Losing prime

Discussion in 'Heavy Duty Diesel Truck Mechanics Forum' started by stayinback, Jan 1, 2020.

  1. stayinback

    stayinback Road Train Member

    3,914
    8,238
    Jan 24, 2014
    chicago,il
    0
    Hey guys, Have a C-12 2KS, I lose a little Prime in the morning come start-up...If I dont manually prime it- It take about 15- 20 second of Crank till it hits.....

    I checked all the usual suspects- All Fuel Lines tight-None leaking- Lift Pump New, Filter Base Tight to head,No Leaks, No secondary Filter- (removed it years ago)

    This just started after truck sat a month for vacation... If I Manually prime it , Fires Right up and Good all day.

    Whatcha Thinkin? Also I do NOT have a fuel pressure gauge- Changed Regulator 6 months ago- Fuel Filter about 2 months ago last service-
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  3. Chubby Fly

    Chubby Fly Medium Load Member

    569
    781
    Nov 25, 2019
    0
    im well versed with the 2ks. so let me see if i can be of some help.
    First of all, the secondary filter is the one mounted to the block. Thats where your primer will be. so im thinking you removed the primary. Whats the reason you removed the primary? The primary is the first line of defense to grab any major debris if any and to grab any water that may be in the tank or the lines. The secondary which is a 2 micron filter from cat is the last line so the injectors dont get clogged. If you were to hook a fuel gauge to your secondary housing, and let it sit over night, its not gonna hold any readable psi. For whatever reason they dont but they hold enough fuel psi to where truck fires up first turnover.
    So in the secondary housing, you changed the check valve/regulator already, and you already put a new fuel pump. so lets rule those out. I wouldnt nother with pickup line from the fuel tank. But you can check those by putting a air fitting on top of fuel tank and putting about 1 psi of air to the tank. Thats how you find a fuel leak the quick and easy way from the supply to the pump. The return can have leaks and not effect anything. So next step before you suspect injector leak, is pull your primer plunger off the secondary and check the valves in the plunger assembly or replace it.
    Im assuming the plunger is loose when you have to prime it? and not hard to push in when you go to prime it when it wont start. Instead of trying to start it tomorrow morning, pop the hood and push the primer and veryify it is not hard to push in.
     
  4. stayinback

    stayinback Road Train Member

    3,914
    8,238
    Jan 24, 2014
    chicago,il
    0
    Thaknks Chubby........

    Yeah,Primer pushes in easy like 3 times then she's primed...So its not a Bad Loss of Prime,But bad enough to concern me,I dont like Dry starting the cold oil for 15 seconds...

    Return line Tight,

    I Removed the Primary filter (Mounted on rt side frame) Many years ago due to constant Failures and never put a new one on.......Never a issue.

    Never had prime prob till now- So Yes to answer your question, It Needs to be pumped a few times for a quick start.

    Tank Issues,Air In Line-Dont think so Biut will check- May be defective Filter base or even filter? Oh and I forgot- I replaced the Plunger from an ####### Aftermarket place about a year ago- Of
     
    Last edited: Jan 1, 2020
  5. Chubby Fly

    Chubby Fly Medium Load Member

    569
    781
    Nov 25, 2019
    0
    I have an extra one cat plunger I can send you if you want to try it. It’s only a year old. Other than that maybe try a new fuel filter also and put pressure to the fuel tank to see if suction line is leaking and allowing air in system. When you put shop air to tank, you will see fuel spraying out from where ever leak is
     
    stayinback Thanks this.
  6. stayinback

    stayinback Road Train Member

    3,914
    8,238
    Jan 24, 2014
    chicago,il
    0
    Thanks Chubby- I'll try some pressure- Whatever it is,We'll Find it,I'll run over to CAT and get a plunger- They arent much-
     
  7. Chubby Fly

    Chubby Fly Medium Load Member

    569
    781
    Nov 25, 2019
    0
    I had same starting issue before with a bad plunger. The check valves looked good but somehow it was causing prime issues. So yeah that would be a good start. Let me know if you still need mine. Start with simplistic things first
     
    stayinback Thanks this.
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

    Every month 400 people find a job with the help of TruckersReport.

  • Draft saved Draft deleted