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Carburetor Problems On Older Cars



  • The resistance wire should be the wire going to the coil and the red wire on the only terminal at the switch should probably be the power/battery wire, correct ?
  • zaken1zaken1 Posts: 556
    Yes, it sounds like that is correct.
  • I'm sure glad you are probably sitting down for this one. Removed the battery ground, found loose + wire on starter and tightened it, tried to start engine, wouldn't start just heard one click and then nothing, tried once more and nothing not even a click, removed ignition key, talking to neighbor while standing next to driver's door and heard click,click, click like the engine was trying to start. Sounds like a short in the ignition switch to me ?
  • zaken1zaken1 Posts: 556
    That is the most likely explanation. Glad I was sitting down...
  • Just trying to add some humor to a frustrating situation. Swapped out the ignition switch and fixed the clicking problem without the keys but engine still won't start just clicks when turned to start position. I have proper voltage going into and out of the brand new starter solenoid.
  • zaken1zaken1 Posts: 556
    If you have proper voltage as described; the brushes in the starter motor have probably worn down to the point where they've stopped making contact with the armature. So you need to exchange the starter motor for a remanufactured unit. There are lots of cheaply rebuilt starters and alternators out there; which often need to be returned as soon as they are installed. My experience has been that NAPA stores sell the best quality rebuilt starters. They are each individually tested, and come with a printout of the test results for the actual unit you buy.

    Some Chevys have thin metal shims under the starter; which are used to adjust the position of the starter with respect to the ring gear on the flywheel. If the starter on your car has shims between it and the engine; they should be reinstalled under the replacement starter.
  • zaken1zaken1 Posts: 556
    I thought you'd like to know that I found out a little more about the year of your engine. The Chevy 350 was only made with gasket type plugs until 1970, so combining that information with the results of Mr. Shiftright's engine number research determines that; if this engine was originally from a passenger car, it was made between 1968 & 1970. If this engine was originally from a truck; it was made between 1969 & 1970. That can be helpful to know when you buy certain parts.
  • Thanks for the engine info, getting ready to pull starter in a few minutes.
  • Pulled the starter and took it to an Advanced Auto Parts store to get tested. Tested fine and worked perfect for them. I not only have a fender mounted starter solenoid but also a starter mounted. I went next door to an Auto Zone to see if they had a new one in stock that I could look at because I have a wire that is "jumped" from the battery cable terminal on the starter to the R terminal. The salesman asked to test the starter because of the difference in the machines used, and I obliged him. He first tested it without the R wire hooked up and nothing happened, second test had the R wire hooked up and it sparked and melted right thru his wire. Use this link to access the enlarged image of the starter to see the wire on a stock starter that is hooked up to the battery on my starter. 1140_100943_0_&skuDescription=Duralast+/+Starter&brandName=Duralast&displayName=- Starter&categoryNValue=&sortType=&store=503&isSearchByPartNumber=&fromWhere=&fro- mString=&itemId=prod61198&navValue=15300045&filterByKeyWord=&productId=91140&app- QuestionText=&searchText=&categoryDisplayName=External+Engine&parentId=cat30063&- questions=%5B%5D

    I went home and bypassed the fender solenoid to no avail and tried to start it while hooked up the original way with both solenoids while the starter was off the engine. I had to run a ground from the starter since it wasn't mounted on the engine. Both tests came with the same result, starter gear comes out and then clicks once. Should I remove the "jumper" and test again?? Am i going in the right direction or should I focus elsewhere ?
  • bartlembartlem Posts: 1
    Just put new worked L28 motor in my Nissan Patrol, trying to connect Weber Carby from an XF ford? Having problems working the hoses out and the wiring. Any help would be appreciated.
  • Installed new starter, truck starts but runs like s**t. I have 8V going into the coil now with 6V coming out into the distributor and 12V going into the ballast resistor with 8V coming out to the coil. Is the ballast resistor bad ?
  • zaken1zaken1 Posts: 556
    You keep quoting a voltage coming out of the coil into the distributor. When the engine is running; it is not possible to use a meter to measure the voltage between the distributor and the coil, so whatever reading you may be getting there at that time is meaningless and misleading. You can only measure the voltage between the distributor and the coil with the engine stopped and the key on, and even then, only when the points are closed. The meter minus lead should be grounded to the engine for that test. The meter reading at that location should be less than 0.25 volts.(but if the points happen to be open at that time; the meter will read full battery voltage) If the meter reads more than 0.25 volts between the distributor and the coil when tested this way; there is a loose connection or a bad wire between the points and the coil; or the points are dirty or burned out. Incidentally, if a greasy feeler gauge is placed between the points; it will coat the points with grease; which is an insulating substance; and that will cause the points to burn, or will create a huge amount of resistance across the points. If you think the points are dirty; try running a paper business card that has been wetted with alcohol between the points, to clean off the grease.

