92 F-150 5.0 4X4 Has no compression in one cylinder doesn't even twitch the needle! Is this a common? What could be the possible problem? No oil smoke.
Thanks for your input, Brian

 

Stuck valve??

 

Uh oh. Either stuck valve, which can be bad or really bad. Might be a lifter pumped up and stuck, unusual. Or a broken ring which is bad, but might still give a wiggle. Or a piston with a hole in it or one that is no longer connected to a rod, both options really bad.

If you are really lucky, You just got a valve that is stuck slightly open maybe a broken spring. Or maybe it is bent a littel and stuck slightly open. either way you will probably need to pull the head to fix it.

If the valve is really bent then you may have some piston work to do too.

If it is a bad ring or piston or rod, then you have significant engine bottom end work ahead, at least dropping the pan.

Good Luck,

Jim Henderson

 

Ouch! Is there a test to pin point if its the valves or the piston without having to tear the engine apart?

Thank you Jim, you said what I was fearing, although I was hoping to hear somthing else, guess we all have our fantasies huh.
Anyone know where to get a good deal on a complete engine. I'm betting the one I have has a hole in the piston. I'm in N.W. IL.
Thanks-Brian

 

Ok so how much blow by do you have. If you have a hole in the piston or broken rings you'll be getting alot, probably blowing your breather line or pcv off. If there isn't alot of blow by its a valve not sealing or blown head gasket. I'd think you would hear a stuck valve. Could it be eating some carbon or pounded a seat The rocker would be making a heck of a racket from the extra play with the valve not returning all the way.

 

No it's actually none of that. First how do I check for blow by, I not experiencing any of those symptoms. Valves and rocker arms sound fine. Here are the symptoms it does have.
1.) ZERO compression
2.) Ping in the exhaust, at idle
3.) Miss fire underload at high RPM, sounds like back fire
4.) No oil smoke out the exhaust

It starts fine, runs fine except for those problems. So where do I go from here? Are there test to pinpoint the problem?

If I were to have broken rings wouldn't I be getting oil smoke?
If it were a headgasket wouldn't I have coolant in my oil?
If it's a valve not seating wouldn't I get some compression?
Valve springs check out O.K.
I'm just trying to pinpoint the problem so I don't have to spend all kinds of money replacing parts in trial and error.

Thanks again, Bri

 

When my rings were stuck i was getting blow-by in my air cleaner, check the filter there see if it is soaked with oil.

 

It almost sounds as if the intake lobe on the cam (or the follower) has gone flat. Even if a valve were stuck open, the compression test should show something, even a wiggle. If the intake valve is not opening, your not charging the the cylinder with anything to compress. Is it possible to run the engine at idle without the rocker arm cover to see if that cylinder's valve train is operating as it should? I don't usually do this as it's prone to being very messy.

Yelrihseam

 

Is it possible to run with the valve cover off? Sure. Did it with a friends Mustang back in high school to adjust the rockers. Yes it makes a HUGE mess. It didn't help that it was very cold outside so we were in the garage with the door 3/4 of the way down to keep out the wind, and he just had open headers on it at the time. Huh, what was that you said?

 

Well, maybe disable the ignition so it only cranks over and doesn't start. You'd like to at least get enough speed on the motor to pump oil to the lifters. Of course, if you turn it by hand and the the rocker on the dead cylinder doesn't move, at least your on your way to figuring it out.


yelrihseam

 

Note this is written as I think so some things may be out of order. For example check the plug first.

You can pull the valve cover and look at the suspect cylinder's spring and valve height. As you turn the engine by hand or remote, you should see both springs and valves move in sequence AND the maximum height should be similar to all the rest of the valves and springs. If one spring seems to be compressed (ie it is shorter than the rest even at the top of the cycle) then that is your culprit.

Check that valve train to see if the spring is binding, use a good light and give it a good look all around and turn the engine to see what happens. Check to see if the rocker arm is moving properly and not damaged or bent. Check to see if the push rod is in it's "pocket" and that it is not bent(actually if bent you would have the other problem of not enough valve movement.

To have low or no compression, one or more valves must be stuck open or there is a problem with the piston. A broken pushrod, bad cam, or snapped rocker or collapsed lifter should not cause low compression.

To check if you are getting a lot of oil in the cylinder, pull the spark plug. If it has a lot of oil on it, bingo, bad rings or hole in piston. A spark plug should be dry and white to tan color. A lot of black goop wil mean oil. For a sanity check pull a couple other plugs and compare. If the suspect cylinder is different from the others, you have the identified the problem. If all the plugs look the same, they are probably old, or your engine is worn out. I would probably do this FIRST since it is easier than pulling the covers,pulling the heads or dropping the pan. The lopk of the plug can tell you whether you even need to look at the valves.

One other compression check, squirt about a table spoon of thick oil into the cylinder and do a compression check, if the pressure goes up, then you have ring problems, if nothing, then valve or a big hole. Since you mention NO pressure, I would not expect this to change anything. Only a stuck open valve or a big hole in the piston would read zero. A long shot might be very badly broken rings.

Other than pulling the heads, this is as far as you can easily go unless you can see through the spark plug hole. But you may know enough by that point to determine if you need to pull the heads.

To decide... if you see an obvious valve problem or spring or valve train, then work on that issue. If the springs and valves all look fine, but your spark plug is oily, then you probably need to pull the head to confirm the diagnosis of a bad piston or ring, oh and another possibility is a badly worn out valve(you will need to pull the head). If it is a ring or piston, you will need to drop the pan and remove that piston and rod assembly as a minimum. You will probably need to hone the bore as a minimum if it is a bad ring. If the piston has a hole, I would want to know why. BTW, do you use nitrous or a blower? These can break rings and burn pistons.

Good Luck, be methodical.

Jim Henderson

 

Ok, lets start over. Do you have a lot of blow by? pull your breather line that goes from your valve cover to your air box (filter housing) off the valve cover. With it running is there alot of air / smoke coming out of the valve cover where the line was. Rev it up a little. Some is normal really blowing isn,t. If your getting ALOT of blow by you've got a hole in your piston/really broken rings. If not youve got head problems. You did a compression test, what are the results for the rest of the motor.

 

ok Ive decided that the rings are bad, very bad. now my options are:
1) rebuild the engine $1000
2)replace the engine $?
3)light a match under the gas tank $I owe I owe I owe
what needs to be done to convert a 302 car engine to a 89 f 150 4x4 truck?
thanks so much for your input it's made a world of difference.
Bri

 

I have a 91 F150 4X4 and my rings were stuck big time. I found a sweet deal on an 86 302 ouf of a Grand Marquie, and for the most part everything will fit fine. You will need to use the intake off of your current engine, exhaust manifolds, oil pan and the oil pump and pickup, and the pully system up front. We had to also use the fan off of my old engine because the one on the older vehicle didnt match up. All in all it took a half a day to swap parts and then just throw the engine in.

 

Check to make sure the little shrader valve on the comp gauge is not stuck or full of crap.

Squrit some oil in the dead cylindar. If it make comp go up then it is the rings, if not then it is the valves or a big hole in the piston.