No Compression in Cylinder 3 and 6

[Slow3.4oh]

Hey everyone! I currently have a 2002 ford ranger with the 3.0 engine and I have ZERO compression in the rear 2 cylinders, which is cylinder 3 and 6 does anyone know what it could be? Any help is greatly appreciated, thanks!!

 

[55trucker]

First thought is the valves in those two cylinders are not sealing

 

[pjtoledo]

camshaft not rotating????

the engines recent history would help.

 

[Uncle Gump]

Broken or worn out cam lobes on 3 and 6 sounds likely.

 

[55trucker]

I'd think that if the cam lobe has worn away then the valve *wouldn't* open instead of *staying* open.

The OP didn't mention if there was any sort of louder than normal noise if & when the cam actually broke?..of course the engine would quit right there & then

 

[MikeG]

0 compression would be difficult to achieve. Valves would have to be stuck open, or the compression tester not installed all the way, etc.

Is "no compression" a measurement, or estimate?

 

[RonD]

Hey everyone! I currently have a 2002 ford ranger with the 3.0 engine and I have ZERO compression in the rear 2 cylinders, which is cylinder 3 and 6 does anyone know what it could be? Any help is greatly appreciated, thanks!!

Welcome to TRS

+1 to all the above

What was the average compression on the other 4 cylinders?

Most likely you have burnt exhaust valves in 3 and 6 so no compression
You can put 3 and/or 6 at TDC and then put in compressed air, listen at tail pipe for the escaping air confirming burnt exhaust valves

You can rent Borescope cameras to have a look down/in spark plug hole

But in any case you will need to pull the heads on both sides which will end the "guessing" as to the problem
Bad rings can lower compression but not to 0, hole in the piston will cause 0 compression, and easy to see that with heads off
Burnt exhaust valves are also easy to see when head is off

 

[Slow3.4oh]

Welcome to TRS

+1 to all the above

What was the average compression on the other 4 cylinders?

Most likely you have burnt exhaust valves in 3 and 6 so no compression
You can put 3 and/or 6 at TDC and then put in compressed air, listen at tail pipe for the escaping air confirming burnt exhaust valves

You can rent Borescope cameras to have a look down/in spark plug hole

But in any case you will need to pull the heads on both sides which will end the "guessing" as to the problem
Bad rings can lower compression but not to 0, hole in the piston will cause 0 compression, and easy to see that with heads off
Burnt exhaust valves are also easy to see when head is off

The average compression on the other 4 cylinders is 120 which is what it should be, and I rechecked compression on those back 2 cylinders and it actually gets about 5-10 PSI

 

[Slow3.4oh]

I'd think that if the cam lobe has worn away then the valve *wouldn't* open instead of *staying* open.

The OP didn't mention if there was any sort of louder than normal noise if & when the cam actually broke?..of course the engine would quit right there & then

The truck still runs and drives so I don't think anything broke, I really checked compression and it had about 5-10 psi while the other 4 had right about 120 psi

 

[Uncle Gump]

I'd think that if the cam lobe has worn away then the valve *wouldn't* open instead of *staying* open.

0 compression would be difficult to achieve. Valves would have to be stuck open, or the compression tester not installed all the way, etc.

Take the rocker arm off an intake valve to simulate an intake lobe wiped off... the result on a compression test will be at or very near zero. If you don't open the valve no air is allowed in to compress.

 

[rusty ol ranger]

The truck still runs and drives so I don't think anything broke, I really checked compression and it had about 5-10 psi while the other 4 had right about 120 psi

3 and 6 would be the hardest to get the tester screwed in good and tight.

With 2 dead cylinders a 3.0 isnt even going to move. Its not a 2.9.

 

[rumblecloud]

I was wondering about that "cam lobe" thingy. For curiousity and for my own interest I was going to ask how would that be possible?

 

[Slow3.4oh]

3 and 6 would be the hardest to get the tester screwed in good and tight.

With 2 dead cylinders a 3.0 isnt even going to move. Its not a 2.9.

Well I'd definitely still runs and drives and I have put the compression tester on it multiple different times and I get the same reading every time

 

[Uncle Gump]

Well I'd definitely still runs and drives and I have put the compression tester on it multiple different times and I get the same reading every time

With two dead cylinders... it must be barely running/driving.

 

[Slow3.4oh]

With two dead cylinders... it must be barely running/driving.

It runs very rough, gets about 10mpg when it previously got 22mpg and it tops out at like 60 mph