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By peeeot - 13 Years Ago
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Troubleshooting this problem has gotten a little tricky, so I thought I'd see if you guys could think of some angles I haven't covered to sort it out quickly.
the background: re-ringed the engine very recently. I initially ran it from a gas can assuming the tank to be full of rust and debris. The tank had had a few gallons of very old gas in it. It was so old that the engine would die rather than burn it. I drained that gas and inspected the tank through the sender hole; it appears to have some kind of liner inside of it but no sediment. I put about 6 gallons of new gas in the empty tank and hooked it up to the fuel pump with a filter before the pump. It ran great, would idle very low very smoothly. Having set the ignition up the way I wanted, I was going to rebuild the carb, but though it ran fine, the fuel smell at the carb smelled more like old gas than new gas. So, rather than rebuild the carb just to potentially gum it up, I decided to fill the tank with fresh gas and a can of gas treatment and dilute the residual fuel varnish out. Once I smelled the right fuel smell at the carb, I'd go ahead and rebuild.
I moved my attention on to sorting out other minor issues, which involved a lot of test drives within the neighborhood (as I didn't have the car registered yet). One day, as I'm returning home to park, the engine starts struggling to maintain idle in gear. It has been this way ever since. I have to hold the throttle up to keep from stalling, and even the idle in neutral or park is not the buttery smooth thing it once was.
Things I've checked: 1. The ignition settings. Dwell angle is 27, initial advance is 6, same as when all was well. I watched a timing light strobe with the pickup on the coil wire while idling to see if spark hiccups correlated to engine hiccups, but there was no irregularity in the spark signal. Consequently, I don't think this is an ignition problem.
2. vacuum leaks: I sprayed water all over the manifold gaskets, carb gaskets, and throttle shafts looking for a change in running or the telltale slurping noise of a leak, but none has turned up.
3. Carburetor: it's a Carter AFB so there's no power valve or secondary idle circuit. I took the carb fully apart and went through all of the passages and adjustments. I found no debris or blockages. Special care was given to the idle circuit. No improvement came of this.
4. Valve adjustment: set at .020 cold.
Other observations/notes: When I took the carb off yesterday for cleaning, the intake passages were lined with a tacky varnish which was not present inside the carb but was present on the underside of the throttle plates. Before the test drive that ended with this problem, I made two adjustments: I adjusted the dwell from 25 to 27, and I turned the idle mixture from 2+ turns out to about 1.25 turns out. Last time I had checked the mixture adjustment it had not been possible to run the engine at 1.25 turns; I attributed this change to the fresh new gas working its way through.
Sorry this post is so long, but I like to cover the scenario as clearly as possible. Now, my theory: I am wondering whether this mysterious 'Valucraft Gas Treatment' I added might be the cause of my problem. The product literally did not indicate what its intended use was or in what way it treated the gas. Someone gave it to me one day and I assumed it was for stabilizing fuel so that it would not gum up over longer storage. I added it thinking it might help clean up the fuel tank. Since reinstalling the carb, I found I had to turn the mixture screws out to around 2 turns again to get the best idle, which is not nearly as good as it used to be. There are two things I want to try: 1. running the engine from a can of fresh gas and 2. putting a vacuum gauge on the intake pre-vacuum-pump to look for signs of mechanical mischief.
Can you think of anything else I could be dealing with here?
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By PF Arcand - 13 Years Ago
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Maybe there's so much gunk comming thru that the filter is partly plugged? Worth a look?
