FIG. REF: PWM-FREQ-01  ·  SUBJECT: FUEL PUMP CONTROL  ·  READ: 6 MIN

What Frequency Should You Run for Holley PWM Fuel Pump Control?
(And Why It's Killing Your Pump)

If you've tuned a PWM-controlled fuel pump on a Holley Terminator or Dominator, you've probably settled on somewhere between 20–50 Hz. It's the number everyone in the forums recommends, and it's the number that works — mostly.

Here's the problem nobody talks about: 20–50 Hz isn't a good frequency for driving a pump motor. It's the frequency your ECU and your relay can survive.

Why tuners land on 20–50 Hz

Two hard limits push everyone toward the low end:

• Holley's software caps PWM output around 1,000 Hz — already low for motor control, but usable.
• Cheap automotive SSRs can't switch fast enough to stay efficient much above 50–100 Hz without overheating from switching losses.

So the tuning community converged on "low and safe" — a number that won't melt a relay, even though it does something worse to the pump.

What's actually happening inside the pump at 20 Hz

A brushed DC pump motor doesn't want a slow on/off square wave — it wants smooth, continuous current. At 20 Hz, every cycle is a hard inrush event: the motor winding sees a spike of current, then nothing, then another spike. Thirty times a second (or fewer), forever.

That produces three real failure modes:

• Current ripple — instead of steady current, you get a sawtooth of high peaks and dead zones, which is far harder on the windings than the pump's rated average draw suggests.
• Mechanical shock loading — the impeller and bearings take a torque hit on every pulse instead of spinning against smooth resistance.
• Thermal breakdown of winding insulation — repeated inrush heating cycles slowly cook the lacquer coating on the copper windings, which is the actual mechanism behind pumps that mysteriously die early despite "only" running at 60% duty.

It's also almost certainly the source of the low-frequency buzz/whine some PWM'd pumps develop — that's the winding physically resonating at your switching frequency, sitting right in the range human ears pick up.

The real fix isn't a different number — it's a translation layer

You can't just tell Holley to output 20 kHz; the software won't do it, and even if it could, a standard automotive SSR can't switch that fast without cooking itself.

What actually solves this is a hardware translator: something that takes the ECU's low-frequency PWM command (whatever Holley is comfortable outputting — 20, 50, wherever you've tuned it) and regenerates it as a clean, high-frequency signal — 20 kHz or higher — before it ever reaches the pump. The ECU sees the same simple duty-cycle interface it's always used. The pump sees smooth, ripple-free, near-analog power delivery instead of a square-wave hammer.

That's the gap Golem is built to close — a 40A high-side switching device that sits between your ECU and pump specifically to solve this. It's not shipping yet, but if this is a problem you've run into, get on the list below and we'll let you know the moment it's available — along with the scope data showing exactly what this looks like on a real Walbro 450.

If you're also wondering whether PWM is even the right tool for your particular pump or fan setup, we cover that separately: Do You Need PWM at All?