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Hi guys, I have a 2000 7.3, bought it over the summer w/ 165k on it, intake, exhaust, and 4 gauges. Unfortunately after I bought it it didn't seem to run right, low power and would dog it some times, no smoke, blow by, or sucking at exhaust. When it started to get cold it wouldn't start. Sometimes it seems like it's only running on one bank and the whole truck shakes on start up.
I did CCT and it showed #3 and #8...thought it was because of grey CPS. I get a 1316 IDM code.

I did a compression test today. The entire R bank checked out good...380-430. The entire L bank was low...the highest I got was cyl #1 at 375psi. cylinder 3 I got 345. #5 and #7 were 270psi...and #5 jumped to 375 after a tablespoon of oil...but #7 only went to 290 after a little oil. I charged batteries and checked and rechecked and L side didn't improve.

So I'm hoping I did something wrong with my compression test, rather than having to replace the engine. Any suggestions would be appreciated
 

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They should all be around 400 for great compression and 300 is considered weak, also you want them within 10% of each other. You do have 2 out of that range which could really impact the starting. Will defer to someone with more knowledge on why the one jumped so much with oil and what that might mean.

When it does start cold you still get no smoke? Would think with low compression on those two cylinders you would see some white smoke till they are up to temp. Have you watched the oil output with the injectors off, those two injectors could be sticking which could have been the cause for low compression.
 

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Bobs 7.3
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2,852 Posts
worn piston compression rings will jump in compression like your are when you put a little oil in the cylinder as the oil will form a better seal between the worn rings and cylinder wall (that is till that oil is pumped out then compression will go back down).
 

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Old Yeller, REBORN
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2,284 Posts
Sounds like you did everything right and unfortunately, you probably need a rebuild. If they are all 300, it runs better than the wide spread you have.

Oddly enough, I had 0psi in 1 cylinder and with OD off and at 60mph with the cruise set, it ran smooth as ever.

There still seems to be a lot of good used motors out there to swap in but even then, you don't know how long they will last.

If you can't do any of the wrenching, it will really cost you.:(
 
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