FUEL PUMP RFI ( ham radio related)

i imagine the high pressure fuel pump emits some pretty high frequencies due to how it operates

 

Honestly, its low frequency RFI/EMI in the spectrum scheme of things.

 

Ive been through that thread a few times, but I was looking for more info relating to the PWM controlling of the pump than most answers I'd get in that thread. All I would get is " needs to be bonded, shorter ground wires, use ferites/toroids", and more examples of things that have little to no bearing on this particular issue as typical with most HAMS .........

I know how to fix RFI, but the fix isn't always universal and the last thing I want is my filtering causing a fuel delivery problem because it alters the modulation signal and potentially having to hack my harness, then it doesn't cure it.....

 

Is there a way you can mock up the HF AE on a magmount etc to try it at different locations on your truck?
That is indeed an ugly amount of noise with the truck fired up.

 

Where it is located now , is the third location I’ve had it and the 4th antenna. I originally had it on both front corners, then when I settled for the back , where it stayed. Up front was a combination of the fuel pump noise PLUS a shit ton of ignition noise and other sensor hash from the coil packs and cam sensors which all have mix 31 snap on ferrites, along with every harness in the cab at all the connection points along with the ECM harness as well.

I think I’m going to buy about 20 more mix 31 snap on ferrites and load up that entire harness from the fuel pump up as far as I can get to see if it helps , before I mess with adding anything in series with the fuel pump wiring harness. it will be about 200 bucks in ferrites, BUT I can always use them over time.

 

Or extend the wire. 4-20ma is PWM current.

 

I suppose you could also try a bonded shield around the fuel pump ECU.. a literal tinfoil hat to start with, and see if that knocks down the RFI to any degree.

 

It appears that the cable from the fuel pump control ECU to the fuel pump is already shielded, which makes sense...

 

I would think the pump (load) side of the ECU is going to be significantly higher draw than a few ma. We're talking about pulsed DC to that sucker.
BTW, the diff lock on OR/Pro and now Trail models also works on PWM.

 

if dropping the tanks wasn’t such a bitch to do to sniff around, I could put the telescoping whip on the analyzer and sniff it that way to.

I’d also unplug the input and output to that ecm and see when it triggers the signal for the pump to run , if the noise is coming from the input signal vs output signal or actually the pump. I’m afraid that if I run power that with no load, it could fry the ecm, but I guess during a pump failure, it could potentially not have a load on it and be almost the same thing.

 

You have techstream running on your laptop? Might have some bi-directional fuel pump controls to speed up testing, easier on / off and don't have to play with the ignition.

 

I do not have tech stream , is that a dealer only tool or cost like 20K?

closest thing I have is a BT OBD2 reader with Carista and another program for creating custom gauges from the PID’s for reading trans temps when I’m towing the boat and that’s on an ipad

 

you can download techstream for free or you can pay for a one day license. kinda pricey though. but it is mainly a dealer tool and the pricing reflects that.

 

I’ll look into it, but I think the money would be better spent purchasing the toroids and ferrites as I basically know where the problem is originating from.

And last year , calls to Toyota corporate to get a definitive answer from someone in engineering was stopped at the receptionist as there was no way for me to talk to someone, so I have up , and now deciding to revisit the issue and no longer ignore it.

 

@tonered has a cracked version in his signature I believe. There's a whole thread on it. Only thing you'd need is an OBD2 cable. But might not be worth it in your case.

 

If u dont have the cable and set-up, it's basically not worth it for you haha

 

Yeah, I was just snooping around various sites for a cable and it’s about 100 bucks.
I have a BT OBD2 reader and a laptop with BT but not sure if it would be comparable in this situation.

at the end of the day, I know what a fix is to eliminating RFI, BUT I don’t know if the solution would create an issue on its own by possibly altering the PW signal.

By adding the toroids and ferrites, it is basically “ de-tuning” the signals radiating over the wiring harness that’s acting like an antenna.

The noise will always be there , but by changing the inductance , it suppresses it from being heard by the reciever.
Kind of like the old days with alternator wine and plug wire noise in cars with am radios and cb’s, you would put a capacitor across the coil and use resistive plug wires. But the newer electronic signatures and schemes of making more efficient ways of operation, create their own headaches in other ways.

 

How is the radio powered up?

I suspect it is not the fuel pump but something else. Often the pump is a 10 bit PWM, but fundamental frequency around 200 Hz. Pumps have inertia, so you need enough time to get them moving. 10bit PWM gives you 1023 steps, but you would use something like 200 to 1023. Pressure regulator measures pressure, PWM adjusted, PID type control.

Wire up your radio to a separate battery. This will keep the two electrical systems independent. Repeat your measurements. Post the results.

I like radios to be wired to "+" and "-" battery posts. The battery is a huge capacitor (suppresses spike)—shielded cable (shied connects to the ground at the battery, left open at radio). If you want "ignition switch power control," have a relay right at the battery to control the 12V to the radio.

