I was just doing a little tinkering this weekend and I have found something perplexing. With the vacuum line off of the AFPR, the fuel pressure immediately goes to 48lbs and stays there steady just like its supposed too. With the vacuum line still off, when I hit the throttle the pressure will drop 5-8 lbs and go right back to 48 at idle. Shouldn't the fuel pressure with the vacuum line off of the regulator stay pretty much right on? I do have a stock fuel pump still..... Any ideas??

 

Hmmm, I would imagine that since fuel is being released into the cylinders through the fuel injectors that fuel pressure would go down a bit. Sorry I can't provide a more definite answer.

 

Perhaps your pump is not capable of sustaining 48 psi. Check your filter lately?

 

I just replaced the filter this weekend.........no change.

 

I wouldn't worry about it. The engine wasn't designed to run with the vacuum hookup off. I would agree with Shoebox and say that your fuel pump probably can't sustain a 48 PSI fuel pressure.

 

Stock fuel pump? May be time to upgrade to the 255lph intank. I have the Walbro 255lph intank. I would definetly upgrade since you plan on running nitrous. JMO.

 

Well it looks like it may be time to tackle the fuel pump. Racetronix........I guess????