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By stuey - 13 Years Ago
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this is just a thought you said the tank had some kind of liner,i assume you mean a slosh around type sealer. the earlier ones were not ethanol resistant and if you've topped up with ethanol it may be dissolving the old sealant. good luck stuey UK
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By Ted - 13 Years Ago
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peeeot (12/21/2012)
.... 3. Carburetor: it's a Carter AFB so there's no power valve or secondary idle circuit. I took the carb fully apart and went through all of the passages and adjustments. I found no debris or blockages. Special care was given to the idle circuit. No improvement came of this. The Carter AFB does have power valves. They are the two pistons resting upon a pair of springs and they are connected to the metering rods. Be sure the vacuum ports on the bottom of the carb that feed the power valve pistons are open or exposed to the carb plenum. Also check that the pistons themselves are working freely. A bent or damaged metering rod can play havoc with power valve operation. Pay particular attention to the small air bleed holes in the fuel discharge assemblies. Beyond that I’ll suggest changing out the fuel again. And this time checking the ethanol content and insuring it’s 10% or less. And use premium fuel if you’re not already.
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By peeeot - 13 Years Ago
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ok, now I'm extra frustrated/stumped. It seems I've been dealing with at least 2 different problems simultaneously.
First, after going through the carb, the new base gasket I used was misaligned just enough to bleed vacuum to the secondary diaphragm. as soon as the secondaries cracked open, the engine would stall. I found that problem and took care of it, and was able to get a nice smooth idle again. I thought I'd found the problem...briefly.
Second--shortly after dealing with the secondary problem, as I let the engine idle it would suddenly die. Even though I felt confident at first that none of this was an ignition problem, with the secondaries firmly shut the only cause I could imagine for "sudden death" was an ignition component dropping out. I replaced first the condenser, then the coil. The points test ok consistently and the timing/dwell adjustments remain in spec. Yet the trouble persists.
Most of the testing I did was running the engine off of fresh premium gas, so the fuel is not the problem. I verified that the fuel pump is moving plenty of fuel through the filter, which means the fuel supply system is OK.
The current symptoms are: generally very nice idle can be achieved, sensitive to mixture screw adjustment (prefers 1.5 turns out). Occasionally, there will be intermittent random misfires. Idle quality deteriorates below about 600 rpm. After running for a while, the engine WILL DIE randomly. It will fire up immediately after dying but will fail to continue running unless revved immediately. Then, it will run a relatively short time at idle again before dying. Applying the brakes or turning on the lights adversely affects idle quality. It will not idle in gear. I will also note that the resistor tests at 1.6 ohms.
I just don't get it. Before that one test drive, it would idle at 500 rpm all day long no sweat, and of course it could run in gear. Just not sure what else could be happening here.
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By Ted - 13 Years Ago
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peeeot (12/22/2012)
...... The current symptoms are: generally very nice idle can be achieved, sensitive to mixture screw adjustment (prefers 1.5 turns out). Occasionally, there will be intermittent random misfires. Idle quality deteriorates below about 600 rpm. After running for a while, the engine WILL DIE randomly. It will fire up immediately after dying but will fail to continue running unless revved immediately. Then, it will run a relatively short time at idle again before dying. Applying the brakes or turning on the lights adversely affects idle quality. It will not idle in gear. I will also note that the resistor tests at 1.6 ohms. ...Here’s a shot into the dark. Your charging system may be the culprit which could be limiting the ignition voltage at low rpm. The misfires you mention are a clue to this although it could be the idle mixture set either too rich or too lean also doing this. I would suspect too lean over too rich if picking one or the other based on what you’ve already mentioned. But you have a number of clues pointing towards the charging system or system voltage at this point. Check the charging system voltage or output at idle and then the voltage with the engine running faster. If you see a significant difference, then direct some attention towards the charging system and/or battery.
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By peeeot - 13 Years Ago
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Thanks Ted. Tomorrow I'll check that out. I also need to spend some time with a vacuum gauge. I have not attempted to adjust my timing at all so far because it hasn't changed (that I can tell) from when things were working properly, but tomorrow I'll throw that into the mix as well. Updates will follow!
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By miker - 13 Years Ago
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This is a long shot in the dark. Several years ago,I had an intermittent problem not unlike yours. All the ignition looked good, and I spent my time on the carbs. Finally, I was running up the idle while the timing light was on, and the timing got real erratic. I hooked up the dwell meter, and got similar results. A new set of points was hanging up on the pivot point, and while they worked fine at idle and just over idle, they'd hang open at higher rpm. Apparently the shake as the engine died knocked them loose. I'd never have found it, but I went back to set them with a feeler gauge, and while I was bumping the motor over with a remote button, they stuck open. Took me a minute to realize they were open and not on the cam. Changed points, problem gone. Really weird, but I saw it happen.
