Fuel starvation

Whilst prepping the SC for a 10 day holiday I filled up the tank to the brim with fuel (WVO that is) checked everything and ran the engine and noted a leak on the fuel filter pump head a known fault with 1kzte, so I changed the filter for one with no primer
an easy job and cheaper filters to boot. But alas on priming the system (we have an electric pump near the tank as part of the WVO conversion) the SC developed serious fuel starvation, misfiring at all speeds. After much tightening of clamps etc we were down to clear pipe on the fuel return pipe showing much  air and cavitation (cream like fuel) . Turned out to be a simple solution to a very simple cause , on returning the retained fuel to the tank there was a sharp sucking noise as a I  released the fuel cap , having filled the tank to the top there was very little air in there so causing greater suction on the pipework etc resulting in serious cavitation , blocked tank breather being the cause. Now its under the van and find that pesky tank breather.

Hello JT69

It’s not just the 1kzte that has the possibly dodgy primer pump head. My 3L had the same problem. I was able to carry out a reasonable fix on my unit by submerging the filter head in a tub of diesel and pumping away until all the seats reset and it’s been fine since then. When they do stop working they can let air in and allow fuel to leak with nasty results.

In the longer term I’d like to fit a Delphi-type filter and pump like is typically fitted on old tractors.

That air breather vent is (one of) the Achilles’ heals of the fuel system. If I had to guess then I’d suggest the check valve at the end of the tube is the most likely culprit. It’s also the easiest to access. If you have access to an airline then it’s well worth (gently) blowing air into the tube (so after removing the valve) and into the tank and replacing the check valve. There are also float valves built into the top of the tank (eg see: https://www.amayama.com/en/part/toyota/7742026010). These should prevent fuel getting up into the venting system but allow air to pass into the tank as fuel is used. I’d expect a little air pressure might unstick these if they are causing the problem and this is a simpler fix than dropping the tank to replace them.

Good luck!!

Great analysis Hiace master but I am a bit more basic , as my problem is possibly a result of using WVO it becomes very sticky when exposed to air, the filler cap has an air ingress valve that was very stuck . So we have to be more inventive as I think we are on our own using WVO, a small hole drilled through the cap solved everything and very cheap and no fuel does not spill out on right hand bends .

Tip top and a top tip.

I think my filler cap might also have a stuck valve. I always assumed the tank breather did all the hard equilibration work but if the cap does some of this then I will need to investigate. I need to have a prod about as the cap is quite complex with a ratchet to prevent overtightening but I don’t understand how it seals and vents, too.

Thanks for your insight.