Fuel starvation, can't fill tank to FULL?
 

I was getting what seems like fuel starvation at Thompson Speedway (CT) today. Starting with a full tank, I went out and after 5 good laps I started losing power. Back off for a bit and full power would return but hammer it for a few corners and it'd fall flat again. Feels like fuel starvation I've had before, but with a nearly full tank! I topped it off (2 gallons), went out again and same thing, falls flat after 4-5 laps. Topped it off again, another 2 gallons. This time I noticed the fuel gauge wasn't all the way up to above the "FULL" mark, but a bit below it, call it 7/8 to 15/16 indicated. Not normal for a fully topped-off tank, hmmm.... Took my student out and got the fuel starvation a bit sooner, 3-4 laps in. Brought it in, tried topping it off all the way to the fuel cap, but could only add 1 gallon this time, with the fuel gauge now indicating just below 7/8. WTF...

Backstory:
I got fuel starvation at NHMS a couple of events ago, coming out of 6 and 7 (extended banked left-hander), at 7/8-tank indicated. Could top it off after every session and it wasn't a problem. After that event I got the Verus fuel door and installed it in the drivers-side fuel tank/basket. The install went smoothly, no probs. Fuel door pins engaged the housing perfectly, and I feel certain I reattached the fuel lines correctly.
Next event was Palmer (MA), clockwise configuration. In this config Turn9 is an extended banked left-hander. I got exactly the same fuel-starvation issues I'd had at NHMS, at the same fuel level of 7/8 indicated. Again I could top off between sessions and it was no problem.

Today, it was a bit different as the fuel starvation seemed like it could happen anywhere, including midway through a right-hander after a long straightaway. And it's happening only a handful of laps in. *And* I can't seem to top off the fuel tank.

I suppose I'll inspect the drivers-side fuel lines and basket to make sure I didn't screw anything up, or see if the fuel door has somehow freed itself and is causing mayhem.

Anyway, DAMN! Ideas?

Are you running a stock pump?

Are you running E-85 or Flex-fuel?

Are you monitoring your fuel pressure?

Have you tried replacing your fuel filter or even the fuel pump?

Yes, stock pump. 93-pump fuel. Not monitoring pressure but may try to log data tomorrow. Haven't tried replacing anything.

Most likely will open up the driver side fuel tank tomorrow to inspect and maybe top that side off with fuel. I just tried filling it up again after 35 mile trip home and it took 1.5 gallons, but gauge reads below 3/4 now...

Not being able to fill all the way could be a collapsing fuel inlet line, I thought that problem went away by the 14 cars but it's possible it returned.

If I calculate fuel expended and refill gallons, it seems like I *should* have a full tank.
Arrived at track with full tank. Track miles: ~16 laps (over 3 stints) * 1.7 miles/lap = 27 miles, / 6mpg = 4.5 gal. I added 2 + 2 + 1 gallons at the track, 5 gallons.
Trip home, 36 miles, figure 27mpg, 1.33 gallons, and I just added 1.5.
So it seems like the tanks *should* be completely full, but the gauge keeps reading lower and lower... Currently just below 3/4 indicated.

Is that a fixable thing by a moron at a racetrack with a lot of friends with tools?

Probably not advisable, reaching up past the fender liner of the right rear, if you get halfway and get stuck you might be SOL. If you fill slowly you should be able to top it off to full instead of the fuel getting choked by the collapsing fill line causing the pump to shut off prematurely.

There's a diy/tsb floating around here somewhere.

Yeah, starting with monitoring the fuel pressure would be a good idea.

If you've run your pump dry, in the past, that could have been the beginning of your problem. Fuel pumps use the fuel as a lubricant and to cool themselves.

Wouldn't be a bad idea to purchase a new pump to have as a spare......just in case.

If I remember correctly, that TSB covered just the first few months of the first model year. The problem was remedied with a newer filler neck material shortly afterwards.

Can you hammer it in a straight line and have any problems?

