gothic_sera

Arrrrrrrgh! I am still having fuelling issues. Installation is in my second gen Camaro.

Fuel pump cavitation seems to be the problem. But I have no idea why it's doing that. Other than the fuel getting a bit warm, but I don't really know why I am having that problem either as there's not much restriction in the system.

The result is the motor going lean as the fuel pressure drops off as demand increases.

Current system is, (from tank outlet to return):
Sumped tank with AN10 outlet.
AN10 hose to 100micron pre-filter - large stainless pleated filter inside
Filter direct to AEM 340lph pump
Outlet of pump to 30 micron HP filter.
AN8 (1/2") line to fuel rail - single piece, no joints
AN6 (3/8") return - flow well and is clear, to top of tank.
Tank breather is clear.

I tried it with the pre-filter removed and it made no difference.

JoeNova

What regulator?

How well is the tank sumped?

gothic_sera

It cavitates with the car stationary after the pump has been running for more than a few minutes. I can bypass the pump relay and make the pump run continuously for testing.

Sump is shown in the pic, the bottom of the tank has a few 5/8 holes drilled in it to allow fuel to flow into the sump.

squarles67

Fuel tank vent?

Sounds like you don't have enough if it does it after it runs for a little while.

gothic_sera

Tried removing the gas cap, made no difference

Old Geezer

iTrader: (3)

"Outlet of pump to 30 micron HP filter.".
Flow rating on the filter is?

gothic_sera

Not sure, but I am going to replace it today with a larger stainless pleated element filter and see if that helps!

.boB

iTrader: (1)

How do you know it's cavitating? With your set up, I would think that would be difficult to do.

You can bypass the filter altogether for a few minutes and see how it run. I doubt that's the issue, though. EFI systems should have a 100 micron filter before the pump, and 10 micron after.

I would guess that the pump is failing. Monitor the feed voltage as the pump is running. If the voltage drops, then it's in the wiring. If the voltage is stable, then I would replace the pump.

imma_stocker

iTrader: (19)

Sure the fuel isn't boiling?

jblankenship

iTrader: (5)

If the return is to the top of the tank with no pipe or hose running the fuel to the bottom of the tank that is where the cavitation is coming from.

imma_stocker

iTrader: (19)

Mind explaning this for an ignorant fella? Just starting to research fuel cells, external pumps, return vs returnless, baffles, sumps, etc. for the next project and haven't come across this yet.

.boB

iTrader: (1)

That would be aeration, not cavitation. There's a couple of videos on this site explaining the aeration issue.

http://www.promracing.com/fuel-suppl...-mustangs.html

stevieturbo

Setup looks and sounds ok, but what's that stupid tiny thing just at the outlet of the pump ?

If you're saying that's a filter, throw it in the bin and use something proper instead of a piece of ****.

Can you flow test the system, by monitoring how much fuel is coming out the return line ? even better if you can run the test at the highest fuel pressure you will see ( ie base + boost )

Ad you have one pump, any details on engine ? expected power ? fuel ? etc

LilJayV10

iTrader: (39)

maybe it's an electric issue. what gauge wire are you running to the pump? What size are the grounds?

Hows the over all condition of your electric system?

RixTrix

Where is the regulator? Should be between the fuel rail and the return line.

You only need one large filter on the pressure side.

Id like to see the tank pump behind the tank so it is flooded during acceleration.

Have you considered a swirl pot in the trunk?
Holley low pressure carb pump feeding a swirl pot and a top return to the tank for air and overflow. Bottom of the swirl pot feeds EFI main pump below and behind pot so it is gravity flooded at all times EFI return to top of swirl pot. Swirl pot is 3" diameter and 12"~18" tall.

The half inch feed line is over kill and the pump has to overcome the weight of that volume of fuel under acceleration first before it charges the rail.

Old Geezer

iTrader: (3)

"Also you have your filters backwards." ?

"The half inch feed line is over kill and the pump has to overcome the weight of that volume of fuel under acceleration first before it charges the rail." His post says the issue is present when the car is sitting still.

RixTrix

If there is no regulator (the OP does not list one) the pump may be catvitating because there is no head pressure.

stevieturbo

The filter to protect the pump is typically 100 micron.

The filter to protect the injectors is typically 10 micron.

And as said before, if that thing attached to the pump outlet is supposed to be a filter, throw it away and fit a proper one.

gothic_sera

OK... to answer a few of these questions. I thought I had fixed the problem, but now I have another similar issue...

I do have a regulator - it's after the fuel rails. Fuel pressure is set at 43psi. The fuel pump wires are 3mm^2 and they are only 2' long, through a relay direct from the battery.

I solved the cavitation issue by fitting a larger post pump filter. I think the small one was causing excessive restriction. This was causing the pump to cavitate and the fuel pressure to drop off.

However today at the drag strip I started getting increasing AFR at the end of the run. The fuel pressure is OK (I know this from my datalog). And when I got home the pump was very noisy.

But the tank and pump was very hot - so fuel temperatures are possibly getting to the point where I am getting vaporization of the fuel in the rails or injectors causing it to lean out.

It's been very hot here (for the UK) - around 90F which probably wasn't helping.

I'd like to see much lower fuel temps.

stevieturbo

Is your tank vent ok ?

What fuel capacity is your tank ? And how much was there in it when this "problem" occurred ?

With one pump and a setup as described there really shouldnt be any issue under any circumstances in the UK...it's rarely that hot, unless you have a really small tank.

If you believe fuel temp is a problem ( log it ) then fit a fuel cooler.