i just installed a complete new fuel system. the only things carried over are the injectors (seimens 57 lbs/hr), fuel presure sending unit, and the tank ( just drilled a hole in the rear bottom and called it a sump ). the system has a rising rate regulator too.

now to my problem, at about 5500 rpm the pressure drops from 65~70 to 40~45 psi. the wide band says my A/F is normal (on the rich side) and i can't figure out why its doing that. it was also doing that before the system was installed.

so can it be a bad sender ? has anyone heard of anything like that ?

 

what pump? used? hotwired? what lines?

test the fp gauge against a mechanical rental from pep boys.

 

it's a new bosch pump ( the one speed inc. sells) and the pump is hotwired.
i was going to buy a new mech guage after i double check on the dyno ( the dyno has its own fuel pressure logging thingy).
i guess i can try the pep boys one out. is the hose on that one long enough to mount it on the cowl temporarily?

 

I was having the same prob. All was fine in 2nd gear, then at the top of third at about 5500 it would take a crap from 55psi to 22psi!!!

I had mototron 60#ers in. Now I downgraded to Bosch 42# and I am not having the FP drop prob.

Still not exactly sure why it was doing that. I am thinking it was my stock regulator but that is not the case with your car.

 

i think i know what it is now. it seems my injectors are going static at around 5000 rpm, and i guess having them wide open like that causes the pressure to drop sice there is no restriction.
i already have some 72's on order so we'll see what happenes when i put them in.