Compression Test Results

[SBpunk]

Guessing my piston rings are done for and probably worse.

1 @ 130
2 @ 150
3 @ 145
4 @ 145 drops to 90
5 @ 145
6 @ 150 drops to 130
Symptoms are shaky idle, strong fuel smell in the oil, hard start on occasion
I've swapped out spark plugs, 4 point fuel injectors (think this might have caused it actually), rotor, cap, wires, air filter, O2 sensor, exhaust manifold back, new throttle body, fuel filter and a few other things I'm probably missing. Has never over heated since I've had it. Any opinions before I start to pull of the head and cry?

 

[Fernando87mj]

Honestly I would just make sure that the fuel injectors aren't leaking fuel into the cylinders which might cause a hard start and smelly oil .

[Fernando87mj]

.

[SBpunk]

That wouldn't cause the low compression though. I have new stock injectors that have been cleaned and tested going in. My RMS has been changed around 4 times now and still leaking so wondering if its even worth attempting again if I'm going to need to pull the block.

[Zebvance]

I Have similar compression results. And the same other symptoms. I blown out rms and every other new gasket in the jeep. Have a descent amount of blow by also. My reasoning behind all my problems is that the combustion pressure is getting past the rings that are showing wear and building up crank case pressure, in turn with causing seals to fail. Basically I got to keep the oil topped off and ride her out until I have the money to rebuild the engine. 

[SBpunk]

Yeah that's what I'm thinking has to happen. Was hoping someone would say "Hey just sounds like your head is (insert some type of head issue here). Get it rebuilt and you should be good to go" buuuuuuut I sort of knew with all the signs.

[Zebvance]

Yeah that's what I'm thinking has to happen. Was hoping someone would say "Hey just sounds like your head is (insert some type of head issue here). Get it rebuilt and you should be good to go" buuuuuuut I sort of knew with all the signs.

 

 

I'm not a expert, I'm just a guy that has been dealing with the exact same issues as you over the past 3 years.

 

Also I have replace every vaccum line a ccv line and sensor there is.

 

Have terrible gas miliage and its running so rich it almost knocks you on the ground if you stand behind it. So much so that I have black sut all over my rear axle truss from the exhaust. Its always running a little warm during the summer and its a struggle to keep it from over heating in the texas 100 degree weather at low speeds in 4wd.  and its very low on power. so much so I can't even brake the tires loose on payment if it tried. 

[Eagle]

Guessing my piston rings are done for and probably worse.

1 @ 130

2 @ 150

3 @ 145

4 @ 145 drops to 90

5 @ 145

6 @ 150 drops to 130

Symptoms are shaky idle, strong fuel smell in the oil, hard start on occasion

I've swapped out spark plugs, 4 point fuel injectors (think this might have caused it actually), rotor, cap, wires, air filter, O2 sensor, exhaust manifold back, new throttle body, fuel filter and a few other things I'm probably missing. Has never over heated since I've had it. Any opinions before I start to pull of the head and cry?

 

 

 

I don't understand your test results. Did you run a compression test, or a leakdown test? You're saying that two non-adjacent cyliders have significant leakdown but the other four have ZERO?

[SBpunk]

It was done at a shop. They wrote the results on the fan shroud. They charged me for a leak down test but it looked like a regular compresson test.

[Dogote]

Those results are a cranking compression test, not a leak down. Leak down results look like:

 

#1 80/75

#2 80/70

 

and so on. Usually you put 75 or 80 PSI in, and measure the amount that the cylinder will hold. While it's leaking, you can usually located where it leaks to. Valves should not leak at all, no air should get in the cooling system(blown head gasket,, cracked head., but rings will loose at least 4% (on a nearly new close tolerance engine like a modern European motorcycle) and as much as 10 % on a healthy cast iron engine. You can hear the air leaking if you pull the oil cap. If it's leaking 20 or more percent into the block, you may need rings.

 

As far as cranking compression, your not doing bad. I have now idea what the "drops to xxx" means. Sounds like they don't understand how to do a leakdown test. Most car mechanics have never done one. I am an aircraft mechanic, it's all we do on piston aircraft engines. It's common in the motorcycle world too, at least for the trained shops.

 

Your cranking pressures actually look okay. No two cylinders are going to give the exact same cranking pressure. I recently had a cracked head on my 2.5. It cranked 90 on the 4th cylinder and 120 on the 3rd. The other two were in the 150 something. I then did a leak down. 4 was leaking out the exhaust valve (pulled manifold to find that) Found out when I got the head off it was cracked.

 

Good luck.

[cruiser54]

What do the plugs look like when compared to one another?

 

What brand are they? 

[SBpunk]

I was just guessing (once again no expert) that the pressure wouldn't hold. I'll post up the pic of what he wrote up in a second. I'm throwing in new stock fuel injectors this weekend and pulling the cowl intake snorkel to see if it helps at all with the power/idle. I'll take a NOD? tester to the fuel injector plugs as well to make sure I'm getting a good signal to all of them. The fuel injectors are pretty much my last hope before I start looking into rebuilding or a new motor. I'll start with getting the head rebuilt and go from there.

 

[SBpunk]

I can't remember to be honest. The previous owner had some 4 point spark plugs in the block. I just pulled them and tossed them without looking. I'll pull the newer ones and check them out. They've been running for about 1k miles or so. Should be able to tell if they're getting burnt up or too wet.

What do the plugs look like when compared to one another?

 

What brand are they? 

[Zebvance]

I went a looked back at what my results were and these where it. The shop did this test after I got the RMS replaced bu then and it blew it out after 20 miles. Then the tech supposed hooked up a pressure gauge to the crank case and said I was getting 7psi in the crank case at 30 mph... 

 

 

Dry Test                                           

Cylinder 1 - 125 psi
Cylinder 2 - 100-105 psi
Cylinder 3 - 145 psi
Cylinder 4 - 130-135 psi
Cylinder 5 - 140-145 psi
Cylinder 6 -140 psi

[Dogote]

I was just guessing (once again no expert) that the pressure wouldn't hold. I'll post up the pic of what he wrote up in a second. I'm throwing in new stock fuel injectors this weekend and pulling the cowl intake snorkel to see if it helps at all with the power/idle. I'll take a NOD? tester to the fuel injector plugs as well to make sure I'm getting a good signal to all of them. The fuel injectors are pretty much my last hope before I start looking into rebuilding or a new motor. I'll start with getting the head rebuilt and go from there.

 

The pressure not holding on a cranking test tells you nothing except the mechanic has a leaky compression gauge. There is a schrader valve in the hose of a compression tester. The cylinder wouldn't hold pressure anyways.