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This morning I went to pull the basket from the driver-side fuel tank. Forgot to pull the fuel pump fuse so got a bit of fuel spray! Fortunately contained within the metal underseat area, nothing got on interior bits. Lotsa fuel vapor inhalation... Unscrewed the big plastic collar, tried to pull the basket but immediately fuel fricking POURED from all around the perimeter. Lotsa fuel, still contained in the underseat metal area. More vapors inhaled... Gave up and put it back together. The good news is that the fuel gauge went from sub-3/4-tank indicated to FULL, which by my calcs it shoulda been. Jostling the basket a bit apparently freed the level gauge up and now it works fine. I'll have to run the tank to empty to investigate further. Have to suspect recent installation of Verus fuel door, which went very smooovely but I have to wonder if it mighta busted loose from its pivot points. FWIW the part I got was a 3-D printed plastic thing and NOT the aluminum part with steel(?) pin shown on the website here: https://www.verus-engineering.com/sh...-wrx-387#attr=.

After breathing normal air for a while, took 'er out for one practice session before TT. Got fuel starvation again after ~4-5 laps. Same as yestiddy. TT is 3 laps so no prob there but damn...

The good (GREAT!) news is I went way faster in the TT than in any practice session. Expected P3 with a high 1:23, but won my class with a 1:22.2 vs. 1:22.6x 2nd and 3rd places. Hellzyeh!

Did open track, again got fuel starvation after ~5 laps. Unlike at NHMS and Palmer, where it happened after extended >180 degree banked lefts, I seemed to be getting it most often halfway through the T1-T2 *right*-hand corners at Thompson Speedway, after a long straightaway! Very very weird...

I'd love to hear any theories about wat dafuq is happening, and solutions that don't involve replacing the stock tank with a fuel cell. TIA!

I think next step is to upgrade the fuel pump unit.

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Have you begun monitoring your fuel pressure yet? Are you absolutely sure your engine is actually starving for fuel or could it possibly be something else?

Surge tank is the next step. I don't think the fuel basket holds enough fuel for long sustained corners to keep the car feed. I am still getting fuel cut too with the verus fuel door. I need to keep at least 1/4 tank in my car.

I think a fuel pressure log overlaid onto lapping data, will be the next thing to do here.

He was getting it at nearly 3/4's full...

More like 7/8ths +

I logged data when it was doing it at NHMS and tuner had a look and said "classic fuel starvation". Same exact symptoms at Palmer and at Thompson. Happened sooner at Thompson though, and not associated with any extended/banked left-handers...

Did you replace the black rubber seal(one time use part) and the green ring? And did you put it together properly? I have yet to meet a twin "expert" who has done it correctly.

Didn't replace either of those parts. Re-installation went very smoothly, didn't see any evidence of leakage or weirdness when I disassembled again the other day. The green washer ring in particular, don't really see how that would be a problem. IMO it's just there to provide another slip surface so you don't rotate the basket as you tighten the ring. Honestly I think those parts were/are fine, but if/when I go back into it maybe I'll have new replacements on hand.

The one thing I'll point out is that the car will not update the gauge reading unless it detects slightly more than 2 gallons added. Otherwise the gauge just assumes you parked on an incline or the fluid is sloshing around. (Fun fact, if you're on too steep an incline or jack the front end of the car high enough, it will adjust the gauge closer to full!)

The needle's movement towards empty is always a calculated value - e.g. it knows how much fuel is being used and subtracts it from the current gauge reading. So if it doesn't detect a fuel level change big enough to trip it's "this guy just added gas" logic, it'll continue its march towards zero and even give you the fuel light way too early.

It's possible that the fuel level reported by OBDII is more accurate but I haven't tested this myself.

Ah-HA!

Wow, this is GREAT info to have and perfectly describes what I was seeing with the fuel level gauge "marching downwards" with repeated ~2gal or less fills.

THANKS!

My gauge definitely changes with small fuel additions. We added a gallon of fuel at the Pro Solo in Bristol the other week and the gas light went off and the gauge moved pretty significantly.

With that said, it has gotten "stuck" before. I was going to Michigan a few years ago and maybe an hour into the trip, I noticed the gauge was at a quarter tank. I stopped to top off and the car only took 2-3 gallons of fuel before the pump shut off. Got back in the car and the gauge stayed at a quarter tank. Gauge didn't move until I basically emptied the tank and refilled.

