mattsimis

I wanted the Denso as it offers better flow than the Walbros and Im running E85 (490cc Injector flow x6). I got the Denso 195130-1270.

The problem: Pump primes with ACC and tries to pump when I crank the car, but the car wont start. The pump doesnt even pull enough fuel from the inlet to the outlet on the top of the pump itself, just sits there foaming! Ive measured the voltage and the pump is only getting 9.5v during Crank (although this was after several attempts). I theorize this Voltage hungry pump is not getting enough power. At full whack they draw 20amp at 14v.

Ive tested the pump straight off the battery and it pumps fine, the pump seems ok. I know from other cars there can be a resistor in the fuel wiring to limit voltage to the pump, does anyone know if Vag cars do this? Car is an Allroad 2.7T (so largely the same as B5 S4). Anyone ever see this happen before?

mattsimis

Come on, some of you tuners or experts have to have an idea? I know VAG cars use the relay to operate on a two state voltage basis to the pump. Under light load (and cranking bizarrely) the voltage is low. I need to get around this limitation.

2.7Lturbo

im at my parents house for a sunday dinner with the family, but when i get home i guess i can bust out my bentley and digg up the damn wiring schematics

Audi42LV8

Hahaha.. good 1

WOWDee

could it be contaminated or might you have a blockage somewhere? why would the electrical system all of a sudden change? seems that something illogical is going on. Any other work ever done on the car? Any changes recently that could have resulted in this problem???


Once I burned up so much fuel in the troubleshooting process on a BMW that I actually ran it out of fuel ..... and didn't realize it until i checked the fuel gage ...... what an eyeopener.

mattsimis

The tank was half full and I tried it connected to the car electrically but in a bucket of fuel. It simply doesnt get enough voltage to start pumping, just froths the fuel like any pump starved for voltage would. When in the same bucket of fuel the pump is connected directly to a 12v source, it pumps fine.

Im surprised this has never come up. On my searching online I found pump voltage (being too low) is a very common problem that occurs on most cars getting tuned. Since pumps scale output with voltage (operating best at 14v), it seems an obvious thing we should be checking or at least improving over stock, before jumping to larger pumps (which in their own right need more voltage anyway).

4Driver4

Are you sure you don't have the leads connected backwards in the car?

mattsimis

The beige and black ones on the underside of the fuel pump cover or the + and - on the Pump itself?

I actually thought I may have done that, but I checked both several times, was like doing this in between rain downpours in the garden over the course of an entire day, must have connected them 10 times, everytime the same.