    The other issue is that you now say there is 12 volts going into the ballast resistor. WHENEVER YOU QUOTE THESE VOLTAGE READINGS; IT IS ESSENTIAL TO SPECIFY WHETHER THE ENGINE IS RUNNING OR STOPPED AT THAT TIME. If the engine is running, the voltage going into the ballast resistor should be 14 volts. If you are getting only 12 volts at the resistor; check the voltage across the battery terminals with the engine running. If it now is 12 volts; this means the alternator, generator, or voltage regulator has gone out.

    If you gat 14 volts at the battery with the engine running; check the voltage of the battery wire at the ignition switch. It should be pretty much the same voltage as at the battery. If it is a lot lower, there is a bad wire or connection between the battery and the ignition switch.

    If you get 14 volts on the battery wire at the ignition switch, and only get 12 volts going into the ballast resistor; it sounds like the resistance wire is still connected between the switch and the ballast; so you are using two resistances in series again. You can only use one resistance device (either resistance wire or ballast) between the switch and the coil.
  • Removed the ballast resistor and I am getting 14V at the coil with the engine running, engine is still idling extremely rough. Checked the dwell and set the timing to 12 BTDC. Hooked up vacuum gauge and it read 15Hg at idle and drops to 10Hg when throtled up, when accelerator is let off of it shoots up to 20 Hg and slowly drops back to 15 Hg.
  • zaken1zaken1 Posts: 556
    It sounds like everything you mentioned is normal now. Make sure the vacuum hose is connected to the distributor. If that hose was off, or if the PCV spigot was open; it would create a very rough idle.

    I would also like to know whether you can feel any play in the distributor shaft when you try to pull and push on the rotor. I still think the distributor bushings may be worn out.

    If that wasn't the problem, try readjusting the idle mixture screws.

    If that doesn't help; I expect you either have bad plug wires or fouled plugs. Measure the resistance of each plug wire, and also the resistance of the plug wire from the coil to distributor cap. The maximum allowable wire resistance is 1,000 ohms per inch of length. For example, a 12 inch long wire should have less than 12,000 onms resistance. If the resistance of any wire exceeds that standard; I would replace the entire set of plug wires with Borg Warner, Bosch, or MSD spirally wound magnetic suppression wires. The spirally wound wire has one tenth the resistance of regular carbon core resistance wire. But you need to make sure the wire you buy is spirally wound magnetic suppression type. It should say so on the box. You need to check that because many companies make both carbon resistance wire and spirally wound metallic conductor wire. You can also buy magnetic suppression wire sets from Summit Racing for about $30. That is a lot cheaper than many such wire sets cost locally. But Kragen, Checker, Shucks, Murray, and O'Reilly parts stores should have Borg Warner magnetic suppression wire at a competitive price.

    If you replace the wires; I would also replace the spark plugs; because bad wires will foul a set of plugs. The preferred plug for your engine is Autolite #85 (standard) or #AP85 (platinum). The gap on these plugs is not pre-set; so it must be adjusted to .035".
  • zaken1zaken1 Posts: 556
    I just wanted to clarify what I meant about the distributor bushings possibly being loose: When I asked you to try moving the rotor, I was not talking about finding play between the rotor and the assembly it is attached to. I expect the rotor to not move with respect to the assembly. What I am talking about is that the shaft in the center of the distributor, which has the 8 sided cam that opens and closes the points, and has the rotor mounted on top; goes all the way through the distributor from the top where the rotor attaches, to the bottom where the drive gear is located. This shaft is only supported at two locations, one near the top of the distributor body, and one near the bottom. The support for the shaft comes from closely fitting brass bushings which have been pressed into the distributor housing. When those bushings were new; they fitted tightly enough that the distributor shaft could not move more than about a quarter of one thousandth of an inch (.00025") from side to side. There has to be at least that much side play in the shaft; or it would become too tight to turn freely. But after the distributor shaft rotates for many years, the bushings become worn and the amount of side play increases. And any side to side play in the shaft changes the size of the point gap; which causes the dwell angle to keep changing.

    Suppose the point gap is set at .016" on exactly the highest spot on the cam lobe. Now imagine what would happen if the bushings had worn to the extent that the shaft was able to move just .001" from being perfectly centered. If you pulled the shaft .001" toward you, while standing on the side of the distributor where the points are located; the point gap would increase, as the shaft moved toward the point rubbing block. Because the rubbing block is at the middle of the movable point arm; the amount of leverage from the arm's pivot would cause the point on the end of that arm to move twice as far as the rubbing block moves. So a .001" movement of the distributor shaft would create a .002" increase in the point gap; which would change the gap from .016" to .018". But if you pushed the shaft .001" away from you; the point gap would close down by twice the amount that the shaft moved; so the point gap would decrease by .002"; making the gap change from .016" to .014".

