Carb issue?? Ignition issue? Bad gas??

[Scoopy G]

Thanks MoPar Man. I hooked the vacuum gauge to the manifold, and it was pulling between 17-18" at idle. I wound the bleeder screws all the way in, then backed them out 1.5 turns. The car would not idle. I ended up backing them an additional one turn, and vacuum increased to just over 18". One more turn got the vacuum to a steady 19+ inches.

I noticed my dwell is about 39 degrees, so I think I need a smaller point gap. Just now, the car did not lope at idle when in gear. Maybe I'm getting closer...

 

[Big_John]

I then rebuilt the carb (power valve was damaged)

Did you change the plugs after you rebuilt the carb?

With a leaky power valve, you could have fouled the plugs. Maybe not heavy fouling, but got some black carbon on them that might cause your issues. Running the car will clean them, so it kind of makes sense that the car is running better as it's driven.

 

[Scoopy G]

Thanks John, I'll pull a couple of plugs and have a look at them. I did a tune-up a couple of months back, and the carb was rebuilt shortly after that, with no road time on the plugs. Not much running time either, for that matter. Thanks again.

 

[WissaMan]

COIL: with the car at idle, the voltage at the + side of the coil reads around 15-16VDC. What do you make of this? It's weird.

Is there a ballast resistor in the circuit to the coil? If not, there should be. If there is, maybe it has shorted. Either way, even if this has nothing to do with the current running problem, I'd definitely get that addressed as that may eventually end up frying the coil and stranding you somewhere.

Also, if your car's system voltage is 15-16v when running, that seems high too. I'll let someone others chime in with their opinion on that, but you may want to check the operation of the regulator. For some reason, I couldn't find the spec listed in my 68 manual, but this is from a 73 Chrysler service manual. 73 had a solid state regulator but I would think the spec should be similar.

 

[Gerald Morris]

I strongly suspect you got a load of "splash blended" gas (the vast majority of gas is final-blended that way, between the terminal and the station, in the tanker sloshing around) that had a too-large dose of ethanol in it. With the new E0 gas, you diluted that.

Back in the 1980s, I was out driving and needed some gas. I was familiar with the private brand and had used their products many times, so I filled the tank with some super unleaded. The farther I drove, the harder it was to keep the car running at idle. When I got home, after an hour or so of freeway driving, the car did not want to idle in gear, so I manually throttled it to keep it from dying. It took longer to start and the exhaust had a different, more hollow sound to it. Flaky gas! So I "drove it out", put new name brand gas in it, and all was well again. It took the second refill that got things completely back to normal. This was BEFORE the times of ethanol'd gas, too!

CRAP-O-line buggers Gertrude's running ever so often down here, and many stations sell it. When running Chevron or Shell, the only two TOP name brands available here, with Warren's QT a distant third in quality, I get good performance, and usually, those grocery stores which have some business connection to either Shell or Chevron also sell good petrol, but the "convenience store" stuff often comes "enriched" with many peculiar fluids. A number of very old stations have been brought back into service with aged, rusty tanks, invariably by south asian sorts, and "caveat emptor" must be observed even with a name like Chevron then. One can tell more easily who sells decent petrol in this 103+F weather, as the moonshined stuff really starts to fail then.

 

[MoPar~Man]

Measure the voltage directly at the battery when the car is idling, maybe a slightly fast idle like when the engine is cold. Put the volt probes directly on the battery. You don't want it higher than 14.4 volts. You really don't want it 15 volts or higher. But use a volt meter you trust. I have a separate ground wire going from the housing of the voltage regulator to the ground wire that comes off the battery cable going to the radiator support. If the voltage regulator doesn't have a good ground connection there will be problems.

 

[Gerald Morris]

Is there a ballast resistor in the circuit to the coil? If not, there should be. If there is, maybe it has shorted. Either way, even if this has nothing to do with the current running problem, I'd definitely get that addressed as that may eventually end up frying the coil and stranding you somewhere.

Also, if your car's system voltage is 15-16v when running, that seems high too. I'll let someone others chime in with their opinion on that, but you may want to check the operation of the regulator. For some reason, I couldn't find the spec listed in my 68 manual, but this is from a 73 Chrysler service manual. 73 had a solid state regulator but I would think the spec should be similar.

View attachment 732339

Over 15 VDC certainly merits a bit of concern. Even my system, with the Powermaster alternator, a brand which several folks on this Forum have observed to run high, peaks just at 15VDC, and that seldom lasts more than an instant. A 67 Newport should have a ballast resistor of about 0.6 Ohms, with a coil impedance of 1.5 Ohms. Lower impedance in the ignition circuit, which should total at 2.1 Ohms, will draw heavy current, which, with a breaker point ignition will shorten the life of the points, and possibly the coil if it isn't supposed to pull too much. Ideally, at warmed up running temperature, the coil voltage should be ~ 3/4 of the alternator output voltage.

