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What could cause this?

1337du0

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Ok, I have a 1968 Plymouth Belvedere 5.2L stock. I just finished replacing the timing chain on it. I fired it up, it ran smooth for a day then started idling rough and died. Reset the point gap, same thing. Ran great for 2 days (drove around town and everything.) then idled real rough and died. This has happened about 5 times now. Each time it runs great (occasional misfire but for the most part idles smooth) then just runs rough and dies. Pull off the distributor cap and play with the points and all is good for another day or so. Each time I look at the points they are a little black and rough. I had thought that they were bad at first so I swapped them out, same thing happened. New points were dirty as well, but not as bad as the old ones. I even have a spare distributor so I swapped it out, same thing happened. When I reset the points it has started up, ran smooth for a minute, then idled rough, smoothed out, then rough again. This happened a few times while I was playing with the point gap. I thought I just didn't have the gap quite right so I would go back and adjust it again and this seemed to fix it. Each time it runs smooth for a day or two and dies. Tried new coil and condensor. New points, new distributor and no matter what the same thing happens. It has new plugs, plug wires. I checked the voltage at the coil and got 6.5 ~ 6.9 volts, is that normal? What else could possibly be causing this issue?
 
did someone jump the ballast resistor ? Check the timing ?
 
Timing was fine, whenever I get it running I set the timing as well. I did not specifically check the Ballast resistor, but I don't think it has been bypassed. I will check it out when I get home. I know I didn't have this issue before the timing chain was replaced. So it is weird that it suddenly started up, but I guess I have seen stranger things. I will post back what I find in a couple hours.
 
Yes,
On analog systems, 6.9V DC to 9V DC is NORMAL with resistor
Digital engine systems should be at 12 VDC
 
If the ballast resistor was bypassed you would see 12+v at the coil. Generally through a good ballast should be around 9 v. as per Ski though, YMMV.

Next time it does it (with the car running) place a wire directly from the + terminal of the battery to the coil (effectively cutting out the ballast) and see if it clears up.
 
Also, what brand of points etc are you using? Even ones from ChinaMart should last more than a couple of days but if you ain't using Blue Streak ignition parts, you're using junk. What is your dwell setting on the points? If you're setting them too close, that could be your problem too....
 
I am using the cheap points for certain. One set is the kind that came on the new duralast distributor. The other is just a cheap set of autozone replacements. Doesn't matter which one I use, they all do the same thing. I will have to check the dwell again to be sure. I will be home in an hour and will add more info as I get it.
 
The condenser can also help kill a set of points quickly......
 
ok ballast resistor is not bypassed. Don't have a dwell meter on hand so I have to wait for someone to come over for that. I just reset the points to .017 (were .016) and it started right up as usual. So i made a video.

http://youtu.be/v1tx9d7JeHM

This is immediately after a I removed points, cleaned them and put them back in at .017. The car ran a full minute, then did that. I can try to start the car as much as I want afterwards and it might start but will immediately die. If I readjust points, even to the same .017, the car will start again and run for a while then do the same thing. If I play with it enough, I am certain I can get it to the point where it will drive for a day or two before dying again but that's as good as it gets.

(Also, no one is in the car. That is just idling. It does die at the end.)
 
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The condenser can also help kill a set of points quickly......

True

Let's back up a little. You said you had just put a timing chain in it. Did you do anything with the dizzy at that time ?

Or any other work for that matter ?

How did the car run before the chain replacement ?
 
Replacement of condenser or condenser ground was not mentioned.

I would be checking distributor/oil pump drive for wear, gear teeth and slot engagement.
 
When I first got the car I had the transmission rebuilt. Then I put on a new Carter BBD Carb, replaced the gas tank, fuel filter, fuel pump, plug wires, and plugs. The car drove fine for about two months and then started idling real rough and dying. I checked the point gap at the time and it didn't change anything. I swapped points and condenser and still nothing. I had a new distributor on hand so I put it in and it fired up and drove fine for about a week. Then it just died out of the blue. I played with the timing for a while and it eventually started up, drove for about 5 min then backfired and died. Once again played with the timing for a while with no success and then it magically started and drove the rest of the way home with it dying and restarting while coasting in gear. When we replaced the timing chain, it was definitely loose. So while that may not have been the original issue, it still needed to be done. We also replaced the oil pan gasket afterwards because it had been leaking a little. Once we were done, it fired right up so we set the timing and took it out for a test drive. Drove fine around town a little bit so we parked it. Next day when I tried to start it, it fired up and idled smooth, then started to get rough, then it died. I tried timing, then the point gap.. that got it started but it died again real soon. I played around with the gap until I found a spot (.018 on the NEW distributor) where it stayed running. It misfired once in a while without pattern and pretty far apart so I left it. Tried to start it the next day and the same thing happened. I did this for a couple days and then noticed that the cap was loose on the NEW distributor so I swapped the OLD one back in just for giggles. It started right up and ran fine for two days. Drove almost 40 miles and then started dying on my about a block from my house. During this process I also added a new coil. The OLD distributor has new points and condenser too. If I reset the points around .016-17 it will start up for a minute and then die. If I try to restart it without changing anything it will idle very rough and then die. The only way it will smooth out is to reset the points to either .016 or .017. Doesn't matter if I actually change the measurement at all, but I have to stick the feeler gauge in and reset it or else it doesn't work. This made me think that the points were getting dirty. The old points certainly were and even the ones on the NEW distributor were a little dirty. But they don't get that dirty in the two minutes that it runs before it dies so it really doesn't make sense to me. I am probably thinking that it is a clue when it really isn't

Come to think of it, the oil light did come on for a minute when I first put it back together. But it went back off after it idled for a few minutes so I had dismissed it.

