3.9 EFi Fuel Rails?

[Nords]

I have 3.9 V8 EFi which has a couple of solid lines with braided 6" connectors to allow some flex I guess? One supplies fuel from the std pump in the tank, with the other returning it back to the tank.

I have had problems with fuel starvation when the vehicle is tilted to around 45 degrees. It will run for 30-45 seconds and then stall. It has to be winched to the hortizontal on the slope, started and then 'unwinched' back to 45 odd degrees.

I'm thinking about a swirl tank like this...

https://fitechefi.com/product/force-fuel-system/

The question is the 50004 has a feed from the tank and a return. It then has a single petrol feed to the EFi and no return. Is it okay to just blank the return feed on the engine?

[scudderfish]

That's very expensive, have a look at OBP https://www.obpltd.com/product-category ... wirl-pots/

A return form the fuel rail keeps the fuel in the rail cooler. You need one if the rail is designed that way, otherwise you're just going to trade one problem for another.

Ultimately, this tank will mask the true problem that your fuel pump in the tank is not up to the job. This will let the engine run when it's given up, but only for the duration of the content of the pot.

[stevieturbo]

I have 3.9 V8 EFi which has a couple of solid lines with braided 6" connectors to allow some flex I guess? One supplies fuel from the std pump in the tank, with the other returning it back to the tank.

I have had problems with fuel starvation when the vehicle is tilted to around 45 degrees. It will run for 30-45 seconds and then stall. It has to be winched to the hortizontal on the slope, started and then 'unwinched' back to 45 odd degrees.

I'm thinking about a swirl tank like this...

https://fitechefi.com/product/force-fuel-system/

The question is the 50004 has a feed from the tank and a return. It then has a single petrol feed to the EFi and no return. Is it okay to just blank the return feed on the engine?

There are many swirl tank setups available. Just watch as the likes of that Fitech does not adjustable fuel pressure, if that matters to you. Given it's aimed at probably teh LS market, it could well be a static 60psi reg.
No big deal really, but would require re-tuning for your car.

Radium, Nuke, 034 Motorsport all make nice surge tanks. Although really you would not need anything more than a simple Walbro 255 or equivalent.

There are of course many chinese/cheaper surge setups, but one with an in-tank pump inside the tank will be neater and easier. Up to you what space you have available, and whether you want to use a reg on the fuel rails, or re-locate this to the new setup as that Fitech does ( would typically be a dead and fuel rail setup )

[stevieturbo]

That's very expensive, have a look at OBP https://www.obpltd.com/product-category ... wirl-pots/

I would not bother with any that then rely on an external pump. Just gets messy with lots of hoses and fittings, and takes up more room anyway

Whilst Nuke or Radium, well renowned brands would be preference...they are a bit pricey.

Speedingparts lists a few more chinese style at fairly ok money

https://www.speedingparts.co.uk/c/fuels ... McbQ6H6l1e

eg

https://www.speedingparts.co.uk/p/fuels ... McbQ6H6l1e

[Nords]

Thanks guys,

That is really useful. It is a standard 3.9 EFi running a K&N and open pipes, on a std pump mounted in the tank. I do have a pressure gauge for the ‘rail’ on the block but never tried it before the line failed. Both supply and return lines have been taken out of the car now.

[GDCobra]

I made one myself from some aluminium thick walled tube and turned up some ends. The high pressure pump (Bosch 044 copy) piggy backs onto it drawing fuel from the bottom via an inline filter. Top has 3 AN fittings welded on for:
Return from fuel rail,
Feed from lop pressure pump in tank,
Return to main tank.

It is only about 80mm diameter but 300mm or so tall so holds about 1.5L and due to the dimensions if means the car would have to be pulling significant G or be on a sever angle (if it were a 4x4) before it would uncover the fuel exit.
It sits in the boot next to the main tank but I guess it could just as easily sit closer to the engine I guess.

[Nords]

Tempted to try the same GD. The application is a bit of a unique one, we are Car 61 on here:



The shortest distance between 13 guardposts (checkpoints) wins, hence you drive as straight as possible even if that means down/up a cliff! The cars can be about to tip sideways or be at 50 degrees plus going up an incline or down the same.

We lasted about 3 mins on the fuel in the line at tickover as we winched out of numerous dongas (dry stream beds cut into hard mud so 8-10 feet way and deep). Then we winched and crossed our fingers the batts would last until we were flat again and the engine would fire up.

[Nords]

Steviturbo, you are spot on. The Fitech one is set to 58 psi, so perhaps a bit more than required. I’m thinking a feed and return to the surge tank / swirl pot with the pumped output going to the engine. I won’t blank the return off, but run a return line to the tank to ensure ‘cool fuel’ is going the EFi supply rail.

[Nords]

Update.

I bought the Deatschwerks 3.5L in the end. It comes with a DW350iL (or twin pumps) but it was the capacity which attracted me. We could spend time at steep ‘tipping’ angles.

My worry was that the Landrover in-tank pump is rated to 150 litres/h and the DW is 350 litres/h. However the tank pumps into the surge tank, which pumps to the rail. If I bypass the surge tank, I’m seeing 32 psi at the rail, if I connect the DW350iL and tank in, 32 psi again so the pressure regulator can handle the faster flow.

Just need to test the whole system at an angle now!

[scudderfish]

Good news The surge tank basically buffers the difference. I had a problem with mine where the rear lift pump couldn't supply fuel at the rate the engine consumed it at high speed so it would appear to run out of fuel as the surge tank drained. Park up for a couple of minutes and it restarts and behaves as if nothing had happened. Provided the pump from the tank can feed fast enough to keep the surge tank fed, it doesn't matter what capacity the HP pumps are (provided it is sufficient) as they just recirculate the same fuel if they pump faster than the LP pump(s)

[Nords]

Exactly Scudderfish, with the Disco being tipped (especially to the right with the in-tank pump being off to the left - looking from the back of the car) it would stall when tipped quite quickly, even with half a tank plus. As the 350 L/h pump returns to it’s own surge tank with fresh fuel being pumped by the 150 L/h it should be fine however will be tested soon. My only worry now, is that I start to recirculate hot fuel in the surge tank, over and over again! Fingers crossed that 3.5L less the internal pump size, is sufficient to combat that.

Edit. Probably worth saying that the 3.9 is standard, less a K&N and homemade exhausts, so 160 bhp or so? According to Deatschwerks, you only need ~60 L/h for that.