Compression
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New User
Joined: May 2011
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Compression
I have a 1998 f150 and want to check the compression do any body know what good wet and dry compression is and what is low compression so I will know if I should keep the engine it is a 4.2 v6 it seems to have lost a lot of power on the take off
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
Ignor what you already know.
Min pressure is 100 psi.
No more than 15 psi spread between highest and lowest cylinders.
Testing needs the throttle opened enough not to interfere with cylinder filling when cranking.
Disable ignition because fuel is still being injected and may cause a fire if a spark is present.
Also you may have codes that show the intake runners are stuck open. This will drop low end torque.
Good luck.
Min pressure is 100 psi.
No more than 15 psi spread between highest and lowest cylinders.
Testing needs the throttle opened enough not to interfere with cylinder filling when cranking.
Disable ignition because fuel is still being injected and may cause a fire if a spark is present.
Also you may have codes that show the intake runners are stuck open. This will drop low end torque.
Good luck.
Thread Starter
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New User
Joined: May 2011
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Ok thanks bluegrass 7
These are the numbers I came up with
Dry-wet
1. 185-202
2. 185-195
3. 175-190
4. 185-195
5. 185-200
6. 185-202
But the truck still acts as if it don't have any power when I pull off let say when I try to pull up on ramps to work on it. It take the gas all the way to the floor in order to get it on the ramps and it still takes a lil time to do that do you think the timing chain my be bad or something like that hope some body can help me with this one I can not figure this one out. Thanks
These are the numbers I came up with
Dry-wet
1. 185-202
2. 185-195
3. 175-190
4. 185-195
5. 185-200
6. 185-202
But the truck still acts as if it don't have any power when I pull off let say when I try to pull up on ramps to work on it. It take the gas all the way to the floor in order to get it on the ramps and it still takes a lil time to do that do you think the timing chain my be bad or something like that hope some body can help me with this one I can not figure this one out. Thanks
Cargo Master
Joined: Aug 2003
Posts: 3,263
Likes: 92
From: BC Canada
The numbers you presented indicate the engine in good condition, if timing (engine) was off the pressures would be low..
Run a fuel pressure system check, pressure (RAW=key on engine off x3), engine running, vacuum disconnected at Fuel pressure regulator while engine runing, pressure bleed down after engine/ignition off.
replace fuel filter....
What is your LTFT?.... Philip
Run a fuel pressure system check, pressure (RAW=key on engine off x3), engine running, vacuum disconnected at Fuel pressure regulator while engine runing, pressure bleed down after engine/ignition off.
replace fuel filter....
What is your LTFT?.... Philip
Lead Driver
Joined: Sep 2006
Posts: 7,907
Likes: 143
The compression looks good.
What is the history of the issue?
If you can't luck onto anything, get a good scanner that can look at live real time data so you can see the ignition timing, fuel trims, and see the OX sensors working outputs.
If the timing has jumped you should see it in the live data presentation.
Good luck.
What is the history of the issue?
If you can't luck onto anything, get a good scanner that can look at live real time data so you can see the ignition timing, fuel trims, and see the OX sensors working outputs.
If the timing has jumped you should see it in the live data presentation.
Good luck.
Elder User
Joined: Mar 2010
Posts: 601
Likes: 0
For the sake of argument, try manually shifting into 1st gear, and see if that makes any difference. As good of shape as that engine appears to be, you problem sounds like drive train issues, like the torque converter, or remotely possible that it doesn't downshift back to first at a start up or stop. How is the trans fluid level ? How many miles on the last fluid/ filter change ? Any burned smell to the fluid.
Dave
Dave
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New User
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Ok I took the timing chain off and it had a lot of play and the top gear is really wore out so I am hopeing that is where the lost of power is from now that I am ready to put it back together I am reading that you have to have a specal to called a synchro positioning tool that I can't find anywhere my question is if I never took the synchro out of the cover do I still need to have that tool to Aline it are cAn I just put the cover back on because I never took it out the cover
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Fleet Mechanic
Joined: Jan 2011
Posts: 1,493
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Ignor what you already know.
Min pressure is 100 psi.
No more than 15 psi spread between highest and lowest cylinders.
Testing needs the throttle opened enough not to interfere with cylinder filling when cranking.
Disable ignition because fuel is still being injected and may cause a fire if a spark is present.
Also you may have codes that show the intake runners are stuck open. This will drop low end torque.
Good luck.
Min pressure is 100 psi.
No more than 15 psi spread between highest and lowest cylinders.
Testing needs the throttle opened enough not to interfere with cylinder filling when cranking.
Disable ignition because fuel is still being injected and may cause a fire if a spark is present.
Also you may have codes that show the intake runners are stuck open. This will drop low end torque.
Good luck.
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New User
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It is good I took it apart the timing chain was no good if had to much slak in it and the tentioner was opened all the way up so it could not take the slak out witch made it have no power when I pull off and it had a miss to it to the thing I had a question about is the cam sensor I never took it off the cover so I was wondering if I have to reset it or can I just put it back on and leave it like it is
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