Carburetor Problems On Older Cars

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Comments

  • isellhondasisellhondas Member Posts: 20,342
    Had a tendency to run like that.

    I think you hit the nail on the head. A HUGE vacuum leak!
  • andre1969andre1969 Member Posts: 26,045
    on my '79 New Yorker, which seems to be possessed? Here's what it does. Basically, every morning, even if it's been a warm night, the sucker will fire right up, with a minimum of fuss. Heck, I think it sat 3 or 4 days, and I tried it this morning and it fired up like it was a brand-new car (and NOT a brand-new 1979 car :sick: )

    But, if I were to drive the thing to work, it's a sure bet it would leave me stranded in the evening when it's time to come home. Even if it's been sitting all day. One day, I drove it to work around 7:30 in the morning. I had to pull some OT that night, and didn't get out to the car until around 8-8:30 at night, and it was after sunset. Heck, even sitting in my yard for a few days, if I were to try starting it in the afternoon, it'll refuse. It'll crank and turn over, but just won't fire up.

    Any idea of what this could be? The car is a 360-2bbl, and only has about 64,000 miles on it. However, it sat around alot. I've put maybe 500 miles on it since I bought it in May. Prior to that, I think the previous owner said he drove it about 10 miles the year before! It was his father's car, and when the father passed away, the car mainly just sat around in the garage. I think the only reason it even had that 10 miles put on it was to take it in for its annual inspection!

    So, I know the car really could use a tuneup. All I've done to it is have the electric choke replaced, and replaced the fuel filter. Also, if I were to start up the car every few hours, even on a hot day, it'll fire up fine every time. But once it starts sitting for more like 4 or 5, it'll refuse. So, does anybody have any ideas on what in the car could be heating up, to make it get cranky in the afternoon/evening?
  • british_roverbritish_rover Member Posts: 8,502
    That is weird. Sounds like fuel isn't getting to the carb after the car is started and sits for a few hours.

    Not sure what could cause that though.
  • texasestexases Member Posts: 11,133
    Is this a recent change, or has it always acted like this? I've got no good idea, but sometimes carbon tracking in the distributor cap can do strange things...

    edit - when it does this, is there gas at the carb? If you get out, take off the aircleaner, and push the throttle do you get gas from the accel. jets?
  • andre1969andre1969 Member Posts: 26,045
    well, I got the car in May, before the weather got really hot around here. Back then, it more or less behaved itself, although it was hard to start because of the malfunctioning choke. However, the first hot day we had at work, it refused to start, although I did get it to fire up eventually. The second time it left me stranded at work, it did finally fire up later that evening, after a line of thunderstorms came through and cooled everything off. I took it straight to the mechanic that night, and he fixed the choke.

    It's a LOT easier to start in the mornings now, or even those times where I only let it sit a couple hours. And for about a month it seemed okay in the afternoon. However, on the days I drove it, I'd park under the shade of a big oak tree at work, to keep the interior cool. Even though it's cloth, midnight blue still gets hotter than blazes! On those afternoons, I'd come out, just give the pedal maybe 1/2 pump, and it would fire right up.

    Then one day I left it out in the sun, and although it sat for 12-13 hours and it was dark when I left the office, it refused to start. And then the next time I drove it, I parked under that oak tree again, to see if the shade had much correlation, but it refused to start then, too. And that was actually a fairly mild day.

    I haven't actually checked the jets to see it it's indeed shooting gas into the carb during those times when it refuses to start. However, I can smell gasoline, so I'm presuming it's getting it? And I have tried spraying some nicely flammable carb/choke cleaner down in the throat when the thing would refuse to start, but that wouldn't help either.

    And oddly, the day I changed the fuel filter, it was refusing to start at that time, but once I had the new filter on, it fired right up. But I just knew that was too easy of a fix. And sure enough, it was just coincidence.

