wreckleford

iTrader: (2)

Having a problem with an Evo 3. It is currently making about 415 hp on E50/E60. It was running lean up top so we rewired the walbro 255 and that helped things a bit. However when we pushed it harder it began to lean out up top again.

We then replaced the walbro with one of the ethanol compatible walbro 420 pumps along with an AEM fuel regulator. We did not drill the siphon in the tank so it overruns the regulator, minimum fuel pressure at idle is 50 psi with the vac. line disconnected.

Under boost (30 psi) the fuel pressure rises to 80 psi but quickly drops back to 60 psi. However if you run the pump manually and wind in the regulator the pressure can be carried to above 100 psi (maximum on the gauge).

The vac. line to the reg. is fine and the battery voltage is not dropping off as rpm rises.

I am wondering now if the stock fuel lines/fuel filter are a restriction at this point and that due to the restriction the pump is unable to deliver enough fuel flow to maintain the pressure when the fuel demand from the engine gets higher. However, the car is not really making crazy power so I am not so sure about that one.

Anyone experience anything like this?

wreckleford

iTrader: (2)

Update: We changed the fuel filter for another factory one and there is no difference.

jagboy

iTrader: (1)

I had a similar issue with going lean in boost, turned out to be a little white spacer on the fuel pump was missing on my evo 9... something to consider

wreckleford

iTrader: (2)

Hmm... could you elaborate some more?

Beemen550

remove siphon and regulate solely with fpr

Ted B

iTrader: (6)

The only difference between those two scenarios is fuel demand from the engine. So long as the in-tank plumbing is absolutely secure and without leakage, that implies either pump or feed line.

Inadequate power or ground wiring would cause the issue regardless of pump used. If you've checked that voltage across the pump terminals does not suffer under high power demand, then it points to the feed.

wreckleford

iTrader: (2)

This turned out to be the problem. The original pump was rewired but it seems that these pumps are more sensitive to voltage. Without proper wiring they don't seem to be any better than a 255. Basically you have to put in the proper infrastructure to be able to feed its appetite for electricity.

michaelrc51

iTrader: (37)

Yeah, higher load means the pump will demand more but the wiring will limit what amperage will be supplied at the pump.

Ted B

iTrader: (6)

Believe it. Glad you got it sorted.