Compression Test Cranking Rpm
Quick Question About Cranking RPM
Going to do a compression test tomorrow, just wondering if my torque app will still show engine rpm with ESS disconnected? I want to log my rpm with torque to find out my true compression numbers |
Originally Posted by DinSum
(Post 4447227)
Quick Question About Cranking RPM
Going to do a compression test tomorrow, just wondering if my torque app will still show engine rpm with ESS disconnected? I want to log my rpm with torque to find out my true compression numbers So IMO no it won't, sorry edit: actually I might be wrong mmmm I should go out and try tonight. I was going to delete this post but ... I'll let it go as my... sub'd |
I'm pretty sure it uses the ESS. Mazda typically grabs it from there. It would be by far the most accurate method, I think everything else would have to be derived from other factors?
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Yeah I read that you disconnect the ESS when doing the compression test to stop spark and fuel but it made me wonder if I would still get the rpm signal, ill find out for sure tomorrow
If it turns out that there is no rpm signal, would I just be able to pull my fuel pump fuse and crank the engine with ESS plugged in to see my cranking rpm? |
Another problem might be that I think power to the OBD2 port is interrupted during cranking...
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disconnecting the ESS will disable the Rpm signal.
however you can get cranking RPM before and after the test and just average it. |
All you have to do is hold your gas pedal to the floor while you crank. There is no need to disconnect the ESS to test with Torque.
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Originally Posted by RIWWP
(Post 4447273)
Another problem might be that I think power to the OBD2 port is interrupted during cranking...
Originally Posted by j9fd3s
(Post 4447275)
disconnecting the ESS will disable the Rpm signal.
however you can get cranking RPM before and after the test and just average it. |
I believe disconnecting the ESS kills the ignition.
Holding the pedal down or disconnecting the Fuel Pump fuse, kills the fuel. |
So Holding the Gas Pedal down Fully while cranking kills Fuel? So I guess even when im doing the compression test I wont need to disconnect the ESS since I will be holding the gas pedal down fully
Good to know thanks |
Pulling the fuel pump fuse is one way, although I'd honestly also disconnect the coils from the harness. During the test you will have 1 or more plugs that are no longer grounded, and a coil firing without a place for the current to go will fry fast. How fast? Unsure, but from other forums and other cars it can be as fast as ~10-15 minutes of firing time. Even if you are firing for less than that, no reason to put your coils through that.
Disconnecting the ESS kills both fuel and ignition WCS. The ECU needs it to know when to fire the injectors, and won't fire them without that information. |
Originally Posted by RIWWP
(Post 4447408)
Disconnecting the ESS kills both fuel and ignition WCS. The ECU needs it to know when to fire the injectors, and won't fire them without that information.
I thought this was the case, but for whatever reason I changed my mind. My mistake. |
Originally Posted by RIWWP
(Post 4447408)
Pulling the fuel pump fuse is one way, although I'd honestly also disconnect the coils from the harness. During the test you will have 1 or more plugs that are no longer grounded, and a coil firing without a place for the current to go will fry fast. How fast? Unsure, but from other forums and other cars it can be as fast as ~10-15 minutes of firing time. Even if you are firing for less than that, no reason to put your coils through that.
Disconnecting the ESS kills both fuel and ignition WCS. The ECU needs it to know when to fire the injectors, and won't fire them without that information. |
Originally Posted by RIWWP
(Post 4447408)
Pulling the fuel pump fuse is one way, although I'd honestly also disconnect the coils from the harness. During the test you will have 1 or more plugs that are no longer grounded, and a coil firing without a place for the current to go will fry fast. How fast? Unsure, but from other forums and other cars it can be as fast as ~10-15 minutes of firing time. Even if you are firing for less than that, no reason to put your coils through that.
Disconnecting the ESS kills both fuel and ignition WCS. The ECU needs it to know when to fire the injectors, and won't fire them without that information. I would disconnect the coils but I would have to remove the intake and tube to get at them which is more work then I want to do, 5-10 seconds worth of cranking when checking for rpm hopefully shouldn't hurt my BHR coils ;/ |
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