18.5 starter will not turn pass compression stroke

did you check the valve train- head to make sure no damage to valves or push rods if their good than need to recheck timing chain

Remove the number one spark plug. Put a gauge in the hole. Top dead center is on the compression stroke when the piston reaches the top of the stroke. When you see the gauge begin to move, remove it and put a straight piece of wire in the hole. Turn the crankshaft clockwise by hand/wrench till the wire comes up and then starts to go down. When it goes down, you just passed TDC. Back it up a bit until you are comfortable with it being at TDC.

5.9 aren't prone to this, But pull the distributor cap. Have someone crank the engine and watch to see if the rotor moves. Also put the number one piston on top dead center on the compression stroke (remove the spark plug to check compression side). See where the rotor sets compared to a diagram At top dead center.. Sounds like the chain broke (unlikely) or jumped.

Right, so you have two TDC's-the exhaust stroke and the compression stroke Top Dead Center-and both occurr when the crank hits the zero mark on the timing scale.
Always set timing with the number one cylinder at TDC on the compression stroke. How do you know which is which? If you have a distributor, the rotor will be pointing to number one cylinder tower, when at TDC of the compression stroke. If you are on the exhaust stroke's TDC, the rotor will be pointing just opposite of number one .
If you don't have a distributor, look at the valves for cylinder one under the valve cover. If at TDC of compression stroke, both valves will be closed. At TDC of exhaust stroke, the exhaust valve will be open.
You can also find the compression stroke on number one by pulling out the spark plug for number one, and either put a wrench or socket on the crank pulley and turn it clockwise, or use the starter and bump the engine over in short bumps. Put your finger or thumb over the spark plug hole and feel for the pressure to build up. As soon as you feel pressure on your finger, (if turning by hand, pressure will be slight, but you can feel it) you are on the compression stroke. Stop bumping the starter and turn the crank on around by hand until the zero mark lines up on the timing scale-TDC of compression stroke! The exhaust stroke will have no pressure build-up as the piston comes to top-because the exhaust valve is open. On the compression stroke, both valves are closed as the piston travels up the cylinder.

#1 cylinder is at top dead center twice during a normal combustion cycle - once at the top of the compression stroke and once at the top of the exhaust stroke. To make sure you're coming up on the compression stroke, remove the #1 spark plug and hold your finger over the hole as you rotate the crankshaft. If you feel pressure, it's the right stroke. If you don't, continue for another complete revolution of the crankshaft.
Once you'e at TDC on the compression stroke, then insert your distributor with the rotor pointing at the #1 position (you may need to adjust the distributor drive shaft - lift it to disengage from the cam gear - to get the rotor pointing as close as possible to #1).

Check and see if you have spark if so then check and see if the safety switches are ok you might need to replace one

the wires to the plugs should not keep the motor from cranking over. If the battery is fully charged the ignition switch should engage the starter. If you think the firing order is wrong you need to determine 1 where is top dead center (the position the motor is in when #1 cylinder is at the top of the compression stroke). 2 what direction does the rotor turn 3 what is the firing order One way to make it easy to rotate the motor is to remove the spark plugs. no compression means no resistance to the starter so the motor should turn over with the key in the start position. If it won't crank over with the plugs out then something is wrong with the starter, battery, starter relay, or ignition switch. I always start with the basics. the battery should have at least 12.5 volts. if it does check the battery terminals. even if the starter is weak you should hear a click when the key is turned to the start position. Once you get the starter to turn over the motor you can tell when the number one cylinder is at top dead center by putting a finger over the spark hole as you crank over. You will feel the compression as the cylinder comes up on the compression stroke. I have used a large socket to slowly turn the motor over and when you are near top dead center you should be able to see the degrees of advance on the timing mark. Set the motor at top dead center then see where the rotor lines up with the wires on the distributor cap. that is where number one cylinder should fire. You then follow around in the direction that the rotor turns and the wires will corispond with the firing order. I always make a mark on the number one spot on the cap with a felt pen. That way you have a fixed reference point. Take care to verify that all the wires are to the proper plugs before trying to start. Take extra care at this point and make sure your firing order and rotor rotation are correct. I would triple check this. The firing order and rotor direction are usually somewhere on the autozone repair web site

Have the battery tested for a dead cell. It may test at 12 volts but that doesn't mean there isn't a dead cell. Also, if the motor has good compression you probably shouldn't be able to turn it over by hand at the fly wheel. Maybe an old school motor with V belt, but not a newer motor with all those accessories attached to the front.

Could very easily be so. Does this unit have points and condensers in it. Could be the timing chain wasn't timed properly when the cam gear was installed. Easy to check without having to take too much apart.

First of all, take the cover of the fly wheel and you should see a couple marks there. One may have an F and the other could be a T, align the T with the boss mark on the side of the engine that'll be right along the edge of the flywheel. When you find this, then take the cover of the top of the side of the engine and get access to the cam gear. There also you should see a mark but no letters, only a dent put there by the factory. If you locate that then locate the boss mark on the engine head itself. Now once you have determined all of this. Put a wrench on the bolt keeping the flywheel on usually it'll be a 17mm socket and turn the engine up on it compression stroke. Once at top dead center (when the piston is up as far as it'll go before starting to go down again) on the compression stroke (not the exhaust stroke) the mark on the flywheel with the T on it and the dent on the cam should align with the boss on the engine head. If it doesn't it's out of time. You have to remove the cam chain, then realign the cam gear until the dent lines up with the boss mark then re install the chain and make sure you don't have any slack after you re install. If they align your good to go. If not then you need to do it again. To determine the difference between top dead center on the compression stroke and TDC on the exhaust stroke, you'll need to remove both valve adjustment covers. One in front and one in back of the cylindere head. Turn the flywheel again with the wrench until you see the front valve open and close and then keep watching until the rear valve next to the carburetor come open and then close. Remove the spark plug and put a small straight screwdriver down in the plug hole and then gently continue to turn the flywheel bolt after the rear valve closes until you feel the screwdriver moving. Keep a very close watch on this. When the screwdriver won't go no higher and you notice it to start to go down a little, then turn it back a little until the piston can't go any higher, Now you have the compression stroke you'll need to align all the marks.

Good luck
Skidooer

Good luck
skidooer

Locat #1 cykinder, remove the spark plug, Put a piece of cleanex in the plug hole and bump the starter. When you blow the tissue out, your piston is on the compression stroke. bump the starter, not crank. If you go to far then go aroun again When the piston is in up stroke compression, hand thurn the crankshaft until the piston tops out and starts going down. back it up so you are on the upstroke agai. then forward again until you crest again. Look on yhe front crank pully for timing marks line them up when you have #1 near its top.. The cylinders are numbered oon the manifold. Good luck