 

[MoPar~Man]

Measuring the voltage at the + terminal of the coil is really of not much diagnostic value unless you're trying to track down the reason why an engine won't start or run. When you turn the ignition switch to run, with the engine not running, you've got a 66% chance that the points are closed, and if they're closed then current will be flowing through the ballast resistor and the coil to ground. So you can go ahead and measure the voltage at the + terminal which should be the same as one of the terminals on the ballast resistor. If the wires are connections are perfect and have zero ohm losses, you've got a circuit where 12.5 volts is passing through 2.3 ohms, drawing 5.4 amps. (.5 ohm ballast, 1.8 ohm coil). In that case the coil voltage should be 9.8 volts. With the engine running, it's going to be more complicated to measure voltage at the coil, given the relatively large voltage spikes and the closing / opening of the points (duty-cycle effect caused by the dwell).

 

[Scoopy G]

UPDATE FRI 8/22 EVENING: I checked the points and set the gap to .017. BUT, the dwell now reads around 22 degrees. The car was very reluctant to start, but when it did, I warmed it up with my foot in the gas, and after a minute it was idling nicely. I walked the idle down to about 600, and the car was idling well.

BUT, now the vacuum gauge is wobbling about 4 inches. This is an indication of sticky valves if I read the guide on the internet correctly. Yet, the car idles smoothly and throttles up smoothy.

I really do appreciate everyone's input and help with this. You guys know an assload more than I do, so your suggestions are very helpful, and again, I thank you.

I plan to take the car out again tomorrow to run it to see how it does.

 

[CBODY67]

Forget "sticky valves". Think "burnt valve". Check at the end of the tailpipe with a red shop rag. Loosely place the rag over the end of the tailpipe. If everything is good, there should be smoooth flow out of the pipe, which will consistently blow the rag away from the pipe. IF there is a burnt valve, everytime the exh valve is supposed to be closed, it will put a negative pressure pulse into the pipe, which will suck the rag into the end of the pipe, for a split second at 600rpm idle.

ALSO, every time you adjust the points, it changes the basic timing setting of the situation. I would suggest you remove the distributor from the engine and chuck tit up in a bench vise. THEN you can more accurately set the point gap and also check it on other breaker cam lobes. Even use a magnetic base dial indicator! I suspect you'll discover that all of the lobes are not worn the same, too.

Just some thoughts,
CBODY67

 

[Gerald Morris]

UPDATE FRI 8/22 EVENING: I checked the points and set the gap to .017. BUT, the dwell now reads around 22 degrees. The car was very reluctant to start, but when it did, I warmed it up with my foot in the gas, and after a minute it was idling nicely. I walked the idle down to about 600, and the car was idling well.

Re-gap your points to .015. That will move your dwell angle closer to 30 degrees, which really is optimal for a V-8. If the dwell still reads low, go to .014. That's the lower limit and below that you would find that they just don't open enough to develop a decent spark. I always gap my points to .015", and consequently have a dwell angle of 30 degrees to start with. When they burn down a bit, the angle drops as the gap increases. I just got Gertrude through AZ Emissions this morning. I last tuned her in January, points and plugs, then replaced the coil this past May. I got her through the first time with 171 ppm, with the State limit being 400 ppm for hydrocarbons, and just 1% CO, with the legal limit being 5%. I made it on the first pass the previous year also, but not with such excellent results, which I attribute to the new 60 yr old coil, and my having cranked the idle jets in a 1/4 turn more, while upping the idle itself to 700 rpm, for the test.

BUT, now the vacuum gauge is wobbling about 4 inches. This is an indication of sticky valves if I read the guide on the internet correctly.

Could be. What are the upper and lower limits? I had a LITTLE jitter in my vac gauge with the same engine I still run, when I ran the original, worn out 516 heads, but after getting some freshly rebuilt 915s on, my vacuum stays at 18, with optimal timing. I use that to finalize the timing in fact.

Yet, the car idles smoothly and throttles up smoothy.

That's good! See how it runs on a highway, and then in some urban traffic. Those make for "real life" tests. If the engine runs decently, run with that.

 

[Scoopy G]

Many many thanks to all you gentlemen for your advice and knowledge on this subject.

The vacuum gauge aided in dialing in the bleeder screws, and that gave me a solid 19 inches of vacuum. I tinkered with the points and came up with a gap (very small!) that gave me 30 degrees of dwell. I then got the timing dialed in at spec, so all seems good. It was really rainy here today, so I wasn't able to get the car on the road for a test.

There is no smoking gun here...the car was tuned to spec when the thing started acting up in February. Ignition parts were a few years old, but were in good working order. There were no vacuum leaks. Yes, the power valve in the carb was jacked-up, but up to that point (5 years) the car ran fine. With the rebuilt carb installed and a full tank of 93 octane gas, and a tune up, now the car seems to be running fine....EXCEPT....start-up is rough for the first minute or so. After that she idles nice and throttles up just fine.