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By Hoosier Hurricane - 13 Years Ago
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You say applying the brakes causes it to stall. Do you have power brakes? If so, maybe there is a vacuum leak in the power booster. If no power brakes, then the brake lights may be pointing to a charging problem as Ted suggests.
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By peeeot - 13 Years Ago
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Miker, that's a strange one! I'm thinking my issue is similarly strange, but points operation has been very consistent by every measure I have.
Hoosier, I should have specified that I have manual brakes.
So, more info. First of all, manifold vacuum is excellent. I get 20-22" with no major fluctuation, even down to about 550 rpm. This morning it was cold outside and the engine was running awesome as I fired it up and let it run. I ran it off of fresh gas again just to keep that out of the loop. I could idle it smoothly as low as 550 or so but it was happier at 600+.
I ran it for a long time with very smooth and consistent behavior. I even tried putting it in gear, and guess what? It stayed running! But that proved to be an isolated incident.
I checked the voltage at the battery. anywhere above about 700 rpm the voltage was about 15.75V. Around 600, it was about 14V. At 550 rpm it was a little under 13. It was always higher than resting voltage with the engine off.
I reset my initial timing to about 12*, which increased engine speed and vacuum. I noticed that I'm getting mechanical advance pretty early, around 700 rpm or so. Mixture was happiest still at 1.5 turns out.
Anyway, after a good 30-45 minutes or more of idling very smooth with no hiccups, during which time I checked all of the aforementioned stuff and made adjustments, things started to decline. There were misfires randomly starting to show up at very low rpms, then even at higher rpms (we're still talking idle range here). It would stall in gear every time, and then, as I described before it would start immediately but die immediately after.
I checked the resistor again and this time it showed 0.9 ohms. As the engine sat a bit that number climbed back up to 1.7 and I never got a read less than 1.6 after that though I tried to reproduce the 0.9. The coil was hot to the touch, hotter I think than it should be given how cold it was but I'm not sure.
So now I'm going to get a replacement resistor and see how that flies. By the way, isn't 15+ volts a bit high for normal running? Maybe that's overheating the coil in time and causing spark to deteriorate?
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By GREENBIRD56 - 13 Years Ago
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Are you by chance using one of the Mallory "variable" ballast resistors? As advertized they are supposed to have a low start-up (cold) value and gradually change up to 1.5 OHMs. I originally thought that would be a good idea - but the part was not only inconsistent - but ultimately failed "open". Replacing it with an MSD .88 OHM unit resulted in instant relief.
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By Pete 55Tbird - 13 Years Ago
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Another shot in the dark. Run a jumper wire from the battery + ( positive post ) to the distributor to by pass the resistor and the ignition switch. CAUTION you no longer have neutral start switch protection and the can AND WILL start while in gear. You said " I checked the voltage at the battery. anywhere above about 700 rpm the voltage was about 15.75V. Around 600, it was about 14V. At 550 rpm it was a little under 13. It was always higher than resting voltage with the engine off." Do you have an alternator? It seems high, I would expect less than 15 volts. You did say new coil and condenser but I still vote for an ignition problem. Good luck. Pete
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By brokengate - 13 Years Ago
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Check your engine ground if you already haven't, you may have an unwanted resistance in the path to the negative battery. Find a good ground source on the engine (shiny bolt etc) connect jumper, connect to the grounded battery with the jumper. Just a thought and real easy to check.
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By peeeot - 13 Years Ago
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Greenbird: the resistor I've been running is what was on it when I bought it, possibly original or else quite old. I tried running a 1.20 ohm unit I got from Napa with no change to speak of.
