I'm not exactly sure what the procedure is but I have a motor out of a parts vehicle that was running when wrecked about 14 months ago. I'm short on time so I thought I would try something. I removed all spark plugs and hooked up my Bosch drill to the crank bolt and turned the engine over at around 1000 rpm. Well at least that's what the drill will do in low. May have only been 500, not sure. I get zero compression on all cylinders. I tried with an air ratchet too. Am I doing something wrong or did the head gasket dry up and shrivel away just sitting? Short of remounting the tranny, starter, and hooking up a battery, is there another way to check like maybe a mighty vac?

-Adam

I think It need to spin faster I'v herd about 1200 rpm

I doubt if the drill could turn it over fast enough. I'm sure the motor is considerably smaller than the one in the starter. Could you fit the starter and spin it over using that on a set of jump leads or similar? I don't think that you have to refit the tranny but you would need to use a nut and bolt to hold the starter in place.

You should only remove one spark plug at a time when checking compression.   I believe it is so you will show compression when there is a leak between cylinders, but I'm not positive.  Just always been told that is one of the rules. 

My compression test kit says to remove all the plugs....

I'll try again tomorrow when I get home from work. It seems that if the starter turning over the engine would be fast enough, you wouldn't have to get it up to 1200 r.p.m. since the starter doesn't move an engine that fast. Or does it? I'll try hooking up the starter but it seems like it bolts to the transmission. Maybe I need to squirt some oil into the cylinders since it's been sitting so long?

-Adam

I'll try again tomorrow when I get home from work. It seems that if the starter turning over the engine would be fast enough, you wouldn't have to get it up to 1200 r.p.m. since the starter doesn't move an engine that fast. Or does it? I'll try hooking up the starter but it seems like it bolts to the transmission. Maybe I need to squirt some oil into the cylinders since it's been sitting so long?

-Adam

You have to spin it fast enough to get the gasses moving properly. If you don't you lose a lot of compression due to the valve overlap.

if you watch your tach yes the starter does reach 1200 RPM. the drill may do the same but not with a load on it. Make sure you have the throttle open as well.

I guess I'll try tomorrow with just hooking up a tranny,starter and battery unless I can hook the starter up without the tranny. My other option is to take a treadmill motor I have hooked up to a circuit for a wood lathe (another hobby I wish I had more time for) or what ever.  Its close to 2 1/2 horse power and can reach speeds of 6000 r.p.m. I had a friend wire it up to a variable speed so I can try running it slow and increase the speed. It's a long shot and it may end up being easier to just put the tranny back on.

-Adam

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You don't have to do anywhere near 1200 RPMs for a compression test.  When I tested my Dad's sidekick a few weeks ago, you could count the compression strokes by watching the needle movement on the gauge.  When you run the starter, you can distinctly hear each stroke.  My test set manual says to run the starter and count 7 or 8 strokes and note the increase between each stroke.

One thing I might ask is whether or not your compression test set has the pressure hold (schrader) valve...  My set does.  I could see you having to runn at 1200RPM's to maintain a gauge reading if your set doesn't hold the reading.

K rules are like this, remove all the spark plugs so it spins over easily. with the throttle wide open and a good battery(or on a charger to keep all readings the same if Batt is weak) spin it over and record the first puff. then spin it again and record what the final compression is, shouldn't take more than four compression cycles (watch the needle jump). Remove the tester drop a few drops of oil in and re spin.

Results as follows:
If the first puff is less than 80% of top compression than the motor is less than healthy,
if all are low but oil squirts bring readings up then rings are toast
If oil doesn't bring the readings up check for internal damage (valves, head gasket)
this is especially true in two adjacent cylenders but you already knew that.

More effective and with out having to spin over is a leak down test
it's a pressurizing spark plug end that will tell you where the leak is going to.
rotate the motor to Bottom Dead Center of the intake cycle, (valves closed)
And see how long it takes to lose pressure. then go and find the leak.
If it bubbles at the Radiator the head gasket is gone
If you can hear it at the valve cover it's rings or a cracked head or cylinder.
check at the tail pipe for sound and the intake plenum and you will find bad valves

Other than that when buying a JY motor smell it to see if the oil was burnt out and if there are any metal bits in the oil.

By the way try disconnecting the coil and running the starter, I doubt it will spin the motor to 1,200 rpm   more like 300-600                                                                              NMc

Thanks for the replys.

Remember, the engine is out of the vehicle so it's not hooked to a tach or anything. As we speak, it's up to $81.00 on ebay. I'm not sure what it's worth but a guy a few hundred miles away that makes it up this way occasionally might be willing to pay up to $300.00 depending on it's compression test. I thought it would be worth testing it to find out if I can. I'm going out to try again now.


-Adam