    Y'know, I've thought about the cap and rotor. When those things start to go, they can make a car act up in all sorts of weird ways. That'll probably be the next thing I try. I had a '79 Newport with a 318-2bbl, and the cap got a hairline crack in it...caused all sorts of driveability and stalling/refusing to start issues that made me think it was fuel or carb related.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    If it won't fire with starting fluid, you have to presume either an ignition issue (that starting fluid is pretty flammable stuff) or that you have some sort of internal leak in the carburator that will allow gas to seep into an already hot engine. Excess fuel in a hot engine just won't work.

    Have you tried trying to start it hot by depressing the gas pedal and just keeping it there (NO pumping allowed!). If there is excess fuel in the cylinders, this should clear it out.

    If you have very old spark plugs, they can become gas fouled quite easily.
  • texasestexases Member Posts: 11,133
    Starting to sound like tune up time - might even throw in a set of wires, if they're old.
  • british_roverbritish_rover Member Posts: 8,502
    Yup if it won't start with carb cleaner then it almost has to be an ignition problem of some type.
  • andre1969andre1969 Member Posts: 26,045
    Have you tried trying to start it hot by depressing the gas pedal and just keeping it there (NO pumping allowed!). If there is excess fuel in the cylinders, this should clear it out.


    Yeah, I've tried that trick too. Believe it or not, there's a label on the driver's side visor (where the airbag warning often is nowadays) that tells you what to do when the car won't start. And it mentions that, holding the pedal to the floor (no pumping) and cranking it until it (hopefully) starts. Just no longer than 15 seconds at a time, to keep from frying the starter.

    As long as this car has been sitting, I'd imagine the spark plugs are pretty ancient too, so I guess I'll just add that to the list when I swap the cap and rotor. It's possible that the car just needs a good tuneup. Once it starts up it runs nice and smooth, and is pretty responsive, but I guess a tuneup would still do a world of good.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    One would suspect vapor lock were it not for the fact that starting fluid doesn't kick it off.

    You could have the classic "combination of factors" that all come together and conspire against you under certain conditions.

    You still have the gear-reduction starter I think? These get lazy over time, slowing down and sucking amperage; add that to old tune-up parts and you have just enough diminishment of ignition spark and cranking power to give you grief.

    The fact that you kick right off on a cold morning also fits into this pattern. A rested battery, dry cylinders and no chance of flooding.

    Try the depressed gas pedal trick anyway, and even if you have to stop cranking, don't lift up on the gas.
  • andre1969andre1969 Member Posts: 26,045
    I went out and started the car a couple minutes ago, at 11:19 AM. It's about 80 degrees, but humid, and the sun's breaking through the clouds just enough to make it feel nasty.

    Car fired right up. I turned the key, and after it started cranking, slowly depressed the pedal, and it fired right up and went into fast idle mode. It did seem to take just an instant longer to fire up than it does earlier in the morning, though.

    I don't think I'm going to chance driving it to work though, until I've done a tuneup on it. And even then, I'll do it on a day that I know one of my roommates will be home, and able to come get me if it doesn't start :P I guess if nothing else, once the weather gets cooler, it'll get less cranky in general, anyway.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Well you could as least do the spark plugs without a B team I think :P
  • andre1969andre1969 Member Posts: 26,045
    Well you could as least do the spark plugs without a B team I think

    Well yeah, in all honesty I could probably do everything this car needs for a tuneup. It has electronic ignition, so there's no points to worry about. Basically just change the cap and rotor, plugs, wires, and for good measure the air filter and pcv valve. I know I've got a timing gun and a distributor wrench around here somewhere, too.

    Problem is, I hurt my shoulder and then my back, so I'm not too hep on contorting into too many positions these days to wrestle around with the car. Changing that fuel filter last week was enough...it's not exactly in the most convenient place on the R-body 360, tucked nicely away sort of under the a/c compressor, and with three lines running to it, instead of the usual two.

    But, a couple years ago, I saw a one-legged old man who looked about 3 days older than Moses take down a 60-70 foot tall dead maple in the neighbor's yard and haul it away. So if he could do that, I guess I can do a simple tuneup!

