Lowest compression reading on a cold engine?

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Neondont_play
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Lowest compression reading on a cold engine?

Post by Neondont_play » Sun Dec 14, 2014 11:48 pm

So, I did some work on a power steering pump, serpentine belt and tensioner. when I was all finished up, the car does not start. I am worried it might be the timing or possibly a rod. It has had what I thought was lifter tick for the longest time but still ran fine. I started it up not long ago and it was very loud but went away shortly after, and a few starts later from that time it just cranks but wont start. I have checked and it does get spark. So I'm kinda worried that the sound I heard was valves bending or something.

Now I know a compression test should be done on a warm engine but in my case it wont start. My readings are 65-70 across the board...That seems really low, but on a cold engine, what is considered too low? Not sure if this would have anything to do with it, but I also replaced valve cover gasket/gromets, and had to clean out flooded oil in the spark plug tubes and then hammer them back down into place because they were coming up and letting oil fill around the plugs. That was AFTER the starting issue though, and I did not let any oil drain into the cylinders. Do those readings sound too low?

occasional demons
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Post by occasional demons » Mon Dec 15, 2014 12:15 am

Even cold, it is a bit low. But it should still fire.

How many miles? Has the timing belt ever been changed?

With over 200,000 miles on mine, it has less than 90 psi cranking compression hot. It still starts and runs, even when it is sub zero temps.

The tubes will still let oil seep in until they are pulled and sealed with red loctite, or replaced with fresh tubes. But that is of little concern if it doesn't run.

If it is getting spark, the cam timing is still (close enough). If it was off, the PCM would not go to the next step of spark and fuel.

You can put a small amount of oil into the spark plug holes, and recheck the compression. If it comes up it is the rings. If it does not seem to be affected, then it could be valve related.
Bill
Olha Koba, a psychologist in Kyiv, said that “anger and hate in this situation is a normal reaction and important to validate.” But it is important to channel it into something useful, she said, such as making incendiary bombs out of empty bottles.
2000 Neon MTX swap with '02 R/T PCM
1999 neon coupe 2.4 swap
2021 Forester

Neondont_play
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Joined: Wed Nov 19, 2014 8:49 pm
Location: Redding ca

Post by Neondont_play » Mon Dec 15, 2014 12:45 am

It has about 150k miles on it. I don't know for sure but there is a gates sticker under the hood that says it was changed about 10k miles ago. I have only had the car for almost 2 years. the previous owner didn't give me any paperwork and I don't really remember much about what he said, but I have driven it everywhere and never had a problem until now.
The battery needs replacing, I know that for sure. There was a ton of corrosion on it, and it will charge, but after a few cranks it will die and I have to throw it back on the charge. I was only able to do 2 cylinders before it died and I had to charge it again to do the other 2. The weird part is, when the battery acts dead, it still shows a little more than 12 volts, So i was wondering if it could be a dead cell and maybe it is just too weak. But when the car first died, it would still crank for a while without starting.
I should also add, that when I replaced the PS pump, I got a used one from someone (bad idea) and the pump would just spray everywhere. I was worried maybe it had gotten on the timing belt, or on an electrical connector, but I have not looked into it yet..

occasional demons
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Post by occasional demons » Mon Dec 15, 2014 9:36 am

The battery could be why the compression numbers are so low. Most when bad will show good voltage until a load is placed on them. then it drops rapidly.

If you can find a good battery, even if it just fits good enough to connect to do a compression test, or try starting it, I would do that first. If it fires up, then you know you just need to get a fresh battery.

You could try it with a good set of 6 gauge or larger jumper cables from another battery. Smaller gauge jumpers may not give you enough amperage.
Bill
Olha Koba, a psychologist in Kyiv, said that “anger and hate in this situation is a normal reaction and important to validate.” But it is important to channel it into something useful, she said, such as making incendiary bombs out of empty bottles.
2000 Neon MTX swap with '02 R/T PCM
1999 neon coupe 2.4 swap
2021 Forester

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