I’ve been doing some fuel injection adjustments on the FiTech, more about that later. I’ve been interested in the PWM, or Pulse Width Modulation, feature available in the FiTech. What it does is instead of running the fuel pump 100% all of the time, it will run the pump at slower speeds during periods of lower fuel consumption, like idle or steady cruise. It does this not by altering the voltage… that stays the same… but by pulsing the power many times per second. This effectively turns the pump on and off very rapidly instead of always just being full on.
As I was researching and learning about this, I discovered that the fuel pump I have is not good for this. Matter of fact, from Walbro’s website, if their pumps are run in a PWM configuration, they will fail very quickly.
I had installed a Walbro 194 liter/hour pump during the build, so that had to go. I bought an Aeromotive 340 liter/hour pump that works very well with PWM. Now understand that the 340 # is at 40 psi. As the psi goes up, the flow comes down. Aeromotive supplies a chart that shows at 58 psi, where the FiTech runs, it will still maintain 300 LPH and only pull a spike of 13 amps. This gives me plenty of overhead for fuel availability, as my engine should only use about 150 liter/hour at max power and rpm.
Removed the fuel pump hanger from the tank. This is the Pro-M hanger that uses 3/8″ in and out lines and has a return tube down in the bottom of the tank for less aeration and slosh. The stock Fox Mustang hanger (this car does use a Mustang fuel tank) has 5/16″ pressure and 1/4″ return lines, and the return tube is way up high in the tank. This is Hi-Po stuff right here. 😉
And here it all disassembled
Old pump and hanger disassembled
Here’s the parts and pieces included with the Aeromotive kit. A few nice things to point out… The electrical connection supplied is the sealed type, with seals between the connectors and around the wires. And the rubber foam insulator that fits around the pump. Hopefully this will make the pump quieter with less vibration.
New Aeromotive 340 pump installation kit
And after getting the pump installed in the hanger and doing a little wiring work, here’s the new assembly all ready to go back into the tank.
Got it installed, hooked the battery back up, turned on the key and thought the pump had failed. I couldn’t hear it. The old Walbro was loud and I could hear it run to prime the fuel injection system for start. This one is silent.
Hit the starter and she fired right up. After letting it warm up, I looked at the PWM settings and it said it was running at 75% of full power. I think I can peel it back some from there, but I’ll work on the other settings first to get it running very, very nicely.
Thanks for following along…