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Thread: Possible Diesel Pump Problems – Advice Please

  1. #1
    Join Date
    Jun 2006

    Possible Diesel Pump Problems – Advice Please

    I seem to have developed a problem with my vehicle’s injection pump since running on Biodiesel.
    I’m after advice and comments from any body out there that might have run into the same problems or from mechanics that have knowledge of possible causes.

    I’ve been running biodiesel (clear but unwashed) in my 1994 Holden Jackaroo (4JG2 Isuzu 3.1 Turbo indirect injection diesel motor) for 1 month ~ 500kms ~60L of BioDiesel. The biodiesel is made from WVO. The glycerine that falls out from this is liquid at 15C. I live in Kalgoorlie and at the moment the ambient temps are around the 30C during the days when the faults have occurred. Prior to putting in biodiesel the car was running fine. I fitted new injectors and glow plugs only 2 months ago to fix a smoky starting problem. This fixed the problem and improved economy.

    After the first week the car sputtered to a stop. I had attributed this to a blocked fuel filter, blocked with the fallout from the tank due to the dino diesel bacteria gunk dropping out. I swapped the filter and drained the sedimentator and she seemed good again. The sedimentator had lots of black particles in it and maybe 10ml of glycerine fallout at the bottom.
    The following week the car did the same thing. I dropped some fuel from the sedimentator and it was clean. I pumped the priming pump on the sedimentator to re-prime the system and she ran again.
    Now she runs ok until she reaches high fuel demand driving(over 80kms and during hard acceleration). In first and second gears she revs up to 4000rpm no worries. However, if booted in higher gears she starts to come on and off power at about 3000rpm and sometimes will die until she either stops or slowly recovers after letting off the accelerator and changing down gears.
    If she does stop I can pump the fuel through again using the hand pump on the sedimentator and she goes first turn. However, the problem at high demand does not go away.

    My Diagnosis
    From my experience of diesel motor problems (I’m no expert though) it is acting as if it is either :
    • Drawing in air somewhere
    • Fuel starvation at high flow due to fuel line blockages/restrictions
    • Fuel starvation at high flow due to higher viscosity of the biodiesel
    • Fuel starvation at high flow due to fuel pump problems deveoped as a result of running biodiesel (either poor quality with glycerine etc.)

    Attempted Fixes
    • I’ve drained the tank to check for more dirt/glycerine. Result: The fuel (BD) was clean and glycerine free.
    • I’ve swapped the filter again and taken the sedimentator off and blown all the lines through with compressed air to check they are clear; the filter was not excessively dirty either. Result: No change – power still drops off at high demand.
    • I’ve fitted double hose clamps to the fuel lines to ensure no air is being drawn into the system from the connections. Result: No change
    • I’ve drained the tank and refilled with dino diesel. Result: I seem to be able to travel at higher speeds (now ~90kms as before it was 80kms) before she starts to loose power and become intermittent.

    Other Ideas to fix the problem yet to be tried
    • Fit an in-line fuel pump at the tank to pump the fuel through to the pump (to allow for insufficient lift on the pump). I will trial this on dino diesel.
    • Have a mechanic remove the pump and have it reconditioned. If I do this I think that I might give up on the biodiesel as I don’t want to risk having the expense of this fault again (I’m guessing this could cost up to $1,500)

    Help Please
    Before going to the expense and unavailability of a vehicle to have the pump reconditioned I would like to know if it is possible that the pump is not at fault. Or if it is and someone has experienced similar problems could they share them with me.
    Obviously I’m very disappointed and disheartened as I had hoped that home made biodiesel was the way forward. If I can get to the bottom of why this has happened and correct the problems there may be a way forward.
    Any constructive input would be appreciated. Hopefully many of us will learn from my mistakes.

  2. #2
    Join Date
    Mar 2006
    Broken Hill

    Re: Possible Diesel Pump Problems – Advice Please

    I had problems with an Isuzo diesel in a early 80's rodeo ute and eventually traced the problem to a blocked guaze filter in the lift pump , cleaned it out and never had the problem again

    Yours may not have that , but thought I would mention it

  3. #3
    Join Date
    Oct 2005

    Re: Possible Diesel Pump Problems – Advice Please

    Try isolating the problem to just the pump. Maybe take a 20 litre cube full of diesel and hook a fuel line into the cube (put the cube on the floor in the cab).

  4. #4
    Join Date
    May 2006

    Re: Possible Diesel Pump Problems – Advice Please

    check your fuel pick up un the tank

  5. #5
    Join Date
    Jan 2006
    ลึก ประเทศอินเด&

    Re: Possible Diesel Pump Problems – Advice Please

    Hello Steve

    Did you put a new filter on or just re-install the old one?
    Is the lift pump in the injection pump or is it seperate?
    Can you fit a temporary clear plastic fuel line from the fuel filter to the injection pump?
    I had a similar problem to yours on my gemini and I could see bubbles coming out of the main filter when reving hard. The problem turned out to be a partially blocked fuel filter.