Maybe it has some logic built-in to ignore small changes in detected level specifically when the tank is nearly full, when it's highly unusual for fuel to be added and probably statistically a lot less likely than a weird reading due to parked on incline.

Another good data point for me to have! I had been assuming something was causing the sensor to hang up, and given that I only just installed the Verus fuel door I was definitely going to go back in and have a look. I might skip that now and just leave it alone.

Though I still had the fuel starvation (I think) issue at >7/8 tank at a clockwise track that has no extended or banked left-handers...

Dan I know how to fix it....


Drive slower!!!

nevar!

Haven't done a thing to address the issue. Palmer2 coming up with a long extended lefthander (turns 1-2) that has given fuel starvation (albeit at 1/2 a tank rather than >7/8-tank).

Anybody got any suggestions? Current plan is to hope I can consistently get 4 good laps (all I need for the time trial) starting with full tank. But "hope" is often a shite plan! Sometimes works OK tho...

Maybe hold out for the gen 2 swaps. They specifically addressed the fuel starvation issues with a redesigned saddle tank and lines, so maybe we'll be able to implement that as a full stop solution.

secondary fuel pump on a manual switch that sits on the passenger side, dumping into main pump cup.

Fuel pumps are cheap, and burning one out once a year from starvation is a relatively small price for going faster. It's less than the cost of a single tire.

How difficult is that to implement? Has anyone documented this? If I wing it I *will* f it up :O
Will it fit under stock seats? Is street car...

Completely in-tank.

Documented.... not really. Been done? Absolutely.

Hhrrmm...

Do you have any thoughts regarding my getting fuel starvation at more than 7/8 tank after a long straight followed by a 90+ degree *right*-hander at Thompson?

That shouldn't be happening. Investigate the fuel pressure drop.

I think I might go in and inspect my Verus fuel door installation. I'll probably remove it, at *best* it didn't improve things at all between New Hampshire and Palmer1. At *worst* that little 3d-printed plastic door (NOT the advertised and illustrated aluminum door with steel pins!) is f-ing things up due to either being broken or possibly too lightweight to work properly.

UPDATE: the part is indeed cnc'd aluminum, NOT 3d-printed plastic! So lightweight (due to being massively hogged-out) and painted shiny black plastic with integral pins rather than previous version (?) pressed steel pin, really gave me the impression of being plastic when I installed it! Just removed it and can confirm it's aluminum

Wait what? I'm 99.9% sure mine was CNC'd aluminum with steel pins. Purchased within the last 3 months.

They changed over at some point. Here's the plastic part:
https://images.rallysportdirect.com/...qejrm9hr0hwms2
https://images.rallysportdirect.com/...nk0i85vhwugtqx

The density of PLA plastic is less than half that of aluminum, and it's only 65% more dense than gasoline. Pretty sure I'm gonna remove it and ask for my $$ back.

They show the anodized aluminum one on the Verus website and here's their description:
SPECIFICATIONS
CNC Machined
6061-T6 Aluminum Construction
Anodized Bright-Dip Black
Viton O-Ring for Ethanol and Gasoline Compatibility

Yeah, that is not what I got...

Dan, you got hosed! I would definitely get my money back, that is way too much money for a PLA printed part!

Talked to some of the GTA guys and they said only starvation at half, and one of them tried the fuel door and it didn't fix it either.

I'd be fine with it if it *worked*. But no way I would have even bothered with it, whatever the price, had I known it was plastic.
PLA is only 1.65x denser/heavier than gasoline.
Aluminum is 3.6x denser/heavier than gasoline.
Stainless steel is ~3x denser/heavier than aluminum and IMO would have been the way to go...

Plastic is a stupid material choice for this application for anything other than making the part cheap.

I think I have an aluminum one on the way to me now. On the fence whether I'll install that when I remove the plastic one or just revert to stock with no door.

You have to ensure the black seal lip isn't hanging over the tank lip before tighting correct? I had a bad seal and replaced it and noticed this as I was putting the lock nut back on. If thats not what you mean can you expand on your comment?

it has been documented pretty well by the 350/370z community. Same principal.

Please keep us updated on what they say! Verus is always revising their parts, but this is the first time I’ve seen them changed for the worse…thank you for doing the math on the density of the part materials.