94 super custom dies when accelerate engine light on

Hi there hopefully someone can steer me in the right direction. I have a 94 hiace super custom that will start with some effort but then cuts out when you go over about 25kmh or just rev it over 2000 for a few seconds. It had some diesel out into it from a farm holding tank that had some moisture in it which is when the problem started. Initially it would just lose power but this has now progressed to cutting out completely and being undriveable. I have cleaned out the fuel tank, all the fuel lines, bled the fuel lines, cleaned the air filter, replaced the fuel filter. I've also cleaned the filter from the fuel tank which was mucky as and so I thought hurray this must have been blocking the fuel but it still doesn't want to run. The primer on top of the fuel filter gets sucked down hard when it runs and won't xome back up until the pressure dies down after its been off for a bit. It seems to be filling OK and primes just fine when it's off. I'm stumped at this point. I know I need to go and buy an obd reader but just wanted to see if anyone might be able to help me as I'm 3 days deep into this wormhole and I really need to go to my actual job which I require the van for!

Hi from GB
The primer getting pulled down indicates a lack of supply suggest you put a test pipe from filter to an open container to see if it does not go down, the fact that the pump head is pulled down shows the lift pump is working, blow air down the fuel line back to the tank to make sure it is clear. Is the tank breather blocked its a foam thing on the end of a pipe comes from top of tank if blocked you will get vacuum in tank . Check fuel return put a piece of clear pipe on it look for air bubbles also the flow should be quite high 1 ltr minute this to tolerate air ingress to an extent To recap the fuel primer should not get pulled down so there is a restriction somewhere. Please let us know the outcome so we can all learn.

Thank you so much for taking the time to reply and help me! after ensuring there were no leaks or blockages anywhere I decided to put a nut between the spring and the top of the fuel primer to briefly prevent it from being pulled all the way down and see if this was the issue and it turned out to be exactly that! So after replacing the fuel filter with a temporary one that does not have a primer (until the new one arrives) It now happily runs again. I would say that I wished I had tried this to start with but after the extensive cleaning the tank, tank filter and fuel lines got, (as well as an oil and oil filter change) it is running far better than it was before and I also learned heaps which was great. I noted the bottom of the fuel filter that has the thread on it was ever so slightly misshapen which may have meant it wasn't sealing 100%.
So i was able to get to work this morning hurray! I did note the engine is sounding slightly more droney than before although perhaps all the crap in the lines has been insulating the sound for so long I'm just not used to the way it's meant to sound

JT69's comment about a vacuum in the tank prompted me to ask about something that i have noticed. When I undo the filler cap to refill my tank there is always a "Whoosh" sound that suggests that there is a vacuum in my tank as the diesel gets used up. Is this normal, or a sign of a problem?

Great , sounds like the hand primer is faulty somehow impeding the supply will keep an eye on mine, it runs on used vedge oil mix and suffers from a blocked filter every so often.

I've noticed lots of discussion on that, where do you get the vege oil from? Diesel is now more expensive than 91 in nz so I would definitely be keen to make the switch!

Local Indian takeaway without a supply of WVO dont bother Vedg oil is now more than diesel.

Hello Sarahw96 and welcome to the forum.

These fuel primer pumps are quite prone to causing all sorts of fuel delivery problems. The whole of the fuel delivery system is under ‘vacuum’ (well low pressure) until the injection pump so the system is prone to starvation or air admittance with various related symptoms. The low pressure system is also very simple and fairly easy to work on.

The filter pump head is key. It’s easy to swap for new (and fairly cheap) but also can sometimes be revived by removing and submerging the pump head is a tub of diesel to pump through to re-seat the one-way valves and clear out other issues. This worked for me when I had the problem of a leaking output pump diaphragm that siphon-drained the pump head after runs and caused air in problems.

There are also various problems with the tank pickup filter or blockages in the tank pressure equalisation system (the famous whoosh). There can also be return line blockages and leaks in the lines, but the thing to remember is the system is simple. The tank is also very well designed.

In case you’ve not seen or accessed the many resources that are out there for Hiaces including various manuals and the EPC, check this simple post. It has pretty much all you need and search for the bolded text there:

https://hiace-super-custom.forumotion.com/t4468-part-numbers

btw, Andonic that whoosh is really not normal. It might mean you’ve saving a tiny bit of fuel but it’s not right. The most likely culprit is that the little orange filter that should allow the equalisation of ambient air pressure in the tank, is blocked. It sits just forward of the tank and is held to the cross-member by a little bracket. The other culprits might be the one-way valves build into the top of the tank or other parts of the air equalisation piping. It’s all beautifully designed and the parts are common to very, very many Toyota tanks (though the piping is a bit unique). Do check the EPC for pictures and parts and the simplest fix might be to replace the orange filter and un-clog the ambient lines with a bit of compressed air, but this could add a dollop of muck into your probably very clean tank. I’ve got my tank off and refreshed so happy to send you some picks if you want to go the full hog, but it’s not a trivial job.

HTH!