Maybe just a cold-blooded 383 that's almost 60 years old?

Thanks again gents, I appreciate the help.

 

[Kuz]

Good news!

 

[Toolmanmike]

Choke/ choke pull off adjustment or choke parts problem. If it starts ok cold but runs rough until it warms up, the choke may be set too rich or the pull off not working or set wrong. The heat riser could be not working properly or the heat passage in the intake plugged. Lots of things happen during warm up. In response to your thread title, I have had issues with bad gas lately in my 64 Polara. I filled up with no ethanol gas and took off for a car show. I got about 45 min into the trip and developed a bad surge. Slow down, speed up, it didn't matter. Pulled off and checked things out under the hood. all seemed on but it felt like half the carb wasn't working like 4 out of 8 weren't firing. I nursed it home and got my other car out for the 4 hour drive to the show. Talking to friends, they had bad running issues after filling up at the same convenience store chain. They switched from 91 non ethanol to 87 and it was some bad juice. It was like everybody in town was having the same issues and all filled up at the same place.

 

[CBODY67]

I'm GLAD the car is now working better!

As to the cold start issues, check the closing of the choke plate (how much gap between the plate and what it closes against) AND the operation of the choke pull-off. Check what the current adjustments are against factory OEM specs in the Chrysler service manual.

ALSO the choke thermostat itself might need some tweaks on it, as the thermostatic spring CAN tighten with age. It IS adjustable. NO need to buy a new one, just adjust the existing one about 1 notch leaner. So the choke plate just closes (gently) at about 68*F.

From there, check the dimension between the choke plate and the carb housing with the choke pull-off manually actuated. If the first starting seems to be a bit too doggy in response, you can take a pair of normal pliers and squeeze the "V-shaped link" to get it to open just a bit more, for a bit more leanness during those first minutes of running. Past that, things can progress from there.

From our experiences, a fully-functioning heat riser valve is no better than one stuck 1/2 closed. At least in our TX climates of old. Personally, I like a choke to be a hair on the lean side, which NGK V-Power spark plugs help with, too. I also consider OEM specs to be "a starting point" for further tweaks toward "a good running engine" on the fuels normally used.

Take care,
CBODY67

 

[Gerald Morris]

Many many thanks to all you gentlemen for your advice and knowledge on this subject.

The vacuum gauge aided in dialing in the bleeder screws, and that gave me a solid 19 inches of vacuum. I tinkered with the points and came up with a gap (very small!) that gave me 30 degrees of dwell. ....

++Good! It's always BEST to set the points on the bench, instead of in the engine. One can control the work FAR more precisely that way. There are even meters which can be attached while on the bench which can help fine tune things.

After that she idles nice and throttles up just fine.

Maybe just a cold-blooded 383 that's almost 60 years old?

Choke! I ALWAYS set up a manual choke on any V-8 I drive, period. The Stromberg WC-3s used by Mopar on many of their C-body V-8s lend themselves particularly well to an easy manual choke installation. The BBD does alright with them too, but I prefer the Stromberg in the 2-barrel Mopar B/RB Universe. One can enjoy much finer control over engine starting with a manual choke. After my cylinder head upgrade, I put a modest little Edelbrock 1405 on, with their excellent choke cable, and cold mornings offer us no serious obstacle to engine starting here. The ONE disadvantage to manual chokes is that I sometimes forget I left the damned thing closed on those frosty mornings until I smell unburned petrol fumes in the exhaust. Aside from that, I prefer the finesse a good manual choke gives a driver for engine starting.

 

[Scoopy G]

Thanks again gents for all the help. With regards to choke....here in Tampa in August, there is no such thing as a cold engine. The choke never activates, it's 90+ degrees in the shop. OK I'll play with it....

 

[Toolmanmike]

Thanks again gents for all the help. With regards to choke....here in Tampa in August, there is no such thing as a cold engine. The choke never activates, it's 90+ degrees in the shop. OK I'll play with it....

Any engine start after setting for hours or overnight is considered a "cold start" regardless of ambient temperatures and can benefit from a properly working choke and pull off system. Oh I know, some fellas with hot rod engines and big double pumper carbs can get by without chokes by just pumping the heck out of them when they start but us normal guys need a properly working choke and pull of system.

 

[Just Carbs]

Thanks again gents for all the help. With regards to choke....here in Tampa in August, there is no such thing as a cold engine. The choke never activates, it's 90+ degrees in the shop. OK I'll play with it....

Tampa. I like Tampa. Have a place down there.
No choke in Tampa can present as if the carb has evaporated all the gas out overnight and needs to be cranked 3 to 6 seconds between stalls and pumping on the first start of the day.
Working choke is a good thing.

 

[Milo]

When the choke is closed cold engine use a hand vacuum pump and hook it to the choke pull off diaphragm, pump the hand pump and see how much the choke opens. Then you can adjust the small linkage with pliers to open a little wider when cold starting I use the Myte Vac for a lot of different things

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