fuel pressure dropping

racer5252

Member
I finally found the problem for the knock. It was the o2 sensor. Put a new on on and 22 lbs of boost and 0 knock. I'm still not sure why my fuel pressure is dropping though.


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Ttype6

Well-Known Member
I finally found the problem for the knock. It was the o2 sensor. Put a new on on and 22 lbs of boost and 0 knock. I'm still not sure why my fuel pressure is dropping though.


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A bad O2 won't cause knock,but a bad fuel pump will. What is your fuel pressure at 22 lbs of boost?
 

racer5252

Member
The only other thing I did was take the torque strap off. Fuel pressure is at 60 psi when boost is at 22


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racer5252

Member
It is raising 1 to 1 because it is only around 36-38 cruising. Or should it still be 65?. It has a new Napa Gold filter


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Heg87t

Slightly Compressed User
It needs to rise up to base fuel pressure setting + boost. Example if your base setting (with vacuum line off the regulator and plugged) is 43 and you run 22 pounds of boost you should see 65 psi. The vacuum line is on the regulator to reduce the fuel pressure during cruise.

HTH
 

GNONYX

Well-Known Member
fuel pressure seems to be raising 1 to 1. but it starts knocking at half throttle. I do have a hotwire kit. Key on getting 11.6 volts to the pump. i did notice when i turn key on i hear the pump run then stop but fp gauge is still at 0 psi until i start it. bl at cruise is 122

You claimed with the key on you're getting 11.6 volts to fuel pump; is that key on and engine running at first start?
What voltage do you get when engine is warm?
What voltage do you get when you are driving it normal?
Are all ground cables including the hot wire ground fully secured to engine block and chassis ground?
Your voltage might be too low for the fuel pump to run it operating level
 

racer5252

Member
11.6 volts is with key on engine off. All the grounds are good. Ill have to check the rest later bc now I'm having transmission problems so I'm getting ready to tackle that.


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racer5252

Member
Heg87t
Thanks for that info, I didn't know to base it from the base setting+boost


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Ttype6

Well-Known Member
11.6 volts is with key on engine off. All the grounds are good. Ill have to check the rest later bc now I'm having transmission problems so I'm getting ready to tackle that.


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You'll want to check voltage with engine running.
 
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