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I have a '96 Civic, SOHC engine. Son in law said it started, ran rough. He tried to drive it. It got about a half mile and quit.

I was checking it for no spark, but noticed the compression is not right. Here are the results of a compression test:

1 - 150
2 - 50
3 - 30
4 - 10

Does this sound like a head gasket? I never saw compression drop off like this over multiple cylinders.

The cam sprocket lines up properly when cylinder one is at TDC.

This is my first Civic, so I am on unfamiliar territory here.

What should I do?

Thanks.

 
Rep Power: 154

Did you rotate the motor so each cylinder was at TDC when you performed the test? 10% compression ... the piston should be missing with that much loss.

 
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I pulled all spark plugs out and cranked it 4 compression strokes for each cylinder.

Before I did it this time, I checked and reset the valve clearances, to make sure they were right.

Putting the engine at TDC on cylinder one, the cam sprocket had "Up" at the top and the marks on the sprocket aligned correctly with the top of the head.

The thing is, I can't tighten the compression gauge down as tightly as I would like, since the plug hole is at the bottom of the tube. It has an O ring and I tighten it down as much as I can. I epoxied the swivel in the hose so I can tighten it down better and still be able to get it back out.

I had the same values before I readjusted the valves, though.

 
Rep Power: 517

That made no sense to me.

4 hits is not enough. Crank it until the gauge is maxxed out then keep cranking it a few more hits just to be sure.

Also use a battery charger so it cranks the same speed for each cylinder. A drained battery and cranking speed that gets slower and slower may cause decreasing numbers like you have.

So might flooding.

If all 4 plugs are out I think that would negate readings declining due to clogged exhaust.


Beg, borrow or steal a different or better gauge set?

 
Rep Power: 154

Hahahaha, my bad, Was envisioning it in my head and was totally thinking of a leak down test.

 
Rep Power: 209

I purchased one of these: http://www.harborfreight.com/compres...-pc-69885.html for a recent compression test and it fit and worked fine. I used the screw-in connector not the rubber stopper type.. just don't over tighten it.

Here's a good vid to follow:

 
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I think I figured it out. I had not shut off the fuel supply and I cranked it so much, I think it washed the oil off of the cylinder walls. I pulled the fuse for the fuel injection, poured some oil down the spark plug holes and did a new compression test. The compression went back up to normal.

The fuse I pulled was in the engine compartment. It is labeled FI E/M. Is that the proper way to shut off the fuel supply? Will that fuse affect the ignition?

Thanks a lot.

 
Rep Power: 517

I figured that might have been a possibility:


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If that got it right again then I would not worry about it.


The thing I worry about on these is pushing an already weak ignition coil "over the edge" by having the plug wires off while cranking it for the tests.

So if you now have no spark since you did the compression test, that's a first item to check.

(I try to crank distributor engines using a jumper wire at the starter, that way the fuel and ignition are never powered up.)

 
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I was originally investigating a no spark condition. I got sidetracked with this compression thing.

I had the ignition module checked and it tested good.

Voltage is going to the ignition coil and module.

The primary resistance on the coil is .8. It should be .6 - .8

Secondary resistance is around 10.8k measured to each primary connector. It should be 12.8k - 19.2k.

So it sounds like the coil.

One other thing to clear up first. The fuse labeled "Backup radio" is blown. I see warnings to keep the battery connected to prevent the anti theft system from activating. The previous owner replaced the radio, but she told me the original radio is still up under the dash somewhere because things would not work if they disconnected it.

Could that cause a no spark condition?

Thanks.

 
Rep Power: 517

The coil resistance checks are not of value in this situation, you will not find the problem.

The problem is a breach of insulation to a nearby ground through the side of the windings. The coil still works right electrically, but the spark found a path to ground that was easier to reach than the rest of the ignition parts.

If you do a spark check (grounded screwdriver) right at the tip of the coil tower you would probably be able to get a spark that can jump a gap of 1/32"-1/8" and not much more.....
.... and the coil needs to be able to produce a spark that will jump a 1/2 inch gap.

So...if the coil can make ANY visible spark at all, then the igniter and all its controls are working and the coil is bad.



You could also use an old dwell meter to check for electrical activity on the negative trigger side (points side to us old timers), any reading other than zero or 90 means the igniter is trying to fire the coil.
3-5 degrees of dwell while cranking is common to see.


Once you get the coil removed from the distributor, peel off the metal shield (if equipped) from the side of the coil and you may find a discolored spot where the sparks were leaking through the side of the windings.


No. The original radio was probably left in the dash so the dome lights and keyless could still operate.
Fix the blown fuse though.

 
Rep Power: 0

Boy, you nailed it!

Thanks a lot.