FUEL PUMP RFI ( ham radio related)

Have you tried doing a quick and dirty foil shielding either on top of the pump or between the pump and antenna to see if you can block the most direct path?

 

From the schematic, do not add filtering between the ECU and pump. Pump motor with its 4, likely differential 2 phase, leads will not respond well. Do filter the power leads to the ECU no harm there. You already have an experiential feedback to tell you if that will work or not. Over analyzing, while I get it, it would be good to narrow down the source; in the end you are looking for results. Yes, do power both radio power leads to the battery as a best practice and add your chokes there as well. I understand it is mostly the antenna bringing in the unwanted RF, but if the DC input has the same frequency removed there is much less likely to have a feedback loop making your noise floor on the resulting audio worse than it really is.

 

Only way to get close to that would be to drop the straps , and lower the tank and remove the filler neck . If I’m going through all that , it will be to either add filters on the lines or yank the pump completely.

 

If I was yanking the pump I’d be looking at doing a ground strap. At worst you’ll have to dremel a bit of the plastic housing to get it to fit, but that can be sealed up with some epoxy pretty easy. Hose clamp a braided strap to the exterior of the pump and then find a decent spot on the frame.

 

Well, thanks for the explanation on the output side of the ecu. That’s what I was originally looking for. BUT I did use an exact radio , on a different power source than the onboard power system and the issue is still there, eliminating any power wiring issues. Also shown in the videos using two different spectrum analyzers…

so I’m beginning to think that the only real answer to this would be to get a braided shield wire directly to the pump housing and bond that to the frame and hopefully drain the RFI that way.

 

Or just yank out the radio and say hell with it………

 

I did not read thru the whole thread but i looked at the early measurements and did search for "brush" and "brushless" in the thread and got no hits.
Have you considered that and could brushes be responsible for offending RF?

 

Have you seen what it looks like on a spectrum analyzer? oops missed that you posted a video I missed it?

 

I do not believe that PWM motors are brushed but brushless or magnetic driven. But I could be wrong.

 

OK found it if its PWM there would be significant spikes equally spaced.

 

Check out the first video from the spectrum analyzer

 

To kind of jump into this thread late.

#1. If there is a PWM circuit at the fuel pump what harm would it be to create a twisted pair circuit? Would achieving this reduce RFI? I know that twisted pair circuits are designed to limit interference in AC circuits like sensors.

#2. The ECU more than likely controls the Pulse Width Modulation of the fuel pump through internal grounding in the ECU. Can a grounded ECU cause your RFI and if so can you place a filter at the ECU ground?

 

I dont believe that twisted pair would prevent signal from being radiated from the source onto the harness like toroids would "detune" the resonant frequency by adding inductance.
as best as i can tell , that ECU is grounded as its mounted directly to the frame and has a substantial metal plate around it. It would most likely be shielded to keep ingress out.

 

Yeah it was a few pages back, but to save your thumbs

https://youtu.be/ICAhlBrbsSs

 

it is possible to control brushed DC motors with PWM.
https://www.machinedesign.com/materials/article/21125511/controlling-brushed-dc-motors-using-pwm

however, searching around, i think our low pressure pump is brushless but i did not hit on an authoritative, definitive answer yet...does seem to
be the consensus though.

 

Looking at the spikes on the analyzer, they looks almost identical to the RFI I get from my
Neighbors water pump in his KOI pond. His pump uses a “magnetic drive” motor that has a flow controller. That fancy term was on the box for it. Aka a variable frequency drive or PWM’d

 

After finding that article about brushed and PWM, I called a friend who designs motors (disk drives, etc) and I showed him that article
and he went ballistic. He thought it was ridiculous and he is an expert in this stuff. I am not. So that someone did something with a PWM power supply to a brushed motor is apparently VERY non standard.
He would take bets the motor is brushless if it is PWM, though he does not know anything about fuel pumps and he admits it would be cheaper to use a brushed motor...hmmm...toyota....probably not though.
It was a very entertaining phone call..had to calm him down.
...and he has a koi pond.

 

I think the brushless motors last a lot longer as you never have that friction wearing brushes , plus I believe a brushless is more efficient as well.

 

many advantages to brushless including not sparking in the tank. supposed to be no oxygen in there but could ruin your day being wrong.

 

Brushed would be a RFI nightmare. Not sure if you are old enough to have this happen , but having an antenna for analog TV back in the day , and your parents using a mixer, you used to get the lines across the tv screen, or an old car from the 70 or 80’s and the blower motor or windshield wipers would make noise through the “high fidelity” center dash speaker….