Car cranks but doesn't fire

[Michael L.]

Guys,

I'm trying to start my rebuilt 69 350 L46. I dyno'd the engine three years ago and it ran flawlessly. I then installed it and restored the rest of the car. I'm finally ready to start it but now it cranks and won't fire. I'm getting 12V at the coil and there is gas in the carb. It was timed on the dyno and the dizzy was tightened at that time. The fuel system is entirely new with fresh gas. What am I missing?

Mike

[Michael L.]

Re: Car cranks but doesn't fire

I checked the gap on the points and it seemed off so I reset them. It still doesn't get any spark tho. What are some of the things that can keep the dizzy from firing on a corvette? As I said I'm getting 12V at the coil.

[Larry E.]

Re: Car cranks but doesn't fire

Michael:This came up in a thread not long ago. Thinking your problem could be an internal leak in the carb. The fuel bowl is
getting MT somehow. Could be the gasket at the power valve or leaking down the intake manifold. At any rate next time put
some gas in the vent tube in the front top of carb and then try starting it. Larry

[Stephen L.]

Re: Car cranks but doesn't fire

Pull a spark plug wire off a plug. Hold the wire near a ground point such as a bolt head. Crank the engine and see if there is spark. (Note: this will be coil output voltage so be careful not to hold the wire too close to the end. It can be a real jolt....) If you have spark, pull a plug to see if it is wet from excess fuel. If the plug is dry, check to see if you have a "squirt" of fuel from the accel pump in the carb when the accelerator is pressed.

Did you mess with anything in the firing order, plug wires, coil etc. after the dyno run, while installing the engine in the car?

Did you check the points with a dwell meter (28-32 degrees)

[Michael L.]

[Larry M.]

Re: Car cranks but doesn't fire

Put a 12 volt test bulb on the coil negative (-) terminal with other test lead to a good engine ground. When cranking car with starter see if test bulb flashes as points open and close. Flashing = good. No flashing = coil will not fire to the distributor and plugs.

During cranking, 12 volts to the coil is supplied from the starter solenoid. This provides a hot spark. When starter stops turning (key goes from START to RUN position), 12 volt power is provided to the coil thru the ballast resistor and thru the normal ignition circuit wiring. The coil (+) positive terminal should have two wires going to it. Both are needed for proper ignition

Distributor points could be corroded/glazed and not functioning correctly, or distributor condenser could be grounded, or the ground wire inside the distributor not connected or broken. Wire from starter solenoid could not we wired correctly to the coil.

There could be other issues as well..........but I provided a few to get you going.

Larry

[Bill M.]

Re: Car cranks but doesn't fire

Mike went crazy for a week one time trying to get a basket case running that i bought. Like larry said the condenser wire was not conected to the coondenser. Could not tell until we touched it. good luck

[Terry D.]

Re: Car cranks but doesn't fire

Could be a bad condensor, that will cause this

[Patrick H.]

Re: Car cranks but doesn't fire

Could be condenser.
You think the points are set correctly.
Did you reinstall the rotor? I forgot that once. Duh.
Cap is securely installed?
Coil is working?
All wires connected, including coil-to-distributor wire nice and tight?

[Michael L.]

Re: Car cranks but doesn't fire

I can change the points and condenser just to be sure. Maybe I'll go with a Pertronix set up. FYI I checked the points when the car wouldn't start and they were not moving so I reset them with a feeler gauge. Yes the rotor is installed and cap is secure and all wires appear connected. Yes the + side of the coil has both wires to it. I'll try the test bulb on the negative of the coil and see what that does. I'll also try a spare wire and plug to see if the timing light is just not working. Can I use a dwell meter to set the dwell with the car only cranking like I do with the timing?

[Larry M.]

Re: Car cranks but doesn't fire

Yes..............

Larry

[Stephen L.]

Re: Car cranks but doesn't fire

How can you set the timing with a light when the engine isn't running? Remember, the crank shaft rotates twice for one rotation of the distributor.
A very simple check to see if you have spark (as I explained earlier) is to remove the high voltage COIL wire from the distributor cap (leave it connected to the coil) and hold it close to a ground point. Then crank the engine with the starter and observe if there is spark or not. Now connect your dwell meter to the coil "neg" and ground and set the dwell using the allen wrench and the "window" on the Distributor cap for 28-32 deg.
If you have spark and the dwell is set correctly then you probably have a timing problem.... Observe the location of the rotor relative to #1 plug in the cap when the timing mark is set to TDC on the crank pulley. If it is close (NOT 180 degrees off) then try to start the engine while moving the entire distributor a few degrees in either direction until it fires. Once it starts then you can adjust the timing to spec. Recheck the dwell.
If the rotor is 180 degree off then you were not at TDC or the distributor was install incorrectly. Unfortunately a Chevrolet distributor can be installed in multiple locations due to the drive gear. It is easy to install wrong and be 1 tooth off on the gear when you drop the distributor into position......

[Michael L.]

Re: Car cranks but doesn't fire

How can you set the timing with a light when the engine isn't running? Remember, the crank shaft rotates twice for one rotation of the distributor.
A very simple check to see if you have spark (as I explained earlier) is to remove the high voltage COIL wire from the distributor cap (leave it connected to the coil) and hold it close to a ground point. Then crank the engine with the starter and observe if there is spark or not. Now connect your dwell meter to the coil "neg" and ground and set the dwell using the allen wrench and the "window" on the Distributor cap for 28-32 deg.
If you have spark and the dwell is set correctly then you probably have a timing problem.... Observe the location of the rotor relative to #1 plug in the cap when the timing mark is set to TDC on the crank pulley. If it is close (NOT 180 degrees off) then try to start the engine while moving the entire distributor a few degrees in either direction until it fires. Once it starts then you can adjust the timing to spec. Recheck the dwell.
If the rotor is 180 degree off then you were not at TDC or the distributor was install incorrectly. Unfortunately a Chevrolet distributor can be installed in multiple locations due to the drive gear. It is easy to install wrong and be 1 tooth off on the gear when you drop the distributor into position......

Sorry I just saw this post. I set the timing on the car when it was dyno'd three years ago. I can't think of anything that could happen to alter the timing since I ran the engine. Of course if all else fails I'll start looking at all possibilities but right now I'm not thinking it could be timing.

[William F.]

Re: Car cranks but doesn't fire

please explain the significance of distributor "being one tooth off." I understand how this could keep you from rotating distributor as needed for advance- vac can could hit intake, but as long as rotor is pointing toward number one wire in cap with number one cylinder at TDC, wouldn't seem to give false timing reading.

[Stephen L.]

Re: Car cranks but doesn't fire

You stated it. You may NOT get full rotation and thus not reach correct timing due to the interference. If you are happy with your distributor not correctly installed then go for it. I personally like to install it as designed.