Fire67

iTrader: (3)

Im running two inline Walbro pumps, plumbed in parallel with y-blocks.

I cant get much above 4500rpm and 2psi worth of boost without seeing the fuel pressure start dropping. It drops to 20psi from 43 within a second.

My setup consists of a -10an feed to a y-block... An -8an feeding each pump from the y-block. A -6an from each pump y'd to a -8an that feeds the rails(holding 75# injectors).

Ive got the 2nd Walbro wired with a Hobbs switch that turns the relay on. Trying to see if I could alleviate the problem, I put a regular switch in place of the hobbs and turned it on manually from cruise rpm. Seemed to hold pressure slightly longer but still dropped and pretty quickly when I got into it.

Im gonna make the 45 minute run to a speed shop to get some more -8an line and fittings. Thinking of trying to run seperate feeds from the tank. Either that or just sell these pumps and try a BIG single pump like the Aeromotive eliminator.

Looking for opinions. Should I even bother trying the seperate feeds? Or should I just ditch these pumps for an Eliminator?

Old Geezer

iTrader: (3)

How is the FPR and return set up?
What do you have for a tank vent?
How is the pick up located?

Fire67

iTrader: (3)

FPR is an Aeromotive A1000-6 (I think -6an inlets and outlet)
I have a -6an from each rail to the regulator, and a -6an from the regulator to the tank.
I basically just clamped the line to the old feed since it was available with the tank being sumped. The old return line is capped off.

I have all the factory venting still in-tact, with the exception of the EVAP system, which I partially deleted. I left the charcoal canister in the back and put a vent cap on the plastic evap line up front.

The pickup is a Competition engineering sump, that I had welded to the tank.
I didnt use their template for baffling, as I had to modify the sump from original to work on my tank. It is baffled well yet has enough open area to keep from restricting anything.
My car is on the rich side all the way up as far as I can go before dropping fuel pressure. So Ive got a buddy coming over with his LM1 so we can get the fueling in line for the part throttle and idle stuff anyway.

Ive seen others with dual Walbros use individual feeds from the sump, which Im wondering if I should have done. Now its down to money, spend a hundred or so replumbing my pumps and hope it works; or just go to a big single and be done.

Old Geezer

iTrader: (3)

"I have all the factory venting still in-tact, with the exception of the EVAP system, which I partially deleted. I left the charcoal canister in the back and put a vent cap on the plastic evap line up front."

canister,[tank] "breathe" thru the line to the ft of the car? If so, could it be a lack of venting, that, when high volume is needed, the pumps are experiencing cavitation???
[Gas will boil at about 135*, and less in a vacuum, creating air bubbles.]
Maybe leave the cap loose, and see if that cures it.

Lonnies Performance

iTrader: (16)

Where is your fuel filter located & what kind is it?
What pump P/N's are they?

The -10 pickup is big enough.
You should have enough fuel line for well over 1000hp.

The other problem with the tank (assuming it is a 67 Firebird) is the location of the pickup.... the tank curves up hill at the rear. Under acceleration fuel will go to the rear of the tank which is higher than the bottom of the tank. At what location did you put the pickup in the tank? My '68 Camaro will sometimes blow fuel out of the gas cap at full throttle when the fuel climbs the back of the tank.

Fire67

iTrader: (3)

Nope the 67 Firebirds been in the garage torn down for restoration for years and years. Car were working on is in the sig, 96 Trans Am... You sold me the ATI balancer and dual keyed hub for this motor

When I suck or blow on the line, it seems to not fight me. The air is going somewhere. I'll get a buddy to come by and listen by the filler neck while I blow air through it or something tonight.

Fuel filters are these:
Front - SUM-230117
Back - SUM-230116

I think they should flow plenty on their own.
The front filter is up in the driver wheel well, while the rear filter is immediately after the sump. With the pumps immediately after the rear filter.

I will try with the cap loose to see if I get any improvement tonight.
I leaned the fuel curve out over the weekend and only saw a marginal amount of increased rpm's before the fuel pressure started to fall. Maybe 500rpms at best.

Old Geezer

iTrader: (3)

Dumb question time:
Can the in line Walbros be put in backwards????

The reason for asking is, you state the PSI drops almost instantly, when the 2nd pump comes on. The 2nd pump being off, allows the main pump to support the engine requirements.. then WHAMO, the 2nd pumps comes on, and the fuel is pumped back against the inlet at the "Y"??

Lonnies Performance

iTrader: (16)

I wasn't sure which car you were referring to.

Try taking the rear filter element out & see if there is a difference. Too fine of a filter will severely restrict the pump. You should only run a screen type filter there. Plus your pumps should be mounted below sump level if possible for best flow. Inline pumps do suck very well.

According to what you wrote, you have the filters in the wrong place. The 100micron stainless goes in the back......

Fire67

iTrader: (3)

I might have wrote it wrong, the 100micron is in the back... I pulled the element out of the rear filter last night just to check it out and it was just as clean as it was when I installed it. Except for a few rather large particles that appear to be left over from the sump welding/sealing.

I'll try removing the elements one at a time tonight to see if it eliminates or confirms the filters as the problem.

The pumps are below sump level, but about 2 1/2 feet forward of the sump on the car.
Both pumps are physically installed to flow in the correct direction, I'll double check the wiring to make sure its not reversing polarity somewhere for the 2nd pump.

Im also going to switch the pump wiring so that pump #1 becomes pump #2 etc.

How can I tell if there's a problem with the regulator?

Fire67

iTrader: (3)

Me and a buddy went to town messing with this thing last night. Evap line converted to vent is flowing air, slowly.

Loosening the gas cap didnt make any difference.

If I turn the 2nd pump on manually, then get into it lightly I can go to about 4000 rpm and 1/2 throttle. As soon as the boost gauge reaches zero vac. my fuel pressure immediately drops to 20psi. This happens with or without the 2nd pump on before getting into the gas. The 2nd pump only seems to get me slightly more rpm's.

I didnt get around to switching pumps from #1 to #2 etc... But I did pull the pre filter element and it didnt change much either.

Tonight I plan to switch pump wiring from pump to pump, and change/remove the element from the 2nd filter.

How can I tell if Im having these issues due to the Aeromotive regulator? Should I pull the regulator and take it apart?

If its not the regulator, then I kinda hope switching the wiring from pump to pump will reveal something that can solve my problem. If its one of them damn Walbro's, Im throwing them both in the trash!! If its the Aeromotive reg. then Im gonna put a bullet through it and buy something else

iGoRa

iTrader: (1)

I would check the regulator first..

Fire67

iTrader: (3)

What am I looking for with the regulator?

Update on the rest:

Fuel pump wiring is 100% ok. I removed my toggle for pump #2 and verified the hobbs switch is working correctly.

I removed both filter elements and found they were not causing any restriction.

Before removing the toggle I switched pump #2 on during the 3 sec prime and got greeted with a weird chirp/cavitation sound. After that I did the 'key-on, let fuel pump prime' deal without the 2nd pump on and heard the same cavitation sound out of the main pump.

When I first put this together, I had a brand new pump that was bad. It made the same sound as these before it started SCREAMING and locked up. So needless to say hearing those sounds is probably not a good thing

So tonight Im going to pull the regulator and do some dissasembly, see if I can see anything thats obviously wrong with it..

If that doesnt reveal anything, then we're gonna just put a big pump on it and hopefully solve these issues so we can get this thing going.