    It's funny though, that as I get older, I just find myself less willing to do this stuff myself, even the simple stuff.
  • texasestexases Member Posts: 11,133
    A few years ago my Suburban was acting up while still under warranty, took it to the dealer, they said 'someone's been poking holes in the plug wires (yea, right :mad: )! No warranty! $300!!' So I said, forget that, how hard can plug wires be?? I found out - an amazing PITA, given all the room. They had them routed all behind various things. So yes, I understand plug/cap/rotor/wires sounds easy, but....
  • andre1969andre1969 Member Posts: 26,045
    The plug wires actually aren't too bad on the smallblock Mopars I've had. I think the most common problem is getting the #5 and #7 wires crossed, though. The firing order for the Mopar smallblock is 1-8-4-3-6-5-7-2 (I guess it's the same for most, if not all V-8's?) Anyway, with the #5 and #7 being next to each other on the distributor, it's easy to get the wires mixed up.

    Oh, About 15 mins ago, I went out to give the NYer another crank. Fired up with just a turn of the key, not even touching the accelerator. Heck, it fired up quicker than I've seen fuel-injected cars do!

    It's also HOT out there now. I don't care what the weather station says, it feels like it's about 90, with 110% humidity! So it's behaving today, so far...

    I probably could drive it to work, although I'd have to go outside and maybe start it up around 10:00, 12:00, and 2:00, to be sure that it would start around 4 when I get off.
  • andre1969andre1969 Member Posts: 26,045
    got back from a Costco/liquor store run, and walked down to start the NYer. Fired right up. I swear, the starter didn't even turn over. It's like turn the key and VROOOM!!

    Now...if it would just do that consistently...
  • andre1969andre1969 Member Posts: 26,045
    The other weekend, I finally got around to getting some tuneup stuff for my '79 NYer. Cap, rotor, plugs, wires. So far I replaced the cap, rotor, and the wire that runs to the coil. Seemed to make some difference. The old cap/rotor were pretty hideous looking. I woulda done the plugs and wires too, but I did something evil to my shoulder, and something even evil-er to my ankle, so there were only so many positions I could get into under the hood! :sick:

    We had our first frost last night. I went out this morning, before the sun hit the car, and she fired up. A little cranky...typical 1979 car reacting to cold weather, but it ran! So hopefully, this whole hot weather-no-start thing is just the car crying out for a good tuneup!

    If the cap and rotor were that bad, I'm sure the plugs aren't going to be too pretty!
  • beymerbeymer Member Posts: 3
    Any help would be appreciated.

    I have dumped about 1,000 into this car and just want it running well enough to sell it.

    The car will start up and idle fine but when I rev it up and come back off the accelerator it chokes out and dies. I can choke it and it will start after turning it over for a few times.
  • burdawgburdawg Member Posts: 1,524
    Does it have a dashpot on the carb?
  • beymerbeymer Member Posts: 3
    No it doesn't, it is a rochester single barrel on a 235.
  • beymerbeymer Member Posts: 3
    I actually tinkered around with it this afternoon and got it running however there is a hissing sound whenever I accelerate. Louder than the normal. It does not make a hissing sound when it is idling, could there be a leak? :(
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Sure, vacuum leak at the carburator base gasket is one possibility. Does it have a power brake?
  • beast56r2beast56r2 Member Posts: 4
    Sounds like you have a serious problem with vaporlock. The fuel is boiling in the fuel bowl and coming out the air vent tubes. You need to insulate the carb from the manifold with a thicker carb gaskets with an aluminum spacer in between. Get rid of the mechanical pump, block off the port on the block, and go to a high performance electric fuel pump and filter on the chassis. It will power through the vapor lock. Push comes to shove you may have to pull the manifold and block off the heat risers in the manifold. Make sure you have the right specs on the float level, there were a lot of carb changes in the 60's. Good Luck.
  • bobbybuchebobbybuche Member Posts: 16
    ok the first thing that should be done with any repair is a visual run down and diagnosis of your cars symptoms. You have a hiss first thing you think is vacumn, ok, well first check your RPM's if there a little too high then thats more likely than not what it is. you should check your air pump because as everybody knows after all that emmision control crap went on to all the cars it caused serious problems at first and a bad air pump can definely cause a vacum leak and you might be able to hear a rattle sound that sound alot like valve knock and if you can i would check replace the air pump but as far as vapor lock if the car is cranking and then dying thats not gonna be it
  • duff333duff333 Member Posts: 41
    I got this car with the factory 440-4 barrell this past summer. The car always fired right up and drove great. In fact I took it on a 150 mile ride when I 1st got it with no problems at all. Probably have driven it a total of 600 miles.

