Fuel pump current ramp

Michael Owner/Technician Quakertown, Pennsylvania Posted   Latest  
Trained By Techs
2005 Toyota Highlander 3.3L (3MZ-FE) 4-spd (U140F)

Playing around with the Pico tonite and thought I would mess with one of my loaner vehicles. Attached is a fuel pump current ramp that i'm trying to get rpms on. Problem is I cant get a clean waveform. I think I have my time base correct but cant seem to see a good starting point with the vertical cursors.

Brian Instructor
Parma, Ohio
Brian Default

I am asking a few questions because I am not able to see on the file.. What was your sample rate set to? Was clamp zeroed and proper scale selected? ( i dont think this will make a difference) I have often struggled to find RPM on fuel pumps unless there was a bad spot.diag​.​net/file/f2skfhvwl…

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Rudy Technician
Montebello, California
Rudy Default

EFI 1 seems to be powering up a few things. That can be an issue. Youll have to scope directly at the pump.(or rather, one of the pumps wires directly) You can also try jumpering the Circuit Opening relay, as that directly feeds the pump and get your reading from there.

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Michael Owner/Technician
Quakertown, Pennsylvania
Michael Default

Funny because I wondered if that spot was going to be accurate. I looked at that opening relay too. I suppose a relay buddy would work to jumper?

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Brian Instructor
Parma, Ohio
Brian Default

Good call Rudy. I failed to look up diagram before replying.

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Chris Diagnostician
Commack, New York
Chris Default

Yep, C/O relay is the way to go on this car

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Richard Technician
Virginia Beach, Virginia
Richard Default

You could also leave your probe where it is at , just don’t have the vehicle running. Use your scan tool to operate it.

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Tom Technician
Missouri Valley, Iowa
Tom Default

I like the dummy relays with the wire hoop to check current flow, quick and easy no scan tool needed.

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Rick Technical Support Specialist
Saint Charles, Missouri
Rick Default

Take a look for the fuel pump fuse or possibly the ground wire for the pump itself will work for current ramping. Most fuel pumps have 8, 10, or 12 segments in the commutator Knowing this you can cursor the amperage pattern and measure the time in (ms) for one revolution of the armature to take place. Ex: 10 segments 1 rev = 11.09ms (.01109 s) Since there is 60,000ms in minute, divide this by…

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