View Full Version : Possible Diesel Pump Problems Ė Advice Please

13th November 2006, 12:56 PM
I seem to have developed a problem with my vehicleís injection pump since running on Biodiesel. :eek:
Iím 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. :confused:

Iíve 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). :confused: 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 (Iím 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

Iíve drained the tank to check for more dirt/glycerine. Result: The fuel (BD) was clean and glycerine free.
Iíve 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 Ė power still drops off at high demand.
Iíve fitted double hose clamps to the fuel lines to ensure no air is being drawn into the system from the connections. Result: No change
Iíve 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 donít want to risk having the expense of this fault again (Iím 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 Iím very disappointed and disheartened as I had hoped that home made biodiesel was the way forward. :eek: 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.:o

13th November 2006, 02:30 PM
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 :)

Terry Syd
13th November 2006, 03:15 PM
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).

sean musso
13th November 2006, 05:16 PM
check your fuel pick up un the tank

13th November 2006, 06:48 PM
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.


13th November 2006, 07:08 PM
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

Tony From West Oz
14th November 2006, 01:26 AM
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.


14th November 2006, 09:56 AM
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?

14th November 2006, 10:03 AM
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.


14th November 2006, 07:34 PM
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.

14th November 2006, 08:33 PM
If anyone wants to see a blocked fuel pickup, have a look at the pics in the Helga thread! My troubles with the blocked fuel pickup issue are pretty well documented there and for the last week I have been running round with a drum in the boot where I removed the fuel tank and the old girl hasn't missed a beat.

George, I did the same thing last week with the plastic drum. You can check for air leaks by using a piece of clear plastic hose on the return line and looking for bubbles coming back. My return line is mostly free of air bubbles except under full revs when the occasional bubble comes back but it is running fine so I am not going to go chasing tiny leaks on a temporary setup. I suspect the leak may be coming from a crush washer that needs replacing under a banjo bolt on the factory filter so I'll get the right part and see how I go from there.

If you use the clear lines and can make sure they are airtight, maybe with quality double clamps, then you can be confident the leak is else where and start tracing it. If you haven't already, I would suggest you change all the non metal fuel lines ( Rubber, for want of the correct term) as well as all the clamps especially if they are those cheap ass factory spring types that manufacturers often use. Given the age of your Vehicle, it isn't a stretch to think any clamps may have have lost their bite and not sealing properly.
Clark Rubber have the good fuel hose at the best price I have found so far.

I would suggest you get some quality bio or diesel in your carboy and if you have run any suspect fuel since your last filter change, swap them over again so you are not trying to problem solve a situation that is being caused by what equates to a maintainence or contamination issue.

I believe the best thing to do is start from scratch with new rubber fuel lines, clamps, filters and clean fuel and see if the problem goes away. If not, then you have eliminated a lot of the possible problems straight off.
If from there the thing runs fine from the drum, then you know the problem is the fuel tank and you have brought the rest of the fuel system up to spec anyway.

Good luck with it.

14th November 2006, 09:18 PM
Injection Pump Damage Assessment:)
Last night I did as some of you have been suggesting and put a 20L fuel jerry can filled with dino diesel and a $2 inline filter with clear line in the passenger seat and ran this straight to the pump.

To ensure a prime and flow I wired up an in tank fuel pump in the jerry can also.

I ran the pump until I'd purged all the bio from the pump then took her for a run. Result: No problems, reving out in every gear with no power loss.

I then turned off the fuel pump and let her suck her own. Still ran with no probs.

Conclusion: The injection pump is not damaged! :D

Further Investigation - Fuel filter and sedimentator
I took the sedimentator and filter off again.
The sedimentator had clean biodiesel/dino (50%/50% mix) with maybe 5ml of dark glycerine in the bottom.
I cut the filter open (new only 2 days ago) and it was totally clean with no evidence of particles or glycerine.
I blew all orifice and lines including the tank lines (feed and rtn) out with an air line. I replaced the sedimentator and filter and ran a line to the jerry can with dono diesel in it in the passenger seat again. After priming using the prime pump on the sedimentator I did a test run and it ran fine. Did run out of fuel very quickly though as I did not run the tank return back to the jerry can.

