When fitting fuel filters do you fill them first?

I always fill my primarys before fitting and I carry a can of fuel for a quick change at sea too.

Engine filters no, too risky.

You run the risk of bypassing your filter with contaminated fuel.


(any contaminated fuel which bypasses the primary will be caught with the engine filter).

Engine filters usually have a good pump fitted on the top anyway so it doesnt take long to fill and bleed the filter.
 
Best to fit them empty, as otherwise you risk filling the "filtered" side with unfiltered fuel. No doubt you have a secondary engine filter that would catch anything, but good practice to do it properly.

Takes a bit longer to bleed, but better practice.:)
 
filters

hi on M M fitted with 2x200 hp (AD41P)firstly i don't empty the pre filter completly.just let enough out so as to make fitting the new one easy,just push it down gently!.secondly i put the engine filter on empty &then spend a few minutes priming &bleeding the air out,a very easy job,i doubt it would start without some form of priming or fuel in the filters.regards mm1.
 
I'd say you have spin on primary, fleetguard , fit primary. And secondary then bleed both together through 10mm bleed screw on top of secondary housing, if the motors won't fire after that then slacken off injector pipes at injectors, crank the engine til you see fuel spit out the pipe union, tighten pipes and they should start.

When you prime the lift pump make sure the engine is not on cam where by the cam lobe is at it's highest point pushing the lift pump diaphragm , you will know if it is when the lever has no resistance , if that's the case rotate the engine a full turn, all should be well.
 
Yes you are right Volvopaul (as usual) I have spin on Fleetguard as primary. I will follow your advice on fitting and bleeding.
Thanks to all for advice, I hadn't realised that what I was doing by filling the filters was not good practice but what you say makes perfect sense.
Since KAD43's are self priming I've never bled the system before but understand that this time I will have to.
That's my job for tomorrow (in Spain forecast rain)
Further advice gratefully received
Thanks
 
I usually fill the primary filters with an injector cleaner and let the engines idle for 10-15 minutes running on this. It really makes a difference . I have done this on diesel engines for years.
DO NOT rev the engine until it has run for a period and is back on full diesel though.
 
birchwood330 said:
I usually fill the primary filters with an injector cleaner and let the engines idle for 10-15 minutes running on this. It really makes a difference . I have done this on diesel engines for years.
DO NOT rev the engine until it has run for a period and is back on full diesel though.
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Hmmm interesting tip that....anyone else concur?
 
DAKA said:
I always fill my primarys before fitting and I carry a can of fuel for a quick change at sea too.

Engine filters no, too risky.

You run the risk of bypassing your filter with contaminated fuel.


(any contaminated fuel which bypasses the primary will be caught with the engine filter).

Engine filters usually have a good pump fitted on the top anyway so it doesnt take long to fill and bleed the filter.
Click to expand...

'Scuse my ignorance but I don't understand this!
Could someone ( Daka) explain please how filling the filters prior to fitting them will contaminate the fuel.
(Genuine question by the way)
 
birchwood330 said:
I usually fill the primary filters with an injector cleaner and let the engines idle for 10-15 minutes running on this. It really makes a difference . I have done this on diesel engines for years.
DO NOT rev the engine until it has run for a period and is back on full diesel though.
Click to expand...

I do this with 'Redex' type product. Both primary and secondary. Saves messing about with diesel and/or bleeding.

My logic (waiting to be corrected!) is these products will be far more effective neat than diluted with 500l of diesel.

Engine seems to run as normal on these products.
 
Thepipdoc said:
'Scuse my ignorance but I don't understand this!
Could someone ( Daka) explain please how filling the filters prior to fitting them will contaminate the fuel.
(Genuine question by the way)
Click to expand...

Must admit I didn't quite follow this. I guess it is possible that you could fill the filter with contaminated fuel but if you use a plastic jug or similar you can see if there ar any major contaminants and worse case scenario would be a filters worth of slightly dodgy fuel, which would quickly clear. Am I off the mark in thinking this?
 
