djm_e22

First all this seems normal but keep reading to see where I get confused. Thanks. When I first start the engine the fuel pressure is at about 42psi. I took the vacuum hose off and it jumps close to 48psi. I did some WOT and it gets to about 46psi. But after about 20 minutes of driving my fuel pressure now is only at maybe 39psi and at WOT it only goes to maybe 40psi. Then this time when I took the vacuum hose off the regulator may have went to 41psi. Should it of still jumped 6-8psi with the vacuum hose off even though I have been driving for 20 minutes. Would this be the regulator or fuel pump? Or something else? Thanks for any help.

SS RRR

I'm not sure if you drove the car with the vacuum hose off, but do that and see what happens. By no means should your fuel pressure EVER drop under WOT conditions. I would venture to say your pump is overheating causing the influx in pressure. Is the pump/regulator stock?

djm_e22

The pump was changed to the walbro 255 or something like that when I put my engine in a little over a year ago. The fuel regulator is stock. I have over 170,000 miles on the engine. Well not really since the engine has been rebuilt, but the fuel regulator is still the same. If I drive with the vacuum hose off the fuel regulator what should I watch for? Also I need to keep the vacuum hose plugged if I test the pressure with the hose off the regulator, right?

SS RRR

You don't have to, no. I take it you have a pressure guage? Hook the guage up, take the regulator vacuum hose off, drive around and do a couple of WOT blips. Nothing crazy, and see if your pressure dips. That should bypass the regulator diaphram alltogether and should be a tell tale sign it's your pump. If the pressure does not drop then pull over, immediately put the vacuum hose back on and repeat to see if the pressure drops.
Are you using the fuel pump bucket or is the pump just hose clamped to the bracket?

djm_e22

To be honest, no it doesn't have a bucket. But I thought the bucket was good for if you are low in fuel and are going around curves throwing fuel away from the pump and the bucket would keep some fuel in it. Also it has been a year with this fuel pump and no bucket and this problem hasn't showed till now. I could be completely wrong about what the bucket does.

SS RRR

You are pretty much right. The bucket's purpose is to keep the fuel pump fully submereged in fuel no matter what level the tank is at. Has nothing to do with cornering. Once you take the bucket away you take away the ability for the pump to be cooled by fuel as it is exposed to air once the fuel level reaches a certain point.
I just replaced my Holley 255 after it had been in the car for two years and maybe 10K miles. I went ahead and put the bucket back in because I'm pretty confident the pump's lifespan was cut short because it wasn't cooled properly.

djm_e22

Sorry last question and thanks for your help. When I do run the car without the vacuum hose on the regulator, do I not need to do it for long? Can it somehow cause a to rich condition?

SS RRR

No. You'll be fine. All you need is a quick WOT blip of the throttle to find out if the pressure drops.