isx 450 hard start

[Rawze]

you did not mention what make/model year engine this is. Its anyopne;s guess if no one knows what engine you have.

Is it a Cm570?.. CM870?.. CM871?.. CM2250?.. CM2350?.. CM2350-X15?.. an ISX 12?... What?.


an engine ser# would help answer this too.

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As far as the ISX goes.. the engine needs to see 50 psi minimum while cranking before it will even consider firing the injectors. Sounds to me like you have a weak or restricted electric lift pump, and last I checked, they were not some ridiculous 13k$.

Could also be a snapped shaft on a gear pump. The CM570/870/871's are notorious for getting a snapped gear pump shaft and running just fine (because it would catch and start working) after cranking it up.. but would be a bear to start up because it would barely make 50+ psi fuel pressure (if at all) during cranking. Your symptoms sound similar to this.

Also, will the engine pass a properly done injector leak test?. if not, then that is the place to start.