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Fuel Filter replacement...

Discussion in 'Daihatsu Hi jet' started by Roadster, Nov 17, 2020.

  1. Roadster

    Roadster Member

    This seemed like an easy small job, and it was, however I thought I'd pass on a few pointers in case others run into issues with their aftermarket replacement filter...

    The Daihatsu fuel filter on my truck (1998 carbureted, mechanical fuel pump) is a small clear plastic unit (very dirty) mounted on the right frame rail with a horizontal inlet and a right angle, vertical 90* outlet. I replaced it with a generic in-line clear plastic unit I had sitting around from my British sports car days. On those cars one mounted the filter either vertically or on a 45* upward angle, never horizontally as it is typically after the electric fuel pump.

    Even though the filter is mounted well below the tank level, the filter seldom seems to get completely full. It is important to note there is a flow direction arrow on these filters and it is important to heed that. Firstly, the incoming fuel circulates around the outside of the filter element in the filter, and deposits any dirt on the outside where you can see it, and second, the engine draws the fuel from the center of the filter element bottom. If the unit is horizontal, the fuel level in the filter may not flood the bottom of the filter enough to supply fuel to the engine.

    In my case, I originally just mounted the new filter in the horizontal existing bracket, thinking that the gravity feed would fill the filter. Not so... The engine started OK (fuel in the float bowl) but soon ran on two cylinders only. Making a bracket and hanging the existing snap-in bracket so as to orient the filter vertically resulted in the filter being half full and the engine running perfectly. So why is the filter only half full, even when it is mounted vertically? I've tried filling the filter with a syringe, sucking fuel through etc. but it seems to just want to return to being half full.

    I suspect there may be a physics reason dealing with low pressure in the filter making the fuel go to a gaseous state or something like that, but perhaps someone with a better understanding of that can chime in...

    Perhaps I should have bought a Daihatsu replacement unit after all... <g>

  2. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    The fuel filter for my 94, S110 is identical to the one left in my spare parts box, which was left over from my long gone 77 Toyota Hilux.

    So if you’re looking for the stock filter to fit your Hijet, check with NAPA or one of the other parts houses for a 77 Toyota Hilux. filter.
    Last edited: Nov 17, 2020
  3. Roadster

    Roadster Member

    Thanks Jigs - I'll check that out!

  4. Sisu Militaria

    Sisu Militaria New Member

    I just replaced the fuel filter on my 91 S83p with a NAPA 3053 and it fit perfectly in the factory spring clip. Inlet and outlet are in the correct configuration. Filter body is slightly longer but there are no clearance issues. Not bad for $6
  5. Roadster

    Roadster Member

    Thanks Sisu, I just ordered one ($8.16 in Canada!) I should have done that in the first place instead of being cheap and using what I had hanging about!

  6. Roadster

    Roadster Member

    Installed the Napa Gold 3053 filter yesterday - the engine actually revs less laboriously to higher RPM's so I suspect the 22 year old one was mostly plugged. It still isn't completely full, however...

  7. Limestone

    Limestone Well-Known Member

    22 YEAR OLD FILTER! REALLY? I guess I just don't understand! Was it parked in a field somewhere? Lost in a junk yard? My Virgin ears! Say it ain't so! Sacgraligious!
    Last edited: Nov 20, 2020
  8. Jim Nelson

    Jim Nelson Active Member

    I have noticed on several applications, actually most, that the filter housing never fills completely and finally gave up and accepted it as a fact of life. As long as it runs well I figure it's just a physics thing that is over my head.
  9. Roadster

    Roadster Member

    Ha! Actually, it didn't get used much for some of that time and the filter was crazed and brittle and full of crud. I replaced the rotor, cap and plug wires, and by their condition, I suspect they were original as well...it's hard to say if the plugs were original, however they are the "BPR5EK-B" dual electrode ones so they might be. Luckily, the timing belt had been replaced in 2013 at 41,200km's (sticker under seat) but I bought it in Aug. 2020 at 42,600km's. The chap had imported it in 2016 and used it around his farm, so very little use for it's final years in Japan or here, for that matter.

    Following Jig's video carb adjusting technique, it runs great now! Next up, check valve lash...

