I was thinking,
*are fuel filter changes really neccessary, at the specified intervals?*
Before everyone jumps on me :)......
Sure, Oil and Air filters visibly clog and I change oil filters along with the oil at half recommended change intervals.....
But Fuel filters....
Amongst the many cars I have had 2 have been in the family long term.
A VW polo bought in 1985 was kept for 16 yrs with me servicing it the whole time.
I changed the fuel filter at the first year end, but from then on just looked at the flow.
As the years went by the plastic and element darkened a little but it was clear the fuel flow was fine ( and very visibly so with the engine running) that was for the next 15 years and 110,000 thousand miles.
On another car, a Maestro with the Perkins prima, I did 130,000 over 6 years and changed the fuel filter at the recommended interval, every time.
I also *drained the water* at frequent intervals, as per the book.
Now this car fueled all over the place between the top of Scotland and Italy and the total water over the whole time came to less than 6 drops.. I used to drain the filter into a glass jar and hold it to the light... Mostly nothing there, at worst a couple of micro droplets the size of a pin head.
I cut one Fuel filter open, at the change interval, out of technical interest and found the whole pleated element to be clean with no trace at all of anything at all. Just slightly darkened by the fuel.
Now I`m aware of the arguments for changing, warranty, water or dirt from a bad fill etc...
But, as you know, modern common rail diesels have a water warning light ( and even with a brand new filter taking on a load of water from a defective tank could overwhelm a new filter)
and where is the evidence that solids would reduce fuel flow enough to be significant, over, say 100,000 miles?
I mean cars fueled from regular mainstream pumps and not commercial vehicle storage tanks.
To conclude, just focusing on the new common rail Diesels, these seem to have a felt type filter and have a water warning device.
Surely changing these on a regular basis increases the risk of getting dirt into the pump and injectors by the very process of changing it?
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Good point. On my old BX diesels I used to change the fuel filters at the specified intervals and "drained" the filters as advised. They did 170k and 150k and I never found evidence of a drop of water. I changed them because the filters were cheap and I reckoned "better safe than sorry".
--
Phil
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When a tractor is not running very well, it is put on a dynometer and the power is measured. Then they put on new fuel filters; the difference in power is remarkable. New common rail engines are very sensitive to dirty fuel, try tapping your old filter in a clean bucket and look at the bits that come out (don't use the wife's washing-up bowl)
I put on new fuel and air filters more often than recommended on my cars, some fuel stations have dirty fuel.
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Much can be written about the subject of fuel filters. The important facts are quite simply that dirt of size > 3 microns will damage a diesel pump and so will water.
If you were clairvoyant enough to know how dirty your fuel is, the change interval could be simply determined by working out the total quantity of fuel passing through it. In the real world, the engine manufacturers take a balanced view, with 20 to 30k miles being a typical change interval. You would not see with the naked eye the type of dirt embedded in the interstices of the filter matrix which would damage a diesel pump.
I can agree with your findings regarding the freedom from water of fuel bought on the high street, but I would urge you to drain the agglomerator at every service. One day, you might be really glad you did. Remember also that water in the bottom of a filter will freeze in the Winter, sometimes splitting the bowl.
659.
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Thanks for the replies.
I remember once asking the tech at a main dealer, whether the diesel fuel filter (old canister type)
whether it should be filled before fitting to avoid air locks.
He said "well I just empty the old into the new" ( shock) This said in a well meaning way to advise me.
I thought about this and I guess it does make sense from the techs time point of view if he is on a clocking off system for each job card.
But for a modern cartridge type common rail fuel filter, this has to be handled by the tech, after he has just removed the top of the plastic filter housing and its pipes.
Given that the engine bay has at best a covering of abrasive dust and this is on the techs latex gloves...
Well, I guess its not a surgical procedure :) but given work pressures and the through put of cars, IMHO, there is more than a possibility of introducing a few micro particles of the quartz dust beyond the filter.
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He said "well I just empty the old into the new" ( shock) This said in a well meaning way to advise me.
I was going to do this when I changed my filter, and didn't like the sound of it. Luckily my Dad had a can full of spare clean diesel I could use.
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