UPDATE: Hard starting Cummins ISM
Good Morning everyone! Cummins ISM. 95,000 miles. Just had it serviced, replaced water separator, filters etc. including Allison transmission service. Generally used Speedco for service but tried out ...
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If your separator is the type with the clear glass on top, there is usually an anti backflow valve in the outlet fitting. Very simple construction- a plastic cage with a ball and spring in it. Any bit of trash can cause a long crank situation, but it takes a while after shutting down to show up. If your engine is running and you shut it down and immediately restart, does it start better? If so then probably not that check valve.
