Fuel Pressure

[Laredo GN]

I need help from anyone out there
I have a 85 GN that has a fuel pressure problem, if I adjust the pressure at 45 line off, at WOT the fuel pressure gauge does not go past the 45 psi's no matter how much boost is there. But if I set it at about 60 at WOT and 17 pounds of boost the gauge will give me a reading of 60+17=77. Could it be that the gauge or the fuel pressure regulator is no good. The car seems to run very strong and I can hear some minor knock. What do you think that a vehicle with these modifications should run in the 1/4. I do not have a Scan Master YET, I will also get an 86 or 87 MAF. How would a Blue Holley external fuel pump would do compared to the Walboro 340. I just don't like to be embarrassed by the Mustangs or Vets on the streets. Daily driver

Enhanced turbo
160 Stat
3 inch UP & DOWN Pipe
3 inch dual flowmasters with 3 inch tubing
390 gears
Home ported heads
Cool air induction 12 inch K&N
Blue Tops
93 Postons Chip
Postons High Performance Overhaul Kit (3,000) miles
Postons High performance in tank fuel pump (Not hot wired)
86 ECM & Coil Pack
Boost & Vacum Gauge
No EGR
Throttle Enhancer Calibrator
2 1/2 Crossover pipe
Trans Cooler
2800 Stall Converter

TOYS
1970 Plymouth GTX 440 Six Pack
1969 Plymouth Roadrunner 510 Cubic Inch 10:70's in the 1/4
1993 Z28 LT1 with several Bolt Ons SOON to be sold to purchase a Lightning

 

[WFO]

what kind of adjustable fuel pressure regulator do you have?

it sounds like it might be bad.

i'd hold off on hammering on it until you get your scantool(scanmaster)so you can see for sure what your o2's and knock counts are.if you are actually hearing knock you are in serious danger of blowing a head gasket.

you might also call poston's and find out what brand their fuel pump is.it might be a walbro...

a holley external pump is a bad idea.the proper single pump in the tank is all you'll ever need.

you've got some good parts and have the potential to go fast with some octane and traction.


later,sean

 

[Laredo GN]

Thank You for replying WFO
I will call Postons and ask what kind of fuel pump they sell and also the adjustable FP regulator is from Postons, and will ask if they have a hot wire kit for their pump. The car feels a lot stronger with the 3 inch UP & Down pipes. It does not smoke at WOT but I noticed that the mufflers are very black, probably from too much gas. What chip would you recomend so that the car can run maybe 20 pounds of boost with no knock

 

[REDS HOT AIR]

stock turbo i take it since i dont see one listed and hotair too....
there isnt any chip that will give you 20# without knock...and your black pipes are from WAY WAY too much fuel.

drop fuel back to low 40's and probly even into the high30's to get the 02's half way close to were they should be.

and is the chip burned for a hotair car with 86 computer?
if it is burned for an i/c car it will never run right.

i went down to 13:0's @ 104-105 mph with my hotair motor on stock turbo ,injectors and fuel pump not hotwired and stock chip in the 85 computer so you can figure it was tuned good to run that and at 20# 110 octane would have knock

 

[Laredo GN]

It's not a stock turbo
It was made (Enhanced) by "Dominic) Turbo & Components out of Westland Michigan. The chip is from Postons for 93 octane for a 1985. But now I have an 86 ECM and no EGR, if I lower the fuel pressure to about 45 line off at WOT the fuel pressure gauge does not indicate any gains, it stays at 45, with about 16 pounds of boost, but if I set it to about 60 PSI at WOT with 16 pounds of boost the gauge gives me a reading of 60+16=76. I know that it is too much fuel but if I lower it to 45 it will not go up and the car does not run good (very slow) and it feels like if it needs more power, but as soon as I pump up the fuel pressure the car runs very strong. The turbo when I goi it I compare it to a spare stock turbo that I have, the fins on the turbine of the stock are very small when compared to the one I got now. I think that the FP regulator may be bad, I checked the fuel line for any bends that would impede the gas to flow freely and the line is ok.

 

[Mike70gtx]

Yes, make sure the chip is burned for a hot air. What was done to the turbo to "enchance" it. Depending on turbo, I think you'd be in the 12's. I'm sure my combo will go high 12's with no problem with some tuning and traction. Your combo looks a little stronger than mine. I'm just getting ready to change to the 86 ecm and have Red Armstrong burn me a chip or two.
good luck

 

[Mike70gtx]

By the time my post go up, you already answered some of my questions. BTW, what is you GTX like? Mine has been a slow process.

 

[Laredo GN]

Mike 70 GTX
Mike I purchased my GTX brand new in November 1969 in Detroit, Michigan and I kep it since. I t has a 440 High Performance with a six pack, which I just recently took it off and installed a 850 CFM Holley. The intake is a Holley Aluminum that is port matched to the heads, valves are 181 and 216, 457 rear end Automatic Trans. I have not started since about 9 monts ago because the carburator went bad. I have a Thermo Quad 800 that I will install soon. It is also in need of restoration (Paint & put fiberglass on the rust spots). My 69 Roadrunner has a better body, but that one is stricktly for racing (13 inch slicks 5 inch front runners & Rollcage), but the GN occupies most of my time now, I want it to run at least mid twelves