Fuel pump problem

Laga

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About a month ago I switched over to E85 on my boosted 05. Definitely an improvement. However.
The car would drive around perfectly until the fuel level got down to 1/4 tank. Just as low fuel level warning came on. Then when accelerating at about half throttle the power would completely quit at 3000 rpm for a split second then return. Did this about 4-5 times on way to gas station, then went away after car was filled.
Now the oblivious culprit would be the fuel pump not picking up fuel when level was low. It’s a new Walbro 400. But why would it do that? And what else could it be?
 

Pentalab

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How much boost..if any ? That fellow who used to tune for VMP....and now tunes for Lund.... was on U-tube.... showing a huge spike in AFR... on a boosted 11+ car, with a 1/4 tank of fuel.

He was essentially reading everyone the riot act about keeping fuel tank > 1/4 at all times.
It spiked on the road, not the dyno. Hit the gas pedal, and fuel sloshes rearward, asap, and no fuel being picked up, eng gagged for a split second, then power back on. Further compounded with front end of car lifting a bit, squatting at rear a bit.

You could see the HUGE AFR spike on the data log graph...at 'XXX' rpm. With E85, your AFR runs a lot richer, whether in NA mode or boosted..... vs... say 91/93 octane. With E85, you are sucking even more fuel for a given rpm (vs 91/93)... which further complicates the issue. Into boost, even a little bit, and your E85 requirements are still more.

Story I got was the fuel itself cools the pump assy. 07-14 GT-500 owners were warned to keep the tank > 1/4 at all times. GT-500 of course has dual pumps.

Just keep it > 1/4 tank.
 

JeremyH

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Keeping it above a 1/4 in general is good advice. On another note since you recently switched to e85. Depending on mileage on your system, the ethanol will "clean" out all the build up varnish etc from you tank and lines etc. So pop the hat up take a look in the tank, check your pump filter sock and go ahead and replace your inline filter under the car.
 

07 Boss

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I was always told to run to run half a tank at the track to avoid any fuel pressure issues with fuel injected boosted cars. Have you guys seen the filter sock from I think Holley? Its a mat that sits on the bottom of the tank and will flow fuel even if just a portion of it has contact with fuel. It looked like something pretty cool.
 

Pentalab

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A few years ago, my 2010 GT auto (M90 blower, 5.8 psi boost) gagged, but only when trying to get into boost, even a tiny bit > 0. FPDC peaked at 98%...and fuel rail pressure dropped down to just 5 psi. (from it's normal 40 psi). Problem turned out to be the totally clogged oem sock filter on bottom of oem fuel pump.

I had previously installed 10 gauge wire from battery post to FPCM in trunk.
After cleaning out the crap on the sock filter, all was well. FPDC is 40% at idle..and 80% at 6.2 krpm. Fuel rail pressure steady at 40 psi...idle or 6.2 krpm.

I was the 7th mustang in town with the dirty sock issue. We all used chevron 94 (no ethanol).
Just something to be aware of. That Hydramat might be the ticket.
 

Laga

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I’ve been emailing with Lito. A possibility is the educator that trans gets fuel from the passenger side to drivers side might not be working. Since the car has two fuel level sensors which averages the two sides. The fuel gauge would be reading 1/4 when , in fact, the drivers side is empty. Will check it out tomorrow.
 

RLF9409

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If diverside is empty your engine would stall since the pumps are on that side...

Sent from my SM-N920V using Tapatalk
 

JeremyH

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Saddle tank with 2 sides. Pump is on driver side which siphons from passenger side when running. Passenger side sender reads full to 1/2 and that side empties first. When you have 1/2 a tank passenger side is completely empty and drivers side is completely full. Sender on driver side reads 1/2 to empty.

To check if siphon is still working properly wait to just under 1/2 tank reading. If you pop open the hat on each side passenger side should be dry and driver side almost full. If not theres a siphon issue.
 

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