    However, about 3 weeks ago , while going about 20 mph I finally decided to "open her up". Took my foot off the gas then floored it - -well the car dropped into passing gear but before it really took off I hastily let off the accelerator (saw a cop on the other side of the street!) which caused the car to "jerk" as you might expect. Anyway, I drove it about a mile to home where it began to sputter on my street then conked out in the driveway. It would start right up then conk out. Let it sit for about 5 hours then it fired right up that evening.

    I drove it about 10 miles with no problem 2 weeks ago then it sat in my garage till last night. It's been cold here in MD (20's to 40's) - -I started it up last night and it idled way low for about a minute then it conked out. Tried it again and it started but conked out in seconds. I let it sit till tonite and - - same thing. I checked the butterfly and it's closed but too dark to fool with it - - any suggestions I can use when I take a look this weekend??

    Thanks for any help - - Mark
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    You might pull some spark plugs and take a reading, see if they are running way rich and are carbonized at present. You might also have carbon buildup in the engine, some of which you can treat by de-carbonizing with special additives through the intake manifold vacuum port.
  • duff333duff333 Member Posts: 41
    I'll take a look at the spark plugs - -hopefully this weekend. Forgot it's time to do some Xmas shopping today!!!

    Question - -I haven't fooled with an engine this old for maybe 30 years ( had a '65 Mustang as a teen) but I seem to remember spark plugs SLOWLY degrading around 10-12K miles. The car might start missing once in awhile and so forth. Would carbon buildup (I'm certainly no expert - -just asking) suddenly "attack' my Chrysler -- I would think there'd be some loss of performance 1st.

    Anyway, thanks for the advice!
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Sounds like you are doing short hops and lots of warm-ups with the choke on. That'll foul the plugs at least.
  • blasepblasep Member Posts: 1
    I recently got a 1960 pontiac catalina 389.. wouldnt start but I was given a new rochester 2bbl carb from a 455 I was told.. after getting the base and choke changed to the new carb I installed it and could not get her running.. It would fire then die then backfire and spit up throught the carb. I set the mixture about 2.5 turns out it runs but backfires bad when cold starting. and when warm is driveable but wants to stall when given throttle.. Im new at carbs and old cars and not sure what to do.. I dont know if it is a vacuum prob not really sure how to check.. any help would be appreciated.
    thanks
  • okko1okko1 Member Posts: 327
    check the engine timing and check base plate for leaks. you can use carb cleaner for this.
  • texasestexases Member Posts: 11,133
    You might double check the spark plug wires, make sure they're connected to the right plugs. Other possibilities, if the timing and wiring are right, might include bad timing chain (I don't know about Pontiacs in particular, but this can happen to some cars), and an incorrectly installed distributor (ditto).
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    Carburetors are rarely (if ever) the problem of a "no start" so I think you are barking up the wrong tree. I'd replace the original carburetor and then do all the things these folks here have suggested. Also you'll need to look up the specs on the new carburetor you were given...it might be all wrong for your engine.

    First think I'd do is a compression test; if okay, then I'd static time the engine to #1 cylinder just to get in the ballpark. Then I'd re-check the firing order of your spark plug wires, inspect cap and rotor and points.

    If the car has been sitting for a long time, I'd also take a gas sample and see what you got in there.

