Fuel Tank puzzle

[petebee]

Evening all

Hope someone can determine the problem but I think I know what it is. Just want to be sure.

3/4 through both races at Brands, when running at high revs the engine would dip and on a couple of occasions almost cut feeling like it was out of fuel. The worst occurance was graham hill bend, flat out in 2nd and coming onto the start finish straight running hard in 3rd. Really bad was paddock but I was mostly braking so didnt notice that much.

My fuel loading for both races was 11 litres, drawing out 5 at the end of both races so I only used 6 litres, Bout right I think.

Ive checked the electrical connections and found no loose connections.

The fuel pipe looks fine, it was renewed over the winter.

The fuel pump runs nicely, no strange sounds etc.

Drained the tank by running the pump and when I pulled it out there was 3 litres still in the tank. Now this is probably a daft question because I think the answer is yes, but, should the car have a fuel pickup pipe inside the tank?

So, I am guessing I need a fuel pickup pipe in the tank, but am I missing something?

Thanks for your help.

[J Chapman]

I'm sure Dave Dibden had EXACTLY the same problem not long after he took the car on. I'll dig out the emails he sent me about it.

If you had five litres left and after you pumped it out there was still three in does that mean you pumped out only two? Or did you pump out five. If your running within 2 liters of the pump suction you might be in danger of loss of suction due to surge but this is more likely to be noticeable when cornering as lateral loads are usually greater than longitudenal loads of acceleration.

You can also get these sort of issues associated with charging system failures follow this link for more info http://www.formulafordzetec.co.uk/linke ... ystems.pdf

However this doesn't really cause such an abrupt loss of power as you seem to be experiencing.

[petebee]

No, i took out 5 and then when I removed the pump etc there was a lot, i am guessing around 3 litres, on the floor of the workshop. I was expecting some but it filled the tray I had.

Now on the path of cleaning everything and changing anything that might be causing a problem but I really am not sure.

[petebee]

Thanks for those emails James, ill let you know how I get over the week. Thankfully our local haulage company is going to let me run the car in their yard up to test. Doubt it will get close to replicating the problem but worth a shot.

[J Chapman]

Yeah that's always the problem when it comes to finding intermittent faults. There's only a certain amount you can do before you have to go testing again to see if its fixed.

Have you got the software to view the sensors make sure they are all working as they should?

[petebee]

Ok, so the fault reared its head again when running the car up and down a 1/2 mile stretch of factory grounds. Thankfully Dax's wheel is telling me my fuel pressure sucks, so it is a fuel problem after all. Only question is where. Only happens under heavy acceleration out of a corner. Makes no difference left or right. I cleaned everything, I think. Grrr.

ideas anyone?

[teamfoxracing]

Try a new fuel pump?

[J Chapman]

I've got a spare fuel rail with injectors and regulator if you want to try it. Where are you located?

[AVIT!]

Hi pete

my car and the swift 1600 I had before both did it if I had less than 6 litres left in the tank.
I have to run 8 litres as part of my ballast or by end of the race it fluffs under hard cornering.
so long as there is 6 litres in I have no problem.
AVIT!

[petebee]

Thanks guys, sorted it. You were spot on Avit.

As long as there is 6 litres in the tank its fine under hard cornering. 5 is ok but if I really throw it into a corner it starts to play up. 4 is probably fine, it plays up like it did at Brands. 3 and I hit 0 pressure under hard left bends. 2 and there is 0 pressure in the right bends. I think I might have just discovered I am driving the car harder.

[stevengriffin]

I had the same trouble with my Cosworth Sierra, every time I turned left when the tank was half full or less it stuttered and coughed. The fitting of a small swirl pot for the fuel has solved the problem.

[petebee]

Should I have a swirl pot? Might it help?

[J Chapman]

Can't see how you'd fit one inside the plastic tank on a single seater!

Do all Swifts have this issue?

Are you able to dip the tank? I made a dip stick for my Van Diemen by run the tank down until the pump picked up vapour. Added 1 liter, called that 0 fuel and added 2 liters at a time and marked off on the stick until the tank was fuel. Makes life a bit easier than having to pump the tank clear after every session.

[stevengriffin]

It doesn't have to be inside. In the side pod would do.

[AVIT!]

Problem is Steven is the pump is in the bottom of the tanks in our ff.
It sits in a small chamber in the bottom of the tank and fuel comes out the tank at pressure.
On cornering the pump runs dry losing fuel rail pressure .
A swirl pot after the pump won't help as it will still only be pumping air so it will then lose pressure at the rail and the swirl pot.
Only fixes for this problem are
1: carry more fuel as part of your ballast keeping the pump submerged.
2: re design the fuel tank ( not as easy as it looks)
3: remove internal pump and replace with straight pickup pipe , add swirl pot before new pump and then pipe to fuel rail ,then if it does suck air in the tank the pump can feed from the swirl pot till the tank catches up.
4: sell the car to Dermot .
AVIT!