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Presented by Bob Pattengale
BOSCH MTS 5200 LAB SCOPE
1-800-71-TRAIN (1-800-718-7246) OR www.auto-video.com
LIVE VEHICLE TESTING (FUEL PUMP)
Using a suitable scan tool we can duty cycle the fuel pump without the vehicle running, and
analyze the waveform on the lab scope. If your scan tool is not capable of this, you may have to
find another way to command the fuel pump on. This can be done by such ways as locating the
fuel pump relay, removing it and jumpering the appropriate connection locations.
Pictured above are two fuel pump waveforms. The waveform on the left is of our subject vehicle
and the waveform on the right is a sample waveform we selected from the lab scope. If you ever
have a doubt in your mind what a good waveform looks like, always go to the lab scope and
select “Example Waveform” to view what a good waveform should look like.
For our subject vehicle, we can see that we have good peaks and valleys in the pattern indicating
a good fuel pump.
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