Fuel Pump problem

[Talasas]

Hey guys,

The story: I've got a 4A-GTE setup that was ready for the dyno, I took it down to get tuned and after measuring the fuel pressure and flow it turned out that the stock AE92 SX fuel pump was pumping only 0.9L/min of fuel.

The car drove fine (in NA mode) and never had any issue with fuel or mixture. So the tuner said to get a new fuel pump, he set up my fuel pressure (using the Sard) and I drove home.

Going on the reccomendation of the tuner, I installed a Walbro 255 in-tank pump, I fired up the car and the pump works (I can hear it at least). The engine idles fine and grabs revs at idle fine.

When I take it for a drive at 1/4 throttle it seems to drive fine just as before. When I use 1/2 throttle however, it struggles and hesitates and really doesn't want to go once it gets to around 3000 rpm.

I touched nothing else when I installed the Walbro.

Can anyone shed some light on what's going on? Could it be that it's now getting too much fuel and/or the fuel pressure has changed because the flow has changed?

I'd really like to be able to drive it down to the dyno again so that I can get it tuned for boost finally.

[EVOSTi]

cant you drive it there on 1/4 throttle?

how is the pick up point in relation to the old pump? does it reach to the same place? could you have crimped a line when reinstalling the tank?

if its using too much fuel to make it run that bad youd be able to see the smoke from the tailpipe. you should be able to still drive it to the dyno though.

[Talasas]

Thanks for the quick reply, I was thinking the only thing that may be out of place was when I was re-installing the tank there were 2 return lines to connect back up and I was pretty sure I hooked them in the correct order, apparently it doesn't matter but I'm pretty sure I did it right.

[EVOSTi]

2 returns? 1 return 1 carbon canister? if thats the case it shouldnt matter if they are the same size.

[Vios-GT_07]

did you install the fuel pump with a relay?

read somewhere on toymods that the current draw out of a walbro is quite high.. and older corollas having thin wiring, maybe that's it?

[mrshin]

Turbo 4AG, just getting it setup, presumably you'd have an appropriate ECU, and you say it hasn't been tuned yet, so quite likely that it wouldn't run too good??

[Talasas]

That's right but my point is the car was running fine before the Walbro, so what could have changed?

I've spoken to a few mates and the consensus is that the fuel volume has increased and the pressure may have increased due to the design of the reg. So the injectors are just feed more fuel now - we'll see. It limps to the dyno on Thursday arvo.

[Ribfeast]

Might need to fit a fuel pressure reg to it? I'd say it is overfuelling too as said above.

[Talasas]

I have one

he set up my fuel pressure (using the Sard)

I'm almost tempted to turn down the pressure a tiny tiny bit, but I'll get a gauge on there and see what the reading is and decide if it's wise or not.

[SillyCarS]

pull off a hose after the regulator and check the flow rate into a jug something?

[Talasas]

That's good thinking, I'd forgot about that despite doing it to check my oil flow rate lol.

[oldeskewltoy]

You have waaaaaay tooo much fuel running through that system. Walbro engineers usually calculate that each liter of fuel per hour can EASILY support 1.8 boosted hp. Taking that number into account and a 4AGTE power peak(is 250hp enough?) that would mean you have a fuel need of about 140 lph for that power output.

Now there can be other issues involved in your specific case.... a walbro 255 can work as long as the return line and the fuel pressure regulator can flow at, or nearly equal amount of fuel volume as the feed line can supply. If your return line or fpr CAN'T flow the volume excess pressure is built in the fuel rail and over fuelling can occur.

I'd recommend getting rid of the GSS341 Wlabro 255 in favor of the GSS279. The GSS279 Walbro pump flows a maximum of 190 lph and is NOT high pressure**


** - Walbro GSS341 is a high volume AND high pressure fuel pump. Not only can it deliver 255lph at 44 psi, but its peak pressure is over 8 BAR! The GSS279 flows fine through 4 BAR.