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Loss of Power - Fuel Contamination OR Fuel Pump Issue???


Well-Known Member
Sep 29, 2014
Country Flag
If it ran well for 5 miles on fresh filter and fuel that tells you theres not much wrong with it. Inspection hatch under the rear seats. Take it off. Check the filter on the fuel pickup pipe. Any shit in the tank will be visible from here. I hazard a guess it's the diesel bug/slime that builds up with modern fuel. It simply doesn't like to be left sitting around now days. Feed the filter from a fresh can of diesel with a fuel additive added in for good measure. Failing that when shall I collect......

@Gav missin @karl webster
Guys, thanks for your input on the fuel problem I had last November, although I've still not addressed the problem yet!!
To be honest, it was the second jaunt on the trot I missed at the 11th hour!! so was p*^*"' off and just lost interest in the truck, especially as I've got to remove so much fitted kit and flooring to sort it!!
Anyway, back in love and now looking to resolve the problem and follow your suggestions. One question that has been in my mind since that day though, is how to clean out an 80 tank without dropping it and wondered if you had any suggestions? .... ie. how easy is it to syphon the crap out, can you get to the tank sump etc.?
Also, is the filter on the pump unit cleanable or best to replace and will the fuel pump need looking at?
Cheers guys.
If you were to Syphon out the fuel not just pick up the crap like a vacuum cleaner (use your imaganation a bit!)
That's all that was in mine when I last checked
I changed my fuel level sender unit and it is a complete assembly....well without the filter!! Seat removal is a few bolts (right hand side), lift up the carpet, undo the little hatch and disconnect the fuel lines and a couple of wires. undo the assembly and lift it out slowly not to catch the level sensor and bend it. As per @fbnss get a bowl and a length of tubing and start a siphon, you can use a torch to look into the tank and you will see the debris in the bottom, just slowly run the tube perhaps half an inch off the bottom of the tank and hoover up the rubbish, at best you will lose half a gallon, if that?

The contamination is from rust, water is common in diesels and always goes to the bottom of the tank, any condensation from the upper area of the tank is because the tank has not been completely filled, without regular filling this condensation results in rust particles which fall into the diesel, this is why the filter under the bonnet has the ability to drain off water if you draw any up, having to do this tells you that as the fuel pick up is around half an inch from the bottom of the tank that there is a lot of water in there. Something else, bacteria can actually grow in the confines of a diesel tank, hence why starting one up after a long period of standing can also bring on bad running after a few minutes as bacteria/rust/ water gets drawn into the filters and blocks them, pull the filter off the pickup pipe and clean it, put it back on, and assuming the tank looks fairly clean button it up and call it done for another fifteen or so years, remember to change the fuel filter under the bonnet, I do mine every year, but then I also change my engine oil every six months regardless if I have done 15 or 5000 miles, and no it does not cost me or waste money. :)


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Thanks Nick @fbnss, I hope by the time I strip out the interior and get to the tank, I can get it as clean as that. What is interesting, is that you can get such a clear photo. 'Hoover!' it is..... cheers.
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That was my 2nd attempt, the first you couldn't see anything but it is a big enough hole. I don't know what anyone else's looks like, I've only seen the gunged up sock filter pulled out never looked in their tanks.
@Dave2000 Thanks Dave.
Must admit, I've had enough experience with the fuels in a generator and garden equipment clagging up through lack of use over the years, I should know better!
I just need to be on top of things a bit more really! Just hope that as it's stood more than it's been used over the last 10 years, I don't find rust to be a major problem!
! might at some point, add an additional coalescent filter, save any unnecessary engine damage aswell. Cheers
@fbnss Out of interest Nick, is that 'sock filter' replaceable or is it just a case of cleaning?
Well Nick @fbnss...... definitely squirted it with something suitable!!
The sock was a bit clogged, but now cleaned and as good as new, I pumped out all the old fuel and fitted yet another new fuel filter.
After a couple of short steady runs, it seemed fine (about 10 miles each), so I refitted the floors and all the kit, but low and behold..... it's started doing the same again after I had to boot it out of a junction, after heavy load!!!
Does anyone have any ideas???
Has anyone had a similar experience?
Could it be a fuel pump issue? lift pump in the tank issue? Pipework??

Any thoughts would be really appreciated.

Diafram in the fuel filter housing. Also check all pipes coming on and off of it. I had a jubilee clip nip through one of mine and that caused it to splutter at top of revs.
Gav you're a star..... I'll check them out. Cheers
@Gav missin Out of interest Gav, anything in particular I need to look out for re the diaphragm?
Never taken filter head apart to be honest. Check to see if its holding pressure by pumping on the black primer button.
I once went to a tractor that had fuel issues.... similar symptom in that it was only when pulling hard at max fuel demand the engine would flutter and die ...back off or change down 3 or 4 gears and it would be ok... it would run faultlessly at tickover or high idle for hours....

It had had several new fuel filters and a lift pump fitted.... with more than luck than skill TBH I eventually traced the fault that had eluded several others....

A piece of wheat that was in a fuel line and at peak demand would get sucked up the line and seal nicely against the hole in a banjo bolt on the supply side of the lift pump.... the minute demand dropped off or the engine was stopped the weight of the grain of wheat made it sink back down the fuel line... undo the banjo bolt to inspect and it was clear and clean .

To aid your diagnosis get a fuel can in the passenger footwell , run a line straight to the primer/filter bleed her up and go for a blast... problem solved ? It's in the line to the tank ... still evident ?

Then get one of those bulb type inline priming pumps .... can in footwell again but this time pipe straight to FIP and have a drive.... if problem gone then it's in the filter head .( only if your can is scrupulously clean )
@Grimbo Thanks for that..... fuel line blockage is certainly in my mind, more of a nightmare if I'm honest!!!
I'll be looking at that aswell.
Thanks for your input, much appreciated.
Never taken filter head apart to be honest. Check to see if its holding pressure by pumping on the black primer button.

That's interesting Gav..... I did have a slight concern when I was priming the filter, the button didn't seem to become rock hard, which I would have expected it to!
And if you're gonna buy a new one. There's two types. With a pre heater and without. I first bought one with the pre heater (not included, discontinued) as that's what mine has. You have to take the old one off yours and put it in the new one.....where you'll find it doesn't seal right and pisses diesel everywhere. If you happen to have the correct size orings I'm sure you could solve this . After much faffing about I bought the non heated type, much cheaper from amayama if you plan ahead, while I was at it I replaced the thing under the filter that lets water out in case that was causing any problems too.
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There is a diaphragm on many pumps to increase fueling when the turbocharger boost increases, this diaphragm also allows for changes in atmospheric pressure.

As an aside, from God know how many years ago, a guy had intermittent cutting out of his Sierra, turned out to be a cap from a smarties tube in the fuel tank, on odd occasions it would get drawn up against the fuel pickup and starve the engine.

Leave the car for ten minutes or so and it would restart, the problem may occur ten minutes later or ten days! I eventually found the problem, and once the cap had been removed the car ran fine. Of note the orange cap had started to dissolve from the effects of being immersed in fuel.

To date I have no idea if smarties caps of different colours would cause the same problem?