compression check

[gandyrail]

So I bought this 1981 2000 last month, figuring out how its put together and finding all the PO sins; not that I wont make any
I fixed the massive oil leak (I hope I did) on the exhaust cam box, I want to drive it some this summer!
I took compression tests and the #'s look low to me.
I could use some input from people here on the forum. #'s are even, the odometer just turned 100K.
#1 Dry 105 Wet 115 #2 104 112
#3 Dry 104 Wet 115 #4 105 115
Are these in the normal compression range for the car, it sure seems low to me?
Gandyrail

[So Cal Mark]

little bit low. since you had the cam box off, I'd recheck the cam timing

[bradartigue]

Low but consistent - which is a good thing. Even wear. Spider 2000 engines were low compression to begin with, so any drop is significant. If it were mine I'd enjoy it until the weather turns. These blocks are super durable and with real even wear you're unlikely to have anything major going on, probably just needs rings, seals, gaskets, that sort of thing.

[gandyrail]

Thanks to both Brad and Mark.
What is the compression of a new factory motor - should I expect 150 psi with fresh rings and good valves?
Yes Mark the cam marks are dead on - had to do that belt twice to get it right, exhaust cam was off one tooth the first time but I can do that project again pretty easy now! I was happy and surprised to find the exhaust valves were still in adjustment

[TStark]

Pardon the inquiry, Did you have the throttle wo when measuring compression?

[gandyrail]

HM no never did anything with throttle
my tester screws in and I crank the engine about 5 times and record the reading
I put some clean chain lube oil in the spark plug hole about a teaspoon and do the same for a wet test
The FI is still injecting gas in the cylinder but I have always done it that way.
all the spark plugs are out when I do the test. a good compression gauge wont bleed off the highest reading

[wizard124]

I checked compression when I first brought mine home. They were 152-155 as I recall. Yours are way low.

I checked the same way you did. No oil added.

[aj81spider]

Measuring compression is subject to a lot of operator error and the quality of the gauge and all the fittings used. When I measured mine I got 120 on an engine that had a newly rebuilt bottom end and a newly rebuilt head. The measurements were consistent, so I didn't worry too much about the absolute value - especially knowing that the operator was prone to lots of error and knowing that I bought a cheap gauge.

If you're not burning oil I'd be happy they were consistent and not worry too much about the absolute value.

[TStark]

Throttle must he held open for a valid test.

[fiatfactory]

.

[baltobernie]

If you're not burning oil I'd be happy they were consistent and not worry too much about the absolute value.

+1

But if you're going to re-test, have battery fully charged; preferably attached to a booster/charger. Remove all spark plugs. Prop throttle open wide.

[bradartigue]

To test on an FI Spider:

Unplug the AFM (this disables the fuel pump, unless the switch is bypassed)
Remove the big air hose
Rotate the throttle and clamp it open, or use a block of wood to hold the plate open
Disconnnect coil from power
Remove plugs
Test

If you disconnect the AFM and the fuel pump still runs then it has been bypassed. While you are going to have to fix this eventually, don't focus on it now. Go under the car and unplug the fuel pump.