68 Valiant dies and runs lumpy, then suddenly runs fine.

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puna_trav

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Pahoa, Hawaii
Wow, out of the blue on this one. Drove the car 45 miles. Parked it for 20 minutes, drove 100 yards and when I went to restart it suddenly ran like crap. Sounds like it's missing a lot (pulled a couple plug wires while running and made no difference in idle) and dies immediately when put into gear.
With throttle it will stay running, but lumpy. I let off the gas and it died.
I limped it to where I'm staying 5 minutes away and tinkered in the driveway for a while.
Adjusting the air/fuel mixture and idle screws do nothing.
Choking the carb makes it run good.
Engine is not hot,
No obvious vacuum leaks. Thats almost what it feels like. Cap, rotor are in decent shape, and the coil and alternator are less than a year old. I remounted the coil yesterday afternoon.
When I started it, I noticed the volt gauge jumps all the way up, then drops to normal as the car runs.

I needed a beer at this point. I'm an hour from my shop on the maiden voyage across the island and I have basic tools with me.

Come back out, open the hood and try to start it again. Idles fine, goes into gear and moves, and acts like nothing ever happened. No problems with voltage. I have a short flashback to my ex.

Any guesses?
 
Sounds to me like it's time for a new throttle shaft. Look at the outside of the carb near the base. If it looks like fuel has been leaking down the sides at the ends of the throttle shaft, it is worn out and you will need a new shaft and bushings for the carb base. To tell for sure, start the car and spray the base of the carb with starting fluid or use an UNLIT propane torch that is cracked open and aim it toward the base of the carb. If the engine smooths out, you have a leak around the throttle shaft. You'd be amazed how much air an engine can suck around a loose throttle shaft.
 
Did you happen to get gas right before it started running like crap ?
Could be you got a little water in your gas. Before you go buying a new carb, etc, etc,
go the the parts store and buy a bottle of Heet, and dump it in your tank, then take it for a good drive and see if it clears up.

Back when I was turning wrenches for a living I saw this happen many times,, car suddenly stalls, runs like crap, wont stay running..etc. Bottle of Heet cleared it right up.

its worth a try.
 
If it's a points ignition try a new condenser.
Major random changes in how the engine runs is the clue I'm going on without seeing it for myself.
 
TrailBeast said:
If it's a points ignition try a new condenser.
Major random changes in how the engine runs is the clue I'm going on without seeing it for myself.
Click to expand...

Wow. I actually have a lot of symptoms from all of these! Spraying carb cleaner at the carb base raises idle. Tightened carb down, but didn't see any leakage around throttle shaft. I did get gas about half way through the trip here, which had been almost all highway miles until this point so I wouldn't have noticed the stutters. I'll grab some Heet tomorrow. I also messed with the wire off the condenser while I was remounting the coil, so it could be the culprit too. Might just be the kick in the pants I need to order a pertronix ignition.

You guys are awesome, thank you! It's still running good for the time being, but I'm gonna dig in when I get home tomorrow.
 
Trail beast above your post sells a ready made HEI kit for your ride pm him i got 1 from him. I went with the magnacore wires. I like that bamboo cruzzah yah got
 
I'd say you have carburetor issues and/or gas supply issues. I'd take the carb apart and clean everything. Check your float too and replace it if you have not already. They tend to get heavy after a while and there's no fix other than to replace them. You may also try changing your gas filter and look inside it for signs of water or other contaminants.
 
Search for posts on "vapor lock". A common problem with the factory fuel tube routing in the slant six and many fixes. If still running points, consider an HEI conversion. That should eliminate the spark variable and give better mileage and less pollution of your lovely island.
 
I've replaced all the factory fuel routing, and the fuel filter is mostly new... Carb rebuilt just a few hundred miles ago.

The issue hasn't popped up since. My best guess is something along the lines of spark just judging by the lack of change when I pulled spark plug wires. I'll be upgrading to an HEI system as soon as I get another paycheck (on a one month break between terms).

I'll give more clues if this pops up again, but for the meantime she's happy. Thanks for all the help everyone!
 
You should not pull spark plug wires off, and ESPECIALLY not with more modern electronic ignition.

A better way is to wiggle the dist. boots up, and use a small grounded probe to work down beside the wires one at a time and ground them out.

Pulling wires can cause crossfire which leads to false conclusions, and can damage electronic modules

This sound to me more like "dirt in the needles and seats.", vacuum leak, or vapor lock


Throttle shaft? These can actually be pretty bad before they run that bad, and typically show up in heavy trucks with governor carbs, because there is so much dirt, force, and "trauma" on the shaft.
 
I had the same exact symptoms. I thought it was fuel related so I disconnected the fuel line from the gas tank to the fuel pump, I blew aair back down the hose to clear it up and clear any dirt. Open your gas cap and have a friend check if there's any airflow out the tank while blowing confirming that the hoses are not an issue. it worked for me!
 
Ok, done more work. Tore down and remounted the carb to make sure everything is sealed, and replaced the throttle shaft with the one from my spare carb. Replaced the cap, rotor and the fuel filter with one that's clear. It gets fuel pretty well, but I'm probably going to try to blow out the lines just to make sure.

The 'alternator' gauge is still going wonky from time to time. I decided I'm just going to replace all the modules once I'm back to my job.

For now it runs good 95% of the time, but will stutter and occasionally die as I pull up to a stop. Otherwise it idles fine most the time at a stop, and really smooth in park.
 
You kmay want to replace the ignition coil. They can have intermittent failures and could make the car run poorly.
 
