Why cant I run multiple Walbro/TI Automotive F90000295 535LPH Fuel Pum

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Why cant I run multiple Walbro/TI Automotive F90000295 535LPH Fuel Pumps in Staged Setup?

Posted on: Mar 16

Filed under 535lph Fuel Pump, check valves, FAQ, Frequently Asked Questions, Fuel Pump FAQ, JDT Racing, TI Automotive, Walbro

The Walbro/TI Automotive F90000295 535lph fuel pumps are high-flow units designed for high-performance applications, but they do not have internal check valves. This presents a problem when running multiple pumps in a staged application.

The Issue: No Internal Check Valves = Fuel Pressure Drop

Check valves prevent fuel from flowing backward when a pump is not running. Since the F90000295 lacks check valves, fuel can backflow through an inactive pump, creating the following problems:

Loss of Fuel Pressure
When one or more pumps are off, fuel can flow backward through them, reducing system pressure. This means your fuel rail pressure won’t stay consistent, leading to poor engine performance, misfires, or even lean conditions under load.
Pump Load Imbalance
In a multi-pump setup, the active pumps could push fuel backward through the inactive ones instead of into the fuel rail. This creates an imbalance, making some pumps work harder while others do nothing.
Startup and Priming Issues
Without check valves, maintaining pressure after shutting down the engine becomes difficult. This can cause longer cranking times and inconsistent fuel delivery on startup.

How to Solve the Problem

If you want to run multiple F90000295 pumps, you must add external check valves on each pump’s outlet. This will:

✔ Prevent backflow
✔ Maintain pressure in the fuel rail
✔ Ensure even fuel distribution across all pumps

Alternatively, if the goal is to run a staged fuel system where pumps turn on at different times, using a pump model with built-in check valves (like the Walbro/TI Automotive F90000285 525lph Hellcat Fuel Pump) or adding external check valves is necessary.

We offer the Walbro/TI Automotive 525lph Hellcat Fuel Pump in multiple different combinations all linked below.