Fuel Starvation?

[shooorn94]

Hi all,

Want to rack your brain a bit.

Like a numpty I left only a quarter tank in the sax before my track time last sunday at silverstone. The car itself performend well until leaving Luffield and enterring woodcote going past the national pit straight... at 95mph at the crest of the hill the engine would cut.

Now my fuel gauge moves as I accelerate/climb up hills... whilst this may sound annoying it has proved useful for me to ensure that I know when fuel is actually be picked up by the pump. Any where else on track at silverstone (even past 90-odd mph) the car was fine - now considerring every other track day this year/strip time I've had 3/4's of a tank and had no issues I put this down to running with a quarter of a tank on the day.

What are your thoughts ladies and gents? Time for a new pump (it does whine for a large period before startup) Or do you feel this is something more detrimental?

[jbrady72]

Hi all,

Want to rack your brain a bit.

Like a numpty I left only a quarter tank in the sax before my track time last sunday at silverstone. The car itself performend well until leaving Luffield and enterring woodcote going past the national pit straight... at 95mph at the crest of the hill the engine would cut.

Now my fuel gauge moves as I accelerate/climb up hills... whilst this may sound annoying it has proved useful for me to ensure that I know when fuel is actually be picked up by the pump. Any where else on track at silverstone (even past 90-odd mph) the car was fine - now considerring every other track day this year/strip time I've had 3/4's of a tank and had no issues I put this down to running with a quarter of a tank on the day.

What are your thoughts ladies and gents? Time for a new pump (it does whine for a large period before startup) Or do you feel this is something more detrimental?

I was out with my mate literally just last night, I was in my Saxo VTR, only had 1/4 tank if that and I was following him and he decided to go round a roundabout several times as fast as he could and I followed, after about 3 or 4 laps, as I pulled off the roundabout the engine sort of spluttered, cut out for a second then got going again, so I guess thats the same sort of thing?

[shooorn94]

Yes it appears you have a similar sort of issue. Although my pump I imagine was working under more extreme temps ;)

If the pump cannot pick up fuel it will not be able to send it down the lines to the fuel rail that's the long and short of it.

I diagnosed the issue on the day and feel I should have just called at shell before leaving.

[axsaxoman]

this is why you fit a swirl pot + second fuel pump to a track car or very fast accelerating road car
once you pull 1g or near it the fuel will all go to one end of the tank he and cause stravation (drop in fuel pressure)
and in worse case ,like a rally car i fitted widetrack kit to itkilled the pistons as it went lean and with no lambda or fuel pressure gauge did not know it was happening - he did notice a little misfire sometimes on leaving corners ,but ignored it ,then when doing a rally in the hotest part of the summer with high engine temps +running lean --bingo .
one of the reasons i like to see a w/b fwith gauge fitted to boosted cars as you can get 1g+ accel any time in lower gears --even if its only used as a a guage and not used to control fuelling
I prefer to see it linked to ecu for corrections for at least all low power parts of the engine + just showing whats happening at very high engine loads ,which is why i like the dta + predator -
omex can,t do this easily ,also makes mapping a lot quicker as well
-car ran lean and now it needs new pistons and rebuild

[axsaxoman]

What are your thoughts ladies and gents? Time for a new pump (it does whine for a large period before startup) Or do you feel this is something more detrimental?
__________________


running pumps dry wears them out VERY quickly ,the petrol is the only lubrication+ cooling for the vanes+ motor inside the pump
this is why all externally mounted pumps on std cars are always below the tnak utlet level --to make sure they are always full of fuel

[shooorn94]

What's your personal opinion fella?

I use the car primarily for track work, hillclimbs, and weekend spirited runs over the summer.

It's not an area that has bothered me before this moment but as you have backed up my claim of fuel starvation I know I only have myself to blame for not filling up beforehand like I did last time I was at mallory/pod ensuring I had enough fuel to cover my time on track. That said I'd rather not run the risk of the engine getting to crazy temperatures because it's running lean on a track day.

The OEM pump is more than good enough for road use where you only occasionally accelerate harsh but I can see the need for a swirlpot, especially if going boost. I've never seen two pumps fitted to a 106/saxo used for track work in NA form. :geek: How is the second pump mounted and controlled?

