fuel pump losing the plot ??

[Draven]

ugh. does that include anything else, or that's just for the tank + welded on fittings?

[ed]

other idea i had today...

lowish fuel level
tilted tank on the dyno
awkwardly oriented swirl pot in the tank

perhaps the fuel surged in the top end as the return flow out of the reg dried up and the swirl pot filling rate was insufficient?

[ed]

hmmm. out for a drive tonight (25L/100km) and had weird issues with fuel starve (1/2 full tank)

was wondering if there was something whacky going on with the fuel pressure again, and pulled over to have a look at the reg pressure. obviously at idle there was nothing interesting to see, but thought- hmmm.... ill pull the vac signal to the reg off (so no longer manifold referenced) and see what happens - viola! no more problems. i wonder if the reg is a bit iffy?

why would a reg (simple little device) get all whacky one me? or am i dreaming?

[oldcorollas]

simple reg is balanced to brake booster and MAP sensor no?

unless reg is rooted (or just shit), then it can only do weird things if it has variation in line pressure...
with your cams and lack(?) of vacuum shoudl mean that the line to the reg is not needed

perhaps (as someone else suggested earlier).. you are sometimes getting vac and then drops the fuel pressure and feels like starving??

got a spare vac gauge you can put in the cabin? can you log from ECU to try adn see what happens to MAP when you have issues?

[ed]

might just ditch the vac reference. as you say, theres not that much variability, im sure we can tune around it

[oldcorollas]

no reason why not... is only there to keep the pressure differential across injector constant, or reduce differential at idle to make it easier to tune smaller pulse width easier....

be good if you could log and measure the problem first.. to make sure it is the problem

[ed]

sure, but it'd be totally odd for there to be a whole surge of vac at WOT

the issue tonight was totally different to previous issues, from idle to part throttle, it surged, and fell over. again and again, car was difficult to pull away from a set of lights, and felt exactly as an engine does when you know youre on the very brink of running out of fuel. we had to baby it off the road, and have a look.

there no way it could be surging with the amount of fuel in the tank though, and simply removing the vac reference line fixed things for the next 2 hours of driving

[oldcorollas]

maybe your brake booster one way valve is not sealing properly??? sometimes holds vac, sometimes pulls air from the common thingy, pulling fuel down as well as MAP...
one danger of having them all connected

a log when it happens would be good...


either that or the reg is shit.

[The Real Roadrunner]

might just ditch the vac reference. as you say, theres not that much variability, im sure we can tune around it

that would just make it work the same as mos' i think his runs 50-60 odd psi constant.

can be tuned to suit but it makes the fuel curves abit funny from memory, oh well it works thats a definate.

cheers

[thechuckster]

ed: how many inlet ports does your vacuum manifold connect to? and do you have a one way valve between it and the vacuum sources? and some sort of filter to 'even out' port pulsations?

[ed]

all ports are connected
theres a 1 way valve between the vac cannister and the brake
theres a filter to the MAP sensor
theres no filter to the FPR

[Skrewball]

what i have personally experienced was a fuel filter issue. the filter said it would handle the flow and pressure, but indeed it would not. i was using a 255L walboro pump for a ramjet 350 and the pump would work great at first, but after a mile or two down the road it would start losing pressure. it would also start making noise. after it was shut off for half of an hour it would work great again for a few miles.

the fix:
a fuel filter from a chevy camaro that has an Ls1. the filter has threaded fittings on both ends and flows great. it is a 10 micron filter so it is usually enough filter.

this may not help you, but i thought i would share my experience.

[chiksluvit]

Hi Ed..
I suppose it's a JZA80 turbo?
what boost pressure is it running and power?
my guess is that the problem is in the pump itself, it shouldnt matter if fuel is only half a tank full, or fully full. though running the tank to almost empty is stupid and heats up the fuel pump well..
the walbro pumps don't really work well with turbos, they claim it flows 255L/hr and supports up to 500hp but never mentioned at what pressure it does that. if the vehicle is turbo charged, then the pressure will be even higher and the tiny walbro pump most likely isn't going to be able to handle that...
if you still have the stock pump, try fitting that again and give it a go, otherwise get a bosch pump

[Mos]

Ed's it's an atmo V8 in an originally atmo JZA80.
If the walbros don't work well with turbos, why do so many people use them successfully with 1JZs and 2JZs in factory locations? Not saying what you're saying is not true, it's just perplexing there's such a disparity in opinions.
Mos.

[oldcorollas]

there are flow graphs available aroudn the net for walbro, bosch, and various stock pumps..

at very high pressures (like when you have a rising rate reg), the walbros fall over earlier than the motorsport bosch pumps.. but we are talking alike 70-80psi here...
on a normal rail pressure of 40psi, thats 30-40psi boost on a 1:1 reg....
but in saying that, they still provide fairly good flow until pressures experienced by most people...

rising rate regs suck balls