It is a simple as google "compression test"

,,, Philip

 

Yeah, I'm familiar with a compression test, and Google too.

Just now sure how a compression test relates to checking timing, and how the F1 fuse is involved. I understand that if the valves aren't closed, the compression will be low or non-existent. I'm curious how the pressure reading will tell me how far off the timing is.

Or is this test just going to tell me if the timing is or is not off. That's more of the kind of thing I was curious about, not necessarily procedures.

When you did your timing belt, did you remove the center 17mm crank pulley bolt (not needed to do, but some do this by accident).

I did not remove the timing gear from the crank, just the 5 smaller pulley bolts. The timing gear is as it came from the factory.

I will test the compression tonight.

 

When you did your timing belt, did you remove the center 17mm crank pulley bolt (not needed to do, but some do this by accident). And if you did, before you do anything else, you need to confirm that this bolt is torqued to 94ft/lbs. Early FSM's give the wrong torque for this bolt, and if too loose, the keyway can shear. So I would check that.
And if all is well as above, then yes, the compression test is needed. Your engine should pull about 150psi on a stone cold engine, or more like 170psi on an engine that has been started that day. Take all the plugs out, remove the F1 fuse, and floor the gas pedal when you're cranking. Post your results.....

 

Aqua & Bex are giving you good info. FI use is removed to disconnect FUEL (no fires allowed). If crank & cam timing gears are off, compression will be affected. Bex noted the 17mm crank bolt, as many loosen it, believing it needed to remove for crankshaft pulley removal (not timing gear) and never re-torqued the bolt to specs, resulting in crank timing gear/crankshaft/woodruff key wear. When doing your compression test, remove all spark plugs, disconnect the distributor, and have a fully charged battery. I like to leave a charger on the battery during the procedure. Good luck & always have a fire extinguisher handy.

 

Compression test results as follows:
Cylinder 1: 110 psi
#2: 122 psi
#3: 120 psi
#4: 130 psi

 

That's terrible. You may want to check timing belt/gears orientation & adjust valves; retry compression test.

 

All I can say, if your engine runs fine with the posted compression numbers, you may want to check you methodology.

 

Your 8v engine should pull about 150psi on all cylinders, on a stone cold engine and 170 at least, on one that's been driven that day. Confirm that all your plugs were removed, and that you floored the gas pedal while cranking - flooring the pedal will bring the compression up about 20psi, which still puts you out of range. Another thing to check is that there are two marks on the cam pulley - the E and the I (or 60 and 80) mark - you should use the E or 60 mark, depending on which you have. Your timing is way off - and frankly, if you advise that this is what the compression was initially, then just wait til you see how much better the engine runs when the compression is where it should be. You should check your valve lash, as well.
You may also want to confirm that the throttle position sensor is calibrated properly, and there are no dead spots on it. But that compression is problematic.

 

Your symptoms are classics signs of incorrect camshaft timing, have you checked the crankshaft keyway?

 

It it as simple as looking to make sure it hasn't sheared? Does it require unbolting the crank gear?

 

I did remove all of the plugs and mash the accelerator. Is it possible the Samurai starter isn't capable of cranking as fast as the Tracker starter, so it would give lower pressure readings?

There are no letters at all on the cam great, just a mark and a dot.

As far as adjusting the valves, will I be alright going with the procedure in the Haynes manual? I didn't find much in searching the forums.

Thanks again for the help; this thing has me so frustrated.

 

Yes, you have to take off the crank gear to look at the woodruff key and the crank snout to see if it isn't damaged. And I wouldn't go with the Haynes manual for much, on this car. Tons of misinformation. Better to search the forum, or ask. I would check the crank keyway, before you did anything else, just to be sure.

Edit: And if you find that all is ok, but SURE to torque that 17mm bolt to 94ft/lbs.....

 

Just a quick update:
Not much new. I wanted to verify you guys noted I am cranking this over with a Samurai starter rather than a Tracker starter. And also I'm at 5,075 feet here, so that impacts the pressure a bit.

Okay, thanks!!

 

And also I'm at 5,075 feet here, so that impacts the pressure a bit.

You are correct, ambient air pressure at 5000' would be 12.228psi (14.7psi at sea level), but that would have absolutely no bearing on the pressure inside a closed vessel (cylinder), The only affect would be that the crank would have to rotate an additions couple of turn to max the pressure at 170psi...

Good try, now perform the required diagnostic steps.

... Philip

 

Good try, now perform the required diagnostic steps.

... Philip

Good one.....

 

You are correct, ambient air pressure at 5000' would be 12.228psi (14.7psi at sea level), but that would have absolutely no bearing on the pressure inside a closed vessel (cylinder),
... Philip

Actually it will have an effect. If you get 170 PSI at sea level then, using your figures, you would expect 141.4 PSI at 5000 ft.

 

Science, yo!
Sorry, too much Big Bang Theory.

If elevation (altitude) didn't have an effect on closed cylinders, they wouldn't have to pressurize aircraft; they could just close the sealed doors and call it good, right?

 

I have been filling scuba tanks with 80cf of air for 50yrs, at all altitudes, the working pressure is 3200psi.. I just takes longer at altitude than at sea level..

The ambient air pressure has no bearing on the final pressure in the closed container... You still need to get the 170psi on your test..

.... Philip

 

I'm sorry, but that's incorrect.

A crude scale is as follows

Altitude Factor
1000 .9711
2000 .9428
3000 .9151
4000 .8881
5000 .8617
6000 .8359
7000 .8106
8000 .7860

While the pressure may be 'the same', the air compressor (engine cylinder) has a maximum it is capable of attaining. That maximum (170 psi) changes with atmosphere.

So the scuba tank compressor has a much higher maximum. It can achieve the needed pressure easily, and does so at sea level. It does so less easily at higher elevation, so it takes longer, where as a weaker compressor taps out.

 

Regardless...still working on the issue. The crank gear did not slip / the woodruff key didn't shear. I put it back together and torqued to 94 ft lbs.

Still looking for the valve lash check procedure so I don't have to use the Haynes manual.

 

OK, found valve adjustment procedure. Valves were a bit tight, but probably within range I suppose. Adjusted, redid compression test, no substantial changes.

 

Just to confirm, lash on all should be .006 on a cold engine....???

 

I know this is elementary, but double check your spark plug wires are on the correct order. I got a tracker dirt cheap cuz the PO couldn't figure out his sluggish issue; he put the spark wires on in the wrong order.

 

ANY SOLUTIONS TO THIS PROBLEM?

As I am battling the same problem.

Checked, checked, and rechecked everything. All seems to be installed and adjusted correctly, but engine still runs rough at idle, and is sluggish.