ignition problems help
03-01-2008, 04:32 PM
#1
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ignition problems help So I was rebuilding my 74 corvette with new plugs, new wires, distributor cap, and starter. After the install I turned the key and nothing but happened other than the starter kicked over. I checked all the plugs they all had the correct .035 gap and they were getting fuel so I was stumped considering that before I changed anything the car started up fine. Any help would be greatly appreciated.
03-01-2008, 05:29 PM
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you might put a voltmeter in the big red power wire that clips into the cap and make sure it has 12 volts when the key is on, did you move the distrubitor at all if so your timing could be off did you put a new coil in? if not you can test it with a ohmmeter just take the cap off with the coil left in it ,connect the ohmmeter between the carbon button in the cap and the grund terminal on the distributor cap to test the ignition coil's secondary coil. Record your reading.
Connect the ohmmeter between the carbon button in the cap and the positive battery terminal on the distributor cap to test for short in the ignition coil. Record your reading.
If infinite ohms or resistance was measured in both measurements, the ignition coil is defective and needs to be replaced.
if you dont have an ohm meter take off one of your plug wires off of a plug and put a screw driver in the plug boot and hold the screw driver about a 1/8 inch away from a ground like you block or exhaust manifold you should have a good blue spark if its good if its bad it will have a week small spark
Ryan
Connect the ohmmeter between the carbon button in the cap and the positive battery terminal on the distributor cap to test for short in the ignition coil. Record your reading.
If infinite ohms or resistance was measured in both measurements, the ignition coil is defective and needs to be replaced.
if you dont have an ohm meter take off one of your plug wires off of a plug and put a screw driver in the plug boot and hold the screw driver about a 1/8 inch away from a ground like you block or exhaust manifold you should have a good blue spark if its good if its bad it will have a week small spark
Ryan
03-01-2008, 05:35 PM
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I don't think that I moved the distributor at all but I turned the key with the cap off to see if the rotor was working and it was but moving slowly, I don't know if that is a good or bad sign though. And If it not the coil what else could be the culprit?
03-06-2008, 10:28 AM
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Points and it's not moving at all. The rotor used to be moving slowly but now not at all, Even when I physically try to move it with my hand it feels like it is locked in place.
03-06-2008, 04:58 PM
#6
with the distributor installed in the engine, you will not be able to turn the rotor. The distributor shaft is geared to the camshaft, so if you turn the rotor you will be turning the cam (which is geared to the crankshaft and then you're turning the whole rotating assembly, not gonna happen).
At best you will be able to turn the rotor about 20 degrees in one direction, which is the amount of mechanical advance going against the springs in the distributor. And that may even feel like the rotor is locked in place, it's hard to tell if it's moving.
When you say rotor not moving at all now, the rotor will turn at half the engine speed because it (the distributor) is geared to the camshaft at a 1:1 ratio. And the cam is geared to the crankshaft at a 2:1 ratio. So if you can turn the engine over by the key, or get a ratchet on the crankshaft pulley bolt, and accurately turn the engine over 1 revolution the rotor will rotate 180 degrees. Rotate the engine 2 full revolutions and the rotor will do one complete rotation. Start with the timing mark on the crankshaft pulley at 0 degrees, and it should be fairly easy to do 2 crankshaft rotations and observe only 1 rotation of the rotor. If you don't observe a rather accurate 2:1 ratio then something is wrong and you're gonna have to pull the distributor.
It is possible the little roll pin that locks the gear on the distributor shaft broke, which would cause the problem you seem to be describing with the rotor not moving but how or why would happen after a simple cap change seems like a 1 in a million coincidence. And that also wouldn't explain the rotor not moving at all because it would then allow you to spin the rotor any which way not being geared to the cam.
If you know how and have easy access, just pull the distributor and verify the gear on the bottom is 100% and there is no play in the distributor shaft and it spins smoothly. Hardest part is getting the distributor reinstalled and back to correct timing but it isn't that hard and can be explained if you need it.
if everything mechanical is sound, did you replace the point set and condensor when you put the new cap on? Points, and especially the condensor, are notorious for a faulty ignition system. And even if you installed a new points set with condensor, I have gotten more than one bad condensor with a new points set when I used to use them. Points suck! I recommend you either get an electronic ignition. Either a whole new distributor with electronic igntion, or you can get a Pertronix kit for your current distributor which is a little module and magnet that fits under the cap. A pertronix kit generally runs $100 and is minimal wiring to install, very easy. But it is only good if your distributor is mechanically sound, otherwise the cost increase for a complete distributor with electronic ignition is minimal, lots of quality name brands to choose from- mallory, msd, and pertronix.
