Low Pressure Drop Across Fuel Injectors

Hello everyone!

I was datalogging a little bit last night and came across something concerning on my 2001 Vortech Cobra. It appears my fuel pressure is dropping at WOT to around 29-30 PSI and my AFR is creeping into a dangerous range (12.35). This is a non-intercooled, boosted application making 11lbs of boost. Also, I logged my returnless fuel pump duty cycle and it was maxed at 1.00. I have the FMS LU47 injectors and a Deatschwerks 340 pump, no BAP.

I realized that I never went back into SCT Advantage and adjusted the fuel pump voltage table, but I'm not sure that would cure the fuel pump maxing out. It still has the data from a stock 2001 Cobra table. I figured that pump would suffice as the engine is stock and should only be putting down around 400 RWHP'ish.

My question is do I need to do something tuning wise to adjust this (log and change fuel pump voltage table) or should I be looking at something mechanical (weak fuel pump or add boost-a-pump)?

Eddie

You may not need to upgrade the pump*, but first thing is to check/replace the fuel filter(s), including the pick-up sock, especially if they've been there for a while.

You are using a referenced pressure regulator?

If you have the ability to , make sure it's getting full voltage and, if practical, also check across the pump to ensure there isn't excessive VD in the feed and/or ground wiring. It's not uncommon for the OEM stuff to be the minimum for the pump to operate to the level needed, and insufficient for aftermarket pumps, especially after a period of time..

* This one? - https://cdn.shopify.com/s/files/1/0414/1681/8852/files/DW300m_Tech_Sheet_9-305.pdf?v=1617899104

Gord,

Thanks for the reply and, yes, that is the fuel pump I'm using. I use the stock Fuel Rail Pressure Sensor that came on the car.

I am replacing the fuel filter this weekend to rule that out and I plan on datalogging a few fuel pump specific parameters that someone suggested to adjust the voltage table. I should have done that long ago, but missed it in the book I use.

The car runs really good, but it has this WOT lean spike I want to fix.

Eddie

From my experience with other cars up to 20 percent additional flow can be had from proper fuel pump wiring and connection, making sure minimum voltage drop is achieved.

georg1970,

Thanks for the info. The pump is in the factory tray and using the factory wiring from 20 years ago. Good point!

I will go back through and make sure all looks ok with the factory connections and make sure the pump isn't sucking any air if I can't tune this issue out.

Eddie