Low or No Compression 89 D50

Hello all,

I posted this in one of my old Threads, but thought I'd start a new one with the correct title. Can someone please assist me with this.


I finally got a compression tool and checked compression on the cylinders. Hopefully I did it right. I hooked it up and turn engine over and the readings I got are below.

1st Cylinder: 60psi
2nd Cylinder: maybe around 20
3rd Cylinder: maybe around 20
4th Cylinder: maybe less than 20

After letting the key go, they pressure immediately went to zero.

What does this mean?

was this done hot or cold? how long did you crank it? also try pouring a tablespoon of oil in the cylinder before cranking. Can't say for sure without that info, maybe bent valves. Which motor is it?

It is the one with the D in the Vin #. Guessing the small 4 cylinder. I did not pour oil in cylinder and I did not do it when engine was hot. The engine was cold when I performed the test.

ok u gotta give us a lil bit more information.. look under the hood on passenger side of the firewall and there should be a plate which indicates info on the truck along w/ the engine type fitted to ur truck.

It says: Engine: G63B

Kinda hard to make out as it is old.

ok that means u got the carb'd 2.0L SOHC 4-cyl.

what u wanna do next is do a leak down test, and like pennyman suggested pour a bit of oil in the cylinder before cranking it ovr to test compression. once u do that post the results here. oh btw, how did u perform the compression test initially?

Quote:

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Originally Posted by blessedguy

Hello all,

I posted this in one of my old Threads, but thought I'd start a new one with the correct title. Can someone please assist me with this.


I finally got a compression tool and checked compression on the cylinders. Hopefully I did it right. I hooked it up and turn engine over and the readings I got are below.

1st Cylinder: 60psi
2nd Cylinder: maybe around 20
3rd Cylinder: maybe around 20
4th Cylinder: maybe less than 20

After letting the key go, they pressure immediately went to zero.

What does this mean?

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if u did ur compression test properly, based on that statement u made it could be leaky valves or a torn up head gasket or worst case scenario its a cracked head.

just rented the tool, came home plugged it in each cylinder and turned engine over. engine was cold and I did not use any oil in the cylinders

With a leakdown test make sure you pay attention to where the leakage goes. The fact that it doesnt hold could be bent valves from a timing jump at some point. Usually rings will hold even when weak. I vote bad head gasket or warped head. If you hear it leak from the radiator cap it's that.

Quote:

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Originally Posted by blessedguy

just rented the tool, came home plugged it in each cylinder and turned engine over. engine was cold and I did not use any oil in the cylinders

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I'd suggest u perform a correct compression test again just to be sure...follow the simple steps below, which is how I does it :cool:

a proper compression test would require the following:
1. engine would have to be at the normal operating temp.
2. take all the spark plugs out
3. take out the fuel pump fuse so it disables the fuel system
4. block throttle wide open
5. connect compression tester to #1 spark plug hole
6. crank the engine over for at least 7-8 strokes
7. repeat step 5 & 6 for the other cylinders

now if u got low compression at first and gradually increases during the strokes that means ur rings are toast.. however, if u got low compression at first and it dont build up w/ each successive stroke as motor is turning over this indicates leaking valves, a blown head gasket or the head is toast. u can try a leak down test as I mentioned earlier for da heck of it to see if #s increase, but i doubt they will (if #s increase after u add a bit of oil, ur rings are def. gone) sooo based on the symptoms u described and the #s u came up w/ I'd say its either 1) leaky valve seals or bent/cracked valves, 2) head gasket, or worst 3) cracked/warped head...

hope this helps.

If you go to Pep Boys they will loan you the tool for free. Put down a deposit, get it back. In the end of the tool, that sticks in the spark plug hole. You should see something like a tire valve core. When cranking it should hold pressure in the tool so you will see the compression build up in the gage. Does it sound like the engine is just free spinning when cranking? You could also pull the valve cover and redo the test. This way you can check the valve train over. But it sounds like there is something bad going on inside.

It should look something like this.

Attachment 4630

Not this. This is a CLT or compression leek tester.

Attachment 4631

Hope you get the issue worked out