Can I run the engine without rockers?
11-15-2012, 10:20 PM
#1
Can I run the engine without rockers? This may or may not be a dumb question... I am trying to isolate a loud tapping noise somewhere around cylinder 5 and 7. It taps at half the speed of the motor, so I think it's valvetrain related, possibly a lifter. I've done what I can through the valve cover and haven't found the source of the noise yet. I don't want to pull the head until I know for sure it's a lifter.
Can I pull both rockers off a cylinder so their lifters aren't being used? If the tapping goes away with the rockers off then I can assume the tapping if from one of those two lifters. If I were to do this, I would only let it idle for 10-15 seconds, enough time to hear if the tapping is there or gone. However, 10-15 seconds would be roughly 100-160 revolutions, ouch.
Here is what I would do... Remove both rockers and pushrods and make sure the lifters stay up in the lifter guide, unplug injector, unplug spark plug. Would I need remove the spark plug? I'm hesitant to because it would make a TON of noise and probably cover the sound of the tapping.
So am I crazy, or is this a reasonable idea?
Can I pull both rockers off a cylinder so their lifters aren't being used? If the tapping goes away with the rockers off then I can assume the tapping if from one of those two lifters. If I were to do this, I would only let it idle for 10-15 seconds, enough time to hear if the tapping is there or gone. However, 10-15 seconds would be roughly 100-160 revolutions, ouch.
Here is what I would do... Remove both rockers and pushrods and make sure the lifters stay up in the lifter guide, unplug injector, unplug spark plug. Would I need remove the spark plug? I'm hesitant to because it would make a TON of noise and probably cover the sound of the tapping.
So am I crazy, or is this a reasonable idea?
11-15-2012, 10:39 PM
#2
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If there is no fuel going into the cylinder than unplugging the spark plug would allow air to freely move in and out of the cylinder when the engine is running. I don't think that it would cause that much more noise then the engine running. You will probably pop a check engine light when you try this. Also, with running the engine with one less cylinder, it might have a hard time starting and when it is running it is going to run very rough. GOOD LUCK!!
11-15-2012, 10:51 PM
#3
If there is no fuel going into the cylinder than unplugging the spark plug would allow air to freely move in and out of the cylinder when the engine is running. I don't think that it would cause that much more noise then the engine running. You will probably pop a check engine light when you try this. Also, with running the engine with one less cylinder, it might have a hard time starting and when it is running it is going to run very rough. GOOD LUCK!!
11-15-2012, 10:54 PM
#4
Teching In
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Sounds like you are going to have to tear down the heads any ways . take the plug out . Its gone run like its on 7 cylinders . I dont know How far the lifters will move if any you may be ok but who knows .good luck
11-15-2012, 11:30 PM
#5
If there is no fuel going into the cylinder than unplugging the spark plug would allow air to freely move in and out of the cylinder when the engine is running. I don't think that it would cause that much more noise then the engine running. You will probably pop a check engine light when you try this. Also, with running the engine with one less cylinder, it might have a hard time starting and when it is running it is going to run very rough. GOOD LUCK!!
My biggest concern is potential damage to the cylinder walls and perhaps other damage caused by doing many compressions in a row without fuel or combustion.
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11-16-2012, 12:04 AM
#8
11-16-2012, 08:41 AM
#9
With the plug installed it would be really no different than how the engine runs normally, it would just be a compression stroke on every stroke. As for how it will run, I think it will run fine. Once I forgot to plug in the coil pack so it was running on 4 cylinders. Ran poorly, but it ran.
My biggest concern is potential damage to the cylinder walls and perhaps other damage caused by doing many compressions in a row without fuel or combustion.
My biggest concern is potential damage to the cylinder walls and perhaps other damage caused by doing many compressions in a row without fuel or combustion.
11-16-2012, 11:25 AM
#10
TECH Junkie
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If you remove the pushrods it will be fine. Unplug the injector but leave the plug wire on or you may damage the coil. I have driven on 7 cylinders many times with no ill effects. The cylinder will get a little oil in it over time and the check engine light will come on.
Kurt
Kurt
11-16-2012, 01:20 PM
#13
Id just tear the head off when my lifter failed I had a broken tray and the pr was pushing on it giving it that tap you had on your other post.. its not that big of a hassle to tear the head off
11-16-2012, 01:57 PM
#14
TECH Senior Member
Unplug the injector connector and unplug the coil primary connector (very important, see what 427 above said).
This is ok to do... air will simply be pulled into that cylinder via intake port, it will be compressed, and then expelled via exhaust port; leave spark plug in otherwise there will be too much noise.
This is how a running compression test is done (pressure gauge screwed into spark plug hole, measuring pressure in one cylinder while engine is running), does not cause any damage.
This is ok to do... air will simply be pulled into that cylinder via intake port, it will be compressed, and then expelled via exhaust port; leave spark plug in otherwise there will be too much noise.
This is how a running compression test is done (pressure gauge screwed into spark plug hole, measuring pressure in one cylinder while engine is running), does not cause any damage.
11-16-2012, 01:58 PM
#15
TECH Senior Member
What if that wasn't the source of his noise...? Not a big deal but certainly a waste.
11-16-2012, 02:24 PM
#16
Unplug the injector connector and unplug the coil primary connector (very important, see what 427 above said).
This is ok to do... air will simply be pulled into that cylinder via intake port, it will be compressed, and then expelled via exhaust port; leave spark plug in otherwise there will be too much noise.
This is how a running compression test is done (pressure gauge screwed into spark plug hole, measuring pressure in one cylinder while engine is running), does not cause any damage.
This is ok to do... air will simply be pulled into that cylinder via intake port, it will be compressed, and then expelled via exhaust port; leave spark plug in otherwise there will be too much noise.
This is how a running compression test is done (pressure gauge screwed into spark plug hole, measuring pressure in one cylinder while engine is running), does not cause any damage.
11-16-2012, 02:28 PM
#17
I would prefer to know what the problem is before pulling the head. This is my daily driver so pulling the head is a big deal. And at the rate I work, it would take me a full day, maybe two
11-16-2012, 02:33 PM
#18
11-16-2012, 02:36 PM
#19
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Just drove mine home on 7, I have the same problem as my truck is my daily driver and I know my cam and lifter is history. I have been driving it about 3000 miles now without cylinder 2, it does well but vibrates when the converter locks and needs 3rd gear to pull the trailer now. It is still pretty quick as once it revs up it seems normal.
Kurt
Kurt
How would you describe the tapping sound? On a cold start it doesn't tap, then takes 20-30 seconds before it will start tapping.
I would prefer to know what the problem is before pulling the head. This is my daily driver so pulling the head is a big deal. And at the rate I work, it would take me a full day, maybe two
I would prefer to know what the problem is before pulling the head. This is my daily driver so pulling the head is a big deal. And at the rate I work, it would take me a full day, maybe two
11-16-2012, 02:41 PM
#20
How would you describe the tapping sound? On a cold start it doesn't tap, then takes 20-30 seconds before it will start tapping.
I would prefer to know what the problem is before pulling the head. This is my daily driver so pulling the head is a big deal. And at the rate I work, it would take me a full day, maybe two
I would prefer to know what the problem is before pulling the head. This is my daily driver so pulling the head is a big deal. And at the rate I work, it would take me a full day, maybe two