- - - Updated - - -

At this point, I would LOVE to upgrade to a PerTronix distributor or something but I am afraid that this isn't JUST a distributor problem and I may damage a $300 distributor.
 
Hows the negative battery cable to motor and also to the body? A weak connection could put a load on the 6 volts going through the points.
 
Just for giggles, why don't you take this to a shop that can service the distributor and check it out. Also, while listening to your video, did you ever give any thought that it may not be electrical at all? How about correct a fuel pressure check...(just to eliminate any fuel feed problems). Vapor lock?, etc.
 
I will take it to a shop if I need to, but I bought the car as a project. I would like to solve the issue myself. The issue is definately not fuel related. I replaced the gas tank, sender unit, pump, filter, and carb. I checked the pressure as well and it is fine.

I will check the battery and motor grounds once the sun comes up.
 
Points getting burned on both the old, and new distributor?

The cap not fitting right is a bad deal. Need to figure out why, and fix it. On the cap, inside where the rotor contacts it, on the center, is a spring-loaded carbon button. Make sure it's there, and not broke. Even seen them busted in half.

Also check the coil lead wire, that feeds to the distributor. The one that fastens to a screw/nut, going to the points and condenser. Make sure that wire, inside and out of the distributor, is not grounding to the distributor. Should be insulated where it goes into the housing.
 
Sorry for the rambling post that follows; hope you can bear with it especially to the last paragraph, where a good candidate for the problem is mentioned:

Listened to the video and I don't think I would be chasing the ignition any more. I would only change the condenser one more time, and then run 2 more tests of the ignition system when it acts up again.
1. Use either a spark tester or set the gap at the end of the HV wire off of the coil to 1/4" from metal, crank, and see if the spark is a good blue color and jumps a gap of 1/4" or more in open air. If so, your cranking spark is fine.
2. When idling rough, place your voltmeter on the end of the ballast fed by the ignition switch and check to see if it stays steadily close to 12v to make sure the ignition switch and wiring to the ballast is not failing or erratic. The voltage may vary some with a rough idle due to the alternator output going up and down but should stay in the neighborhood of 12v.

You have done lots of proper work with the ignition system and your measured coil voltage is good, and all that you have done pretty much eliminates that. I think your time spent messing with the ignition allows an erratic fuel problem to come and go. The 'dieing while running on the road' and the suddenly erratic point to that or an erratic manifold leak.

Vacuum: When it wants to die on the road, does it run better if you open the throttle? That would point to a vacuum leak. Can't see what you have for vacuum connections, but this exact behavior can easily be caused by an erratic vacuum hose leak but that only shows up at idle or with the throttle near to the closed position.

As for fuel, I would put my #1 vote on a fuel issue; just because a lot of the fuel system parts are new is meaningless; new parts fail too. The 'start-idle-then die' sequence really sounds like the carb is full of fuel at first and it will idle long enough to empty the bowl and then die; it will act just like your video. Similarly, a leaking hose from the top of the tank to the main fuel line or from the fuel line to the pump, will suck in air and cause erratic operation at idle and when driving. And of course the fuel pump itself will do this if erratic. You mentioned Duralast for the distributor and if you are getting parts from the chain stores, a failing fuel pump out of the box is sadly not all that uncommon.

Tee a fuel guage into the line to the carb and see how that behaves when the car wants to die at idle. The pressure should be steady with maybe just a little pulsing; if erratic while running, then you have a fuel blockage, air leak into the lines, or a bad pump inlet valve. Then shut it off; the pressure should stay up for many minutes; if it drops after stopping the engine, then then the fuel pump's outlet valve is shakey/bad.

Also, is there any reason to think that the fuel pump's drive lever is not aligned right or the fuel pump is not set into the block right? The fact that you just replaced the timing chain and the fuel pump eccentric is right there makes me suspicious that the eccentric or pump is not installed right and is not moving the pump lever properly. Was there any thing odd about the eccentric? Did the keyway get lined up right? Again, a fuel pressure test is in order.
 
Way back in the late 50's / early 60's while working at the Cotton Owens garage in Spartanburg, I would occasionally go by the used car dealers at night and start the used cars (at midnight)--just to check them out. Now, just to eliminate items,...... take a jumper wire from Battery + and connect to the + side of the coil. Leave the keys in your pocket. Then using a wrench of some sort, short the Battery relay (big post) to the starter relay connection. That should fire it up. By doing so, you just eliminated all the wiring, ignition switch and loose connections under the dash and on your firewall terminal block. Now, assuming that you have already hooked up a fuel pressure gauge, watch the fuel pressure....guessing between 6 to 9# depending on your pump.

Report back what you find.
 
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