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It cranks vigorously but won't start. How do I go about troubleshooting?

So far, I've:

  • Changed the battery,
  • Checked all spark plugs and cap

Could it be the carburetor?

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    It would help to know some history on the vehicle. For instance, is this a new problem on a previously running vehicle? Or a you trying to "resurrect" one that has been off the road for a while? Anything you can tell us about what you notice as you try to get it to run would help too. – dlu Nov 17 '16 at 0:48
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    You say it won't start, but does it kick over at all? Do you hear any life in it when you crank the engine (as in running noise)? Any backfires? have you had the distributor out? Is there power to the distributor? It's most likely an HEI distributor. The power hookup should be on the driver's side of the engine. – Pᴀᴜʟsᴛᴇʀ2 Nov 17 '16 at 0:59
  • Haven't taken off the distributior yet but will to check thanks – Carlos Nov 17 '16 at 2:13
  • One more thing on the carburetor the little flap get stuck and it doesn't close all the way you think it I was should replace the carburetor or am I don't know what to do with that but it does get stuck there to meet the gas in it opens up you'll get stuck in it won't close no more and then I'll stay stay like that until I have to force it down to close let me know what you think on that thank you – Carlos Nov 17 '16 at 2:16
  • Had the truck running good from one day to another this problem happen it cranks with good power n seed but it just won't start now?? – Carlos Nov 17 '16 at 4:39
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If there is air, fuel, and a well timed spark it is pretty much guaranteed to at least try to run if you've got the battery to crank it. So it's a process of taking each of the areas in turn and verifying that it is working. Here are some things you could do:

  • Check for fuel smell, if fuel is being delivered and the engine isn't starting it will be coming out the exhaust. You'll probably be able to smell it.

  • If you don't smell fuel, pull the air cleaner and try dribbling a small amount of fresh fuel or starting fluid into the carburetor, if that gets the engine to fire up – even briefly – then the problem is likely to be in the fuel delivery system. If the car has been sitting for a while it may be gummed up parts in the carburetor, if it is a new and sudden problem I'd be inclined to start by looking at the fuel filter and fuel pump. Unless you know when the fuel filter was last replaced it wouldn't be a bad idea to do that.

  • With the air cleaner open, you're pretty much guaranteed to have a good air supply. So if the engine started easily with it off, it would be worth looking at the filter and the air pathway to see if there is a blockage.

  • That leaves a spark. There are lots of possibilities here. One is that the wires are bad or installed incorrectly. Your coil could have failed, or the timing could be way off. You can probably check for a spark by pulling a plug wire and holding it close to the block as you crank. You should see a spark when the wire is close to, but not touching, the block. Be careful! The voltage is high and you can get injured both by your reaction to a shock as well as by the shock itself.

That is probably enough to help you narrow down the problem. Then you can ask a more focused problem if you don't get it sorted out.

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    I do smell fuel n does come out to the carburetor two days in a row started with no problem and then this happened something in your price correct I will check the spark plug see if there's any spark and then I'll check the distributor my have to replace it is older truck or do you think you can be the carburetor because a little flap doesn't close all the way in to get stuck add a little breathing flap on the carburetor – Carlos Nov 17 '16 at 2:15
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    If your talking about the choke, you can open the throttle all the way by hand and manually close the choke. Also, when you open the throttle, you should see fuel squirt into the cylinder. Even if you smell fuel, it is possible there isn't enough, make sure you can see it squirt in. – rpmerf Nov 17 '16 at 15:06
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Checklist for older non working vehicles:

  • Does it have spark?
  • Is the spark in the correct firing order
  • Are there any cylinders without spark
  • Do you have fuel
  • Is there too much fuel
  • Is there too little fuel
  • Do you have compression

All the above should be checked and adjusted, then you should be good to go. Let me know which one is missing.


for your specific vehicle and the possible carb issue you are having is the butterfly valve that is getting stuck closed the automatic choke by chance? or is it your pushpull cable bends when you press the gas and the throttle does not move. can you take a picture of the valve and upload it?

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    best answer that is simple. – Dan Z Nov 17 '16 at 10:03

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