98 tdi won't keep prime

Discussion in 'VW Mk3 Jetta, Passat TDI and other/older diesels' started by MK3di, Oct 12, 2016.

  1. MK3di

    MK3di New Member

    Joined:
    Oct 12, 2016
    Messages:
    4
    Car:
    98 VW Jetta TDI
    Location:
    Jacksonville, FL
    Hi guys, I'm new here and new to the diesel world. I did a few nights worth of searching various forums in hopes of finding a solution to my problem. So here's my story. I just recently picked up a 98 jetta tdi from a buddy of mine who owns a car lot. 3 months agoish he replaced the injection pump with what appears to be a used one. Not sure if it was replaced or re-sealed. Was told it was running fine and he drove it to his new shop location before he let it sit and now it won't start after sitting. Not sure time frames are exact but it sat long enough to let the battery die. I'm having an issue getting fuel to get to the injection pump and staying there. I drained and refilled the fuel filter with fresh diesel, pulled a vacuum on the return hose going to the fuel filter, and that brought the fuel level up to the injection pump in the clear inlet hose. I then tried to start the engine and it would not start. Fuel level again dropped further away from the pump after cranking. Pulled a vacuum again to get the fuel back to the pump. Once that was done, I cracked the fittings at the injectors and was able to get some fuel to seep out, not sure at what pressure it should be coming out, tightened them back up and tried to start and the fuel level went back down in the inlet hose. The engine will fire over on starter fluid, I just cant maintain a prime on the pump and I'm not sure where to look next.
     
  2. Seatman

    Seatman Well-Known Member

    Joined:
    Jul 9, 2010
    Messages:
    5,818
    Car:
    2000 Mk4 Golf Estate 1.9tdi 174 bhp
    Location:
    Scotland
    Mods:
    PP764's, turbo and mapping
    It's possible the pump is faulty especially if it's sat dry at all.
    Could be you're just not getting enough fuel up.
    A friend had an old 1.6 td mk2 I think it was, I set up an iv line type set up so gravity could do its thing. Still took a bit of cranking and bleeding injectors but eventually it burst into life.

    Anyway check around the pump for dampness from fuel leaking, could maybe also spray something around the joins while pulling vac and see if it gets sucked in.

    Fuel should kinda spit quite well out the tops of all four injector pipes.
     
  3. MK3di

    MK3di New Member

    Joined:
    Oct 12, 2016
    Messages:
    4
    Car:
    98 VW Jetta TDI
    Location:
    Jacksonville, FL
    It does look like it was wet at one point around the 4 injector outlets of the pump, but its hard to tell if it's just a sloppy repair cleanup or if it was leaking while running. It does seem as though the fuel not wanting to stay up at the inlet of the injection pump would be an issue. At least I would think. Are you saying while pulling vac on the return line to spray for leaks, or pulling vac from somewhere else? Also, with the injection pump, does it draw fuel or does it just pressurize fuel that's pushed to it from another pump somewhere in the system? I did a little more searching since my previous post and found a link on another site that said the fuel filter should be primed by applying vac to the nipple of the fuel outlet that runs to the injection pump until steady fuel runs out. While doing that process with the vac pump I was getting fuel with air bubbles and I thought I could hear air sucking in from around where the fuel return T fitting mates to the fuel filter housing. Unfortunately my vac pump broke as I was using it and wasn't able to confirm. If it did have a leak there, would that be an issue for keeping fuel primed? Appreciate the help.
     
  4. Seatman

    Seatman Well-Known Member

    Joined:
    Jul 9, 2010
    Messages:
    5,818
    Car:
    2000 Mk4 Golf Estate 1.9tdi 174 bhp
    Location:
    Scotland
    Mods:
    PP764's, turbo and mapping
    Yes to pulling vac through the pump return while checking for leaks.

    And definitely a problem if the t piece is leaking air in. Any tiny leaks will cause the fuel to run back to the tank.

    The IP has a lift pump built in, it's all mechanical.


    Some people add a lift pump from a mk4 PD engined car which would help with priming etc.
     
  5. MK3di

    MK3di New Member

    Joined:
    Oct 12, 2016
    Messages:
    4
    Car:
    98 VW Jetta TDI
    Location:
    Jacksonville, FL
    Thank you for your help seatman. I finally got the pump primed and now the engine will fire off with the assistance of a small amount of starter fluid and will idle. It won't take throttle over 2k rpm and its very hesitant to get there. So I'm onto my next issue now. I'm going to start a new thread but figured I would update this one as well. Maybe you'll have some input. I have searched around and done a few tests but not sure where I should go from here. After idling for a short period of time, the glowplug light comes on and will flash, followed by the cel light which stays constant. I check the glowplug fuse and it tests fine. I tested between the two glowplug terminals on the glowplug harness and there is no voltage. Tested with the key on, and with the engine cranking. I'm not sure if there should be voltage between them, or if they're both positive and the glowplugs are grounded in the head. Any help is appreciated.
     

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