Fuel Pressure Problem

[my1stgn]

Here is the problem. Under boost say over 15lbs, my fuel pressure strarts to drop down to around 40psi. Im going off my KB hood mount gauge. I have a 340 Walbro maybe like 1-2 years old (bought it new) with a hotwire kit. Also run 60lb injectors with a PTDBB 61 turbo. Have a Extreme Extender chip also if that matters. Heres what I have tested so far.

I checked the adjustable fuel pressure regulator. With the hose off is at 48psi and when I use a vacuum pump and run 15" of vac, the feul pressure drops. At idle when I increase pressure with a pump at the fuel press. reg to say 15-20psi, the fuel pressure increases that amount and it doesnt dropp off if I hold it there. Also checked for power. Found with the car running and under boost Im still seeing 13.5-14v @ the alternator and the same voltage at the wire right before the fuel pump near the tank. So I think I ve eliminated a "wire/power" problem and the regulator seems to work fine. Could it be the fuel pump that is bad? And which fuel pump should I go with? I plan eventaully to run in the low 10's. Also fule filter was changed less than a year ago. Thanks!

 

[Turbo1dr]

Sounds like the fuel pump can not keep up with the demands of the engine.


OR your fuel filter is clogged.

 

[TurboMonte 2]

OR, you have a major leak in line to adj FPR that typically INCREASES FP w/ increasing manifold pressure (in place of vac @ idle)...

 

[my1stgn]

Sounds like the fuel pump can not keep up with the demands of the engine.


OR your fuel filter is clogged.

But I thought the Walbro 340 was good for 10 sec 1/4 mile? Im just running about 18psi when it starts to drop fuel pressure. At first when under boost the fuel pressure will rise to about 60psi then when I get over 15psi of boost it starts to drop down. I hit around 20-24psi boost and its way down to around 40-45psi fuel pressure and a/f goes from about 11.0:1 at WOT with good fuel pressure and when fuel pressure drops to around 40psi my a/f increases to about 13.5:1 so I get off it. No knock or anything. I might try to fuel filter first. What fuel pump do you guys recommend if I end up changing it? Thanks again!

 

[2 QK 4 U]

I had exact same problem. Fuel Pump was garbage.

If you bought your Walbro 340 in the past 2 years...chances are you have the new design "169" pump that accepts a stock type strainer instead of the big one "GSS340M" pump.

I've been seeing a lot of these "169" pumps thrown in the trash can due to the same problem.

255L/hr is enough for mid 10s, any faster you should consider a double pumper, or an external aeromotive setup.

If you're only using a single in tank pump I would try to find a good used old style GSS340M pump or roll the dice and buy another "169" pump.

 

[TurboMonte 2]

But I thought the Walbro 340 was good for 10 sec 1/4 mile?.....What fuel pump do you guys recommend if I end up changing it? Thanks again!

Yes, a GOOD one should be--but yours is likely now DEFECTIVE--for whatever reason. FPR vac/ pressure compensation diaphragm questionable? Try replc't 255 l/h kit (for turbo buick) from fullthrottlespeed... Good luck!

 

[my1stgn]

I got my Walbro from Poston's a little over a year ago. So they are common to fail huh? I have a buddy who has a Red's Armstrong fuel pump for sale for $100. Are those any better? What other fuel pumps are people running here successfully? Thanks again fellas!

 

[83ttypecooled]

Hi,
Walbros are prone to failure. I would say yours is on the way out. They are great pumps, but they don't last long.

 

[my1stgn]

Hi,
Walbros are prone to failure. I would say yours is on the way out. They are great pumps, but they don't last long.

So then Walbros only last 1-2 years before failing? Thats pretty crappy seeing as I have my stock fuel pump on my Grand Prix for 7 years and 180k miles and never had a problem. So which fuel pump do people go with for high performance and longevity?

 

[my1stgn]

So either the people who read this post don't use a fuel pump,or don't know what type of fuel pump they have. I doubt everyone here changes out their fuel pump out every 2-3 years right? What other brands are there that are good? The one ft has is the same one I got

 

[2 QK 4 U]

So either the people who read this post don't use a fuel pump,or don't know what type of fuel pump they have. I doubt everyone here changes out their fuel pump out every 2-3 years right? What other brands are there that are good? The one ft has is the same one I got

I think it's just like anything else. When units are made in mass quantities there tends to be some defected ones.

I bet if you roll the dice and get another "169" Walbro it will work for ya.

Just like when I had to take 3 starters back to the parts store before I got one that worked...but that's autozone though.