a whileback, i went a made a thread about hesitation here


what I thought was the car... it turns out it's the pump...


last night I went to install my CDI box, and the walboro...

i installed the Pump using the stock wiring points, grounded to the "case" of the pump and the stock power supply...

put it all back together... car idles fine, revvin is kinda poppy and jerky and stuff..

under load.. the car is ok until 4k RPM at which point it just hits a wall...

at exactly 0psi (most the time)


I tried minusing the hell out of it on the AFC, makes little to no difference...


i can run it out to redline under light throttle.. but 100% TPS kills it...


can the walboro NOT run with stock wiring?
or is my walboro faulty?

i'm gonna put the old unit back tonight after work just to make sure it's the pump

I removed the CDI box, made no difference to the hesitation...

 

common guys

someone musta run a walboro 255 on stock wiring before?!

 

It's called a Walbro...

That pump is way too big for your NA. Even if the pump isn't the problem here, it will cause excessively rich mictures. You need to get a stock pump in there.

 

noo NZ

i put it walbro in my TII the other night!

and now i'm having similar results..

except it's pegging at 4,000 rpm... unless i go easy on the throttle

 

Since you posted a link to your NA problems, you probably should've mentioned what car you put the pump in this time. We ain't mind readers...

I wouldn't run a Walbro on stock wiring, but I doubt that would cause this problem. If you put the stock pump back in and the problem goes away, I guess you can blame the pump.

 

hehe, sorry about that, i guess i forgot to add that "minor" detail :P


why would the pump work at 6Vdc but not kick in @ 12V?

is that possible? anyway i can test the pump outside of the car?

 

Pump voltage should never be as low as 6V. The 2-speed system should only lower the pump voltage to 8-9V.

The pump can be tested outside the car by putting 12V across its terminals. Unless you're running petrol through it, only do this for a few seconds at a time, or it'll overheat.

 

oh i see...

could it be submerged in any liquid while testing? say water for exmple? or the pump is only designed for Petrol?

i don't understand how the stock pump would work in high and low step

but the walbro only works at low and not high thought it would be an all or nothing kind of thing...

 

Water should be fine, but I'm not 100% sure. A few litres of petrol in a bucket is no big deal ayway.

On S4 turbos and all S5's the fuel pump circuit has a dropping resistor switched in and out by an ECU-controlled relay. At low load the current flows through the resistor so the pump sees ~9V. At high load the resistor is bypassed and the pump sees full battery voltage. Look in the FSM for the wiring schematics.

It has nothing to do with the pump itself, only the voltage fed to it, so the system works the same with aftermarket pumps. Walbros draw more current than stock pumps, so the wiring needs to be upgraded. Read this for more info in the system and and how to rewire it for less voltage drop.

http://www.1300cc.com/howto/how2/rewire.htm

 

i'm familiar with the rewire... but before ripping up everything in the car...

in ur expert opinion..

seeing as how the pump didn't work at the "higher step" on 2 different cars..

do u feel it's more probable that:

a) the pump DEMANDS higher gauge wire to function properly and that's why the pump is falling flat on it's face at WOT...

or

b) the pump is faulty.. and when the secondaries open.. the pump just can't provide the needed fuel flow to maintain the fuel pressure/flow

 

No, don't use water!
These roller vane pumps use the gasoline as a lubricant.
You're taking a chance that the water will rust the internals.


-Ted

 

thanks man

so what do u say Ted... A or B

 

I would worry about why it's working at 6VDC.
Lower voltages can drive electronics crazy; you might be prematurely killing it running the voltage that low.


-Ted

 

no no ted.. its not 6VDC... (i threw that out arbitrarily didn't know at the time 9vdc was the low step)

the probem is the pump doesn't work at FULL voltage... (well whatever the stock wiring is giving that is)


plz review post #10.. with alternatives A and B... (the only 2 reasons i can think of anyway)

 

Check the GROUND side of the circuit.
I think my car has crappy grounds - I only see 8VDC at my fuel pump.


-Ted

 

ya my car grounds aren't so hot either..

when i press the brake, the lights dim...

I only get 13+ volts at 1,000+ rpm.. below that my afc reads low 12's...


maybe i need to redo the car grounds as well as the fuel pump re-wire all at once..

it's gonna be a long night... *sigh*

 

If your lights are not steady bright, I'd test the battery, alternator, and primary wires first.

Engine running, headlights & heater fan on high:
Alternator post to alternator frame = 13.5-14 volts (verifies the alternator output)
alternator post to battery (+) = 0 volts (verifies the primary + wire)
alternator frame to battery (-) = 0 volts (verifies the primary ground)
Turn off the motor, but leave the lights on.
Battery (+) to battery (-) = ~12.5 volts and holds steady. (verifies battery)


(end of hijack)

 

Damed disjointed post.

Does this car have a Fuel Pump Relay and Resistor or NOT?

What is the voltage at the fuel pump connector at idle?

What is the voltage at the fuel pump connector when the ground from the ECU to the Fuel Pump Relay and Resistor is removed?

What series car is this? It started life as a non turbo? Or turbo?

What's the voltage at the pump when your in boost?

What's your fuel rail pressure at idle? At or in boost?

 

Not likely. People have run Walbros on stock wiring without serious problems. You just don't get the pump's full potential.

The opening of the secondary injectors has nothing do do with this. When they come on, injector pulsewidth is halved, so fuel flow increases at the same speed it was before. There's no sudden jump in fuel flow. If there was the car would drive like ****.

If you have the same problem in two cars, the pump has to be the number one suspect. But like I said, you need to get a stock pump (or even another Walbro) in there to confirm this.

Thanks Ted, I forgot about the lubricating bit. I wouldn't worry about rusting if it's going straight back into the car, but you wouldn't want to leave it wet...

 

****.. that's not good news...


my stock pump worked fine in the the Turbo II.. it was only in my S5 that the stock pump was shot.... and the only reason i had even opened the wrapping of the pump was to just get the S5 running.. otherwise i was saving it for my S4 which ran fine.. i was waiting for my Rtek and 720's before putting it in...

and on the S5, u guys thought i was just drowning the engine... but now the plot thickens :S


I ordered the pump months ago from the states... like 2,000 miles from here... don't even know if I can return the damn thing now...

stuck between a rock and a hardplace



I still don't understand how the pump "half" works...