What intervals are the D-4D fuel filters replaced?

[Riv39 Advanced Member Find all posts View Profile Close Riv39]

Well done Michael great post, explains it well.

[Rick NZ Member Find all posts View Profile Close Rick NZ]

Just a short awakening for all to see... The engine receives all it's fuel via the under bonnet filter from the main (front) tank. And only that tank. Which is sucked via the injector pump on the engine. Now, that main tank is constantly replenished of fuel from the rear tank via a recirculating pump, mounted within, through a venturi effect. That venturi sucks fuel from the rear tank.
The recirculating does not supply anything, it just recirculates. As the fuel recirculates, in and out back into the tank, it is constantly filtered via the centre, under body filter. That filter filters 100 times more fuel then the under bonnet one as it is under constant use. The under bonnet one only filters what is consumed by the engine.
That is the reason why TOYOTA schedules the replacement of the under body filter many more times more often then the main filter. It does more work.
I concluded that after a breakdown that required TOYOTA to rectify, under warranty. Of course I quizzed the service manager as to the workings of the whole fuel system. He even supplied a schematic diagram of it. That was a revelation to the unnecessary complication to it all.
I hope this will shed some light on it all.
Thanks for reading.
Michael

I see the system a little differently

The venturi effect is created by the returning fuel from the engine to the main tank (often refered to as a jet pump) - in doing this the rear tank actually keeps the main tank full ( until the rear tank is empty that is )
The underbody filter filters this fuel as it is transfered from rear tank to main tank
The under bonnent filter does the main work - as it filters ALL the fuel the engine needs and all that is returned to the main tank

NZ spec has single tank - with only the underbonnet filter from factory

I do agree that the high pressure pump draws fuel (ie by suction ) - this is also the reason the pump is fitted so low on the 1KD as it reduces the amount of suction required to draw fuel

anyone else have a view on this?

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

My Racor is recommended every 16,000 km. After talking to Roo was looking at 20k intervals on Toyota filter. Might be lazy and just do both together every 15,000 km to be safe.

Toyota want over a hundred bucks for the main under bonnet filter, that's a bit rich to be chucking it away every 15,000km when we know it is actually designed to last a lot, lot longer. Especially seeing as the Racor gets the flick at 20 - 25,000.

[matt150 Avid PP Poster! Find all posts View Profile Close matt150]

I agree. I'm looking long term at trying to extend the life of my fuel pump and my injectors. I could get 25k easy out of the factory filter as I'm using the big Racor in front of it.. Guess its the over cautious diesel mechanic coming out in me..

Everyone is different I know, I've been on the repairing end of many a diesel failure in the past and I see filters as alot cheaper and easier than pump and injector changeouts.. But you are right, I could get more km from them.

Remember too, time shags fuel filters also, not just kms. As I've got a lease car for work now, it's taken me over 12 months to rack up 30k.. So different maintenance strategies, for different situations I say

[Bushbasher Out of control poster! Find all posts View Profile Close Bushbasher]

Maybe we need to bring back the old toilet roll filter!

[gxl_d4d Advanced Member Find all posts View Profile Close gxl_d4d]

If you want a cheaper alternative, use a toyota filter from a 1kzte or the aftermarket equivalent. I believe these ones are 10 micron and much cheaper. Install a good primary filter after the factory filter head with the cheaper filter. I've got a CAT setup. The CAT elements are 5 micron and are $22 each so changing one of these every 10-15000km isn't a to heavy on the wallet. Toyota filters have a lot larger water holding volume under the filter elements compared to the CAT so it would make sense to use the factor filter to separate the bulk of the water in the fuel and perform a first past filter to remove the bigger stuff.

Toyota want over a hundred bucks for the main under bonnet filter, that's a bit rich to be chucking it away every 15,000km when we know it is actually designed to last a lot, lot longer. Especially seeing as the Racor gets the flick at 20 - 25,000.