The Stovebolt Site Forums The Shop Area Engine Shop Help!!!

I was wondering if anyone on this site could help me crank my engine the first time. I live in Jacksonville, Florida, and was hoping one of you Chevy experts might live in the area. I just rebuilt my 46 Chevy one ton with a 235 and I can't seem to fire it up the first time. I have fuel and compression, but no spark. I have also tried a new condensor and coil, so it must be the points which I am clueless about. If ANYBODY in the Jacksonville area could help me out personally or point me in the right direction for local help, it would be greatly appreciated. I have been restoring this truck for the past year by myself and I need to finish it in time to return to school at the end of August. Please help!

Thanks
Adam

Bring it to my house and I'll help.

If you have a shop manual, it should be helpful for you.

I am sure someone will chime in that lives closer.

Do you mean no spark as in, pulled a wire, slid back the boot, and held near the plug, and no spark?

I had trouble starting mine the first time. There were many things including; carburetor, timing and points gap that were all a little off and she just wouldn’t start with the slow cranking 6V battery. Without changing any settings I connected to a 12V battery and it started right up.

Sounds like you need to insure there is spark to the Distributor first.

-Get a test light
-get a good ground, touch it to the wire coming from to the starter to insure you have a good connetion.
-Turn on the Ignition
-Check to see if there is power to the coil
- If no power, you will have to hot wire the ignition switch.

If you have power, the problem is most likely in the distributor.
- With the cap off crank the engine and see if there is spark at the point,

- if you have spark at the points, then you have wire problems or timing problems.

I have a spark from the starter to the the coil, but I can't tell if there is a spark from the coil to the distributor. What's the best way to test for spark from the coil to distributor, and then distributor to points, and so on? I am new to this so my terminology is poor. When guys say points, exactly what points do you mean (please be descriptive. This is a fresh rebuild, so the only wiring I've done is from the battery to the starter, the battery to ground, and the starter to the coil. There is no ignition switch yet. Do I need to do anymore wiring at this point (ground the coil?) Thanks for the help and please keep trying with me.

Adam

P.S. It's a 12v system.

We may be getting ahead of ourselves if the engine/distributor is 'out of time.' When the cylinder is is at the top of the compression stroke; the points open, releasing a small spark stored in the condenser. This is the little spark(lower current) that goes to the coil, signaling it to release the big spark(much higher current) to the center of the distributor, which then sends it to the correct cylinder.(we hope) In a running engine, all of this happens over 1000 times per minute.Click here for an explanation of the process with graphics. If you would like an even more detailed explanation, click here.

Points are electrical contact points that work off a cam on the distributor shaft that can be seen with the cap removed. As the distributor rotates, the contact points are adjusted to ride the shaft where raised lobes push the contact points open and closed as the dist turns. If you remove the distributor and turn it by hand you'll see how this works. The the rotor and distributor cap then take the current and send it to each spark plug in a particular firing sequence called the firing order. The distributor must be installed and adjusted correctly for the ignition timing to be in sync with each rotation of the engine. Contact points have an adjustment that allows them to open and close to a certain gap tolerance measured using a gap measuring device. A manual describes this and also gives you exact numbers as to point gap, timing (measured using a strobascopic timing light pointed at a mark on the the crankshaft pulley or harmonic balancer.) If the distrutor has been removed, you line up reinstallation by placing the number one cylinder at top dead center on the compression stroke. The metal "pointer" on the rotor should then be aimed at the number one plug wire on the cap. Distributor is then dropped in and turned to fine tune the timing. You need a manual and/or someone to take you thru the process. Once you see it, you'll find it's incredibly simple. You need current from the battery to the bat side of the coil and then a small wire from the dist side of the coil to the dist. You can bypass an igition switch by using a jumper wire from the battery to the bat side of the coil and then crank the engine using a starter button either the one in the truck or one you make up and attach to the starter for this purpose.
NB: Some of these old trucks have a balast resistor that lowers the voltage from the battery to the distributor (to 9 volts?). I don't know too much about that as I have eliminated this on my truck but I'm guessing that if you have one, it's a white ceramic device located on the firewall and you would need to come off that with your jumper wire to the + side of the distributor if you are bypassing the ignition switch. Otherwise you might burn the points. Am I right about that guys?

