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  • 1KZ fuel starvation

    We broke down with fuel starvation nearly a month ago, coming back from a weekend away towing the camper. Called NRMA who put 20L of diesel in the tanks and followed us the nearest servo to fuel up. We got home fine - driving around 400km. The next day I dropped both tanks and checked for a cause. I cleaned the pickup strainer in the main tank which was badly clogged and checked/cleaned the aux pickup, jet pump etc. I thought I had the problem solved, but I wasn't entirely confident so after I carried a 20L jerry can of diesel in the back. Glad I did, the other morning 3 weeks later it broke down again on the way to work. It now had a similar amount of fuel in it as when we broke down last month (about 1/4 of total capacity of both tanks or 1/2 full on the 90L gauge). Anyway - I put the 20L into the tanks and drove it home that afternoon.
    Next day, dropped the main tank (which was almost empty - so obviously not transferring from aux tank) initially expecting to find maybe a pin hole or split convoluted hose on the pickup / sender assy that I maybe missed last time. No dice, all checked out - holding vacuum on the hoses and sender assembly. Checked the return line back to the aux tank (it has a check valve in the aux tank pipework) and that was flowing well and in the correct direction. The jet pump was cleaned and inspected again, no crud inside etc. This is a 1KZ remember and it works differently to the 1KDs (they use an electric pump which circulates fuel from the main back to the aux tank - just through the pipework in the aux tank - and back through the filter above the tailshaft to the jet pump).
    So I connected a supply hose from a fuel container to the fuel filter in the engine bay, connected the return from the aux to the jet pump and used a clear vinyl tube to connect the aux pick-up back to the suction connection on the jet pump. Started the engine and found there was little to no flow from the injector pump, so no suction at the jet pump to draw fuel from the aux tank to the main. Bingo.



    Now to the cause (if you're still reading... )
    Years ago my car was suffering from a metallic rattle/vibration/resonance from the passenger footwell area when the engine was running and would change with revs. Pretty common apparently on the 1KZs. Someone (on the internets) found the probable cause was the outlet valve on the injector pump and the noise was travelling along the return fuel pipe under the floor. The fix was a 5 minute one, take the 14mm banjo connection cap off the valve and stretch the spring by a mm or 2. Noise gone. Gear pumps commonly make this noise in hydraulic systems - it's like a buzzing resonance that travels along steel pipework.
    So - I took the spring out again and carefully squashed it lengthwise back to what it would have been originally (around 14mm from memory), refitted it and ran the engine again. Now I had return flow back to the tank and the jet pump was working!
    Put it all back together and put another 20L in the tanks at the servo (and filled the jerry can to carry in the car *just in case*). Now to drive it until the fuel level is down to the point when it starved...
    So if you have a 1KZ Prado and have modified your outlet valve, I would take the outlet hose off at the injector pump and using a length of tube or hose into a container, check you have a good flow of fuel. See the pics of my jet pump and how much it is flowing at idle. If you only have a trickle it's only a matter of time and you have fuel starvation issues..
    And if you're still reading.. You're probably wondering where the flow from the pump and leak off line is going? You would think it would pressurise the pump and blow the seals out right? There is a pressure reg valve in the pump body, excess pressure from the transfer pump is vented back to the intake side of the pump so basically just circulates inside.




    Silver '04 KZJ120~Manual~GXL~Dobinson/Kings lift~Custom valved Ironmans~Detroit Locker~Endless Air~X9 Superwinch~Madman EMS1~TJM Dual Battery~Rhino Roof Tray~120W solar panel~Foxwing awning~Bushskinz UVP~Long Ranger water tank~Bushman fridge~Steinbauer P-Box~Beaudesert 2 3/4"~Airtec Snorkel~TJM Sliders~Prico Boost Gauge~BFG-KO2s~TPMS~GME TX3420~Front and Rear Cameras~Ultimate Camper hanging off the back!

