Thread: 2.25 Diesel - fuel delivery issue under load

Update - had a look at the fuel lines before the lift pump, all good. I was hoping for a blockage there

I then re-bled the top union on the fuel filter housing. Then I re-bled the pump, nice stream of diesel comes out. So I am now thinking its with the pump or possibly a timing issue?

Would timing affect the upper half of the throttle range, even tho its great from idle?

I will rebuild my secondary pump, got the rebuild gasket kit from Bundy Bears Shed so may as well have that one sorted and swap out as a test.

Lastly if all else fails, then its likely just a tired engine and should get the compression checked and live with it as is until a future refurb.

OK, I have SUCCESS!!!!

Now everything I have done was around fuel flow, or rather where it may not flow! Today I had one last item, the fuel filter and housing. Now I knew the filter wouldnt be the issue, but changed it anyway. Fuel inside looked very very clean.

However, this is where it got interesting. The spill rail on top of the housing that has the fuel hose run to the last injector, when I inspected the banjo bolt, there was no hole in it! It means that the fuel never flowed from this spot, and I am thinking there was an air pocket, or perhaps vacuum that did not allow fuel to flow past a certain point.

I drilled the hole, cleaned up it, buttoned it all back together and bam, got fuel/response that was missing. To say that I am happy is an understatement. Funnily enough tho, my spare fuel filter housing banjo bolt also was only partially drilled, so wondering if this is by design or a manufacturing error.

EIrrespective, I now have the 'black mist' on load and response is much better... I recon I gained half a horse (which is like what, 50% extra power ).

Fuel Banjo Bolt.jpg

The bolt going into the fuel fitting should have a hole in it, normally it has a spring and ball which acts as a check valve to prevent fuel from the filter going back to the tank. In a normal situation the banjo has a an inlet from the injector return line and another going to the tank, as stated the returns normally go back to the tank but some can go into the filter if needed. This is as I remember the normal fuel flow if your vehicle does not have a banjo with two fittings( one from the injectors and one returning to the tank) then the following may not apply.
As a result of normal injector operation some fuel bypasses the needle in the nozzle due to operational clearances this fuel exits the nozzle and fills the cavity in the top of the injector before the excess returns to the tank. If this fuel canÂ’t return, pressure will build up in the injector and reduce the output of the injector which will effect the engine output. I believe if your system returns to tank you should check with a Diesel Fuel injection workshop and purchase the correct banjo bolt with the check valve as this will keep the correct fuel pressure in the fuel supply to the pump. This will also allow the injectors to vent correctly keeping everything in balance. As it is the fuel priming pump will be pumping constantly to keep the injector pump supplied and the rest will be returning to the tank hence the need for a check valve. Only the injector return fuel should be going to the tank as this is in excess to the system requirements.
i know this is a bit long winded but I am trying to explain the correct operation of that side of the fuel system.
Regards Gippy 😀

Hi Gippy - many thanks for the details, by all means the more detailed the better!

I had another look at the spare banjo I had, and this one has a tiny pin hole (which my other one didnt) as per picture:



I did put this one in to test, and basically ended up with the same symptoms as with the other non-holed banjo. All checks I have done involve having this tiny pin hoel arrangement, no banjo with ball.

So I am at a loss here, currently with the banjo I drilled with the hole (much bigger than the picture) it performs well. I completely understand what your saying but again the banjo with pin hole arrangement doesnt work as well... perhaps theres another issue I havent come across as yet.

Aside from the banjo, the fuel lines are a stock arrangement, nothing has been modified and as per pic: