kevinapex

iTrader: (22)

I was on dyno yesterday with the new SFR TT kit, 750 injectors, AAM stageI-II return fuel kits.
Made a few runs at 11.5 psi. the fuel pressure was set about 50psi stacic, it would gain and 1to1 with the boost increase and hold solid. Everything looked good.
The tuner richened up the map a went to 14.5 psi. boost, at this level the injector duty cycle was 85 to 90% to keep around 12-13 afr.
He did another pull, we noticed near 14psi or so the fuel pressure was dying off like 20psi!
The Bosch 44 was pumping, not warm to the touch, the surge can was full to the over flow. Did another pull, same thing, the fuel pressure would get unstable and dive off at upper boost levels, (14psi or so).
We took the boost back down to 11.5 to see if the fuel pressure would maintain at wot, it did not, pressure got unstabel and droped around 10 psi. around 1/2 way through the run. We could not even get a wot run at 11.5 psi any more without loss of pressure.
We thought, kinked supply line, it's a -8 ss braided, TOUGH to kink!! Walbro 255 failing? the surge can was full at the start of the runs! I have the Bosch 044 run with a decitated 12G wire.
Some part of the system is failing, any ideas?
Oh ya, the fuel tank in the car was over 3/4 full.
Kevin

QuadCam

iTrader: (8)

i had a walbro fail on me......It worked, but the outpur was severely diminished.

here's an idea..
Pull you return line off and divert the return line into a bucket. run your pump for 1 minute at idle and see how much volume of fuel comes out. In theory, a walbro 255lph should pump out approx 1 gallon per minute. when I tested my walbro, I was getting less than 1/2 a gallon per minute. swapped the walbro, and the problem was solved.

another thing that I noticed as a sign of my bad walbro....as soon as I would turn my car off, my fuel pressure would immediately drop to about 10-15 psi. when I changed to a new walbro, my fuel pressure would hold steady at about 40 psi with the car off.

kevinapex

iTrader: (22)

I will give it a try, thanks Quad.
It makes me think that the Bosch pump is bad because at the start of the dyno run the surge tank is full, it is filled by the Walbro 255. I can't beleve that the car can drain all the fuel in the surge tank, (it must hold 1.2 qts.) in 10 second dyno run! Makes me think the Bosch pump can't keep up the needed supply.
Thoughts?

QuadCam

iTrader: (8)

sounds more like the the walbro to me....

remember the walbro is feeding the surge tank..and the bosch is pumping it through the system (constantly.) if the walbro can't keep the surge can filled, the bosch will run it dry.I am not too familiar with your fuel system, but essentially, the walbro has no pressure on it and should flow even better than normal (pumps flow more with less pressure.) It is only about $90 for a new walbro.....you might just want to try it.since you have 2 pumps, inline of each other, it makes diagnosing it more difficult.....one pump could mask the deficiency of the other...until its too late!!

Tuning Factory

iTrader: (5)

Walbro is failing........your using the AAM kit correct? Well the AAM relies on the OEM or Walbro pump to make enough pressure and volume of flow to full the surge tank and then the Bosch does the work from there but if it is not filling that up then the bosch will not move the volume it should hence the loss of pressure, so either the walbro is not fulling the surge or the bosch is not taking the fuel that is coming into the surge out of the surge, pull the feed line off that goes tot he surge and put it into a bucket and start the car see how much comes out just like Quadcam said.............here is a tidbit of information for you about Walbro though.


I can truly say 40-50% OF Walbro's fail right out of the box or soon after and the best part about it is Walbro themselves will not warranty there own pumps even if purchaes and fail the same day............,(this coming from someone who has been selling walbro pumps directly as a wholesale distribution for over 7 years now............which is me!!!)