Immediate Fix
I drained the tank of the bio/dino mix and filled it with pump dino diesel, connected the tank line back up, purged the lines and she is back running with no problems as per pre-bio condition.

Probable Diagnosis
Given that the engine runs fine on dino and has problems with high fuel flow on bio I am concluding that the problem could be:

The lift on the Injection Pump cannot 'suck' enough bio through the filter system at high demand due to the higher viscocity of the bio and hence the greater losses through the lines and filter - it is becoming fuel starved.
The residual methanol in the fuel is causing problems when the pump is working hardest - don't know the science behind this but it is just an idea.
Longer Term Solution
I want to run the bio-diesel in this vehicle but it is not quite as straight forward as I had hoped. My plan is to:

Wash my biodiesel
Add an in-line fuel pump
Fit a higher flow filterThanks to you all for your input into this problem;)

15th November 2006, 07:02 AM
billyh did you have any other problems with your 85 cruiser when you went bio . I am in the process of changing over my 86 cruiser and would appreciate any hints , tips you might like to share eg fuel lines filter setup etc cheers shayne

15th November 2006, 08:24 AM
I have a bit to do with Perkins/MF135 tractors. They have a combination of several filters. A conical one above the fuel tap in the fuel tank, A mesh filter above the bowl on the lift pump and 2 CAV filters. All 3 can give problems. One problem that seems to come up frequently is a pin hole in the diaphram of the lift pump. So is you use a separate diaphram type lift pump be aware it may be the culprit.

Terry Syd
15th November 2006, 08:28 AM
1) The lift on the Injection Pump cannot 'suck' enough bio through the filter system at high demand due to the higher viscocity of the bio and hence the greater losses through the lines and filter - it is becoming fuel starved.

2) The residual methanol in the fuel is causing problems when the pump is working hardest - don't know the science behind this but it is just an idea.

As far as numer one, this is what Robert initially thought when he had his first problems. Then he did a viscosity test and found that there was very little difference in the viscosity. Have you done a viscosity test between your biodiesel and dino diesel in order to support your theory?

Number two stands in contradiction to number one, a bit of methanol would reduce the viscosity. More methanol would thin it even further.

Since the problem seems to have cleared, I would bet that if you filled your tank with biodiesel the vehicle would run.

Tony From West Oz
15th November 2006, 11:44 PM
You have proven that the IP and filters are fine.
You have not proven that the fuel lines to the tank and the tank itself are free from obstruction.
You need to get your fuel pump (that you used for the test, priming the fuel system) and pump fuel from the tank. Ensure that the fuel flows easily at a good rate, not just a dribble. Repeat for the return line. If may not be submerged like in the Mercedes cars, but you may be lucky there.
If the fule flows clean and with good flow, the tank and piper should be OK.
Put more biodiesel in and drive.

Please ensure that the biodiesel is free from methanol and glycerol, to avoid any glycerol in the sediment bowl.

19th November 2006, 06:01 PM
I have an 89 Hilux that's been on BD for about 30,000km now. Last Xmas I had a problem similar to yours Graham and it turned out to be the rubber diaghram in the primer pump on top of the fuel filter. The diaghram had a tiny hole that would suck air after the vehicle would stand overnight. It'd drive okay for about 1.5km then would start starving for fuel and I could barely limp home on it. I took the fuel tanks out and checked inlets etc (twice!) and eventually narrowed it down to the primer pump. Sounds a bit different to your problem but what I learned was to consider every little thing for a possible air leak.
My theory was that the BD had possibly contributed to the perishing of the rubber diaghram which led to the hole. I ended up cutting the pump assembly off so I could check it out and there was a lot of black scaly stuff in there. This rubber component was the only rubber in my fuel line that hadn't been changed to newer non-rubber compounds. Since putting one of the CAV style filters on with a slant-type primer pump it's been running at 100% again.
As mentioned - probably a different problem but it might offer you some clues?