At best you will be able to turn the rotor about 20 degrees in one direction, which is the amount of mechanical advance going against the springs in the distributor. And that may even feel like the rotor is locked in place, it's hard to tell if it's moving.
When you say rotor not moving at all now, the rotor will turn at half the engine speed because it (the distributor) is geared to the camshaft at a 1:1 ratio. And the cam is geared to the crankshaft at a 2:1 ratio. So if you can turn the engine over by the key, or get a ratchet on the crankshaft pulley bolt, and accurately turn the engine over 1 revolution the rotor will rotate 180 degrees. Rotate the engine 2 full revolutions and the rotor will do one complete rotation. Start with the timing mark on the crankshaft pulley at 0 degrees, and it should be fairly easy to do 2 crankshaft rotations and observe only 1 rotation of the rotor. If you don't observe a rather accurate 2:1 ratio then something is wrong and you're gonna have to pull the distributor.
It is possible the little roll pin that locks the gear on the distributor shaft broke, which would cause the problem you seem to be describing with the rotor not moving but how or why would happen after a simple cap change seems like a 1 in a million coincidence. And that also wouldn't explain the rotor not moving at all because it would then allow you to spin the rotor any which way not being geared to the cam.
If you know how and have easy access, just pull the distributor and verify the gear on the bottom is 100% and there is no play in the distributor shaft and it spins smoothly. Hardest part is getting the distributor reinstalled and back to correct timing but it isn't that hard and can be explained if you need it.
if everything mechanical is sound, did you replace the point set and condensor when you put the new cap on? Points, and especially the condensor, are notorious for a faulty ignition system. And even if you installed a new points set with condensor, I have gotten more than one bad condensor with a new points set when I used to use them. Points suck! I recommend you either get an electronic ignition. Either a whole new distributor with electronic igntion, or you can get a Pertronix kit for your current distributor which is a little module and magnet that fits under the cap. A pertronix kit generally runs $100 and is minimal wiring to install, very easy. But it is only good if your distributor is mechanically sound, otherwise the cost increase for a complete distributor with electronic ignition is minimal, lots of quality name brands to choose from- mallory, msd, and pertronix.
Last edited by 1 FMF; 03-06-2008 at 05:14 PM.
03-06-2008, 09:16 PM
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Thanks a lot man and if i go HEI does that mean that my problem would be solved? And also I took the distributor out and the gear seemed in good condition and i could spin the rotor. So what would be the correct way to put it back in is what i'm wondering now/
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03-06-2008, 10:45 PM
#8
would you problem be solved: most likely. Of course that's if your problem is entirely caused by the points. I haven't seen what you got, and it could be a loose wire or something silly causing the problem. So don't just go out and buy a new distributor and ignition setup without at least checking basic wiring stuff first, you might still have a problem even with new distributor! At a minimum, you should be getting +12v at coil + post when cranking the engine. And you should have 1-2 ohms resistance between coil + and - posts but you need to disconnect all wires going to coil posts to check this. You also might just need to clean the inside of the distributor, the points and condensor might not be making good metal to metal contact for ground, and check the condensor wire and connector isn't touching causing a short to ground. This is if you want to use points, but if you don't mind a few hundred on a new ignition then it will definitely be less problematic.
how does it go back in :
if you had asked me prior to pulling the distributor this might have been easier, although that assumes it was installed correctly to begin with
you can google this for explainations in greater detail if you're not that knowledgable about how everything works too, there's lots of good writeups on the web.