    What this means is that if the shaft has just .001" side play (or is bent just .001", which is also not uncommon) the point gap can vary from .014" to .018" while the engine is running. And that would cause the dwell angle to change by SIXTEEN DEGREES (a .001" change in point gap is equal to about a 4 degree change in the dwell angle). When the dwell angle varies this much; it becomes impossible to tune the engine to run properly!!!

    This is why even a tiny amount of side play in the distributor shaft can ruin engine performance. And this is why it is vitally important for you to very carefully check the distributor shaft for side play; by holding the distributor body with one hand, and, preferably while resting the heel of your other hand on the edge of the distributor body, try to feel for ANY movement between your two hands when you rock the distributor shaft (holding it at the rotor) from side to side. If you can feel any side to side movement at all; the distributor bushings are too loose.

    If there is no perceptible movement in the shaft; I'd like you to make one other test: Connect the timing light to the plug wire for #1 cylinder, and very carefully note the timing with the vacuum advance hose disconnected and plugged. Then move the timing light pickup to the wire for #6 cylinder (the third cylinder from the front, on the passenger side), and check the timing of that cylinder the same way. If the distributor shaft is straight, and the bushings are tight; the timing on the #6 cylinder should be exactly the same as on #1 cylinder. If the timing on those two cylinders is more than 2 degrees different from each other; the shaft is bent and you need a new distributor. This test works because the #1 and #6 pistons both reach top dead center at the same time; and the plug wires for those two cylinders are directly across from each other, on opposite sides of the distributor.

    High performance distributors don't use bushings to support the shaft. Instead; they use ball bearings; which have zero play and don't get loose over time. And those distributors also don't have breaker points; so there is no dwell angle variation that can change the timing. Once the timing is set on a high performance distributor, it does not have to be adjusted or rechecked again (unless the engine's timing chain stretches or breaks).

    Please let me know the results of this test.

    I also would like to suggest a more accurate way to adjust the idle mixture scews. Just connect the vacuum gauge, and watch it while you turn the screws. Find the setting that gives the highest vacuum; and then turn the screws inward (clockwise) to lean the mixture; until the vacuum just starts becoming lower. The best mixture setting is as lean as you can go; without losing any vacuum. BUT THE MIXTURE SCREWS CANNOT BE ADJUSTED IF ANY CYLINDERS ARE NOT FIRING, DUE TO BAD WIRES OR FOULED PLUGS.
  • zaken1zaken1 Posts: 556
    I need to add that, if you decide to replace the distributor, please consult with me first about an appropriate brand and model. Many performance distributors would not be suitable in your application; for a wide variety of reasons. So it is important to know which ones would be a good choice for use in your truck.
  • Replaced the plugs and wires, plugs are AC Delco R34S set to a 0.35 gap, nobody had the Autolite #85 or AP85 that you suggested and these were the crossover plugs, the wires are Borg Warner magnetic suppression wires that you suggested. Engine starts and runs fine but has a constant slight backfire while running. The fuel level is getting low and I didn't know if this "backfire" was caused by it running low on fuel ?
  • zaken1zaken1 Posts: 556
    I'm glad you replaced the plugs and wires. The backfire you hear could come from a mistake in the firing order when the plug wires were installed in the distributor cap. The firing order should be 1-8-4-3-6-5-7-2; reading clockwise. If you find the wire to #1 cylinder, and then follow the next wire that is clockwise in the cap; it should go to #8 cylinder; the next clockwise wire after that should go to #4 cylinder; the next wire should go to #3; and so on through the order listed above. The cylinders on the drivers side are numbered 1-3-5-7 going from the radiator to the firewall. On the passenger side they are numbered 2-4-6-8 going from the radiator to the firewall. If the firing order is correct; the idle mixture screws might be set too lean. I don't think low fuel level in the tank could cause such a backfire.

    If the cam in your engine is radical enough; it might be normal for the engine to sound like that; but it is very difficult to know without listening to the engine. I will say that while my nephew was learning about tuning cars, I once went with him to a shop that deals in race parts. While we were there; a pickup drove up, and sat there with the motor idling. My nephew turned to me and said "That truck is missing." I listened to it for a minute, laughed and then said "That truck is not missing; it has a racing cam in it. That's the way engines sound when they have a big cam in them!"

    Did you compare the timing on #1 and #6 cylinders? How did that turn out?
  • Once again you were correct, I had the firing order set in this order 1-8-4-3-6-5-2-7, I swapped the 7 and 2 wires and it eliminated the backfiring. I won't be able to do the timing check on the 1 and 6 cylinders until Sunday due to obligations at a new job Friday and Saturday.
  • zaken1zaken1 Posts: 556
    Sounds like you've really started cookin!!!
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