Greg2 said:
Must admit I didn't quite follow this. I guess it is possible that you could fill the filter with contaminated fuel but if you use a plastic jug or similar you can see if there ar any major contaminants and worse case scenario would be a filters worth of slightly dodgy fuel, which would quickly clear. Am I off the mark in thinking this?
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I must first qualify my answer by saying I'm no filtration expert, so others may well, and indeed are likely to correct me on this but my understanding on this is as follows.

Typical fuel filters will filter the fuel down to anything between 5-30 micron depending upon spec of filter. Microns are very very small - smaller than you can see, so don't think that because it looks clean in the jug it's as clean as filtered fuel.

And remember that the size of the hole(s) in injectors, particularly modern ones is minute, to get maximum atomisation for fuel efficiency and good combustion. Again someone shortly will no doubt clarify exactly how small the injector holes are.

Finally, in spin on filters the fuel flow direction goes from the outside (in through the small holes around the top edge) to the inside (out through the large central threaded hole you can see). So when you fill up the filter with fuel, you're filling the filtered side with unfiltered fuel out of a jug...

As Daka said above, probably not a major problem for the primary filters because you almost always have a secondary engine filter. But you should never fill the engine filter prior to fitting.
 
Trundlebug said:
I must first qualify my answer by saying I'm no filtration expert, so others may well, and indeed are likely to correct me on this but my understanding on this is as follows.

Typical fuel filters will filter the fuel down to anything between 5-30 micron depending upon spec of filter. Microns are very very small - smaller than you can see, so don't think that because it looks clean in the jug it's as clean as filtered fuel.



As Daka said above, probably not a major problem for the primary filters because you almost always have a secondary engine filter. But you should never fill the engine filter prior to fitting.
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+1 including qualified statement.

A filter rating of 30 micron doesnt really mean a lot, you need to buy a filter from a quality source who actually checks the rating (not all quality sources check the ratings).

30 Micron of cellulose paper (99% of traditional boat filters are cellulose) may only stop 30% of 30 micron particles .

Its just like a ball of wool dumped in a loose ball, some holes will be 5 micron some will be 100 micron most will be 30.

There are better filter inserts now made and they are tested and expected to stop 98% of particles at the specified micron rating.

The idea of putting unfiltered fuel into your injectors is crazy.
 
I had the CMD Technician replace my filters last time out and he filled them (canister type on the engines) prior to fitting, with fresh fuel. Made bleeding much easier, and no issues as a result. I will do the same next time.
 
rafiki_ said:
I had the CMD Technician replace my filters last time out and he filled them (canister type on the engines) prior to fitting, with fresh fuel. Made bleeding much easier, and no issues as a result. I will do the same next time.
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Amazing what the professionals will do for expediency!

I bet he wouldn't do it on his own engines though, at least if he had any real understanding or care.
 
rafiki_ said:
I had the CMD Technician replace my filters last time out and he filled them (canister type on the engines) prior to fitting, with fresh fuel. Made bleeding much easier, and no issues as a result. I will do the same next time.
Click to expand...

You cant be certain that your injectors are not already partially blocked from the particles he allowed passed the filter.

Perhaps not blocked enough to make a significant difference now but blockages are almost always accumulative and if you do the same each year sooner or later you will block your injectors.

My CMD pump only takes two to three pumps to fill the filter, cant see what is saved by pre filling , certainly 5 years x 2 minutes = 10 minutes

It will take longer than that to remove the injectors for cleaning.
 
DAKA said:
You cant be certain that your injectors are not already partially blocked from the particles he allowed passed the filter.

Perhaps not blocked enough to make a significant difference now but blockages are almost always accumulative and if you do the same each year sooner or later you will block your injectors.

My CMD pump only takes two to three pumps to fill the filter, cant see what is saved by pre filling , certainly 5 years x 2 minutes = 10 minutes

It will take longer than that to remove the injectors for cleaning.
Click to expand...

Surely it dpends on the flow of fuel around the filter? If it fills down the centre, then this is no different to filling with fresh fuel. If it draws from the centre into the injectors then you may have a point. I will take a look at the filters before filling next time.
 
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