KempieZ

So what other pump do you recommend?

kevinapex

iTrader: (22)

The surge tank is not filling! I ran it at idel for 3 or4 min. the surge tank never filled up to the point of overflow! I think the Walbro is junked out!!
Or there is a clog in the line from the tank to the surge?
Thanks,
Kevin

kevinapex

iTrader: (22)

Changed out the Walbro, no change!!!!
All the gaskets/ seals look good in the pump housing. The return line that runs from the rails has a mega flow to it, it returns every bit of gas back to the gas tank! The Damn surge tank will hardly never get full to over flow, all the fuel that the Walbro dumps in the surge is grabed up from the Bosch in line pump, sent to the motor then dumped back into the tank, the return from the rails needs to go to the surge tank not the gas tank? wouldn't you think. The Bosch has a higher flow rate than the Walbro + what the motor is useing, the surge will never over flow with load on the motor!!! Once the Bosch drains the tank, the Walbro can't feed it fast enough, the system looses pressure under heavy loads. Does this make sense? I have the pressure at 50 psi, I guess I could jack the pressure up so, so much fuel wouldn't return to the tank?
Kevin

Sharif@Forged

iTrader: (92)

I am rarely one to challenge another vendor, but this is so far out there...I just couldnt resist. I can't even count how many Walbro's we have installed and sold, and I have had "maybe" a grand total of 2-3 bad pumps out of literally a couple hundred we have sold....not to mention that every FI kit for the 350Z uses this pump.

That said, Walbro pumps can fail with time, but DOA pumps are extremely rare, IMHO.

Sharif@Forged

iTrader: (92)

Kevin, can you check your voltage levels to the Walbro? Maybe you have an electrical issue that is keeping the pump from running at the proper 12-14V level. We are using the Stage II system on my car, and a couple other customers's cars...no issues with pressure drops at the boost pressure you are running. I am sure at some point, even the StageII will run out of steam, but I havent seen it yet..up to 22psi of boost pressure. You usually see a flutter or oscilation in fuel pressure prior to the plunge, when you are reaching the limits of a pump. Is that what you are seeing?

Juztin

iTrader: (9)

Hey Kev, how about just running stg 1 and seeing when the walboro starts to have issues delivering enough fuel?

meatbag

iTrader: (9)

I thought that the AAM stage II had the return go to the surge tank first then had an overflow line from the surge tank to the stock gas tank?

Colorado S14

http://www.sdsefi.com/techsurge.htm
http://www.honda-tech.com/zerothread?id=1485767&page=1

This is what I found Kevin, I agree that you need to have the fuel returning to the surge prior to hitting the fuel tank with its return.

Sharif@Forged

iTrader: (92)

The way AAM recommends the install, is to have the return go to the pass side tank as normal. The surge tank is filled by the walbro, and at almost zero pressure, the walbro has no problem keeping the tank full. When the surge tank is full, it returns back to the driver's side tank.

Hope that helps. This is the first I have heard of the surge tank not filling up.

If the return does not go back to the main fuel pump assembly, then you will loose your siphoning capability whenever the surge tank is not full. Not sure how that would work in practice.

kevinapex

iTrader: (22)

This makes much more sense to me than how AAM has it layed out.
Here is a link to how the systen is presently set up. All the wat at the bottom is a layout, http://www.forgedinternals.com/store...cat=251&page=1
Sharif, my DC voliage to ground is 13.8v at the plug to the pump housing, is your stageII set up exactaly like mine? What do you think about returning to the surge after the regulator, then the over flow from the surge would go back to the in tank pump housing?

kevinapex

iTrader: (22)

How the hell will the surge ever over flow when the Bosch pump has a greater lph than the Walbro? Its takeing more out than can be put in!

QuadCam

iTrader: (8)

the walbro is pumping at essentially 0 psi into the surge tank. with no pressure, the walbro will have a significantly greater flow rate than its rated (255lph) output (which is rated at 43 psi, I believe).

Carlitos

iTrader: (1)

because at the other end of the fuel rail you have the fuel psi regulator restricting the flow of the bosch back into the tank, remember that the walbro is at zero psi flow rate vs the bosch at +-40psi flow rate.

BTW from personal experience in many aplications, walbros are very relaible pumps.

kevinapex

iTrader: (22)

OK, I let the car idle, the tank did fill and ran out the overflow, it would take about 5 min. to fill a Coke can, slow overflow! Is this sound right?

meatbag

iTrader: (9)

Sounds like your walbro is shot. Did you check all the lines to make sure nothing was in them from the walbro to the surge tank? Or get a voltmeter and see how much voltage the pump is getting.