Low comprssion numbers
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Senior User
Joined: Sep 2006
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From: Savannah
Low comprssion numbers
I run a compression test today. 1-342.5 2-318.5 3-285.5 4-308.0 5-288.0 6-306.0 7-333.0 8-315.5
As you can see the engine is trash. The thing i want to know is when i run a contribution test it looked good but 1 and 2 they where 5.0 and 7 was only 1.0. What I was wandering 1,2,7 are higher than most . The truck will crank if it is warm out and always if you plug it up regardlesss of temp. I have always heard if you did not have 350 it would not start. That is not true. it just has to be 100 out. I know that as long as all your numbers are close the contribution numbers will be low due to their not being much diffirence in their output. So why are the 1,2 7 the highest when they have more compression than 3,4,5,6 wich are 0.0.. I am saving for an engine it is not in the works now but befor winter. I have 3 new injectors would you put them in 1 and 2. And no i dont have the new cps. PS 6 and 7 sounded week in the buzz test.
As you can see the engine is trash. The thing i want to know is when i run a contribution test it looked good but 1 and 2 they where 5.0 and 7 was only 1.0. What I was wandering 1,2,7 are higher than most . The truck will crank if it is warm out and always if you plug it up regardlesss of temp. I have always heard if you did not have 350 it would not start. That is not true. it just has to be 100 out. I know that as long as all your numbers are close the contribution numbers will be low due to their not being much diffirence in their output. So why are the 1,2 7 the highest when they have more compression than 3,4,5,6 wich are 0.0.. I am saving for an engine it is not in the works now but befor winter. I have 3 new injectors would you put them in 1 and 2. And no i dont have the new cps. PS 6 and 7 sounded week in the buzz test.
Posting Guru
Joined: Nov 2006
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From: Herndon KY
First off, with a K & N most likely your engine has been dusted, but there is a possibility that bad compression numbers could be injector hold down bolts not torqued properly, there was a TSB out about that. I would go in and check the torque on the bolts that they are to spec. If your turbo is dusted then you might not bother.
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From: Savannah
The k & N has only been on for the last year and the turbo was rebuilt with a WW a year and half ago. But on the other hand it was not dusted then. This truck is never used off road so the dusting is not a huge problem. what is the spec on the hold downs it is still apart so i could check. also the numbers that are the lowest are the prone to dust. When i purchashed the truck it had 200,000 it now has 313,000 it prolly had 260,000 when the k&N was put on. it was hard to start then. any help is great....
Post Fiend
Joined: Feb 2006
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From: Middle Tennessee
All of your #s are marginal for a diesel. 375 is the cutoff for a good engine. 326 is the cutoff for a marginal one. 276 is the cutoff for a low compression diesel, and anything below that for the highest reading is a no crank situation. Your readings of 342/285 puts you just outside the 342/292 acceptable reading but just barely. It should still start with those compression #s and should run fine when warmed up. Majors defects aside, you could expect many more miles of service from this engine. Diesel no start begins at about 275/206 for the highest/lowest reading.
Not addressing your other questions at the moment, but my truck is not a compression king either.
Not addressing your other questions at the moment, but my truck is not a compression king either.
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Senior User
Joined: Sep 2006
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From: Savannah
All of your #s are marginal for a diesel. 375 is the cutoff for a good engine. 326 is the cutoff for a marginal one. 276 is the cutoff for a low compression diesel, and anything below that for the highest reading is a no crank situation. Your readings of 342/285 puts you just outside the 342/292 acceptable reading but just barely. It should still start with those compression #s and should run fine when warmed up. Majors defects aside, you could expect many more miles of service from this engine. Diesel no start begins at about 275/206 for the highest/lowest reading.
Not addressing your other questions at the moment, but my truck is not a compression king either.
Not addressing your other questions at the moment, but my truck is not a compression king either.
Posting Guru
Joined: Nov 2006
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From: Herndon KY
I just pulled my injectors for the same reason, low #s, I got good checks after injector o-ring kits, 120 inch lbs is the number that I found, and worked for me, but the standard disclaimer applies. Also you can only torque the lower hold down bolt with the injector in place, the other is meant to be torqued into place prior to installing injector.
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Postmaster
Joined: Feb 2004
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From: Levittown
Also agree to above.
Its common. If copper gasket is leaking you will see it.
Bill
Its common. If copper gasket is leaking you will see it.
Bill
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Thread Starter
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Senior User
Joined: Sep 2006
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From: Savannah
What are the torque numbers for the injectors. I can get a set of heads for 600 with new valves and cups and springs . Do you have to pull exhaust manifolds to pull heads and how hard is it pull them in the truck.
Posting Guru
Joined: Nov 2007
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From: Tupelo,Ms
usally rings get worn out thus turning around to where there not staggard set anymore and compression just leaks right on by
Fleet Owner
Joined: Jun 2004
Posts: 25,090
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From: Rio Rico, AZ.
Injector hold downs to 120 inch pounds. (Something like 7-8 foot pounds, not very much.)
