Fuel cuts when you hoof it with 1/4 tank...WHY??!

[dukenukem]

For ages I thought this was a design fault and the petrol tank needs a baffle plate to stop the fuel swishing all the way to the back of the tank when you floor it or throw the back end round with only a 1/4 to 1/3 of a tank left. After speaking to Caseys tonight I've discovered this is in fact far from normal!! Has anybody else had this problem? Could this be because the fuel pump or something is loose? In which case, why does it only happen with less than 1/3 of a tank?

 

I've also been seeing big fluctuations in the AFR lately on the dyno charts - probably a separate problem. The car's been dyno'd 3 times on the same RR over the past 7 weeks. From 4300 to 6700 rpm the AFR was a constant 10.8. A month later it was a reasonably constant 11.8. The latest one its dropped below 10, off the scale of the graph (...which stops at 10). What's going on? Is this the fuel pump? Fuel pressure regulator? Other?

 

....help?

[dangerous brain]

Below 10's is rich as fook not lean which is what normally happens. I do recall seeing a question pretty much the same as yours before but without Jake levels of search ability I won't be able to find that thread.

[w41k3r]

yeah i posted a queston, mine was doing it at quater of a tank when i floored it the petrol light would flash on and it would be like hitting a brick wall just wouldnt rev then i`d let off go put more petrol in and it would be fine hasn`t done it for a good few week now but did it a few times then i thought it was summet to do with fuel filter

[wile e coyote]

I have had this and posted it up but no responce

I have since fitted new fuel filter but not properly tested to see if it still happens

[dukenukem]

I just changed the fuel filter a couple of weeks ago and it's still happening. This fuel cut happens when you floor it and reach 4,000 rpm, when the second turbo kicks in the sudden boost in acceleration is followed a second later by slamming your head on the steering wheel as the power is completely cut before coming in again. This might not be so applicable with NA's, although I know it happned in my mates SZ when throwing the back end round whilst close to empty.

 

Poll now added in the interests of science.

[dude]

When your guage is reading 1/4 or wherever it starts doing this then take the sender out and see how much fuel is really in it!!!

[dukenukem]

When your guage is reading 1/4 or wherever it starts doing this then take the sender out and see how much fuel is really in it!!!

 

I'll have look. I'm guessing the gauge is accurate though as I usually get around 160 miles from completely full to 1/3 left, which is when I normally fill it back up to avoid this problem. There have been long journeys when I've done 250 miles on a tank down to nearly empty, so there must be 100 miles worth of fuel left when this problem starts happening.

Edited August 1, 2009 by dukenukem (see edit history)

[paul mac]

there is definately something wrong with your car, on pressurised injection systems as long as you have the fuel pump intake covered it should not make a jot of difference what the fuel level is, fuel cut happens when the ecu see's to high a voltage on the injectors exactly why the injectors max out when you have less fuel i dont know, in your position i would start by replacing the fuel pump and the FPR as it does point to starvation causing the injectors to max, maybe the hose off the fuel pump to the top of the hanger if holed or kinked

[miko_supra]

Mine used to do this when the fuel warning light was on

[brettjones]

i have had this happen to mine 4-5 times i have just put it down to air getting in the fuel pump ?

[Chris Wilson]

My best guess is someone's made a bugger of fitting an uprated pump and the flexi rubber pipe between the pump and hard pipe of the tank / sender unit i leaking. Once the fuel gets low it draws air in at the fault. What happens if you run the fuel level desperately low, does it run OK without giving it any real stick?

[SUPRALOOPY]

My best guess is someone's made a bugger of fitting an uprated pump and the flexi rubber pipe between the pump and hard pipe of the tank / sender unit i leaking. Once the fuel gets low it draws air in at the fault. What happens if you run the fuel level desperately low, does it run OK without giving it any real stick?

 

I was going to say intake fuel pipe sucking air due to split hose/pipe. Just corrected this problem on a aston db4/5 classic.

[dukenukem]

Cheers guys. Will check the hose off the fuel pump to see what it's like. Sounds like a cheap fix.

 

P.S. Damn you Supraloopy! - I know it says "DO NOT CLICK THIS LINK!!" in your signature, but there's something about being told not to do something that means I have to do it.... To everybody else wandering what it does.. DON'T DO IT!!!

[dukenukem]

My best guess is someone's made a bugger of fitting an uprated pump and the flexi rubber pipe between the pump and hard pipe of the tank / sender unit i leaking. Once the fuel gets low it draws air in at the fault. What happens if you run the fuel level desperately low, does it run OK without giving it any real stick?

 

Yeah it runs fine right down until empty without giving it some, but the more empty it gets the bigger the jolt when the power cut happens. As far as I know the fuel pump is stock but will check the hoses/connections. Cheers

[w41k3r]

mine is a sz n\a and did this hasnt done it for a while now

when it was at a quater of a tank id say put my foot down hit 4000rpm fuel light would flash on gauge would drop to allmost empty and it wold be like hiting a limiter but no noise it just stops but never kept my foot on the pedal as you poo it lol but driving normal its fine and the gauge will rise bk up slowly