downunder

Hey Guys.

I have a 3DR Cossie that the fuel pressure drops under load all of a sudden, was fine until recently.

Original Tank
044 Pump
Upgraded Pump Wiring Loom

From the pump to the front of the pressure seems fine. This made us think that there is a problem from the tank to the pump so we dropped the tank today to have a look inside to see if the pickup is blocked or something. The tank is clean as inside (based on what we can see through the sender hole) but what we noticed was that if we tip the tank to one side we get a small amount of fuel out of the pickup pipe (that would go to the pump) and then it just drips where as I would of thought it would just flow out the pipe. We have emptied the tank, tried blowing air in it (as close as we can to the plastic swirl pot with air gun nozzle extension) as well as blowing air into the back down the pickup pipe as we thought this might be blocked.

Has anyone else come across the above problem........?

The only thing I can add, the vehicle has always been ran on normal fuel and recently we changed it over to E85 which was fine. The car does not get driven much so it has only had one tank full of E85 then it started to lean off (almost overnight). I have since gone back to normal fuel (had it tuned for both fuels) as I was thinking it was the E85 causing the vehicle to lean off. But, it is still doing it on normal fuel and like I said above, I think we have traced it back to maybe being a problem between the tank and pump.

Cheers.

downunder

Are the tanks pressurised somehow .....?

It I blow air with the air gun into the smaller pipe (next to the pickup pipe) then fuel pours out of the pickup pipe. As soon as I stop blowing air, fuel only drips out the pickup pipe.

Paul_RS

iTrader: (4)

The small pipe beside the outlet pipe is the fuel return. The tanks do have a very small breather hose on top of them, make sure that is clear as well.

downunder

Thanks for the reply.

With the tank out of the car on the bench and 3/4 full of fuel and the fuel cap removed, fuel only drips out of the pickup pipe. If we shake the tank around a bit we get a bit of a dribble of fuel and then back to dripping again. If I pressurise the tank via the return pipe using an air gun and fuel cap on fuel pours out the pickup pipe. With low to high pressure the volume of fuel coming out increases and decreases depending on the pressure.
I have had a look inside of the tank via a inspection camera, I can see the filter in the centre of the plastic swirl pot and it looks clean.

So I am rather stumped why fuel only flows out when I pressures the tank.

costina

iTrader: (1)

Is it happening with the cap on or off?

Brendan

iTrader: (1)

no the tank is not pressurized, but if the breather gets blocked the pump has to work a lot harder, as the pressure in the tank gets lower as fuel is used!

PM me your email and I will send you some basic diagrams and some pics

my thoughts are blocked breather and may be some debries in pump causing a stall under load, or the pressure regulator is not restricting the flow back to the tank when you are under load, therefore the pressure will drop a lot as you will be flowing too much petrol through the pump!

see if you can borrow some ones fuel pressure regulator!

good luck!