Is there a Check Valve between Diesel Fuel Filter and Fuel Tank - 1KZTE ?

[panama120 Lurker Find all posts View Profile Close panama120]

Hi all,

Recently changed the diesel fuel filter for the first time myself after reading all the posts here I could find. Everything went to plan until I tried to prime the new filter. I kept pumping long enough to suspect something was wrong (at least 100 times). I disassembled and tested the pump on its own by dipping the inlet in diesel and it pumped the fuel without any problem.

Thinking maybe I had too much air in the fuel inlet line for the pump to create enough suction, I grabbed a small funnel and began pouring diesel in the fuel line to fill the line. Well I kept pouring and pouring, then pouring at a faster rate. It would get close to being full when pouring at a fast rate but the fluid would just drain down the line when I backed off pouring. I am pretty sure I poured between 1 and 2 liters down the fuel line. I checked under the vehicle and no leaks anywhere. Go figure?

I am puzzled and really hope someone with a lot more experience can shed some light on what happened. Is there a check valve (non return valve) in this line?

Cheers


2006 KZJ120 with 197k on the clock

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

The check valve is built into the fuel filter assembly cap, so pouring back into the inlet fuel line just goes back to the main tank as you found out.

Did you prefill the filter before attaching it and priming (as it will take a lot more than the 100 pumps to both draw the fuel up the line from the tank and fill the filter.

[panama120 Lurker Find all posts View Profile Close panama120]

Thanks ptommo59 for clarifying the location of the check valve.

Yes, I did prefill the filter taking care to pour the diesel into the unfiltered section of the filter. I attached the outlet tube loosely and pumped a couple of times to work all the air out of the outlet side.

Then poured diesel rapidly down the inlet pipe until it filled to the top, quickly placed a thumb on the end and then attached to the inlet of the filter assembly. This time I think I pumped maybe 25-30 times and didn't feel any resistance. I stopped at that point thinking I might damage the pump by dry pumping so much.

Then I started the engine just to check if it would run and she ran smoothly. I had seen a youtube video where the engine ran very rough due to air trapped in the fuel supply. After that I drove around closeby to make sure I wasn't going to simply run through the diesel I had poured into the filter when prefilling.

I have drove a few hundred km and she has run as smooth as ever. However, now wondering if I could have some air trapped in the filter. Is that possible?

Appreciative for any feedback on that, since I lack the knowledge and experience.

[ptommo59 Senior Member Find all posts View Profile Close ptommo59]

The way the fuel filter is designed and positions of the inlet and outlet at the top means its unlikely that it would retain air while passing fuel to the outlet at sufficient volumes to run the engine, so I would suggest you are OK on that front.

The primer pump if you didn't fill the filter would have gone through the stages of:

* little resistance when only passing air, to
* some resistance as it started passing fuel, to
* stiffer resistance as it compressed the fuel in the outlet, to
* not pumping when you maxed out is achievable pressure in the outlet line.

I would guess you managed to get to the last point within a few pumps using the method you used above.