Crawler OC3 won't Start . Timing And compression questi

My Name is Alex and I am trying to help my father-in-law get his Crawler going and have some questions that hope you can help.

It is and OC3 with an XB4000 distributor. Found the distributor bad. Changed the coil and condesor per spec and it worked and is spark is seen on all 4 plugs. Followed the Zimmerman tech tips about timing. Believe I got that correct.
When I didn't get compression on #1 with the thumb over the plug hole I got a gage and found that a hand crack yielded no pressure but a rev or two with the starter yield 30 lbs.

Occasionally I will get a back fire through the carb...but nothing that sounds like starting.

Should I go after timing or compression?
I read a post that talked about filling the pistons up with ATF and soaking for a week. Wasn't sure I understand how to do that and then how to get it out.

Seems like a have spark, tried starting fluid, inthink I have timing... other then an occasional smoke out the exhaust... I have nothing to show for it. Any help would be greatly appreciated.

30PSI is way to low for it to run. As for the ATF that is simple pull a plug at a time and pour ATF into the spark plug hole. Put the plug back in and move to the next plug. Then after a week pull ALL the plugs but make sure to keep track of them for the firing order. Spin it over with the starter and using 12 volts is best. Yes it will make a mess but unless you can figure out a way to put a hose in each plug hole that is pretty much the only way to do it. BTDT many times and even on an OC3 I had a few years back

Valves could be stuck as well.

I agree with checking the valves. Make sure they're all gaped right and are working. If not pull the head.

Check for stuck valves. Valve-in-block engines have a tendency to stick when left unused for a period of time. Those engines are tough little buggers
though. Had an OC3 on the farm years back. Used it for pulling a spray rig when nothing else could get on the field(muck farming). The operator would
wind the little Hercules up and let 'er go across the field. Very rarely would the machine get stuck. You could hear the straight-pipe exhaust bark
from quite a distance!

An OC3 engine is going to need all 4 cylinders to be functional. My family owned one for 30 years. Doing an informal cylinder leak down test is easy
and will diagnose the problem. The process can use your compression gauge adapter to work. (this assumes you have, or access to, an air compressor)
the piston in #1 cylinder should be positioned at TDC compression. Put the transmission in high gear, and rope back the track brakes to prevent
motion. Open the throttle, and make sure the choke is not on. Apply 100 PSI or more to the spark plug hole. The entering air will leak out of the
cylinder through the fault causing the low compression. Listening in the muffler, intake to the carb (remove the rubber hose is best to hear), and oil
breather.
If air from exhaust, it is the exhaust valve, if from the carb opening, an intake valve, if from the breather, it is past the rings. This allows
knowledge to be ahead of teardown/repair. Stuck valves or valves with a chip of carbon under them can be assessed by removing the cover over the
lifters on the side of the engine. With the #1 at TDC both valve clearances should be near specification. If one is near zero clearance it is likely
a burnt valve. If it is a wide gap it could be carbon holding the valve open. Jim

Thank you very much. I really appreciate your help and time.
Does the ATF give a temporary compression solution just to let one know where to spend more time or does the soaking take care of some problems?

Thanks again

Thank you for helping . I am going to look into that for sure. Thanks for reach out and helping.

Thank you Sir. I appreciate your help and will check on it.

Thank you sir. I will look into it. I haven't heard it run yet... but I will be sure to where ear plugs. Thanks

Janicholson
Thanks for your help and that detailed information. I am going to do as well.
May I ask.... you mention the 3 points the compressed air could travel.
Exhaust (exhaust valve), carb opening (intake) and breather ( piston Rings)
It's the breather I had a question about. The breather attached to the carb opening? It seems like the same location... am I mistaken?


I assume you would then TDC cylinder No.2,3,4 and listen for the same things and take note.

Thanks again.

I am new to the forum so I thought my many thanks yous were to each off you individually.

I just wanted to express my genuine gratitude for your help.

I once read book that said "great people share information and are interested in helping others to be better and to succeed"

Thanks.. you guys are great people.

ATF frees up sticking rings and valve so the compression goes up and stay up unless it is then parked for years again.

Air cleaner is an oil bath type and yes the tube going to the air intake of the carb come off the air cleaner and if it is clogged up or the oil cup is full of mud and water it will cause problems

Did you test compression wet and dry? Put a little oil in cylinder and recheck.if it's the rings compression should rise. Regardless if it has sat for long soaking the rings with oil is a good place to start.

No sir. I did not do a wet and dry test but I will today before I follow the recommendations you gentlemen have suggested. Thanks

Firing order is 1243 , I got that mixed up