    Limestone and Jigs-n-fixtures like this.
  10. Limestone

    Limestone Well-Known Member

    I had an old timer, my buddy Tim, explain to me one time that the fuel filter is kinda like a jug of milk. When we were young and we went to pour it on our cereal. It gulped and gurgled, until it got the air that it needed! Made sense at the time! Take a look at the installation in most cases to better understand; On a Diesel, the fuel filter is usually found on the frame rail, somewhere, for easier vertical installation! On a gas, or petro, as termed elsewhere, there usually found installed horizontally, hence the air, above the gravity center line! Make ya say Hmmmmm! Don't it? Makes me say all kinds a crazy stuff! LOL!!!
  11. Jim Nelson

    Jim Nelson Active Member

    That makes as much sense as anything I could come up with.
    Limestone likes this.
  12. Limestone

    Limestone Well-Known Member

    I'm not sure if your agreeing with me or not! lol! But I like it! HAHAHA!
  13. Roadster

    Roadster Member

    Yup, probably some things are best left to the old adage "if it ain't broke, don't fix it"...
    Limestone likes this.
  14. Jim Nelson

    Jim Nelson Active Member

    I'm agreeing for sure.
    Limestone likes this.
  15. woopee

    woopee New Member

    My fuel filter is definitely horizontal. There seems to be a "clip" to hold it so. No right angles on mine. Here's my notes on fuel filters:

    Fuel filter: Fram G12 5/16 to 5/16 (2020 tip: Also trying a Sierra 18-7830 from O-Reily's boat parts section) The Fram is in the photo and more-or-less matched the one that came with it from previous owner, Sierra skinnier. I see air in mine, not sure what to say!! This is way before the fuel pump.

    Both filters seem to work okay.

    Some other dude on this forum (use the search for context):
    Fuel Filter: napa #3053, or Purolator #F20005
  16. Roadster

    Roadster Member

    Whoopie; I think we've ascertained the fuel filter is OK to have some air in it, just not sure why? The Napa #5053 is oriented much the same as the original one was, with the inlet horizontal and the outlet vertical mounted in the bracket like yours.
    The aftermarket one I used had too much air in it I couldn't get rid of and the fuel level in it was partially below the pick-up (inside the filter element) to run the engine properly. Yours appears to have gas about 1/2 way up, which probably allows the pickup to be submerged... For me, the Napa one solved that. Orienting your filter 45* up towards the engine might help getting more fuel and less air (it did on my aftermarket one, and the truck ran on all cylinders again) but on Sisu's advice I ordered the 3053 and replaced it with that as it is more like OEM, and they are inexpensive...

    I have an idea Daihatsu wanted the filter to be below the fuel tank level so that the mechanical fuel pump wouldn't have to work very hard to get the fuel to it, and the design of the filter, with its vertical outlet may help with that. - purely conjecture on my part, though...

  17. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    The bracket and filter on my S110P is identical to the bracket and filter on a 77 Toyota Hilux.

    I was digging through one of the spare parts boxes, and found the mount bracket, in tank fuel pump, and the in tank fuel pressure relief valve from a mid seventies Hilux, and am thinking of converting from the electric fuel pump I now have to the Toyota set up.

    Horizontal fuel filters will always have air in them above the outlet level, as there is no way for it to get out. On carbureted engines a little air in the line will not hurt things. The only time they have problems is if the suction side of the line gets too hot and the fuel actually boils, which is known as vapor lock. the fuel pump is still moving the same volume, but as vapor, and the new fuel is also boiling as it comes up to the heat of teh engine, resulting in a situation where the pump is only getting vapor to move. This typically happens in hot climates, when the fuel suction line runs to close to the exhaust system. If you have a vapor lock issue, the simplest solution it to add an electric pump as near to the fuel tank as you can, and install a regulator as close to the carburetor as you can.
    Limestone likes this.
  18. Roadster

    Roadster Member

    Thanks Jigs:

    I think you've hit the nail on the head with that - there will always be some air in the filter and, if the fuel gets too hot, the resulting bubbles might collect in the filter and migrate up to the fuel pump. As it cools, the fuel should always come back to its original level in the filter, I would think... Considering the fuel tank, line and filter are "out in the breeze" so to speak, I'm not sure we would need to worry about vapour lock? The fuel pump bolted to the top of the engine above the exhaust manifold might not be the best place for it, however...

    Have you heard about vapour lock being an issue on these trucks? Here in the Okanagan Valley we can see the odd day up to 40*C in the summer, so I guess under certain circumstances, it's possible. I haven't had this truck long enough yet to know...

  19. Jigs-n-fixtures

    Jigs-n-fixtures Well-Known Member

    I’d be surprised if there was an issue with vapor lock anywhere besides the bottom of the southwest. I bypassed the stock fuel pump early on in my ownership, and live where it is cold to warm, so I would never expect to have issues with it.
  20. Hegels

    Hegels New Member

    Just as an FYI, The napa filter referenced above crosses to fit a bunch of Datsun/Nissan vehicles
    WIX 33053, Nominal micron rating listed = 10 micron

    Principle Application: 70-83 datsun pickup, 79-82 Nissan 210, 68-81 Nissan pickup, 71-78 Nissan B110 & B210, and the 83-87 Nissan Pulsar NX to name a few.

    Being a diesel guy I had a mercedes diesel with a right angle fuel filter so i am including that as well.
    WIX # 33006, Nominal micron rating listed = 140 micron

    Principle Application:Mercedes-Benz 200D, 300D Series (76-85) - 5/16" inline - can be used with gas or diesel

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