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 > UPDATE: Hard starting Cummins ISM

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Executive

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Posted: 04/14/19 08:23am Link  |  Quote  |  Print  |  Notify Moderator

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 a new facility in Arizona. My engine has always started within 3-5 seconds, I'll call it a short crank. After service it will still start but it now takes a long crank. That's the best way I can describe it. I'm not used to cranking an engine for an extended period of time. What could be the cause? It appears they used the correct water separator when it was changed Racor RK12963. Any insight will be appreciated....Dennis

* This post was edited 04/17/19 10:29am by Executive *


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ppine

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Posted: 04/14/19 08:28am Link  |  Quote  |  Print  |  Notify Moderator

Try some additive for diesel to make sure you have gotten all the water out of the system. Many will add some cetane which makes for easier starting. They help take out some varnish in your engine.

JaxDad

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Posted: 04/14/19 09:01am Link  |  Quote  |  Print  |  Notify Moderator

Typically a longer crank to start after a service would indicate you still have some air in the system. Unusual on a newer diesel, but not unheard of.

How far / long have you driven it since the service was done?

Bird Freak

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Posted: 04/14/19 09:14am Link  |  Quote  |  Print  |  Notify Moderator

Sounds like air in the fuel system. Maybe a bad seal on filter.


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Posted: 04/14/19 10:03am Link  |  Quote  |  Print  |  Notify Moderator

Are you using the water separator with the clear bowl on the bottom? Some installers get confused as to proper installation of seals on these.

wildmanbaker

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Posted: 04/14/19 10:06am Link  |  Quote  |  Print  |  Notify Moderator

Contact the shop and voice you concerns after the service. There may be a small leak allowing air into the fuel line.


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Posted: 04/14/19 10:10am Link  |  Quote  |  Print  |  Notify Moderator

Thanks everyone so far. You've verified my suspicions. Air somehow leaking back into the fuel was my initial thought. I've only driven it about 8 miles since the service..I;ll repurge the system today and see if that helps....Dennis

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Posted: 04/14/19 02:59pm Link  |  Quote  |  Print  |  Notify Moderator

If it's a Racor, make sure the Tee handle is tight.


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Posted: 04/14/19 05:48pm Link  |  Quote  |  Print  |  Notify Moderator

the most likely cause is the wrong engine mounted fuel filter. The cummins N14, M11 and ISM engine fuel filter must have a metal tube down the center of the filter or they will have long crank time. There are a lot of filters that will screw onto the cummins filter base but whatever they installed should cross to fleetgard number FS1000

JackMS

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Posted: 04/15/19 09:24am Link  |  Quote  |  Print  |  Notify Moderator

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.


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