Pete: I'm running a generator. I thought the voltage was high too, but the ford manual says the regulation point is between 14 and 16. At one point the volts went off the scale though, as in more than 16, so I took the regulator off and removed the cover. Everything looked fine. I moved the contacts with my fingers. Not knowing what else to do and having no replacement handy, I reinstalled it, and noticed that now average volts were more like 14-15 than 15-16. Didn't really seem to affect the way it ran.
brokengate, I could stand to recheck that.
So eventually I got exasperated to the point that I wanted to try to drive the car to its normal resting place and take a break from this problem until after the new year. I was able to keep it running in gear with 2-foot driving, wasn't as hard as it had been when I started this thread. It drove very well and I made it all the way to the garage. It was idling in gear at around 600-650 rpm, though not smoothly. When I arrived at my destination I sat in drive and just let it run, waiting for it to stall. It never did, though it started to miss and get unhappy the longer I let it go. I tried to back the idle down a little (maybe an eighth turn of the screw) at this point, which it did not like, and it was much rougher but still running. I then proceeded to turn the mixture screws out bit by bit at the same lower idle. When I hit 2.5 turns out, it dropped into gear and ran smoothly for a little while before getting lumpy and irregular.
I keep the car at a friend's house, and one of his neighbors worked at Ford and teaches auto tech and is generally a bit of a guru. I ran into him when I was making those adjustments and he wants to work on it with me after the new year, so hopefully we'll get this sorted once and for all. I'll keep you posted when I have more info.
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By lyonroad - 13 Years Ago
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I don't recall you mentioning it and you probably have you checked distributor cap, rotor and spark plug wires. You mentioned that the weather was cold. Where I live (Pacific Northwest) all kinds of ignition issues come up in the winter. I helped a friend once because her car was running crappy. We went out at night, opened the hood and sparks were flying all over the engine compartment from rotten spark plug wires. You couldn't see them in the daylight. Anyway good luck. Mark
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By peeeot - 12 Years Ago
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I spent several hours today working with my neighbor to try to sort this problem out. We quickly confirmed that the idle quality deterioration and stalling was due to spark breaking down. We found that, while idling through the resistor, when the quality started deteriorating, we could "fix" it instantly by connecting a jumper wire to the starter solenoid direct lead to the coil, aka bypassing the resistor. With the jumper connected, idle was great. Disconnected, not so much. So, we attempted to run the car for a bit with the resistor out of circuit, but the points couldn't take it, and after a while of running well, all spark dropped out. Sanding the points would bring it back for a limited time. Voltage drop through the points was unacceptable.
I was pretty sure I had left the ignition on (unintentionally of course) right before this problem cropped up so it seemed I may have burned the points from that and that was all that had ever been wrong. I bought a new set of points and when paired with the new resistor and coil I had already installed, the idle was like butter. Honestly as smooth and steady as one could ever ask for. With the dwell at 27* and mixture screws at 1 1/8 turn out, it would idle in gear under 500 rpm, though it preferred to be around 550. Problem fixed, right? No. Of course not. haha.
I was ready to take it out and stretch its legs at last, but I never got out of the driveway. I packed up all of my tuning stuff and the sun had nearly fully set, so once I started the car again I needed to turn the lights on. Immediately noticed irregularity in the idle with the lights on. I hit the brake (again, no power assist) and it got a little worse. Dropped it in gear, instant stall. I tried a few more times but the only way it would run with an electrical load in gear was if I held my foot in the gas.
So it seems that the electrical problem runs deeper than the ignition components themselves. I will certainly be checking the charging system, but really, with a good battery I would expect it to be able to run for at least a short time with the generator disconnected. I suppose that expectation is ill-founded.
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By oldcarmark - 12 Years Ago
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Just a suggestion-have you considered the ignition switch itself possibly being the problem?
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By peeeot - 12 Years Ago
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Only casually. I'm not sure what could be wrong with it that would cause my trouble except perhaps excessive resistance, but that should show up whether the lights are on or not (right?)
