Join Date: Apr 1999
Location: Newbury Park, CA
Re: PWM fuel pump
Though the pump is PWM compatible, there's a bit more to it for the pump and control systems to function properly.
For PWM controlled pumps in a closed-loop electrical system a minimal amount of fuel must pass through them during operation. This amount is more than what the engine needs at idle can cruise. Hence, a high pressure bypass (controlled leak) is needed. We have had good success with similar tank/pump arrangements by drilling a small hole in the hardline tube that is inside the tank where the hose from the pump connects. This way the bypassed fuel is simply returned to the fuel load.
In other applications an external fitting is can be used. For a TI450lph a 0.041" x 1/8" long restrictions works well. For an Aeromotive Stealth 340, a 0.025" bypass is appropriate. I've not tested the TI F90000288 that is in question by the OP but something in the 0.025 - 0.032" is likely in the ballpark. Only testing will tell.
The OEM's however put this bypassed fuel to work by driving suction pumps. These pumps fill the module reservoir and/or transfer fuel from remote sections of the tank. These reservoirs have a huge advantage vs. anything else in the market: 1) slosh control, and 2) pump inlet head. Slosh problems are a thing of the past with the reservoirs. The inlet to the pump, especially at lower, and hot, fuel levels is the primary cause of "vapor lock." Fuel boils at the inlet to the pump and pressure falls. By reducing the speed of the pump (PWM), keeping heat out of the fuel load (non-recirculating), and having a high inlet head pressure (reservoir) helps keep the pump properly fed.
Simply put, there is nothing in the aftermarket that is in the same orbit as an OEM fuel module.
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