Old Cummins PT fuel system issues?

Discussion in 'Trucks [ Eighteen Wheelers ]' started by albertaphil, Jul 18, 2010.

  1. albertaphil

    albertaphil Bobtail Member

    47
    7
    Mar 31, 2010
    Calgary, Alberta
    0
    Hi there, I have an old NHC 250 that I put a new cylinder, piston etc, and two new injectors.

    She ran great for about 10 hours, and then at the end of the day I noticed it would hunt a bit at idle, and it maybe seemed a little more rattly. Power was about the same.

    The next day it started fine, but had no power and wouldn't rev up.

    I changed the fuel filter and blew back through the fuel line to the tank to dislodge anything that might have been plugging the line. It helped, but it still isn't running right. After idling for a minute or two, the throttle becomes quite unresponsive until it is revved up for a few seconds, at which time the throttle is acceptably responsive, but not like it used to be.

    The power seems to be off a bit, but when it is out on the road the drivability is mostly normal. And it still seems to rattle more, and maybe vibrate a bit.

    What is going on here? Do I have a worn out P-pump? Am I getting air in my system somewhere? Do I have multilple injectors failing?

    The engine starts okay and doesn't make much white smoke, if that helps at all.

    Also, I don't know if this has anything to do with it, but my engine brake becomes erratic above 1800rpm.

    I appreciate any experience you have.

    Thanks,
    Phil
     
  2. Truckers Report Jobs

    Trucking Jobs in 30 seconds

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

  3. Bush chook

    Bush chook Light Load Member

    144
    43
    Apr 27, 2009
    Geelong
    0
  4. albertaphil

    albertaphil Bobtail Member

    47
    7
    Mar 31, 2010
    Calgary, Alberta
    0
    Okay, I changed all the suction lines to the fuel filter and fuel pump.

    I checked the filter in the pump...clean. I sealed the cap for that filter just in case.

    These made no difference. Like I said before, out on the road the engine runs pretty much normally, although it might be a little louder...engine knock. I'd also say the engine doesn't start as well, and it idles poorly...up and down.

    After idling for a minute, the engine doesn't want to rev up, but after revving for a few seconds it acts more normally.

    It seems like all I'm left with is a faulty pump. Do they fail over the course of a few hours? I suppose that since this all started with a plugged fuel filter that some junk might have gotten through and damaged the pump. I'll accept any other ideas that are cheaper and easier:) Thanks for the help.

    Cheers
    Phil
     
  5. stranger

    stranger Road Train Member

    3,640
    4,958
    Oct 10, 2006
    NC
    0
    Recheck that all injectors are tight in the cups. It is also possible that an injector o-ring is pinched, and that is where you are sucking air. Check to see if you are making oil, and smell for fuel in the oil. I had a friend lose a crank on a 250 from an injector o-ring being pinched. It idled rough, puffed white smoke on takeoff, and was just a little off in general.

    The only way to know if it is the pump for sure is to have it bench tested. If anyone in your area still has a pump stand, they could tell you right away.

    edit: Check you fuel crossover screws to make sure they haven't worked loose.
     
    albertaphil and 1989 Pete Thank this.
  6. albertaphil

    albertaphil Bobtail Member

    47
    7
    Mar 31, 2010
    Calgary, Alberta
    0
    Update: I put some more fuel in my tanks and drove the 6 miles to the gravel pit for a load. By the time I got to the pit the old truck was running like normal. So then I brought the load home and after idling for about 10 minutes I noticed a hint of the acting up again

    So I got another load and didn't idle longer than a few minutes, but overall I'd say the the problem has mostly fixed itself. I guess it was just air in the system that takes quite a bit of driving, with warm fuel and perhaps fuller fuel tanks to purge.

    Anyway, thanks for all your input and experience.

    Cheers,
    Phil
     
  7. stranger

    stranger Road Train Member

    3,640
    4,958
    Oct 10, 2006
    NC
    0
    Your pickup tubes in the tank could be cracked or rusted near the bottom. It could be as simple as needing to keep the tanks fuller, or just run on one is you have two.
     
  8. earthmover

    earthmover Medium Load Member

    563
    20
    Jan 27, 2009
    castalia , north carolina
    0
    hay albertaphil my buddy replace the fuel line between the 2 filters and now its back to normal the line must be coll. inside so hope this helps you out some mike
     
  • Truckers Report Jobs

    Trucking Jobs in 30 seconds

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