Surely a pump deliverring a higher pressure would be more beneficial then running two pumps?

Would you reccomend running a 4.5bar FPR in my instance as at present I'm running a 3bar FPR mounted by the tank not at the rail like most VTR's.

[Gandi699]

what injectors are you using? the VTR uses a 3.5 bar FPR as standard with the slim injectors. I run a 3 bar one too but i'm using bosch brown injectors from a rallye s2.
Either way that shouldnt make too much difference to be honest in regards to fuel starvation, i'd be inclined to check the pump over and install a new one and a new fuel filter

[shooorn94]

Injectors were orderred brand new 3 years ago and are OEM VTR injectors... I will grab the cc and part number when I get in from work. :y:

Fuel filter could do with a change to be fair as it is one area that has not been changed since the car no longer became my daily.

This concerns me somewhat as the S1 rallye runs a 2.5bar FPR iirc and I will be fitting my S1 rallye inlet over the next two weeks before Combe at the end of the month. :fcuk:

[Gandi699]

i'd try a 3.5 bar one to be honest as its running a pretty much standard vtr injection system. I wouldnt drop to a 2.5 bar one in all honest

[shooorn94]

Neither would I in all honesty. I'll see how the car fires up with the 3bar FPR and s1 inlet I may use combe as a shakedown run with new pump, s1 inlet, and fuel filter as I'm only out there for 40mins. If I experience similar I'll look elsewhere.

[axsaxoman]

What's your personal opinion fella?

I use the car primarily for track work, hillclimbs, and weekend spirited runs over the summer.

It's not an area that has bothered me before this moment but as you have backed up my claim of fuel starvation I know I only have myself to blame for not filling up beforehand like I did last time I was at mallory/pod ensuring I had enough fuel to cover my time on track. That said I'd rather not run the risk of the engine getting to crazy temperatures because it's running lean on a track day.

The OEM pump is more than good enough for road use where you only occasionally accelerate harsh but I can see the need for a swirlpot, especially if going boost. I've never seen two pumps fitted to a 106/saxo used for track work in NA form. :geek: How is the second pump mounted and controlled?

Surely a pump deliverring a higher pressure would be more beneficial then running two pumps?

Would you reccomend running a 4.5bar FPR in my instance as at present I'm running a 3bar FPR mounted by the tank not at the rail like most VTR's.
higher pressure doesn,t help
if the fuel is moving to one side of the tank and pickup is dry . as soon as the pump sucks ANY air the pressure will drop
std tank is flat and wide and pump is not in the middle either and there is a hump in the tank so its easy with sticky tyres and high corner speeds to get fuel surge ,
you try driving round a track with a cup of coffeee in your lap and you,ll soon see what happens as you corner[[you get burnt bollocks .
if you don,t want to run two pumps +swirl pot then keep it half full all the time .

[shooorn94]

So I presume we'd have one pump at the front of the tank on the right and one at the rear to the left for example?

I fully understand the principle hence the diagnosis on track.

I suppose at GMC you can provide the aftermarket tanks, fuel lines and secondary pump?

How is the secondary pump controlled and how is it often plumbed in?

Due to my time frame for Combe I will be changing fuel filter, look at changing pump in time and focussing on getting the car running right on the intake side of things. I will of course run with more than half a tank to ensure this does not happen again and I will feedback after. :y:

[axsaxoman]

no that is too complicated and still would n,t cure the problem .
the onlyways are
1- use a "bag tank" --which has a rubber ballon type lining which contacts as it gets empty --very ,very expensive
2 - fit a swirl pot which the std pump pumps to and a the std return line goes from this back to tank
you then have another pump which sucks from this small tal container supplys injectors and the return line from the injectors goes back to this small tank .
the std pump will keep this full at all times and if the return linis slightly smaller even better --no need for a pressure reg on this std pump .you have the fuel reg after the injectors on the second pump circuit .
If your battery is inside car simple place to mount all the extra bits is to make a trayand fit it to the batterytray
that way you leave std pipes as they are --no fuel inside car and no problems with scrutineering
ring me if you like to discuss