white93 GT

I have a BBK adjustable fuel pressure regulator. I am trying to track down a potential fuel leak. I can run the pump and pressure builds to 40, but as soon as the pump is off the pressure drops to zero over a period of 5 seconds. I don't see any obvious leaks in the lines, and don't smell any leak at the regulator or at the vacuum port on the regulator.

Should the BBK regulator hold pressure for a while? If so, then I definitely have a leak somewhere. I would think that If I run the pump for a while I should be able to smell the fuel leak if it is outside the engine or somewhere along the lines back to the tank. If the pressure should hold, then either the regulator is not doing its job or the fuel pump (walbro) is leaking or could a leaky injector cause these symptoms?

I guess my question is whether I should **expect** the pressure in the line to hold for a while after the pump is turned off.

Thanks,

Tims 88GT

the problem is the bbk regulator. the threads dont hold a vaccum so once the motor is off the fp goes away. a aeromotive its a little better mine will hold 10psi for about 1 hour after the car is off.

93BlackNotch

The Walbro pump might not have a check valve in it... Not sure, but if it dosn't, once the key is off it will lose all pressure... I am actually having the same problem with my BBK regulator, I'm putting the stock one on tomorrow to see if it clears up... My fuel pressure is bouncing all over the place... Good luck either way...

Tims 88GT

yep it does, my holley is made by walbro

white93 GT

Thanks for the help. I had my fuel pump go out, so I replaced that and it got me started looking at the system. I don't have a lot of background with this car, thats why forums like this are go great. I would like to ask about the vacuum reference on the pressure regulator. The regulator is set to 40psi at idle with the vacuum reference removed. This car has a mild cam, so vacuum at idle is only 12 Hg. I haven't looked for vacuum leaks yet, but I have been told that 12Hg is normal for this cam. The vacuum builds to 17Hg as RPMs increase to > 2500.

The vacuum port on the BBK regulator lowers the fuel pressure as the vacuum increases. I see the fuel pressure drop as I build RPMs from idle. It drops to about 36 PSI (the gauge flickers around there at 2500 RPM). This is with the new 190lph fuel pump. The car still has the stock 19lb injectors and the pump should have no trouble maintaining the pressure set by the regulator when running 2500RPM in my garage.

I know the car is not stock, but is the bevaviour described above typical for a stock engine? On a stock motor should fuel pressure drop at higher rpm's

I won't be long before I tune the car, but I wan't to get my new components in place before I do that.

Thanks,

Dearborn5.0

How do you stop the vacumn from leaking out of the FPR and loosing all the pressure?

white93 GT

You don't. My understanding is that you set base fuel pressure with no vacuum present. With zero vacuum present, my FPR holds 40PSI (as long as my fuel pump is running).

white93 GT

Got another question. Does the computer duty-cycle the fuel pump, or does the fuel pump run all the time while the engine is running? I guess I could tap the power to the fuel pump and put a lamp on it to see if it is flickering (I only have a digital voltmeter).

My car has a poor idle. I have looked at the usual suspects (TPS, IAB, EGR ...) and just kind of concluded that the poor idle was related to my cam. I just noticed that there is an erratic drop in fuel pressure that corresponds with the poor idle. The fuel pressure drops a min of 5psi at or about the time the idle bogs down.

If the computer duty-cycles the fuel pump, and if my pressure drops about 10psi/sec when the fuel pump is off, I could be seeing some side effects of a defective FPR.

Thanks,