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Discussion Starter #1 (Edited)
Hey guys,
I'm having a problem with my fuel pressure dropping. When I turn on the fuel pump the pressure is at 7 lbs., as the car runs the pressure drops and within a two to three min. the pressure is down to 3 lbs. I ran the motor on my run stand before putting the motor in the car using the same fuel pump, regulator, and pressure gauge with no problem. Even after the motor is shut off and sets for a few min. the pressure is still at 3 lbs. but after a half hour or so the pressure returns to 7 lbs. I felt the pump to see if its getting hot and it is warm but not hot. I'm using a holley blue pump and a holley regulator. The pump is below the fuel cell and both vents on top of the fuel cell are open. There are two outlets in the sump of the fuel cell, I'm only using one and I would'nt think it makes a differance which one. Do I just have a bad pump? As always, thanks for the help.
 

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Pump pressure

I run 2 of the Holley blue pumps . Check these things: if your fuel cell has the foam in it sometimes it will get into the pump screen or filter if you have a filter ahead of the pump and cut the fuel flow way down. Also Holley pumps work best mounted straight up, if its on its side pressure can vary, the factory instructions say to mount it straight up. I run 2 750's and I set my regulator to 8-9 psi which is pushing the limits of the needles and seats . I have noticed that these older design pumps have a limited lifespan and pressure drops with motor age, I'm getting maybe 2 years of street use out of them. There are better pumps on the market now, when the current ones I'm using go, I'm going to upgrade.
 

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When this occurs does the pump change the noise it makes? Also does the performance seem to change or just showing lower pressure? Are you using a liquid filled gauge?

If the performance is not affected and you are using a liquid filled gauge that would be the first suspect.
 

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First check and make sure you have 12+ volts at the pump and do a voltage drop test on the ground wire. If that checks out I would say the regulator is bad. I used the cheap Holley ones for awhile with good luck but then I just kept getting one bad one after another. They would just act strange kinda like what you are describeing. I went to a better quality regulator and all my troubles went away.
 

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Discussion Starter #7
Thanks for the help. I checked the fuel filter, It was fine. So I broke down and took the regulator off my other car ( hate to screw with something when its working fine ) put it on, cranked it up and it stayed at 61/2 lbs and did not drop. So I just ordered a new regulator and I think that will fix the problem. Thanks .
 

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easy , get a new pump
 

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sounds like what my liquid filled fuel pressure gage would do. I hope your regulator was the culprit tho since you changed that.
 
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