Starts During Relative Compression Test

[Keith Browning]

Don't think I have ever run into this before.  It's a 2006 E450 ambulance that has a base engine concern. I was attempting to run a relative compression test and the engine started every time I cranked it. If I hold the throttle to the floor the RPM's rise and the engine stays running. If I hold  the accelerator to the floor to begin the test then let off (yes you can do that) the engine fires and slowly stalls. It's not due to any fuel leaks or oil and the engine was actually running. All stock and the modules are up to date.

I ended up pulling the FICM relay and successfully ran the test but I have no explanation for why this was going on. Really strange!

[forddieseldoctor]

I’ve had enough of them do it that I automatically pull the ficm relay before I start.