- understand the firing order. however the cap was on the distributor, the wire from cylinder #1 will go to some receptacle on the distr. cap. From this spot on the cap, the rest of the wires will go to the various cylinders. Standard chevy 350 firing order is 1-8-4-3-6-5-7-2. Memorize the sequence. This sequence will go clockwise on the distributor cap, when looking down on it. http://www.boxwrench.net/specs/chevy_sb.htm
- know that wherever #1 cylinder spark plug wire goes to on the distributor cap is arbitrary. Technically, you can have it positioned anywhere. What will limit you is something like a vacuum port coming off the distributor or the shape of the cap if it can't rotate to that position. Usually, you position the location of #1 on the cap so when you connect the rest of the spark plug wires (in the correct sequence) it facilitates routing the wires. Usually you'll try to get #1 on the cap closest to the front, but it's up to you. If you still have the cap hanging off all the wires on the engine, you can easily figure out where #1 was originally located.
- Realize however you route the spark plug wires on the cap, you'll need to be able to rotate the distributor with everything connected about 30 degrees in both directions to be able to set it to have the correct timing. So think before you connect everything up and use the correct length wires on the correct cylinders to allow you to rotate the distributor.
- rotate the engine so the timing mark pointer is on 0 on the crankshaft pulley. Simply doing this is a 50/50 chance of having the engine at top dead center (TDC) on cylinder #1. If you checked before pulling the distributor, you could've lifted just the distributor cap and checked for the rotor pointing under #1 spark plug wire in the cap. If the rotor was pointing in the opposite direction, then you know your 180 degrees out so you rotate the crankshaft 1 revolution, get the timing pointer at 0 on the pulley, and the rotor should be under #1 wire on the cap. This assumes you had the timing set correctly to begin with. You can also pull the spark plug and feel with your finger for compression rotating the engine, when you feel air then stop with timing pointer on 0. Or if you pull the valve cover you can watch when the intake valve closes, then stop on 0.
This also assumes your crank pulley and timing pointer are correct! But it should get you close enough to at least install the distributor and get the engine running (just with incorrect timing).
- with engine TDC for cyl #1 and timing pointer at 0, rotate the engine backwards a hair so the timing pointer points to 10 degrees before top dead center (BTDC) on the crank pulley. This sets your initial timing for after you've dropped the distributor in and will allow the engine to immediately fire up.
- Look at the bottom of the distributor and you'll see how it interfaces with the oil pump. Use long flat blade screw driver to reach oil pump and orientate it to allow the distributor to drop fully in. This is the hard part, because the distributor gear is beveled it will cause the rotor to rotate about 30 degrees as you drop the distributor fully in and you need to end up with rotor pointing in correct location for #1. Don't be surprised if it takes you a few tries. Once in, check with the cap on that you can rotate everything 1/8 a turn in each direction, to allow you to adjust timing.
- with distributor fully in, the rotor will be pointing in some fixed direction even if you then rotate the distributor. Provided it's pointing in the relatively correct direction, now put the distributor cap on and rotate the cap (and distributor body but the rotor won't turn! ) so that the rotor is under the receptacle in the cap for #1 cylinder. Eyeball it best you can. Once cap is on and you have it located best you can, tighten down the holding clamp for distributor. You're initial timing should be set close enough to 10 deg btdc, because you have the timing pointer on the crank pulley pointing at 10 btdc.
- cap is now installed and distributor is locked down. Before installing all the wires, just look and make sure it looks like you'll be able to rotate the cap about 1/8 turn in each direction, to allow for adjusting timing. If not then pull the distributor and you'll need to rotate it one gear tooth and re-eyeball the cap with the rotor. Install all your wires in correct firing order. Engine should start right if it has fuel and nothing else is wrong. If it doesn't, get somebody to turn the key while you rotate the distributor *slightly* clockwise, then back to initial position and *slightly* counterclockwise. Your eyeball accuracy might have been a little off, but you shouldn't need to rotate the distributor more than 10 degrees in either direction, and certainly not more than one wire position on the cap.
- If it doesn't start then:
check for spark from the coil first,
check for spark at the end of a spark plug wire,
if you have spark then re-check your firing order is correct,
if firing order is correct then verify you're not 180 degrees off with the distributor (you didn't have the engine on #1 TDC compression stroke, it was on the exhaust stroke for #1).
how does it go back in :
if you had asked me prior to pulling the distributor this might have been easier, although that assumes it was installed correctly to begin with
you can google this for explainations in greater detail if you're not that knowledgable about how everything works too, there's lots of good writeups on the web.