EMI suppression is huge for automotive. I would expect the alternator to be a much larger noise source than the fuel pump.

Ford has BEMM (Body & Equipment Mounting Manual) that would go through tons of electrical details. So you have electrical points for radio power and grounds (think fire & EMS) retrofit. Toyota doesn't have anything like that available to the public. Still same basic ideas apply. Little things like making sure the instrument cluster has a 21.75Mhz XTAL seem odd until you look at the fourth and fifth harmonics and compare them to FM Band (88 to 108). ECU's are often around 40Mhz for calculations, but everything is designed for a reason.

A bad battery can cause problems btw.

Things to look at:

Separate battery (temporary to help identify the issue).

A shielded wire from the battery to the radio (two conductors with shield). Battery and Ground direct to radio, shield only connected to the ground terminal of the battery.

Can you sketch a diagram of the test measurement and connections? It's common with scopes to see all sorts of electrical noise but induced from a 4" ground lead. WHen I used a "pigtail" to connect to a ground 0.1" from my signal, the noise wasn't present. It was fun to watch faces light up when my Engineers realized they were chasing fluorescent lighting of the lab (we had a faraday cage for sensitive measurements).

My classic "this doesn't make sense" was an op-amp circuit that went crazy. 1983, first job at National Semiconductor. Once a day (not every day), my analog circuit went crazy. Later discovered the SR71 before landing at Moffit Field did a huge data dump. RF energy is unlike anything else. The only clue was one of the techs always took a cigarette break about the same time, and talking with him, he said, "the minute the noise increases, go outside to see the SR71 landing." Hol' up. There was a huge issue about Russian spies who hung out a "Charlie Browns," a local after-work watering hole. It sounds like a Warren Zevon song, but the truth is strange at times.

So don't get ahead of yourself—no cutting wire harnesses. Ferrite beads are wonderful for high-frequency harmonics, but capacitors help more with lower freq. I'm still not sure if you see 1.4M or 14Mhz issues.

I'm that crazy old gray-haired guy. Still have my books by Henry Ott and spent way too many nights chasing harmonics. Hey, it paid well, and I got to travel all over the world.
http://hottconsultants.com/EMCE_book_files/emce_book.html

tl;dr: Step back and look at basics first. Grounding, shielding, wire routing.

 

The battery is brand new, issue was same on old battery.

As for how its wired up, ill do my best to articulate it.


ALL IN SERIES -------- From the battery, I ran 8 ga to a 30 amp CB- to a 50 amp line filter ( used in car audio to reduce alternator whine) - to contacts of a 50 amp relay ( under hood on fender) - to binding post under drivers seat - to rig. Coil of relay is controlled by a LIND shut down timer https://lindelectronics.com/product-category/shutdown-timers/page/2/ to kill power after 15 minutes ( or whatever i set it to) after vehicle shuts off OR voltage drops below 12.xx v or whatever comes first. ( the shut down timer and relay were a recent add to curb parasitic drain ive been having since the truck doesnt move until the weekends) and the noise was prior to any of that.

GROUND is taken from a binding post under seat and straight to seat bolt.

Antenna base is bonded to side of bed ( flat braided wire) to chassis, cab also has flat braiding on both sides of cab to frame, fenders , hood each bonded to frame, doors bonded to cab. Between each section of exhaust, muffler and cat is also bonded to frame with flat braid. When testing with my VOM, I get no resistance between any of these points when testing continuity to ground and also continuity between each point and the negative terminal of the battery as well .

On the antenna feed, I have a mix 31 toroid with about 15 turns at the RF deck antenna input.

Ill take my second radio that's exactly the same as the one mounted in vehicle that has a LIFEPO4 battery for its power source and use the same antenna and mount and see if it does the same thing. ( I think i've done with before but cant remember)

I have an old ass techtronix scope laying in the garage , but I think the controls were so dirty, it was almost impossible to get any readings. Ill try the scope as well rather than RF spectrum analyzers after I double check the second radio with separate power source.


I guess I COULD try running a ground directly to the battery, but everything in my life has always told me to keep the ground as short as possible to eliminate ground loops...

Also, I know its coming in through the antenna as the noise isn't there with the antenna disconnected from the radio.


I also thought about the capacitor across the FP wiring, but again back to the PWM, not sure if that will change signalling at all. PWM is all new to me.

Its definitely not alternator whine and the alternator wine would only happen when the motor is running. You can see the noise starts and stops when the fuel pump ceases its operation based on when you hear it stop running.

And my error on 14MHZ / 20 meters. I said in one video 1400 MHZ but mean 14 MHZ or 1400 KHZ.....

 

This may help, good tips on "running power leads" directly to the battery.

The author has a great tip about fuses, bonus is his installation is in a Tacoma:

https://hamradioschool.com/going-mobile-install-a-station-in-your-vehicle-part-1/

14MHz is the 20-meter band.

1400Khz or 1.4MHz is a much lower frequency (Medium Frequency) but that was 1940s ground-based systems that are no longer used.