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Low fuel pressure/0300 misfires

I check the hose in the pump assembly, could not find any leaks. I hooked it all up and pressurized it and the connections at the pump are dry, the lines under the car are dry, connections at the fuel regulator block is dry. If it does have a leak I can not find it...

Thanks for the help, I figure I am over looking something but I can not figure out what that might be yet...
 


I hate sounding like a broken record here like we all may be, lol.

But if you bypass injectors....they aren't the problem.

FPR shows a drop in the pressure when there basically isn't anything in between the outlet of the pump and the return line, I keep wanting to think that the pump isn't holding pressure like it should. Something is just off or whatever, it's just not making sense. Unless the FPR is bad internally and isn't holding the pressure steady as it should.
 
You think you are a broken record? I keep changing out the same parts...lol.

I think the one regulator was bad internally, I swapped out with a different one and now I have 40 psi with the pump running, 30 psi with it off, and it barely leaks down now.
 
Arkanzan Wheeler said:
I have 40 psi with the pump running, 30 psi with it off, and it barely leaks down now.
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This sounds gound. With my walbro pump and GPsorenson regulator i see 45psi at low idle. over 50 under load and after shut down it drop very slowly (15 minutes) to 30 psi.

Did you deadheap the the fuel pump or are you done with this?
 
I took it to a shop that could clean the fuel system and pressure test the whole thing, they told me that it is common for the new replacement pumps to not flow as good as the stock pumps, inferior parts I guess. I put my old regulator back on with the new pump and cleaned lines and I am at least at stock fuel psi levels now. When I get some time I am going to still try and put my walbro pump in the new assembly since I am hoping it was just the check valve that was bad.

BTW, I will never be done with this...lol. I am also going to get a new adjustable fuel pressure regulator and make new lines to replace the nylon ones coming up the firewall, maybe go stainless steel back to the tank. Who knows yet...
 
dont mess with an afpr....you are only puttin a bandaid on the problem. i would do a pressure check at the fuel filter. on the tank side of the filter. this will tell you, if the pump/wiring is good. if you have good pressure there, you have a restriction somewhere, or the regulator is bad. go to auto zone and use a gp sorenson regulator.
 


I was trying to find a higher psi fuel pressure regulator that is stock like from a LS1 or something but nothing I have found fits, that is why I am going with an adjustable.
 
phat_ridegt said:
dont mess with an afpr....you are only puttin a bandaid on the problem. i would do a pressure check at the fuel filter. on the tank side of the filter. this will tell you, if the pump/wiring is good. if you have good pressure there, you have a restriction somewhere, or the regulator is bad. go to auto zone and use a gp sorenson regulator.
Click to expand...

X2 only its easier to get a fitting on the filter outlet. Deadhead the fuel pump at the filter! I got a 1/4" NPT to a 3/8 flnge adapter and was able to hook up my fuel presure gauge to the filter. Fuel pressure maxed out at 70 psi. Just do it...
 
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