FUEL PRESS. PROBLEM

[racingluv]

5.3L 2001 SUBURABN P1SC INTERCOLLED...IN THE BOOK IT STATES THAT I SHOULD HAVE 80 TO 95LBS OF PRESS. AT MODERATE TO FULL BOOST..I ONLY GET 60-65LBS...THE BOOSTER FUEL PUMP WORKS GREAT...THE FMU FUNCTIONS PROPERLY..(CRIMPPED THE RETURN LINE AND PRESS. GOES UP..PEGS THE 100LBS GAUGE) MY BOOST GAUGE IS TIED IN WITH THE FMU...SO I KNOW WHAT THE FMU SEES..AT 5500RPM AND 7 LBS BOOST FUEL PRESS IS STILL AT 65LBS WITH A HINT OF DETONATION OCCURING....HELP..ME... IS IT A POSSIBILITY THAT THE BOOSTER PUMP IS GOING OUT AND CANNOT KEEP UP...IT IS ABOUT 3 YEARS OLD WITH CONTINUES DUTY

[KS91Z28]

It could be you in-tank pump getting weak, a clogged fuel filter, or the in-line pump getting weak (not likely). You could also try taking out the little white restrictor that's in the vacuum line for the FMU. That will let the FMU get a stronger signal.

[racingluv]

i have removed the restrictor already and fuel press is still the same. i have off the rest of the day..i am going to check the voltage to the booster pump.....now that you say somthing about the stock fuel pump...before i put the procharger on i had some starting problems kinda....if the motor was running and i turned it off and try to start it back up it would not. i would have to turn the key to the on position let the pump prime then it would start...i had already replaced the factory fuel press reg

[Hotrodvdog]

I have a similar problem. Last week I replaced the fuel pump with an intank 255lph but that didn't cure my problems. The FMU has a restrictor? What does it look like? I remember when I first had the procharger kit installed the fuseable link that powers the inline pump fried itself up. Now, if the inline pump is indeed failing would it restrict the flow of my in tank pump? Fuel press is great at 45-50 at start up but when I rev it at idle after say 10 minutes the car will go really lean and stay there while fuel press goes down to 30. Sorry to hijack your thread.:teeth:

[racingluv]

UNDER THE FUSE BOX WHERE YOU WIRE INTO THE FUEL PUMP RELAY....NOT A GOOD "CRIMP"....IT IS SOILDERED NOW...RUNS LIKE A BAT OUT OF HELL NOW.....7200LBS OF IRON FLYIN DOWN THE ROAD:happy:

[racingluv]

THE FMU RESTRICTOR IT A SMALL WHITE SPLICE IN THE VACUUM LINE...IT HAS A SMALL BRASS ORFICE INSIDE.

[racingluv]

IF YOUR INTANK PUMP HAS TO PUSH THRU THE BOOSTER PUMP THE PRESS. WILL DROP...IT IS THE SAME PROBLEM I WAS HAVING...BUT THAT IS ONLY BECAUSE THERE WAS NO POWER MAKING IT TO THE BOOSTER PUMP....HOPE THIS HELPS

[Hotrodvdog]

My fuseable link is just stuck in a relay power slot. I'll have to check if it's loose and the power at the pump. I'll let you know. thanks

[Hotrodvdog]

Checked the fuse link and it was fine. Crimped the fuel return line between the stock regulator and FMU and it lost all fuel pressure. Does this mean that the stock regulator is Kaput! Or, since I pinched the line after the stock fpr and the inline pump is out, then it must mean the inline pump is preventing any fuel pressure from building up. I turned it off and just turned on the ignition with no start and no fuel pressure at all. sucks