After rewiring walbro, I have this problem.
 

I've got an autometer volt guage hooked up to my fuel pump. it reads 10-11 at idle and cruising, and then kicjs up to 14.4 volts once the car starts to be beat on (like above 3k under some boost).

The problem is sometimes I catch the car right at the threshhold and the volt meter bounces back and forth from 11 to 14.4 and causes some hesitation and bucking.

Should I just run my pump at a full 14.4 volts and then tune the car with my safc???

I've noticed similar issues before. It's probably moreso a wiring problem or a problem with the resistor relay.

The rationale behind running the fuel pump at 9v/12v is mainly to save wear and tear on the pump, and prolong longevity. I don't think there would be any problems as far as fuel pressure is concerned, though.

I've been thinking about doing the same thing on my car just for simplicity's sake.

Dale

Any other oppinions on wiring a 255 lph/hp walbro to a constant 14.4 volts and eliminating the stock resistor????

I took out the resistor but havent started the car yet so dunno.

-Morbius

i was gonna say "i'm running full voltage all the time its fine" but why dont you jumper the relay and see if it likes it?

mike

I thought there's something that makes the fuel pump signal do that on purpose

Works great. I just wired a hot wire on a relay to switched ignition to my aeromotive external pump.

However, I have an upgraded FPR. With the stock FPR, running full flow (from full voltage) at idle and low load throttle will over-run the flow of the stock FPR and cause the fuel pressure to go above 30-32 psi. This will cause the engine to run rich, compounding an already problematic issue of carbonizing at idle and low loads.

I verified this with a stock FPR and my fuel pump, hooked up to a fuel pressure gauge inside my car. This was with a pump putting out greater than 400 lph.

ya well your 1200hp areomotive fuel pump isn't the best for testing compared to a walbro LOL :D

scath what kinda gas mileage do u get?

16-22 mpg.

Pump flow rate does not affect fuel economy, engine usage of fuel does.

So this weekend Im going to eliminate the resister circuit and allow the pump to run at a constand 14.4 volts. I'll post up some results in a few days.

GOOD NEWS! Rewired the pump to run at a constant 14.v volts. Sinch to do. All I did was cut the 2 wires leading to the resistor and twist them together. If I have to, I can put the resister back in line in about 5 minutes on the side of the road.

Anyways, started up the car with the original settings on the safc. Idling a bunch richer so I turned things down a bit from 1k to 4k (since the switch from 11 to 14v happens usually about 3500). on the safc I was set to 0% at idle, now I am at -6%. I've got to say the problem is 10x better now. My hesitating at mid throttle openings are almost nil. I can probably tune the rest out over time.

I give this mod a thumbs up, as long as you have something to tone the fuel down below 4k rpms.

This thread should be put in the archive. My car runs soo much better now. Hasnt hesitated at all.

after installing a walbro f/p and rewiring it ....my car will flood after it is hot .....the inj were cleaned about 5 months ago ......i belive that the fuel pump is pumping to much pressure and the stock fuel pump cannot handle it .......has anyone made a adjustable fpr for a s5 if so have any pics and part #s?

i found my flooding problem was crossed vacuum lines at the acv (actually between the bonus vacuum rail and the regular one) once i had all the vacuum leaks fixed it would start hot no problem.

mike

i dont have the acv ....its blocked off!

?

are you sure its not still leaking? i have had the block off plates leak too

mike

Seems to me it would have been easier to just go to pin 3D at the ECU, and disconnected it there or at the relay, if you wanted the full voltage all the time.

Even with the fuel pump rewire, that wire from 3D is the one that switches the pump voltage from low to high.

BARWICK'S idea.

JPG

thats a good idea, super easy

mike

maybe that is why my car starts leaning out like crazy around 3800 I have the walbro also I will give it a try

great thread