[shorod]

Many remote start systems have a voltage sensing mode that does not require a tach signal. If you can find an installation manual for the system you might be able to set it to voltage sensing. You'll also want to set the crank time to something reasonable so in the event it doesn't detect the voltage quickly enough it doesn't leave the starter motor engaged long after the engine starts.

If this seems to work reliable for several starts, then you can be a bit more confident the tach signal is the issue. Do you have a digital multimeter with a continuity test mode? Have you ever noticed the tachometer jumping around or not behaving? Does your van have a tachometer?

-Rod