I have been trying to find an issue with fuel pressure falling off on my Racetronics/225 pump. One thing that I've noticed is that the fuel pressure drops off as soon as the motor shuts off. It use to hold for days. I have a gauge at the end of the rail. Is this something to be considered as the reason I'm loosing pressure at wot?

 

How much are you losing at WOT?

 

Its dropping from 60 lbs to 30 lbs.

 

Ouch! Yeah that's not good! Is the hit wire kit working fine? It's a 255 pump I'm assuming?

 

I changed the fuel filter and checked the wiring. the ground stud near the battery was a little grotty. Cleaned it up. I have run a #8 wire from the battery back to the stud that holds the relay on. I'm still putting together an extension of a fuel line so I can see the fuel pressure gauge at the cowl to check fp while the car is running. Nothing on the fuel system has been changed since the 102/102 set up was added other then the fuel rail that came with that setup. There really shouldn't be much more demand on the system from the old setup.

 

If the voltage is good at the pump, maybe its the regulator?

 

Going back to my original question, could the fact that the fuel pressure drops off immediately after the car is turned off account for the drop in fp under wot.

 

Well my car drops a lot when I shut it off but is fine under WOT

 

I don't know if it has anything to do with your pressure drop at WOT but the pressure drop of as soon as it's shut off but many pumps have a one way check valve so they hold pressure after it's shut off. This helps cold starts, Without the check valve it may not start instantly.

 

Here is a long shot possibility that I came across one time. The short hose between the pump and the housing was loose and was leaking off pressure. At idle it wasn't a problem but at WOT the motor would stumble at higher rpm. When I went to replace the pump I found the hose loose at both ends so who ever installed it forgot to tighten the clamps. Ran fine after that.

 

Does it drop to 0? After the pump primes the pressure should hold 40psi+ for quite some time. If it doesn't, its either the checkvalve in the pump or regulator. If either of these fail (especially the regulator at WOT) then fuel pressure will suffer.

 

Yes it does fall to 0. I have been talking with Racetronix. They have been helping me try and solve this. I was thinking about putting an aftermarket regulator on the return line to the tank without modifying anything in the tank. Has anyone tried this?

 

Racetronix has been a big help, it sounds like I would need to remove the factory regulator if adding an aftermarket one.