Diagnose fuel injectors

Write up a learning guide about how to Diagnose fuel injectors with a lab scope

Include resources that are helpful in learning about fuel injector patterns. If the resources are on-line include the URL address so others can easily access the article

Choose and explain a good pattern for both voltage and current. Include the pintle hump

Provide helpful information on how to set up the scope to capture a pattern and how to find the best place to backprobe with the scope leads. Be sure to point out that leads can be hooked to injector directly, the positive wire that leads to all injectors when using current and the computer to get to all negative wires when injectors are too hard to get to.

Provide ideas on how to determine if a bad pattern shows a problem with the injector

Below are patterns you have captured.
More patterns will be added as you collect them

To use these in your report you can right click on the image, copy, and then paste it into your document.

current ramp of port fuel injectors
1994 Ford Taurus 6 cyl Port Fuel Injection (current ramp for all injectors) 10/11/2004

current ramp of one port fuel injector
1994 Ford Taurus 6 cyl Port Fuel Injection (current ramp for one injector) 10/11/2004

current ramp of throttle body fuel injector
2001 Chevy Cavalier 4 cyl - current ramp injector 10/11/2004

voltage trace of port fuel injector
1995 Dodge Intrepid 3.3L (6 cyl) Voltage trace of one port fuel injector
10/18/04 Colby, Dale, Jason, Craig

dual trace port fuel injectors
1993 Ford Taurus (6 cyl) Voltage triggered off of one port fuel injector (blue trace) current ramp of 5 injectors (red trace)
10/20/04 Chris, Adam, Gary, Levi, Kevin

dual trace port fuel injectors one open injector
1993 Ford Taurus (6 cyl) Voltage triggered off of one port fuel injector (blue trace) current ramp of all injectors (red trace) showing one open circuit injector
10/20/04 Chris, Adam, Gary, Levi, Kevin

fuel injector
1993 Ford Escort 1.9L (4 cyl) Voltage triggered off of one port fuel injector. What could be done to show a better view of the pintle hump?
10/20/04 Dale, Jason, Colby, Craig

current ramp fuel injector
1993 Ford Escort 1.9L (4 cyl) Current ramp of all fuel injectors.
10/20/04 Dale, Jason, Colby, Craig

dual trace fuel injector
1993 Ford Escort 1.9L (4 cyl) trigger on one injector backprobed on ground side. Current ramp of all fuel injectors.
10/20/04 Dale, Jason, Colby, Craig

dual trace fuel injector
1993 Ford Escort 1.9L (4 cyl) trigger on one injector backprobed on ground side. Current ramp of all fuel injectors. Pattern shows one open injector
10/20/04 Dale, Jason, Colby, Craig

Current ramp throttle body injector
1986 Dodge Aries 2.5L (4 cyl) Current ramp throttle body injector. Cold no-start suspected pintle not opening
10/25/04 Adam, Kevin, Levi

To review sample patterns from last year's class go to www.linnbenton.edu/auto/fall/scope/inject.html.

voltage trace throttle body injector
1986 Dodge Aries 2.5L (4 cyl) voltage trace of throttle body injector. Cold no-start suspected pintle not opening.
10/25/04 Adam, Kevin, Levi

voltage trace close up of pintle hump area
1986 Dodge Aries 2.5L (4 cyl) voltage trace of throttle body injector. Cold no-start suspected pintle not opening. This is a close up of the injector "OFF" signal. This is where the pintle hump should be visible
10/25/04 Adam, Kevin, Levi

current probe - all injectors
1990 Lincoln Continental 3.8L (6 cyl) current probe showing all injectors.
you guys are lame...told me it was a 1989 on the work order.
(notice the amp probe was not zero'ed.)
How many amps each injector is using?
10/27/04 Gary, Chris, Adam, Kevin, Levi

current probe - one injector
1990 Lincoln Continental 3.8L (6 cyl) current probe showing one injector.
notice the amp flow is the same as previous waveform.
Can you see the pintle hump?
The probe is getting a fair amount of interference from the running engine. repositioning the probe or moving the leads can sometimes reduce this interference.
10/27/04 Gary, Chris, Adam, Kevin, Levi

current probe - one open injector
1990 Lincoln Continental 3.8L (6 cyl) current probe showing one open injector.
red waveform is secondary ignition on #1? plug wire with Electronic Ignition (three coil waste spark system)
Need more clarity for the secondary ignition pattern. The inductive probe is very sensitive to the firing of the other plug wires
Properly done it will narrow down the open injector to one of two possible cylinders once the firing order is known (1 6 3 5 2 4)
The spark plug will fire once for #1 and once for #5 compression stroke (the second firing is known as the waste spark)
It might be easier to identify the cylinder by hooking the second channel with a current or voltage probe to one injector and counting the firing order
10/27/04 Gary, Chris, Adam, Kevin, Levi

current and volt probe - one injector
1992 Buick Skylark 3.3L (6 cyl) current probe showing one injector bank and voltage probe of one injector.
how long is the injector turned on?
can you see the injectro opening and closing pintle hump?
how might the scope be adajusted to better show current, voltage for spike and pintle humps?
Voltage probe is on a 20:1 attenuator, how many volts are there when the injector is turned off (constant volts - not the spike)
11/01/04 Craig, Jason, Colby

To review sample patterns from last year's class go to www.linnbenton.edu/auto/fall/scope/inject.html.

To view sample reports from last year go to www.linnbenton.edu/auto/fall/scope/.