LOST COMPRESSION ON ALL CYLINDERS

[JPG350]

Hello gents,

I am not sure if this is the correct place to post this question, if it is not i apologize.

My 2017 recently shut off on me while driving, no bang, no knock, just shut off. I verified fuel, spark successfully. next i bought a compression gauge and conducted a compression test and my results have me scratching my head. Across both banks on all cylinders I am getting 30psi which has me very confused.I do not have oil/coolant mixing anywhere.

My question is, how is this possible? May i possibly be doing something wrong while conducting the test? Any type of recommendations or advice is greatly appreciated.

BTW my engine has about 18k miles and has following mads:
Procharger stage 2 kit, Longtubes, Cat/Res delete, RXT1200 clutch.



THANKS

Juan G.

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[Lilmags500]

Sounds like you lost your timing chains , can you verify your cams are turning when you crank the engine over ? Pull the valve covers and
have a good look ..... Sounds like your valves aren't opening / closing ....

 

[95CobraR]

All eight cylinders showed 30psi of compression?

 

[Hack]

Are there instructions in the service manual that you followed when running this compression test? With a carbureted car, it's easy to access the throttle blades to hold them open and there are no electronics that might be "confused" by the open throttle during cranking. On a modern complex engine I would probably not run a test like this without a manual to follow.

 

[JPG350]

Sounds like you lost your timing chains , can you verify your cams are turning when you crank the engine over ? Pull the valve covers and
have a good look ..... Sounds like your valves aren't opening / closing ....

i will pull the valve covers and take a good look at that. thanks

 

[JPG350]

All eight cylinders showed 30psi of compression?

yes sir, i got 30 PSI on every single cylinder. its very confusing

 

[JPG350]

Are there instructions in the service manual that you followed when running this compression test? With a carbureted car, it's easy to access the throttle blades to hold them open and there are no electronics that might be "confused" by the open throttle during cranking. On a modern complex engine I would probably not run a test like this without a manual to follow.

I did not follow the manual since i do not have one yet. i did watch a few videos and followed those to the t. to bypass the throttle blade issue, i actually removed the throttle body completely so there would be no restrictions thru the intake.

 

[Lurker_350]

I did not follow the manual since i do not have one yet. i did watch a few videos and followed those to the t. to bypass the throttle blade issue, i actually removed the throttle body completely so there would be no restrictions thru the intake.

Cliff notes from manual:

1. Make sure oil is correct viscosity and level. Make sure battery is charged. Operate vehicle until engine is to temp. Turn ignition to OFF and remove all plugs
2. Remove air cleaner outlet pipe
3. Disconnect throttle body electrical connector
4. Set throttle plate to wide open
5. Install compression gauge on No. 1 cylinder
6. Install auxiliary starter switch in starting circuit. With ignition in OFF position, use auxiliary switch to crank engine minimum of 5 compression strokes. Record highest reading.
7. Repeat on all cylinders.
8. Put it back together.

Seems like removing the throttle body would accomplish steps 2 through 4.

 

[honeybadger]

That sounds like user error or a malfunctioning gauge to me. Are you sure you're getting a good seal? I can't think of anything that cause compression issues across all cylinders

 

[JAJ]

If something was doing a really good job of blocking the intake, you'd have big manifold vacuum and low compression numbers like this.

 

[JPG350]

That sounds like user error or a malfunctioning gauge to me. Are you sure you're getting a good seal? I can't think of anything that cause compression issues across all cylinders

I am going to take a picture of what im using and hell maybe even a video of how i'm doing it and the results.
i actually watched your video sir and did it exactly like you did except i removed the throttle Body to make sure nothing would be blocking intake.
the car had been sitting for 2 weeks at a body shop and i made it about 2 miles from the place and it just shut off. no low oil lights, oil pressure alerts, banging, knocking or anything.

 

[lonegunman]

Reread that first post about jumping time.

 

[Tank]

Hook it up to an OBD reader and see if you're throwing any codes.

Seems to me a compression test is a step or two down the diagnostic testing tree from the symptom you described and the mods you have.

 

[JPG350]

Hook it up to an OBD reader and see if you're throwing any codes.

Seems to me a compression test is a step or two down the diagnostic testing tree from the symptom you described and the mods you have.

P0017 CMDTCs
P0138 CMDTCS
P0339 CMDTCs

 

[JPG350]

Now when screwing the 14mm adapter in, does it usually screw all the way down to the o-oring?

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