- understand the firing order. however the cap was on the distributor, the wire from cylinder #1 will go to some receptacle on the distr. cap. From this spot on the cap, the rest of the wires will go to the various cylinders. Standard chevy 350 firing order is 1-8-4-3-6-5-7-2. Memorize the sequence. This sequence will go clockwise on the distributor cap, when looking down on it. http://www.boxwrench.net/specs/chevy_sb.htm
- know that wherever #1 cylinder spark plug wire goes to on the distributor cap is arbitrary. Technically, you can have it positioned anywhere. What will limit you is something like a vacuum port coming off the distributor or the shape of the cap if it can't rotate to that position. Usually, you position the location of #1 on the cap so when you connect the rest of the spark plug wires (in the correct sequence) it facilitates routing the wires. Usually you'll try to get #1 on the cap closest to the front, but it's up to you. If you still have the cap hanging off all the wires on the engine, you can easily figure out where #1 was originally located.
- Realize however you route the spark plug wires on the cap, you'll need to be able to rotate the distributor with everything connected about 30 degrees in both directions to be able to set it to have the correct timing. So think before you connect everything up and use the correct length wires on the correct cylinders to allow you to rotate the distributor.
- rotate the engine so the timing mark pointer is on 0 on the crankshaft pulley. Simply doing this is a 50/50 chance of having the engine at top dead center (TDC) on cylinder #1. If you checked before pulling the distributor, you could've lifted just the distributor cap and checked for the rotor pointing under #1 spark plug wire in the cap. If the rotor was pointing in the opposite direction, then you know your 180 degrees out so you rotate the crankshaft 1 revolution, get the timing pointer at 0 on the pulley, and the rotor should be under #1 wire on the cap. This assumes you had the timing set correctly to begin with. You can also pull the spark plug and feel with your finger for compression rotating the engine, when you feel air then stop with timing pointer on 0. Or if you pull the valve cover you can watch when the intake valve closes, then stop on 0.
This also assumes your crank pulley and timing pointer are correct! But it should get you close enough to at least install the distributor and get the engine running (just with incorrect timing).
- with engine TDC for cyl #1 and timing pointer at 0, rotate the engine backwards a hair so the timing pointer points to 10 degrees before top dead center (BTDC) on the crank pulley. This sets your initial timing for after you've dropped the distributor in and will allow the engine to immediately fire up.
- Look at the bottom of the distributor and you'll see how it interfaces with the oil pump. Use long flat blade screw driver to reach oil pump and orientate it to allow the distributor to drop fully in. This is the hard part, because the distributor gear is beveled it will cause the rotor to rotate about 30 degrees as you drop the distributor fully in and you need to end up with rotor pointing in correct location for #1. Don't be surprised if it takes you a few tries. Once in, check with the cap on that you can rotate everything 1/8 a turn in each direction, to allow you to adjust timing.
- with distributor fully in, the rotor will be pointing in some fixed direction even if you then rotate the distributor. Provided it's pointing in the relatively correct direction, now put the distributor cap on and rotate the cap (and distributor body but the rotor won't turn! ) so that the rotor is under the receptacle in the cap for #1 cylinder. Eyeball it best you can. Once cap is on and you have it located best you can, tighten down the holding clamp for distributor. You're initial timing should be set close enough to 10 deg btdc, because you have the timing pointer on the crank pulley pointing at 10 btdc.
- cap is now installed and distributor is locked down. Before installing all the wires, just look and make sure it looks like you'll be able to rotate the cap about 1/8 turn in each direction, to allow for adjusting timing. If not then pull the distributor and you'll need to rotate it one gear tooth and re-eyeball the cap with the rotor. Install all your wires in correct firing order. Engine should start right if it has fuel and nothing else is wrong. If it doesn't, get somebody to turn the key while you rotate the distributor *slightly* clockwise, then back to initial position and *slightly* counterclockwise. Your eyeball accuracy might have been a little off, but you shouldn't need to rotate the distributor more than 10 degrees in either direction, and certainly not more than one wire position on the cap.
- If it doesn't start then:
check for spark from the coil first,
check for spark at the end of a spark plug wire,
if you have spark then re-check your firing order is correct,
if firing order is correct then verify you're not 180 degrees off with the distributor (you didn't have the engine on #1 TDC compression stroke, it was on the exhaust stroke for #1).
