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The other day, I was discussing a loss of power, odd miss under power, dipstick ejection issue on a friends ford. While we were running a compression test, I started thinking, how does someone do a compression test on a Volt? Every car I have even performed such a test on, I do by jumping the starter solenoid to the battery with the throttle wide open (among other steps) but since the Volt does not have a starter motor, how do you do it? I assume there is a way to tell the Voltec to close the clutch from MG1 to the engine and to rotate MG1, but after searching, I came up blank.

If I were to shade tree it, I might try installing a starter off a Cruize if it would fit.

Im not having any problems with my Volt nor do I anticipate any, just curious.
 

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The Volt does not have a flexplate (flywheel) like the Cruze. You can not install a starter or jump any relays to get the engine to turn over. You need a scan tool like GDS to perform a compression test. There is a scan tool function for performing a compression test on these cars, the car needs to be in service mode and you can command the compression test to run and the engine will turn over a few revolutions and then stop so you can take the readings from your compression gauge.
 

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do a leak down test,seems much easier to do on a volt than a compression test,plus it will show if the piston has a hole or leaky rings,,or that 1 of the valves are leaking.just need to turn engine over w./ a breaker bar to the test cylinders tdc.
 

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The Volt does not have a flexplate (flywheel) like the Cruze. You can not install a starter or jump any relays to get the engine to turn over. You need a scan tool like GDS to perform a compression test. There is a scan tool function for performing a compression test on these cars, the car needs to be in service mode and you can command the compression test to run and the engine will turn over a few revolutions and then stop so you can take the readings from your compression gauge.
And there is your answer. This thread needs to end before more bad information gets into circulation.
 

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We'll defer to the Volt technician in the room, rather than answers that while accurate for some cars, are not Volt specific. Thanks, mpmoore :)
 

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Discussion Starter #6
The Volt does not have a flexplate (flywheel) like the Cruze. You can not install a starter or jump any relays to get the engine to turn over. You need a scan tool like GDS to perform a compression test. There is a scan tool function for performing a compression test on these cars, the car needs to be in service mode and you can command the compression test to run and the engine will turn over a few revolutions and then stop so you can take the readings from your compression gauge.
I figured it would require a command from a scan tool. Never considered that it would not be equipped with a flexplate and thus does not have a ring gear.

Just curious, the compression test procedure, is it like the old days, disable fuel and ignition, throttle wide open, charged battery, crank for X seconds, compare with others....or does the ECM derive relative compression difference by looking at crank speed peeks and valleys?
 

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You do use a compression test gauge and compare numbers, you do not have to disable the fuel system or work the throttle, the scan tool and ecm does that for you. Also a leak test will not show compression only leaks so if you have a stuck closed valve, you would see good leak numbers but still have low/no compression.
 
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