    I'm thinkin' you are way ahead of yourself at the moment and need to back up some.
  • isellhondasisellhondas Member Posts: 20,342
    I doubt if that is the problem but Pontiacs of that era were well known for timing chain problems. The plastic gears would wear out.

    I suppose this could be it if it has jumped a tooth.
  • texasestexases Member Posts: 11,133
    Yes, kind of a last resort idea. I like Shifty's idea on cap and rotor, I forgot about that, even after having that exact thing happen to me as a mechanic (well, 35 years ago...).
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    For me the basis of all diagnosis is from simple to complex, from system/circuit to next system circuit, and from most likely to least likely

    So compression test (without compression we have to go no further) comes before a bad camshaft (least likely); then fuel is the next system and we go from most likely (bad fuel pump) to least likely (the carburetor or clogged fuel filter); then the next system is ignition, and we go from from bad points, cap and rotor, wires and plugs, firing order, etc. (most likely) before we even think about bad ignition coil or ignition switch(unlikely).

    I even will discount new parts out of the box as being faultless, as this screws up the diagnosis as well.
  • duff333duff333 Member Posts: 41
    Good morning. Just wanted to update from post 182. I finally got around to having the New Yorker looked at. I got pulled away for 6 weeks+ for company travel and just now getting back to my car. Anyway, last week I checked the oil - - it was fine - no coolant in there. I then pulled a spark plug, and sure enough, it was carbon build up. I then found a mechanic who works on older cars only about 5 miles away and had it towed.

    Thanks for the advice - -I think by mentioning the carbon buildup the mechanic was quickly able to diagnose the problem - - he checked it out real good - - she needed a major tune-up, adjust carb, plus some safety things repaired. At least it wasn't a blown engine or head gasket as I feared. I should have the car back next week - -it should be ready to go for the summer.

    Thansk again, Mark

    P.S. Yipes, gas prices have jumped about a buck since I last filled the car up!!!
  • scooterhvscooterhv Member Posts: 1
    I HAVE A 1986 MONTE CARLO WIT A 383 STOKER BUT I THINK MY CHOKE IS BAD IT DOES NOT OPEN AND CLOSE WHEN IT SHOULD AND SOMETIMES WHEN I DRIVE IT SHUTS ALL THE WAY AND CUTS MY CAR OFF. CAN ANYBODY HELP
  • okko1okko1 Member Posts: 327
    if it is an edlebrock with an electric check for power supply. but i never used the choke on my strokers. it may need to be fattened up. :)
  • rmills33rmills33 Member Posts: 2
    Hello everyone,
    I have a 68 mustang with a holley 4bbl 600. It sat up for several years and I got it running the other day. I decided to rebuild the carb. After the rebuild the car is back fireing repeatedly at idle. I have not touched the timing and it didnt do this before the rebuild. This was my first carb rebuild and I didnt count the turns to get the mixture right. Could air/fuel mixture be the problem. If so is there a starting point I can try with the number of turns on the 2 adjustment screws for mixture.
  • okko1okko1 Member Posts: 327
    yes all the way in then back out 2 1/2 turns. check your float level and make sure youi are sealed to the manifold. does it have a manual choke and did you start and run the engine just before the rebuild?
  • carguy4spcarguy4sp Member Posts: 1
    I have a bad idle surge that seems to be getting worse. The vacuum lines are ok and I checked the carb mounting bolts they are ok.

    The carb is a 650 rebuilt 6 months ago on my 69 Torino with a 302 engine.

    The problem seems to be temp sensitive as it runs good when cold and gets continually worse as it warms up.

    I live in SW Florida so the choke is not hooked up or used.

    Thanks fo any ideas
    Rod
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    You might check for a vacuum leak at the base of the intake manifold where it bolts to the cylinder heads.
  • okko1okko1 Member Posts: 327
    does it have a spacer plate between the carb and the manifold.also make sure you have the right vacuum line to the distributor. does it have a vacuum tree on the thermostate housing?
  • andre1969andre1969 Member Posts: 26,045
    but how much trouble can one little loose or misplaced vacuum hose cause? Sunday before last, my '76 LeMans decided to quit running. It would turn over but wouldn't fire up, and seemed to be flooding out. It's always been kind of cranky to start, especially the first start of the day, but it got to the point it was just flat-out refusing.

