of same type-Holley 600
Checked PCV valve
Ran new alternator wire through firewall same for battery feed
Cleaned the connections at the bulkhead that were not replaced
New Plugs-Wires-Cap
Replaced Pick up Coil
swapped ignition coil
Replaced Ballast
Replaced ICM
Cleaned every connection and ground I could find
Battery Voltage checked at 12.55 not running
Over 14 volts running at batt terminals
Replaced alternator-no change
Tried bypassing amp gauge

I have done some testing as shown on this forum for voltage at coil, etc., everything seemed to check out. Problem has persisted off and on for a couple years until it's to the point of not being driveable, it has gotten worse. It will only idle in gear if vacuum advance is hooked up to manifold port on carb. Timed port will cause it to stall in gear immediately. Timing is set at 14 initial. Engine runs fantastic, it just won't idle with any type of electrical load on it.

Frustrating thing is when I think it's fixed it will be fine and then all of the sudden the problem is back. In my 35 yrs of fixing cars this is the only time I truly feel defeated.

Specs: 1973 Plymouth Duster with 360 ci, 4bbl 600cfm Holley, 904 Torqueflite, RV Cam, 8:00/CR, Headers, 78amp alternator.

Somebody please chime in with some advice.
 
I don't know. Try eliminating whether it's an engine / carb /tune problem, or electrical.

One thing you might try is to "rig" a meter that you can monitor while driving, with a wire strung so you can move it around. Monitor the battery. Do some test drives with the regulator unplugged. That is, run off the battery. Move the voltmeter to the "high" side of the ballast resistor, that is, the wire coming out of the bulkhead feeding electrical loads / ignition under the hood.

If that indicates trouble, try to figure where the drop is, IE bulkhead connector, ignition switch, or the switch connector.

Some of this you can check in the garage. "Walk" the multimeter from ignition to bulkhead to ignition switch, etc, to wherever the feed comes from the battery.

No1, 2, 3 suspects in no particular order.........

Bulkhead connector problems

Ammeter circuit or what's left of it

Original ammeter splice in the black wire originally to ammeter in the inst. panel.

Ignition switch or switch connector

If none of this shows anything, might be an intermittent right in the ignition system.

"How does it act" for idle? If the idle is too lean, etc, you can have similar problems.
 
Rig up a wire to check voltage at 2 places and monitor the voltage while doing the things that make the car stop running:
- The 12V feed into the ignition module
- The 12 IGN supply into the ballast

All the actions that cause problems will drop the voltage some normally , but I suspect that there is wiring problem that is causing a big voltage drop at either of these supply points to the ignition system. Find what is going on at those 2 points and let us know.

Also, measure the ballast resistance; it needs to be under 1 ohm cold. The original was 0.5 to 0.6 ohms cold. If it is higher, then you have the wrong ballast.

We recently found where someone had wired IGN1 and IGN 2 wrong and the field current was going through the ballast! So wiring muckups happen...
 
Have you checked the alternator amperage?

If it is unusually high with no load, that could indicate a bad battery. It that's the case, that could cause your problem. The alternator would be putting out all it can trying to charge the battery and be difficult for the engine to turn at idle. Just a thought.
 
Check the engine to body ground. Use a voltmeter, measure between engine ground and body with headlights on. No need to run the engine, good is near zero.
 
are you running any after market toys? stereo w/amp(s), extra lighting, fuel pump, etc. that you have wired into a circuit that could be causing too heavy a load draw?
 
At first glance this is an easy fix;
Tell me if I got this right;
You are running full manifold vacuum to the V-can,and
you set the initial to 14,with the V-can so hooked up,and
Then you set the idle speed to what? 650 to 700?
Then you set the mixture screws for best idle,, and
now it idles at 19inches in Neutral/Park.
And you have a stock low-stall TC

Is that correct?
 
At first glance this is an easy fix;
Tell me if I got this right;
You are running full manifold vacuum to the V-can,and
you set the initial to 14,and
Then you set the idle speed to what? 650 to 700?
Then you set the mixture screws for best idle,, and
now it idles at 19inches in Neutral/Park.
And you have a stock low-stall TC

Is that correct?