Thanks for the help so far guys. I think I'm getting it. Just to get things straight before I try again: without any other wiring (no ignition), I have a connection from battery to starter, battery to coil, coil to distributor (condensor side), then the main insulated wire from the coil to distributor. I have a positive and negative side on the coil, so I assume everything runs from the positive side. Should I ground the coil? Do I ground the coil. I have the shop manual, but that just confuses me more. Please try and ignore my ignorance in the subject, I am learning on my own. Thanks again.

Adam

"I assume everything runs from the positive side"

Not quite.
1. Battery to "+" side of coil (through optional igntition switch)
2. "-" side of coil to side terminal on distributor.
3. Hi-tension (spark plug-style) wire from coil tower to center of distributor cap

The coil is grounded by being bolted to the engine.

The distributor is grounded by being bolted to the engine.

regards,
Leon

The coil is grounded to the engine. If the strap around the coil is secure, and the engine is grounded, the coil is grounded. The + will go to your battery, and the - will go to the distributor. It's a good idea to use an alligator clip, or jumper cable, from the battery to the coil. If you need to shut the engine down quickly, you can yank the wire loose easily.

In addition to basic hand tools, there are a few items that are very useful in working on most any vehicle. A simple test light (you ground the wire end and then touch the pointy end to the wire you want to test. If it's hot the lamp lights up), a service manual for your vehicle and a wiring diagram specifically for your vehicle. Put on your reading glasses and study the diagram, specifially the circuit you are working on and you will see how it is configured on paper. I don't know your particular truck and it may have cloth covered wiring which makes it a challenge to recognize wire colors but it's a place to start. Once you get the engine to fire, it may run poorly owing to the poor adjustment of the timing. Be careful because a misfire can cause a backfire that can cause fuel in the carburator to ignite. You'll want to disconnect your jumper as the above bolter stated. Oh yeah, you probably want to extinquish the fire too. Good luck!

Thanks again guys. One last question before I make the attempt: do I connect the - wire that runs from the coil to the terminal side that's connected to the condensor wire? Another stupid question, but let me know please, I am ready to fire it up.

Adam

Yes, the - side of the coil connects to the wire on the distributor that leads to the points/condensor.

Thanks again! I'll give it a shot and let you know.

Adam

So far nothing. I have a voltage regulator that reads voltage from the coil to the distributor and I'm even picking up voltage on the points, but still no spark from the plugs. What can I do next????????

I meant I have a voltage reader, not regulator. Sorry.

You need to see if you are getting a spark from the coil. Pull the coil wire(big center wire) from the distributor, but leave the other end plugged into the coil. Crank the engine while holding the wire about 1/4 inch away from the block itself. Hold the wire with insulated pliers, or you will get a jolt. You should see a spark jumping between the wire and the engine. You can crank the engine from under the hood by using a long screwdriver to press the button on the starter down. Please be sure it's out of gear before trying to crank it from under the hood.

I'll give that a shot right now and let you know. Thanks.

It might help for you to understand a little about how an ignition system works. Here's a diagram that shows the basics of a points-type ignition system as well as providing an explanation of how it works.

Here's how a points-type ignition system works. 12V from the battery (or 6v in the older systems) is connected to the distributor (usually through a connection on the side) so that it passes through the points. The other side of the points is connected to the plus side of the coil. The coil is then grounded, usually by a wire connected to the coil's negative terminal and to the coil's mounting strap, which is bolted to the engine and therefore grounded. When the points are closed, current travels through the points and the coil to ground. The current flowing through the coil creates a magnetic field around the coil. When the points are open, the circuit is interrupted and no current flows. When the current stops, the magnetic field collapses.

The on and off fluctuation of current is controlled by a cam in the distributor that the points "ride" on. At each high point (there are six for a six cylinder engine and eight for an eight cylinder engine, and so forth) on the cam, the points are opened and current stops flowing. This causes the magnetic field in the coil to collapse and that collapse generates a very high voltage spike (10 to 20,000 volts on older systems, 60,000 volts on newer ones.) The voltage spike is then transmitted from the center tower of the coil through its "coil wire" back to the distributor.