Ok, more work:
Found out the vacuum advance nipple on the carb was hardly pulling any vacuum. Switched that to another free nipple and that improved things significantly. However, the first start in the morning is still always really rough. It seems like it misses a beat every few seconds, and then once in gear will nearly die. If I throttle, it dies. If I feather the throttle and get it moving, it will cooperate, but still stumbles a little from a complete stop after that until it gets to operating temp.

Once it warms up, it's good for the rest of the day. It starts on the first crank, and idles and runs pretty smoothly. It doesn't seem to have much power though. Foot on the floor will get me to 50 mph in around 15 seconds, but it sounds healthy doing it.... just no real 'guts'.
The carburetor is ice cold when I start it in the morning until the motor warms up. The intake manifold gets quite a bit of condensation on it, and it smokes heavily for the first 5-10 minutes after I start it for the first time in the morning.

Did a plug read. The little metal arm (electrode?) is really white, but the rest of the plug is pretty black. Looked like it was rich with too hot a plug. Turns out I had Autolite 66's in it, swapped them for the correct 65's. Haven't read it again yet.
 
Generally drivability issues from cold start until fully warmed up are caused by incorrectly operating choke. Check vacuum pull-off for leaks if equipped, adjust amount of choke pull-off once engine lights off to about ¼ inch, check that bimetal spring is able to freely move choke plate, and adjust its closing tension with as little force necessary to just fully close choke plate. If closing force is too great full choke opening will be delayed producing an over rich condition for too long causing the chugging and fouled plugs you have been experiencing.
 
"ALT' gauge goes wonky" ? They do need 12 volts to run right. Just brake lights can draw a faulty system down to engine failure.
So my question is.. do your headlights dim at idle and blare up with acceleration ?
ALT gauge needle twitch with turn signal operation ?
I'll add the following just because of previous responces to these questions...
How good the battery is and how well the starter spins really has nothing to do with how the rest of the cars electric works. The large wire from battery to starter goes nowhere else.
And by the way, Blowing compressed air into the fuel line will blow the sock off of your pick up assembly inside the tank.
 
I got a few things I should have mentioned. The car has a fuel cell in the trunk with no pickup, and the choke has been removed from the carb by the PO. I was planning on installing a cable operated choke but since I am almost never in temps under 70 degree weather, I didn't think it was much of an issue.

The alt gauge is pretty steady most the time, but with flick back and forth about 1/32 of an inch randomly while driving. The headlights will pulse a little while driving, and the turn signals so speed and slow slightly as they click on and off. I'm planning on replacing the voltage regulator with my first paycheck.
 
Last week I started the car and when I shifted into gear, some sparks came out from under the dash. They looked like they originated from the left side of the steering column. After that, the voltage followed the rev of the engine, and it wouldn't run off idle.

I replaced the voltage regulator, and the alternator gauge now sits steady at highway speeds, but shoots up momentarily the middle of the right side of the gauge. There's no noticeable change in how it runs when that happens.

I had the coil and alternator tested and my buddy at the parts store pointed out that the alternator only has a single field connector, but the listing for the car showed a two field alternator. I have one connector on my car. I've seen some threads on one vs. two wire alternators, but didn't look at them much. Gonna start reading.

There is also an audible "tick" as the alternator gauge goes from 12v to ~17 volts. It almost sounds like the turn signal relay click. At idle in park, you can hear a slight change in revs when it happens.

I replaced the ballast resistor, and cleaned up every electrical connection I could find with dialectric grease and sandpaper. Pulled the bulkhead connectors and cleaned them.

I've heard that alternator gauges themselves can go bad. Is there any harm in bypassing it?

Solved the lack of guts... turns out the trans kickdown linkage had slipped in the channel. So far, it runs good, and pulls decently up hill. I'll see tomorrow if its still grumpy in the morning.
 
The alt guage bypass is highly recommended, and while you are in there you may very well find out that's where the sparks came from.
This was a cause of more than a few burned down Mopars so you should take care of that ASAP.
 
Alrighty. I'll try to get to the alternator gauge bypass asap. I haven't seen any sparks since I replaced the voltage regulator, but I certainly don't want to be driving a future cinder. I drove the car last night, and when I give it any throttle, the headlights dim and brighten significantly as the gauge flicks back and forth. When coasting in gear it stops, when I hit the brakes, it stops. I also noticed that at on a light throttle there is a slight lag as the gauge drops below the middle line.

Thank you, everyone, for your help. :prayer::prayer::prayer::prayer:
 
sounds like the alt. gauge problem and stalling could be related to a dead short to ground under the dash . I had the same thing happen on mine . Mine was the power wire for the dash lights that rubbed through and a p/o had used a piece of aluminum foil and wrapped it around the fuse because it kept blowing the fuse . my alt gauge would show a strong discharge and the car would not idle and the more gas you gave it the more of a charge it would show but was intermittent some times fine for days then all the sudden bam it dies at an idle. after i found it and fixed the prob it ran great
 
I tried the alt gauge bypass, and no dice. Same symptoms, but without the alt gauge, the left turn signal indicator light on the cluster wouldn't turn off. Put it all together as it was before, and didn't find any indications of a short.... EXCEPT a white wire going up the column that had rubbed through. I have a feeling this is where the sparks came from. I wrapped it up and bundled all the wires going up the column with electrical tape.

Still the same symptoms, but no sparks since.
I'm going to invest in a multi-meter after christmas and get to the bottom of it.
 
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