2400 stall
 
At first glance this is an easy fix;
Tell me if I got this right;
You are running full manifold vacuum to the V-can,and
you set the initial to 14,with the V-can so hooked up,and
Then you set the idle speed to what? 650 to 700?
Then you set the mixture screws for best idle,, and
now it idles at 19inches in Neutral/Park.
And you have a stock low-stall TC

Is that correct?

So, no, this in not right.
You set the timing to 14*, and then hooked the V-can up to full-time manifold vacuum; But did not re check the idle timing after that. Then you set the idle speed to 650 to 700, and adjusted the mixture screws. It now idles at 19" in Park/Neutral. It has a 2400 TC in it.

Is this correct?
 
So, no, this in not right.
You set the timing to 14*, and then hooked the V-can up, But did not re check the idle timing after that. Then you set the idle speed to 650 to 700, and adjusted the mixture screws. It now idles at 19" in Park/Neutral. It has a 2400 TC in it.

Is this correct?

I don't have timing tape on the balancer but I did check timing with light after hooking up vacuum. Can is working. Don't know how much advance but it moves it 15-20. Yes everything else is correct.
 
OK now we are getting somewhere.
Here is what I think you have done; With 14* initial plus 15 to 20 in the can, it is now idling on around 31* timing. This is reflected in the 19 inches of idle vacuum.So to get it to idle at 650 to 700,you had to back out the curb-idle screw, waaay out.By doing that, you shut off the transfer ports and had to give it idle fuel from the mixture screws,which now are richened up. So now it seems to idle pretty good, right. Right up until the engine sees a load, or you gently step on the gas.
EDIT: and here's what I think may be happening;The load drags the rpm down, which causes the timing to EDIT; start to drop out, which immediately causes the engine to want more fuel, but since the transfers are dry, she can't get any gas, so she goes lean and dies.
Sound about right?

"Where's your T-port sync set at?"

Here's what you need to do;
1) Defeat the Vcan
2) Get your T-port synced up, and
3) reset the timing to 14* at 700rpm
4) verify the float level
5) reset the mixture screws
6) put the Vcan back on the timed port
7) Prove the power timing is limited to 34/35;whatever it takes to stay out of detonation. And more is not necessarily better.

the T-port sync is right when the exposed part of the slot, under the primary blades ,is looking like a little square to a little taller than wide.Once this is established try not to dink around with the curb idle screw any more than about 1/2 turn,either way .
If the idle speed does not dial in with the T-port synced, then you have to use the secondary cracking screw to fine tune it.

If you have a carb with no idle fuel on the secondary side, sometimes the engine doesn't like very much secondary air.If that happens to you, you will need to figure out an alternate way to give the engine the air that she wants, but do not stray far from the T-port sync..
 
It is more likely a poor engine to chassis ground. That is why it dies at idle, and when going into reverse. Those are when least pressure on drive shaft. It is grounding by the drive train, that is why it runs good under load, the pressure at gears and bearings conducts the current. Bad thing, the current pits bearings. Simple check see post #5.
 
Lot of good things to check for the OP. I would start simple:
- Clean/check the chassis ground as per Kitl this includes both the battery - to block ground, AND the head to chassis ground back at the firewall
- Monitor the voltages while this is going as I suggested in post 3 to make sure the 12V to the ignition module and ballast input is not dropping seriously and just killing the ignition
- Then work on AJ's ideas; he has some good points. I assume by t-port sync, he is talking about the secondary idle stop crew setting. And he is spot on about the idle timing being waaay advanced due to the use of manifold vacuum, but I would not think that just putting the car in gear would drop all the advance out; it may drop the advance back some amount. And it seems a stretch to blame the stalling on this if just putting on the headlights kills the idle. But, this secondary stop screw adjustment will indeed screw around with the idle and off-ilde operations if not right.

Before going too much further into the timing, I would be check for true TDC and seeing of the timing marks on the damper are truly correct. And at some, point, if I had not installed the cam, I would be checking the cam timing, since this has been changed out.
 
Sorry; twitchy finger;double post...
But since I'm here;Based on your reports of 12.55 and 14Plus, I doubt there is a problem in the charge circuit. However;
You could try this; Disconnect the VR, and turn everything on that has a switch. Still stalls? IDK.I'm going back to my previous post.But
if no stall,reconnect the VR,sub in a different fully charged battery;then retest as at the beginning. Still stalls? run a large guage jumper from the alt output to the battery positive and another jumper from the alt. case to the battery neg. Then retest as at the beginning.Still stalls? Shut everything off, do an off-draw test; maybe the alt is trying to satisfy a dead-short somewhere.If you find an off-draw evidence at the battery, go find it in the wiring. If you find no off-draw, turn the key on;still none?Switch to an amp-draw test and start turning things on, 'til you find a reading that seems out of the normal range.
 