    I finally did get it to start this past Sunday. I took an old sock, sprayed it with starting fluid, and stuck it in the throat of the carb. Car fired right up.

    Well, I tried to start it again today, but it pulled the same stunt. Until I did the sock trick again. Then it fired up. Well, it also tried to swallow the sock! There was a vacuum hose attached to the side of the air cleaner, that didn't look quite right to me. I think it had come loose at some point, and I just stuck it there without thinking. Well, I pulled it out of there, and stuck it in this other spot that's actually underneath the air cleaner intake. And now it's starting just fine. I can turn it off and turn it back on and it fires right up. Where before it wasn't doing that without the sock in its throat.

    I just went out after letting it sit about an hour, and again, it fired right up. So could it just have been that misplaced vacuum hose? Or is the car just behaving for the time being, waiting for me to drive it someplace far away so it can strand me? :surprise:
  • texasestexases Member Posts: 11,133
    Sounds like it was putting vacuum in the wrong place? But wasn't it running before this? Just a vacuum leak from one unplugged hose wouldn't seem to do what you describe...
  • andre1969andre1969 Member Posts: 26,045
    Yeah, it had been running before this. In fact, it did start Sunday before last, and I drove it around a bit. But then I put it back in the garage, and a few mins later tried to start it up again and it wouldn't. I figured maybe it just got hot and was vapor-locking, but then it wouldn't start later that afternoon or evening, either.

    I pulled the whole air cleaner top off, but can't remember if that hose was already loose, or if I disconnected it. When I finally got it started just this past Sunday, with the sock in the carb, I put the air cleaner top back on and that's when I hooked that hose in what I think was the wrong place. That's while the car was actually running though. I drove it around a little bit, swapped cars in the garage so that it was in the back and the 5th Ave was up front, and then turned it off. But didn't bother to see if it would fire back up.

    Then yesterday, it wouldn't start, until I did the sock trick again. For some reason, I started thinking about that vacuum hose, because it didn't seem to fit quite right there anyway, and I moved it to the other spot, while the car was running. It didn't seem to make any difference in the way the engine idled. I put the car back in the garage, and turned it off, and started it back up a few times. Fired up just fine. Tried it a bit later, and then about an hour after that, and every time it started up.

    I guess the real test would be if I went out there this morning to see if it starts. Which I might try to do, once this coffee finally kicks in. I think I'm driving the convertible today, though. Supposed to be a nice day out. 91, sunny, no rain.

    Oh, one other thing I did notice about the LeMans yesterday, as it was sitting there idling in the yard. I could see a little smoke coming from its tailpipe. Not blue oil smoke or white head gasket smoke, but just a little gray smoke, like maybe it's just not burning the gas completely. Guess it could just be running rich, and needing some adjustment.
  • bumpybumpy Member Posts: 4,425
    but how much trouble can one little loose or misplaced vacuum hose cause?

    On a '70s car with Rube Goldberg-esque emissions contraptions? Plenty. :(
  • andre1969andre1969 Member Posts: 26,045
    I started the LeMans up this morning, with that vacuum hose back in now what I think is the proper place, and it fired up about how it normally does. It usually takes 2-3 tries first thing in the morning before it fires up, and it's back to doing that. So, no sock laced with carb cleaner down the carb this morning for it.

    So, hopefully it'll behave itself for awhile, now.
  • hankjoeyhankjoey Member Posts: 13
    1960 Rambler American with 1963 engine.

    1. After the car is shut off gas leaks around the base of the carburetor. I have replaced the gasket. It may be also be leaking through the linkages. help.

    Thank you.
  • Mr_ShiftrightMr_Shiftright Member Posts: 64,481
    I'd guess a sticking float needle or a badly adjusted float level OR better yet, a hole in the float itself (take it out and try to float it in water and see what happens).
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