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By oldcarmark - 12 Years Ago
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One other thought.Is the ground strap(little braided wire) in the distributor actually connected between the breaker plate and the distributor body under the breaker plate?It may appear to be intact but when you check its actually broken from the breaker plate advancing and returning.
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By peeeot - 12 Years Ago
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It's fixed!
My neighbor came over and worked with me again today. The first thing we found was that the misfiring began when the voltage seen on the positive side of the coil dropped below 9. It stalled by 8.5 V every time (8.5 being the spec'd minimum). Turning on the headlights and other electrical loads dropped the voltage more aggressively and killed the car. Naturally, dropping the trans into gear dropped RPMs and voltage, so the spark would stop. At this point I was pretty convinced that the voltage regulator or generator was at fault, especially since I frequently saw charging voltages as high as 16. We tried bypassing the resistor briefly and found that it didn't help improve matters this time.
At this point we somewhat arbitrarily got around to checking the indicated advance when shifted into gear. I was genuinely surprised to find that advance was dropping from about 12 to about 6 before the engine died. I was surprised because I had tried idling way down in the rpms and thought I'd seen the mechanical advance floor already, multiple times. My neighbor didn't like the apparent lack of initial primary spring tension in the distributor and so we pulled the distributor and thoroughly cleaned and lubed all the working parts. In the end we didn't have to alter the spring tension because the cleaning and lube allowed even the very light tension to fully seat the advance mechanism easily.
Upon reassembly, with an initial advance of 12 degrees, the engine would idle without hiccup or misfire down to 375 rpm. Maybe it could have gone lower, but that's as low as we went. I couldn't believe it! It dropped into gear smooth and strong from 700 rpm down to about 525.
I'm still a bit puzzled as to why all of the electrical load problems and spark breakdown went away. It makes sense that the advanced spark made the engine more powerful at a given rpm and thus able to run in gear. I suppose that the timing also required less energy from the ignition system such that the supply voltage drop no longer caused the spark to fail.
So, I believe in the end I was fighting just 2 problems: bad points and a false initial advance reading--both items I thought I'd already ruled out! Go figure. Oh, and the old resistor was no good, so it was worth replacing that as well--tried hooking it back up and the engine ran poorly.
Thanks for all of the help and input! I'm so happy to have this resolved, as the car is very fun to drive.
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By Pete 55Tbird - 12 Years Ago
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peeot I am glad to hear that you have the car running well again. But I do not think you have found the real cause of the problem. A cars electrical power ALL comes from the cars battery NOT from the generator or alternator. The gen and alt supply power to the battery and then the battery supplys power to the ignition and lights and all the rest of the cars electrical needs. If you had a fully charged up battery and removed the fan belt that turns the generator your car will start and run until the battery is discharged. The fact that your car ran until the voltage to the coil dropped to 8.5 volts make me wonder if you do not have a defective battery. It might be worth checking. Pete I
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By oldcarmark - 12 Years Ago
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Thats a good suggestion.A load test will tell you real quick if the battery is no good.
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By jrw429 - 12 Years Ago
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peeeot (1/5/2013)
I will certainly be checking the charging system, but really, with a good battery I would expect it to be able to run for at least a short time with the generator disconnected. I suppose that expectation is ill-founded.
I bought my wagon in Bend Oregon and drove it home to near Denver Colorado. In western Wyoming the generator failed. With the help and advice of this forum, I drove the final leg of my trip with no generator, only battery. Made the trip fine and I think I could have gone quite a distance further. A good battery will get you quite a ways.
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By peeeot - 12 Years Ago
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I'm still not 100% confident in my voltage regulator's performance, but I believe the battery is sound. I have started the car too many times to count and have never had to jump it. I've started actually putting some miles on it over the past week and it continues to run well and reliably, so I think I can give the battery a clean bill of health for the time being 
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By peeeot - 12 Years Ago
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Maybe the problem indeed is not completely resolved.
