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Old 04-30-2005, 01:42 PM
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Nitrous Problem, Maybe fuel pump?

Hi, I just recently installed a a Performer RPM nitrous setup installed on my 427. My fuel setup is an external Comp Pro 140 pump at the tank -> filter -> y fitting -> fuel pressure regulator for the carb and a fuel pressure regulator for the nitrous solenoid. Tried doing a wet flow test and was able to keep the pressure for the carb at 7 - 8 psi but I couldn't put the fuel pressure past 4 psi. I didn't want to risk leaning out the nitrous/fuel mixture so I haven't run the car yet with the spray on. From what I'm gathering the 140 should be enough to support both the engine and the nitrous system. But for some reason it isn't. The possible things I have come up with are:

1) Pump is going bad (hope not as they are expensive)

2) Pump is dirty, needs to rebuilt

3) Pump isn't getting enough amperage over the wiring

4) Fuel sock is clogged.

I don't believe it is #4 as the car runs great otherwise with no surges or anything of that sort. I'm just seeing if anyone has any other suggestions as to how to find out exactly is wrong. The carb is a 850 Holley DP. Thanks a lot.

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Old 04-30-2005, 02:54 PM
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If you have 7 psi at the carb you should have 7 psi at the solenoid, if they are both fed by the same pump. This could change slightly at full throttle but a static test should show the same pressure at both points. I think you have a different problem. Maybe the gauge?

Larry
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Old 04-30-2005, 02:55 PM
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Just to clarify, when you flow tested the carb maintained 7 PSI and the nitrous side maxed at 4? Just trying to confirm if the carb side maintainted it's pressure.

You were wise to not hit the nitrous yet as if the system is based jetted for say 7 PSI you'd have leaned things out drastically.
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Old 04-30-2005, 04:58 PM
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Quote:
Originally Posted by Rick WI
Just to clarify, when you flow tested the carb maintained 7 PSI and the nitrous side maxed at 4? Just trying to confirm if the carb side maintainted it's pressure.

You were wise to not hit the nitrous yet as if the system is based jetted for say 7 PSI you'd have leaned things out drastically.

Yep, the carb side maintained at 8 psi and the nitrous side would max at 4 psi regardless of how we adjusted it. I adjusted it slightly at the pump itself and was able to move it up to 5 psi. I'm pretty sure the regulator isn't bad since it is a brand new out of the box holley regulator from Jegs but it wouldn't be the first time something wasn't good. But since it will adjust the pressure down but just not up I'm guessing it is good.

To clarify I'm testing this by taking the fuel supply line into the nitrous plate out (including the jet) and putting it in a bottle) and then by turning the pump on, turning the nitrous system on (to power the fuel solenoid) and activating the microswitch. As soon as the switch is activated the pressure drops from the 7psi on the nitrous side to 4 psi. The carb side stays steady at 6-7 psi with just a little movement. As soon as the microswitch is deactivated both regulators steady at 7psi. After just spending 3000 on various parts and safety stuff I'm not really looking forward to spending another 300 on a new fuel pump since I'm not totally convinced it is bad. Thanks again
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Old 04-30-2005, 06:29 PM
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Solenoid leaking?

Can you verify voltage at the pump?
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Old 04-30-2005, 08:46 PM
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I doubt it's the pump as well. If the pump exceeded capacity you'd see the drop on the carb side. Give Holley a call as I would start with the pressure regulator.
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Old 05-01-2005, 10:08 AM
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Ok, I took it apart this morning and cleaned everything out a bit. The screen had a miniscule bit in it and I cleaned that out. Messed around with all 3 adjusting screws and got it to the following mixtures:

Carb Pressure - 8 psi
Nitrous - 6 psi w/ the microswitch activated.

As soon as I hit the microswitch the nitrous side drops to 5 1/2 for maybe 1/3rd a second and then stabilizes at 6 psi. From what I've been told the safe minimum pressure to run a 150 shot at is 5 1/2 with at least 5 3/4 being a safe minimum. So I'm taking it that the 6psi should be adequate enough. My main concern is obviously the safety of both my car and myself. I don't want anything to happen as I'm going down the dragstrip.

Again thanks for the help!

Eric
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Old 05-02-2005, 05:21 AM
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nitrous

HOLD on a second....

In your nitrous testing i did not see where you used a gauge in the fuel line that attaches to the solenoid???

The proper way to do the test is to have a flow block with a pressure gauge in it plus a holley jet in the line that goes to the catch can for the fuel... the manufacturer of the system will tell you want size jet you need in the flow block for testing....... They will also tell you want the fuel PSI should be for the correct size flow jet..... This is all determined by the HP level the system is set to.......

On my system i use the standard holley regulator on the juice side because they will creep up some on the fuel pressure. That will make up for the split second drop in fuel pressure when the system HITS......

My gauge on the car reads 6psi when the system is activated but the fuel flow block only reads 5psi when doing the testing.... I will not turn on the nitrous fuel pump untill i am done with the burn out and the purge..... It will creep up to about 8 psi before i leave......

Keith
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