  • #2
    So the noise came back.
    I did some more research and found the 70 series cruisers with the 1HD engine had a similar problem and Toyota retrofitted a fuel damper to the supply line at the pump under warranty. 70s built after around 2003 have the damper factory fitted and it is mounted on the inlet manifold. HDJ100 series have a similar damper fitted on the outlet side of the pump and it is bolted on the inner guard.
    So, ordered a 100 series damper and a couple of hoses and test fitted it to the outlet. Noise gone!
    Spent an hour today permanently mounting the damper to the inner guard and hosing it up properly. Before the mod I could hear the buzzing of the pump on the return line along the chassis with my stethoscope, now with the damper fitted there is no noise at all along the line. The damper basically is an empty canister, I am guessing it retains a volume of air that acts as a compressible void damping out the pressure oscillations that cause the noise.
    Part numbers
    Damper 23290-17010 x1
    Hose 23273-17040 x1
    5/16 hose barb connector x1
    Silver '04 KZJ120~Manual~GXL~Dobinson/Kings lift~Custom valved Ironmans~Detroit Locker~Endless Air~X9 Superwinch~Madman EMS1~TJM Dual Battery~Rhino Roof Tray~120W solar panel~Foxwing awning~Bushskinz UVP~Long Ranger water tank~Bushman fridge~Steinbauer P-Box~Beaudesert 2 3/4"~Airtec Snorkel~TJM Sliders~Prico Boost Gauge~BFG-KO2s~TPMS~GME TX3420~Front and Rear Cameras~Ultimate Camper hanging off the back!

    Comment


    • #3
      What do you think changed with the setup between when you modified the relief valve years ago to now when the it started having issues? Good info on the fuel damper!

      Comment


      • #4
        Originally posted by ejukated View Post
        What do you think changed with the setup between when you modified the relief valve years ago to now when the it started having issues? Good info on the fuel damper!
        I tampered with the spring's free length a couple of times over the last year or so
        Silver '04 KZJ120~Manual~GXL~Dobinson/Kings lift~Custom valved Ironmans~Detroit Locker~Endless Air~X9 Superwinch~Madman EMS1~TJM Dual Battery~Rhino Roof Tray~120W solar panel~Foxwing awning~Bushskinz UVP~Long Ranger water tank~Bushman fridge~Steinbauer P-Box~Beaudesert 2 3/4"~Airtec Snorkel~TJM Sliders~Prico Boost Gauge~BFG-KO2s~TPMS~GME TX3420~Front and Rear Cameras~Ultimate Camper hanging off the back!

        Comment


        • #5
          Hi Adrian5800, thanks for the info. I have 120 with kz and I'm getting fuel starvation at 1/4 to 1/3 mark on fuel gauge. Is there a filter screen that needs cleaning on the14mm banjo bolt on return fuel on the injector pump or just the spring that needs ajustment?
          I repaced the pickup in aux tank and fitted new rubber fuel hoses on pipe work between the two tanks hoping this would sort the issue. Gauge is at half and so far no problem.
          Do you think I need to check fuel pickup in the front tank?
          Thanks again for goog post.

          Comment


          • #6
            Originally posted by BJ74 View Post
            Hi Adrian5800, thanks for the info. I have 120 with kz and I'm getting fuel starvation at 1/4 to 1/3 mark on fuel gauge. Is there a filter screen that needs cleaning on the14mm banjo bolt on return fuel on the injector pump or just the spring that needs ajustment?
            I repaced the pickup in aux tank and fitted new rubber fuel hoses on pipe work between the two tanks hoping this would sort the issue. Gauge is at half and so far no problem.
            Do you think I need to check fuel pickup in the front tank?
            Thanks again for goog post.
            Yes there is a screen in the outlet fitting on the injector pump. There's also one in the inlet but that one is inside the pump body. If no one has fiddled with the outlet valve spring as I described in my post above and you have good flow out of the pump back to tank (check with a clear pvc hose to a container with the engine idling) then I would be dropping the main tank and check the jet pump for a blockage etc. The swirl pot the jet pump is housed in can get pretty cruddy.
            Silver '04 KZJ120~Manual~GXL~Dobinson/Kings lift~Custom valved Ironmans~Detroit Locker~Endless Air~X9 Superwinch~Madman EMS1~TJM Dual Battery~Rhino Roof Tray~120W solar panel~Foxwing awning~Bushskinz UVP~Long Ranger water tank~Bushman fridge~Steinbauer P-Box~Beaudesert 2 3/4"~Airtec Snorkel~TJM Sliders~Prico Boost Gauge~BFG-KO2s~TPMS~GME TX3420~Front and Rear Cameras~Ultimate Camper hanging off the back!

            Comment


            • #7
              Thanks Adrian.

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