Thank you everybody for the replies, I will take everyone's suggestions and put them to work troubleshooting this beast. Will report back with results.
 
Spent some time troubleshooting this weekend:

Voltage Drop at firewall with accessories on and running ground checked out:


Same at ground on radiator support:


Voltage drop at run terminal:


Voltage at coil:


Plenty of juice at idle in neutral:


Not shown but dropped below 12 volts in gear with accessories on, never dipped below 11.5 volts. After swapping carbs again I noticed how much more throttle it took to maintain idle than on my 350 Chevy which has same cam specs as the Mopar. Carbs have same jetting, not that it matters much at idle or at least it shouldn't . I pulled each plug wire while running, no dead cylinders found. Next step is to check the T-Slot. Did notice after swapping carbs again that it took allot more idle throttle than the donor 350 Chevy engine took to run on it. Both engines have same cam spec and similar set ups. Both carbs hesitated slightly on ported vacuum with this car, perhaps because of over exposed T-Slot. Neither carb hesitated on the 350 Chevy. So next step is to pull the carb again and check that out too. You may be on to something A J.
 
Engine ground looks good. 12V to 11.5V at battery in gear not good, should be 13.8V to 14.5V if cold temperature. 5.4V at coil is low by a couple volts, assuming your measurement is on coil + ? Low voltage at battery in gear could be, low idle speed, loose belt, poor connections ..... a good battery will be closer to 12.5V, even without alternator, if it has a good charge. The positve battery terminal looks oxidized in picture. Have you cleaned them?

Never pull plug wires on electronic ignition, to check, use spark tester or short to ground.
 
Are you sure the timing marks / timing is "where you think" it is? How 'bout cam timing?

It is troubling that coil voltage is a bit low. What does the ballast resistor measure. Be certain the ballast is hooked up correctly. The section hooked to the coil is the LOW resistance side. If the factory connectors are not "broke" they originally had a plastic "tit" which engaged the open "U" in one end of the ceramic resistor. This "keyed" the resistor so it hooked up OK
 
Are you sure the timing marks / timing is "where you think" it is? How 'bout cam timing?

It is troubling that coil voltage is a bit low. What does the ballast resistor measure. Be certain the ballast is hooked up correctly. The section hooked to the coil is the LOW resistance side. If the factory connectors are not "broke" they originally had a plastic "tit" which engaged the open "U" in one end of the ceramic resistor. This "keyed" the resistor so it hooked up OK

If not stated voltages(other than battery in picture) were taken with car running, accessories on with car in gear. I don't know what the voltage at + terminal on coil should read while running but shows around 6 in neutral with no accessories on. Do you know what the spec is for that voltage? I have seen allot of 12v coils listed that state will run on 6-9 volts. Ballast tested at 1.37 ohms. Spec is I think 1.25-1.5? Wires are hooked where they are supposed to be. Hook still present on connector and fit into slotted U on side of ballast, round hole on ballast lined up with the bump on the firewall.

What else should I be checking with the volt meter?
 
Typically the voltage at the + side of coil is 1/2 the IGN1 (high side of ballast) voltage, when the negative terminal is pulled low. That is because the ballast resistor is often nearly equal to the coil primary resistance. Because the transistor in the Mopar control box has a saturation voltage of about 2V, the (+) side may run higher. Some say 7V to 9V is typical with engine running. When the engine runs the (-) is going up and down at a rate of 4 times the RPM, so the voltage varies some with RPM.

The IGN1 voltage is going to be slightly above 12V with car off and close to 14V running and charging. You may read 6V off, 7V running.

I would check why your voltage drops to 11.5V, running with some loads on. To me that may be your problem. What is your idle speed?
 
I have ran my Old 64 Sport fury till the battery was stone cold dead, and it ran no problem. I doubt the voltage drop is the issue. It might be exposing the bigger problem. Have you hot wired to the coil side of the Ballast? If not that would be my next move.
 
-
Back
Top