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Fuel filter and inline pump

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I'm looking at fitting a higher micron fuel filter and a in line lift pump, I was talking to a dealer about it and they said that the standed lift pump struggles if you put a second filter in.

Knowing that Australia does not have the best fuel quality I'm trying to improve it

And trying to improve my fuel ecomany along the way.

any ideas?

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Dealer is right, VP44 (injection pump) especially struggles. So lift pump like Carter 4600 can help and adding another filter/water (like 10 micron Racor or CAV sedimenter/filter) separator than might be useful too. Don't forget you need to modify spill line so full is returned to the tank.


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Filters will only improve the " particulate" quality of the fuel.

The quality the stealer was talking about relates to a whole lot of other things, mainly the Cetane value of the fuel. A filter will do nothing to improve this.

Diesel fuel is not a pure substance, it is a mixture of a variety of components and most of those are determined by the distributor. Unless you get a dodgy distributor that is adding in turps or paint stripper or something else into the fuel ( which has happened many times) you fuel should be fine.

In any case, a simple fuel filter will do Jack to improve the chemistry of the fuel.

Some members here add 2 stroke oil to their fuel and say it makes a huge difference to the way the engine sounds and feels. A number of people report economy gains but personaly I see no physical reason for that to happen at the reccomended ratio of 200:1

You can also add other things like transmission fluid or vegetable oil. all of these things have proponents that say they get benifits from them. Best to try them yourself and see how you go. They won't hurt your engine or your wallet to try.

In the case of the commercial additives, if you look at the MSDS sheet, they ALL contain NAPTHA. This is available at your local Bunnings for $10 a litre I think it was when I last bought some. It's basicaly lighter fluid but used for cleaning purposes as well.

ALL the commercials additives have this as the main component Wether it be fuel system cleaner, combustion improver, oil flush, or whatever cleaner/improver. Far cheaper to go buy a litre at bunnings and throw 1/4, 1/2 or a full bottle in your tank (or sump) and see if it helps.

It is not so common to get sediment or particulate in fuel unless you are buying it from drums. In any case, the filters on the vehicle should be fine enough to protect the fuel system from damage.

That said, I have seen studies done by engine manufacturers (Cat) that said modern high pressure systems need cleaner fuel. They also said that the most damaging particulate size is 5-7 Micron because that is the most common tolerance of moving parts in the fuel pumps, injectors etc.

Many manufacturers specify 10um filters, some 5. I believe the standard for modern cat engines is 2.

In any case you would have to get a filter with an ABSOLUTE rating of 3 Um or less. The only ones I know of that do that are the Racor filters which are very expensive but very good. They do a 2UM cartridge for their units. There may be other makers that have specific absolute ratings that I am not aware of but to my info, most specify a "NOMINAL" rating which means a percentage of matter much larger will still also pass through that filter.

If You want to get a better filter, make sure you find out if the rating is absolute or nominal because there is a big difference between the different types

If you can only get a Nominal rating, get one for 1UM or .5 if anyone does one to give yourself the best safety margin.

In reality, I wouldn't bother with 2 filters. There is no point when one is going to be far finer rating than the other. For one thing it means you have to have 2 different filter types. If you block a filter, which one is it? The coarse presumably OEM filter or the finer filter catching the crap the first one missed? If you change them both before they block, you are potentially wasting twice as much money if they could have gone another service interval.

Your fuel will have a given amount of crap in it for whatever volume. Wether you catch this on one filter or 2 is irrelevant. It's still the same amount but the complication and added expense of 2 filters actualy makes changing 2 half as often more expensive than changing one twice as often. When you get a filter blockage with a single filter you know which one it is and you can carry twice as many spares and not have to worry about not having the type you need.

I use industrial Nominal sized 1Um filter bags for my fuel which I put through before it goes in the tank. Anything that gets into the fuel IN the tank is likley to be something that has broken away from the tank walls or lines and is going to be a chunk of something that the onboard filter will catch easily. To me it's better to use the bag filters which are cheap and have a huge capacity to keep the fuel going into the tank clean than have the crap in the tank and then take it out of the fuel later. This would not be a practical thing for many people though.

There is no doubt having 2 filters will put greater strain on the lift pump. What sort of reserve it has to overcome this is the question. I'm guessing you have a 3.0 which I have no experience with in knowing the strength of the Lift pump. With my 4.2 however, I ran the standard filter and a disposable or a CAV with veg oil and in standard tune, the lift pump handled it fine. I forget the viscosity difference between Veg oil and diesel but it is magnitudes. Milk and cream type comparison.

With this in mind, I would think that the same pump would barely notice 2 filters passing Diesel fuel.

Again though, I don't have any knowledge of the relative strength of the 3.0 pump.

As for lift pumps, The walbros are good but tend to be not the highest flowing. I don't know what sort of return rate the 3.0's have in their various Guises so for that reason the one I'd reccomend to you is the Mallory 4140. These are a gear pump and while I forget the flow rate, I believe it is around or over 300L+ per hour which should keep any diesel looped fuel system happy.

To avoid any overpressurisation of the system, I'd put a "T" in the line right before the IP. This will enable the IP to have all the volume it wants with minimal pressure by feeding the excess back to the tank. The IP will have a slight pressure and a huge volume to draw from then.

The thing is, I think if you stick to one filter, even a better rated one than the OEM, you will save yourself a lot of mucking around, expense and have less failure points to go wrong.

Edited by Glort
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