The high voltage spike then travels through the center terminal of the distributor to the rotor, which then transmits that spike to one spark plug terminal depending on the rotor's location at that moment.

So, the first thing to do is ensure that you have 12v on the coil side of the points with the points closed. (The easiest way to do that is connect your voltmeter to the plus terminal of the coil, but keep in mind that the wire between the points and the coil could be broken or defective.) Then manually open the points, and that voltage should go away. If it does, the points are functioning properly electrically. (You could still have a mechanical problem.)

The next step is to leave the voltmeter right there, set it to the lowest range that's still above 12V and have someone crank the engine briefly while you watch the meter. If it goes up and down rhythmically, then the points are working mechanically as well. (You could still have problems with timing or dwell or sticking points throwing off the timing.)

Once you've confirmed that the ignition's primary circuit is working as expected (but adjustments may still be needed to tune the engine properly), move on to the secondary system.

Pull the center wire from the distributor cap and hold it with an insulated tool. Put the metal shaft of a screwdriver in the middle post of the distributor and hold the coil wire close to the screwdriver's metal shaft. Watch it while someone cranks the engine. Is there a spark? If so, the coil is working and so is the coil wire. (It may still be too weak to start the engine.) Is the spark strong? Does it make a snapping noise? If so, the coil is probably good. If not, then either the coil or the coil wire probably needs to be replaced.

Replace the coil wire in the center terminal of the distributor cap and remove one of the outer spark plug wires and repeat the same test. Is there a spark? If so, the mechanics of the rotor-cap system are working. (But they still may not be providing enough spark.) Is the spark as strong as it was at the coil wire? If not, replace the cap and rotor. If it is, the secondary system is working up to the spark plug wires.

Repeat the same test with one spark plug - remove the wire, holding it with an insulated tool, and hold it close to the plug. Is there a spark? Is it strong? Does it snap loudly? If so, the entire ignition system is working correctly electrically. If not, replace your spark plug wires.

Next, remove a spark plug. Connect the plug wire to the plug and hold (always with an insulated tool!) the spark plug tip against the engine (touching the engine.) Is there a spark across the gap of the plug? If so, your plugs are probably good.

Once you've done that, what's left is timing (is the distributor installed correctly so that's firing on the right cylinders? Is the timing close enough that the plugs can ignite the fuel?) and dwell (Is the gap in the points set correctly? Are the points opening correctly mechanically? Is the cam on the distributor worn? Are the points "hanging" or getting stuck?)

1-5-3-6-2-4

Success!!! The engine sputtered and spit for a second, then quit. White smoke came out of the carb too. My next question is the carb. There is always a good amount of gas sitting at the bottom of the heads when I look down the carb. When I pull on the throttle, a healthy amount of gas squirts out into the body. I guess my question is with the adjustment screw. Currently I have the screw set at two 360 degree turns from being tight. I assume there's too much gas because it was blasted out of the top of the carb and it chokes out the engine when I crank it. So, what should the adjustment screw be set at and should I choke the engine when firing the first time. It's a rebuilt Rochester carb for the 46. Thanks for all the help so far guys and don't give up on me just yet!

Adam

Actually I believe the coil is grounded in two places. First through the points when they close. The path goes through the distributor body to the engine block, then through a motor or transmission mount bolt or a strap to the frame then through another strap to the battery. Secondly the coil is grounded through the spark plugs when its field collapses. The outside body of the coil should not be carrying any current to the block.

You are correct, Sir. Thank you for the clarification.

The screw in the side of the throttle body is the idle mixture screw. You shoul hand tighten it to bottom and then back it of 1 1/2 turns. When the engine is running it is adjusted for a smooth idle.

I don't know what you mean by gas sitiing on the "heads" but unused gas tends to leak out aroun the throttle pivot.

Now is the time to move the timing ever so slightly. I would try a very small clockwise rotation first. This would give less advance.

Good luck and please let us know how it goes.