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wtmtnhiker's avatar
wtmtnhiker
Explorer
Feb 28, 2018

Fuel Filters change ISC Cummins

My 2005 Cummins ISC has 2 fuel filters. One has the water sensor and drain which Cummins manual says is the suction filter and the other is the pressure filter. I changed both filters but according to
Cummins I only pre filled the suction filter. The manual states to cycle the key on for 30 seconds then off for a minute and do this 3 to 4 times while the lift pump fills the pressure filter. I followed this procedure and expected the engine to easily start but instead it cranked excessively and was very hard starting. Anyone knows if this is normal? Is there another step in the procedure that I missed maybe? Seems to me that cycling the key didn't do anything to fill the other filter. It starts okay now and seems to idle alright but I won't actually hit the road with it for a few days. Likely from now on I will prime both filters.
Class A
  • ScottG's avatar
    ScottG
    Nomad
    Feb 28, 2018
    Do the cycling of the key about 10 to 12 times. Makes all the difference for me.
    Listen for the fuel pump running. cycle the key after it stops - if it stops. There was a s/w update to some Cummins platforms that causes the pump to continue running rather than stop. If it continues to run, you can hear it change pitch once the filters are full.
  • wtmtnhiker's avatar
    wtmtnhiker
    Explorer
    Feb 28, 2018
    ScottG wrote:
    Do the cycling of the key about 10 to 12 times. Makes all the difference for me.
    Listen for the fuel pump running. cycle the key after it stops - if it stops. There was a s/w update to some Cummins platforms that causes the pump to continue running rather than stop. If it continues to run, you can hear it change pitch once the filters are full.

    Maybe that was it, I only cycled the key 4 times but the manual said I only had to do 3. I did hear the pump running for about 30 seconds each time.
  • wtmtnhiker's avatar
    wtmtnhiker
    Explorer
    Feb 28, 2018
    sch911 wrote:
    I fill both filters and have never had any issues.

    I think that's what I'll do from now on.
  • ScottG's avatar
    ScottG
    Nomad
    Feb 28, 2018
    I also have two, one is very large. I let the pump do all the work and this reduces the likelihood of getting debris in the system - your common rail fuel system is very sensitive.
    It's also the fastest, easiest and cleanest method.
  • Popsie's avatar
    Popsie
    Explorer
    Feb 28, 2018
    When I change the fuel filters, I use a threaded pipe plug in the center hole then pour oil into the outside holes. That way, the only oil that gets to the engine is oil that has passed through the filter material.

    We've been fulltimers since 2003, and when I change the filters, I just crank the engine and it fires up shortly. Never any problem.

    YMMV
  • ScottG's avatar
    ScottG
    Nomad
    Feb 28, 2018
    Popsie wrote:
    When I change the fuel filters, I use a threaded pipe plug in the center hole then pour oil into the outside holes. That way, the only oil that gets to the engine is oil that has passed through the filter material.

    We've been fulltimers since 2003, and when I change the filters, I just crank the engine and it fires up shortly. Never any problem.

    YMMV


    "Just cranking" the eng can lead to nightmarish results on some diesels. It can require opening injector lines and more endless cranking.
    While you may get away with it, many won't and in some cases forcing air through certain inj pumps will severely shorten their life (esp the CAPS system).
    Modern, Common Rail systems are the most forgiving and will purge themselves.
  • Ivylog's avatar
    Ivylog
    Explorer III
    Mar 01, 2018
    Both of mine are on the suction side and the water sep one is low enough that fuel keeps coming out when I take it off. I immediately put a dry filter on and only completely tighten once fuel starts to overflow. I thought my second filter was on the pressure side but in trying to help a friend with a problem I loosen it and had the DW turn the key on expecting to have fuel on the rag I'd put around the loose filter. It's on the suction side too and I've never put it on with fuel in it...cycling the key 4 times for the 30 seconds the lift pump runs before shutting off. Has always started immediately.
  • wtmtnhiker's avatar
    wtmtnhiker
    Explorer
    Mar 01, 2018
    Ivylog wrote:
    Both of mine are on the suction side and the water sep one is low enough that fuel keeps coming out when I take it off. I immediately put a dry filter on and only completely tighten once fuel starts to overflow. I thought my second filter was on the pressure side but in trying to help a friend with a problem I loosen it and had the DW turn the key on expecting to have fuel on the rag I'd put around the loose filter. It's on the suction side too and I've never put it on with fuel in it...cycling the key 4 times for the 30 seconds the lift pump runs before shutting off. Has always started immediately.

    This is similar to what the Cummins manual said to do however it didn't work well. I had to excessively crank to get it started and I hope I didn't damage anything but it seems to start ok and idles ok now. I'll hand fill both filters from now on, don't see what it can hurt except it's a little more work.
  • AikenRacer's avatar
    AikenRacer
    Explorer
    Mar 01, 2018
    I fill both filters and then go through the priming process...no problems.

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