Compression levels - LBZ

[YoungGunDiesel]

Did a compression check on my 2006 LBZ and got the following,

Cylinder #1: 350
Cylinder #2: 320
Cylinder #3: 320
Cylinder #4: 240
Cylinder #5: 330
Cylinder #6: 350
Cylinder #7: 310
Cylinder #8: 300

Should I be concerned for #4?

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[TheBac]

Yes. Id also be wary of 7 and 8 myself.

 

[YoungGunDiesel]

Yes. Id also be wary of 7 and 8 myself.

Do you think it can still be ran before any issues arise? There was no blow by. But I needed to change injectors so I decided a compression check would be a good start before I order new injectors.

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[02greysixer]

You sure you got accurate readings? Doesn't take much of a leak to give a lower reading? With a 100 psi difference I would think you'd have a noticeable miss at idle. And a 240 psi you'd probably have smoke when cold too.

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[YoungGunDiesel]

You sure you got accurate readings? Doesn't take much of a leak to give a lower reading? With a 100 psi difference I would think you'd have a noticeable miss at idle. And a 240 psi you'd probably have smoke when cold too.

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Here's the kicker. It does sound like there's a miss and it smokes like a train from the bad injectors. So I'm not sure if its a combo of two or what.

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[YoungGunDiesel]

P.s these readings where received from a 29$ harbor freight compression tester.

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[WVRigrat05]

I'd run it up the interstate at 100+ for 3-5 miles and see what lets loose, if nothing does then nothing's wrong.

 

[YoungGunDiesel]

...I...I can't tell if your being serious. Or sarcastic...although with bad injectors ill melt down pistons well before I reach 100mph

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[zakkb787]

I'd run it up the interstate at 100+ for 3-5 miles and see what lets loose, if nothing does then nothing's wrong.

And we wonder why yoir piston let loose...:roflmao:

 

[WVRigrat05]

And we wonder why yoir piston let loose...:roflmao:

Hey I didn't say I did it lol. I've done a few 75-120 pulls but only a handful of times. I did it non stop in the Lilly and it took it. Damn quality control.

 

[Awenta]

...I...I can't tell if your being serious. Or sarcastic...although with bad injectors ill melt down pistons well before I reach 100mph

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Oh no... he was serious :rofl:


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[Chevy1925]

Here's the kicker. It does sound like there's a miss and it smokes like a train from the bad injectors. So I'm not sure if its a combo of two or what.

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Injectors are not your worry here. At 240psi, you will be smoking/hazing like a sob cold and still haze a ton when hot.

With compression like that, injector balance rates tell you nothing. The only way to know if those injectors are bad is to send them out. Your engine is too hurt

 

[ikeG]

Being an lbz, the injectors are probably returning most of their fuel and will fail testing too.

 

[YoungGunDiesel]

This is saddening news I wasn't expecting a motor rebuild

Just out if curiousity. If I disconnect the injector to cylinder 4. Would the smoking stop considering theres no more fuel going to it?

And also why doesn't the low compression cause blow by? I can take the oil cap off, flip it over. And it doesn't move.

Could it also be a burnt exhaust valve? I ask cause my truck mimics this guys exactly,

https://youtu.be/YK1nrGocHmg

 

[WolfLMM]

Low compression won't cause blow by, because your rings are sealing fine, your rod is shorter is the reason.

 

[YoungGunDiesel]

Low compression won't cause blow by, because your rings are sealing fine, your rod is shorter is the reason.

Excuse my newbie-ness but what your suggesting is a bent rod?

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[WolfLMM]

Yes sir, that's a real possibility. However like you said, a leaky valve can cause low compression as well. You'll have to do some testing to figure out which it is.

 

[YoungGunDiesel]

Yes sir, that's a real possibility. However like you said, a leaky valve can cause low compression as well. You'll have to do some testing to figure out which it is.

I'm looking around for a leak down tester for a diesel but cant really find one. I have one for a gas motor but no adaptor for a glow plug hole. I shall keep looking into this though.

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[Chevy1925]

I'm looking around for a leak down tester for a diesel but cant really find one. I have one for a gas motor but no adaptor for a glow plug hole. I shall keep looking into this though.

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use the end of your compression testor. IIRC its just an air chuck on the gauge end where you connect it

 

[WVRigrat05]

...I...I can't tell if your being serious. Or sarcastic...although with bad injectors ill melt down pistons well before I reach 100mph

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Won't melt, you'll crack a piston first, trust me.