Fuel Pressure

tmsbuic

Member
I noticed a lean condition on the wideband. I verified my base fuel pressure is 43 vac. line off. I taped the fuel pressure gauge to my windshield and drove the car. My boost is set at 20psi and my fuel pressure only went to 50psi at wot.
Should have went to 63psi. My first thought was the fuel pump laying down but I hooked a regulated air sorce directly to the fuel regulator while the car was running and set it at 20psi. The fuel pressure shot right up to 63psi. I then tested the connection of the hose to the regulator thinking it was letting pressure leak by but its not and I tested the other end at the vac. block on top of the throttle body and all held good pressure.

So, what is going on that my regulator isn't getting the pressure to raise the fuel pressure with boost? My BLMs sit steady at 131, so I don't think I have any other type of vac. leak.
 
Pretty good detective work. One hypothesis would be that your fuel pump is capable of building pressure with minimal demand for fuel flow (idle), but it cannot maintain high pressure at high flow demands (WOT). Hope that made sense. Bottom line is your fuel pump is still suspect. By the way, how old is your fuel filter?
 
My fuel filter is fairly new. Now that you mentioned the WOT demand flow, it makes perfect sense. The pump has around two years on it.
 
60# injectors have too much fuel demand for a single 340 in-tank pump to supply when duty cycle becomes high (>90%).
 
I purchased the one from turbo tweak(GSS340M from racetronix). My pressure is increasing one lb. per lb. of boost. I have it set at 22 psi on boost and my fuel pressure is 65psi at WOT. I'm taking it to the local 1/8 mile track tonight. I will have some good cool air, so I might have to increase some percentage of fuel in the system. I'll just see what the WB will show.
 
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