Bad Cylinder?

Hey guys: I think I might have an issue with the number one cylinder in my jeep. Plug is oily, and I do get smoke from the exhaust.

I did compression test and 2 4 and six are about 150... 3 and 5 are 180.. number one I added oil , but maybe too much. Would the oil in number one effect 3 and 5?

These numbers are cold..

Thanks,
Chris

 

What was the reading on number 1 cylinder?

I can't see how oil in number 1 would affect the others.

Sounds like oil blow-by from excessive ring gap or some other malady.

 

Yeah, that's what I figured too.. I checked 1 3 and 5 and they were about 100.. did the other side and went back to 3 and 5 and they showed 180 and 185. Something weird. Maybe I had compression guage installed wrong..

Also, I have lifters making noise.

Thanks,
Chris

 

Usually I would check cranking pressure dry. Then if it was low recheck with a little oil. If it improved by a lot then probably poor ring sealing. If oil didnt affect it much then its something else. Like poor valve sealing.

 

Thanks chilly. I'm not sure what numbers I should be seeing, I have a service manual but I don't see the figures. Would oil added yesterday still effect the cylinder pressure?

I also have a leak down tester, but haven't used it yet.

Chris

 

I seem to recall reading here that the factory never wrote down any compression specs, at least for the V6...?

Now it is a Buick 225. Maybe specs do exist as a GM engine.

 

Yeah. I couldn't find em anywhere.

Thanks,
Chris

 

From all the people who have posted up compression tests, that I have read, I've can't recall anyone having numbers in the 180's. That seems high to me.

 

Do a leak down test..........the only way to get true cylinder condition readings......and will tell you much more like if its rings , head gaskets or valves that are leaking..

 

Pour a quart of ATF, in oil, drive under 2000rpm, 20 - 45 min .
Then change oil. Drive longer if ticking doesn't go a way. Up to 1 hour.
This sometimes flushes dirt out of a noisy lifter,
Done this several times.
On u r weak cyl, just drive it?
If it's missing, fix the miss.
If it smokes, use some oil additive for oil usage, ( no smoke, stp, Lucas, motor honey),
I like the Lucas blue label oil additive best.

 

Hey Tarry, When doing a leak down test the engine is warmed first? Then all plugs removed, right? I tried this a couple of days ago. Process I did: bring compressor to 100 psi, and open guages to 90 psi..... removed dist cap to see number one, then rotated crank till TDC.. I did this: actually both guages dropped, i think. Then it seems that the 2nd guage showed 40 percent leak..... (that's 90- 50 on 2nd guage) . I heard air escaping from breather on valve cover i removed.

Would this be the rings on number 1 are shot? And those high numbers be carbon on valves?

Do you test all cylinders in firing order? I'm guessing valve covers to be removed so valves can be seen closed.

Thanks,

Chris

 

Hey 70, I had just changed oil and added a quart of MMO. I had a terrible noise, which turned out to be a broken alternator bracket. Swapped it out, and now have the ticking with a miss. Could I have a bad lifter?

Thanks,

Chris

 

Section 60-4 explains the compression pressures, what could be wrong in the engine to create a difference difference and a chart to correlate highest to lowest pressures and engine specs for it.

bookmark this
225 Cubic Inch V-6 Engine, 1966 Buick Chassis Manual

 

Thanks Chris... It looks like lowest compression number needs to be at least 75 percent of highest. Dang battery was dead, I left key on... Charging tonight, more testing tomorrow.

Thanks,

Chris

 

The compressor must have enough air volume to keep a steady pressure on the gauge during each cylinder test............and if you have a big leak sometimes a small compressor has a hard time keeping up the pressure to have a consistent steady reading.

Warm engine , Yes
All plugs out , Yes
You have to rotate the crank to the proper position for each cylinder........so timing mark on Number 1 is only the correct position for checking # 1 cylinder.........but keep in mind that could also be on the exhaust stroke...............so best to pull the valve covers and watch the valve action on the cylinder your checking..........

I like to use the end on the leak down gauge that has the threaded adapter for the plug hole on one end........and if it doesn't have an o-ring put one on for sealing.........and the other end is normally a quick release that can be removed from the gauge...........I use that first by itself to get the the piston at TDC , by screwing it in and then putting your thumb over the blank end and then while watching the valve action as you turn the motor over.........look for the intake valve to open and close and then you'll feel pressure building coming from the cylinder pushing on your thumb which means your on the compression stroke and your nearing TDC.................or another method is you can stick your thumb or finger over the plug hole and do the same while watching the valve action and feeling the pressure build............
Bottom line you want to be near TDC with both valves closed........that's why the covers need to be off..........if your on the exhaust stroke the exhaust valve will either be opening or starting to close after TDC.

Sometimes you can roll the pushrods and feel if there's pressure on the rocker but with hydraulic lifters it's hard to feel as sometimes they don't pump down that quickly..

Get each cylinder at TDC with both valves closed and do your test and be prepared to follow the air leaking and write down the info..........also while your doing the test and still have a breaker bar on the front hub.......take the breaker bar and try to rock it either direction a few degrees and if you see a noticeable change in the leak that normally is saying the rings our not fully seated....

Air escaping from the breathers which is connected to the crankcase normally means Rings.........
Air escaping or heard from the Carb normally is an intake leak.
Air escaping from or heard through the exhaust pipes is an exhaust leak.
Sometimes you may hear leaking in a cylinder next to the one your checking..........A head gasket would be suspect.

Follow the leaking air sound..........

 

Might be lifter?
Or a wiped out lobe on cam?
Been using oil additive for flat tapett cam ???
U might want to start up and idle with valve covers off to determine what's going on?

 

The only way that could happen is if the points were closed so the points are likely welded together. Most likely won't start.

 

Tarry, thanks for your reply. Yeah, I have a new leak down tester. It's an OTC 5609.. has disconnects on both sides, can't remember if its o ring seal on plug... compressor is a 5hp 30 gallon tank. Gonna take another look at it today..

Thanks for your help,

Chris

 

Thanks 70. Its a possibility that the issue is in the valve train. When I got this jeep I noticed the dist was way advanced and the vac advance not hooked up. Maybe this is because timing chain is off... maybe the noise I'm hearing is a timing chain..

Thanks ,
Chris

 

Walt, hope that didn't happen. Those points are a hassle.. its getting a pertronix I'd it did. And that's my luck these days.

Thanks,

Chris