Engine 304 backfire through the carb

[FFEH]

I have a 1973 CJ5 AMC 304 AMC manual Transmission . The tub is off and I am trying to get the engine to start. I am getting a backfire through the carburetor which suggests timing to me. I have the jeep at TDC and the picture #1 shows the picture I am using to get everything in the right place according to the picture. I noticed today that my rotor is not pointing to the distributor cap where I have the number one plug wire picture#2. My finger is on the #1 wire. This doesn't match the picture in relation to the cap screws. The rotor is pointing to the # 1 one spark plug. So I think I have the spark plug wires wrong. My question is should I put the plug wires as they are shown in the pic or is the cap orientation wrong to begin with? If you look close you can see the distributor cap screws are not in the same orientation as the picture. Thanks for any help.



Pic1 pic 2 pic 3

 

[TSB8C]

With the engine at TDC, put the #1 wire on the cap where the rotor is pointing, regardless of whether that is straight at the front as shown in the first pic or not. Then put the other wires in the proper firing order clockwise around the cap. If you really want the #1 wire to be where the pic shows (straight at the front) you may need to pull the distributor and rotate it a bit (a tooth or two on the gear) to achieve that alignment.

Also keep in mind that you could be 180 degrees out. That means while the #1 piston is at TDC, you may not be at the top of the compression stroke where the plug should fire. You may at the top of the exhaust stroke instead. With the #1 piston at TDC, where is the timing mark on the harmonic balancer? Is it at or near the zero mark also?

 

[trans builder]

that is correct. if the #1 piston is at TDC you can put #1 wire where the button is pointing on the cap and wire accordingly. if you want it where the rotor button is pointing at #1 on the cap the distributor will need to come out and dropped in so the button is pointing at #1 to ensure the engine is at TDC make sure your timing mark pointer is pointing at your mark on the harmonic balancer and the #1 piston is at the top. but was the engine running? what made it stop running?

 

[Turbogus]

Here's hoping it's a true backfire and not a stuck valve, that's wheat happened to my 360 in my CJ5

 

[1979GabeCJ5]

With the engine at TDC, put the #1 wire on the cap where the rotor is pointing, regardless of whether that is straight at the front as shown in the first pic or not. Then put the other wires in the proper firing order clockwise around the cap. If you really want the #1 wire to be where the pic shows (straight at the front) you may need to pull the distributor and rotate it a bit (a tooth or two on the gear) to achieve that alignment.

Also keep in mind that you could be 180 degrees out. That means while the #1 piston is at TDC, you may not be at the top of the compression stroke where the plug should fire. You may at the top of the exhaust stroke instead. With the #1 piston at TDC, where is the timing mark on the harmonic balancer? Is it at or near the zero mark also?

How would you fix that? If it’s at TDC of exhaust stroke?

 

[TSB8C]

You can confirm TDC on exhaust stroke vs. TDC on compression stroke by checking if the exhaust valve is open or not. Obviously TDC on compression stroke will have neither valve open on the #1 cylinder, whereas the exhaust valve will be open if you're at TDC on the exhaust stroke. Pop the valve cover to see or use a bent wire clothes hanger inserted into the spark plug hole (with the plug removed). If you're at TDC on the exhaust stroke when your distributor rotor is pointing at the number one wire location, then move the wires 1/2 way around the cap; or pull the distributor, rotate it 180 degrees, then re-install it.

Back to what "Transmission builder" asked - was the engine running before? What made it stop? Your original pics (cap on and you pointing to #1 wire and then cap off showing the rotor) show it about 90 degrees out (you're pointing at the wire at the front but the rotor is pointing down toward the driver side). Odd for a running engine to suddenly jump 90 degrees or more out. Normally worn gears (cam and distributor) might skip a tooth or two. Gotta skip more than that to get 90 or more degrees off. Your original post also stated you were getting backfire. That does usually indicate timing is off, but still somewhere in the vicinity. I recommend just confirming TDC on compression stroke, move the wires as needed for #1 wire to be wherever the rotor is pointing, then re-try starting again. If it starts, then of course you also need a timing light to get it all right.