I have continued to get reliably from point A to point B as I've driven the car since last posting, but on one occasion with the lights and blower on idling at a traffic light there was a flicker of the old trouble, and twice when coasting to a stop in front of my house the engine has stopped altogether.
Pete, are you certain you're correct about the car's power coming from the battery? My understanding and observation has always been that the battery's purpose is only to start the car and store energy for when the charging system can't keep up, and that a running vehicle will continue to run with the battery disconnected. The charging system restores the battery and supplies power for the running vehicle. Either way, a faulty battery would not keep starting the car, especially in dropping temperatures, so I think my batt is ok.
I have ordered a replacement 30A voltage regulator to see how that affects things as I have already expressed some doubts about the function of the current unit. I'll post back with any updates.
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By lyonroad - 12 Years Ago
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I would do that. In the old days on the farm we always had a few extra voltage regulators hanging on the wall because we didn't trust them. In fact I have one out of a 1977 F350 hanging on the wall right now.
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By peeeot - 12 Years Ago
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I got the new regulator on. As far as I can tell, it performs exactly the same as the old one. At least now I'm sure, and I have the old one as a less cosmetically appealing spare 
Still having idle problems. The beautifully smooth idle down to 375 RPM is gone. Now the smoothest I can get it is at about 650 rpm with the mixture screws out 2 turns. Tried playing with all the usual tuning parameters (mixture, idle speed, timing) and unable to improve on that. Checked the distributor shaft but it feels like it's still moving freely and returning to rest. Checked to make sure secondaries weren't floating open but holding them closed by hand made no difference. No trouble idling in gear, it's just sloppy. Don't know where my consistency went, but I suspect more ignition problems, or possibly the valve adjustment needing to be revisited yet again. Runs awesome off idle though.
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By Ted - 12 Years Ago
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I’ll suggest hooking up a battery charger to the battery while the engine is idling and see if the idle quality improves by doing so. If the idle at low rpm does indeed improve by doing this, this gives you an idea of what direction to take in solving your problem.
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By peeeot - 12 Years Ago
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Thanks Ted! I have figured it out, though I haven't fixed it yet.
It's the AFB secondaries. Even when I hold them closed as snugly as I can, they are leaking air, and since they have no idle circuit it's the same as a vacuum leak. I should have checked them more thoroughly before. Back when I had the mixture at 1-1/8 turns and smooth slow idle, the secondaries were sealed shut with old fuel varnish. That varnish has since been cleaned off and I made sure the secondaries were not stuck--at the expense of idle quality apparently.
It's looking like I will have to loosen the throttle plate mounting screws and re-seat the plates in the secondary bores.
I'd heard these vacuum secondary AFBs were troublesome, so I suppose I shouldn't be surprised!
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By peeeot - 12 Years Ago
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So, it turns out I was wrong--but this time I really have figured it out. I think. haha.
I went through and reseated the secondary throttle plates. I could not eliminate all light around the edges when they were seated in the bores, but I got it the best I possibly could. Upon installation, it seemed there was an improvement at first, but once the engine was really good and hot (as in, after a road test), it was clear nothing had changed.
Usually I have had the air cleaner off while running tests on the engine trying to solve this issue. Today, I happened to listen to it from the passenger side with the air cleaner on, and from that position I heard what sounded like a major vacuum leak. Eventually I found the source: the choke thermostat. When the choke spring got hot enough, the little piston inside the choke mechanism dropped far enough in its bore that the vacuum supply was allowed to completely bypass the piston. It was at this point that my idling problems showed up.
The cause? The new base gasket that came with the rebuild kit. The bore holes are much too large. Instead of passing through a restriction in the carb body, manifold vacuum was passing directly to the choke hole. Once the choke piston was far enough down its bore to be bypassed, the choke heater became a vacuum leak. The reason I was able to tune the engine so well previously was that at the time I was using a gasket I made from some material I had handy, which was quite well-matched to the actual throttle bores.
I removed the choke stove pipe and blocked the heated air intake. There was immediate improvement. So, now I just need to find (or make) the right gasket!
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