    Last edited by tillyfromparadise; 14th November 2006 at 12:10 AM.

  6. #6
    Join Date
    Sep 2006

    Thumbs up Re: Possible Diesel Pump Problems – Advice Please

    hi steve, your prob sounds like a blocked gause filter, is sometimes located after the main filter or on the lift pump,should be a small round thing with fuel lines going in and out with screwes all around the outside.about 5 or 6 small screws. could be on the injector pump. look hard you should find it somewere. i would also wash the bio to stop this happining .95% this is the prob. good luck , hope this helps

  7. #7
    Join Date
    Sep 2005

    Re: Possible Diesel Pump Problems – Advice Please

    I agree that the symptoms indicate a blocked fuel filter. Others have indicated that there may be filters at the fuel pump inlet and possibly at the IP inlet. I have fould some vehicles do have filters at these locations. I am not familiar with the Isuzu engine, so I cannot give precise instructions.

    The fact that things improve with diesel indicates that a fuel restriction is the cause.
    You have changed the most obvious filter. There may also be a strainer or filter in the tank (MB have a strainer), or a fuel pump there (unlikely as you have one at the IP).
    You may also have a blocked tank vent, which results in the tank drawing a vacuum as fuel is used. The test for this is to drive until the symptoms occur then stop, remove the filler cap while listening for the "woosh" as air enters the tank.

    While you are probably thinking the worst at the moment, I doubt that you have caused any IP damage.


  8. #8
    Join Date
    Aug 2006
    Southern Sydney

    Re: Possible Diesel Pump Problems – Advice Please

    I have almost the same symtoms and have been trying to isolate the problem.
    The main clue is the pump on the top of the CAV filter: It was being sucked down at high revs and stayed down.
    I'm 80% certain that there is a blocked strainer in the tank pickup but it is imposible to get to it without removing the aftermarket tank.

    I'm currently testing with a carboy in the passenger well. I didn't realise that I should have also put a return hose to the carboy and the 'fuel'* is being sucked out too quickly to drive anywhere. (About 5 litres to drive 5k).

    *I've put 'fuel' in quotes because while the tank was drained and flushed, and it's 'fuel' was yellow in appearance and clear - without any trace of sediment, glycerene or water - it came from VP labeled as a 'Biodiesel blend'. What the blend is is anybody's guess. BD & paint thinner perhaps?

    To complicate things for me, my vehicle's vintage is '89 which possibly brings the fuel lines and seals into the equation.

    With the carboy it will now run, but it is still not getting the revs it used to and is 'missing' at higher revs than before. - Could that be an air leak in my bypass setup or another blocked strainer somewhere?

  9. #9
    Join Date
    Jan 2006
    In the sunshine state.

    Re: Possible Diesel Pump Problems – Advice Please

    I have seen a few pick up screens that were so dirty the fuel would try any path other than through the wire screen.

    Take out your fuel pick up (ie off and out of the tank) and check the pickup. It could be clean, it should be very dirty.

    Last edited by Matt; 14th November 2006 at 10:07 AM.

  10. #10
    Join Date
    Sep 2005
    Hornsby Heights NSW

    Re: Possible Diesel Pump Problems – Advice Please

    I had similar problems in my 1985 land cruiser. Which in the end I think was fungus in the fuel.
    A couple of years prior to switching to Bio I had similar problems for which I had the tank cleaned, or so I thought up until I started using Bio, then, the fungus seemed to really multiply caused me to change many filters before I tweaked.
    In the end the fungi made a ball inside the pickup strainer which would get to the pickup tube and block it. Then I would have to disconnect the fuel line and blow the fuel back through the line and into the tank. This would get me another 20 to 120 K's before the ball got sucked up again.
    Because you have to remove the tank to get at the pickup I gave the fuel a good dose of Diesel fuel additive with fungaside ( I have found out that not all additives have fungaside so make sure you get the right one). I had several filters ready incase the dead fungi clogged them but it hasn't so I guess that I burned them in the cylinder and I have several filters ready for the next emergency.
    I was planning to remove the tank and clean it out properly but the right circumstances haven't occurred yet e.g. near empty tank and time to do it but the longer that I have no problems the less the chance of me actually doing it.
    Now every tank full has additive and touch wood I haven't changed any more filters.
    I hope this helps someone else.
    Last edited by Billyh; 14th November 2006 at 07:36 PM.


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