PicoScope 7 Automotive
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Diagnosing Unit Injectors
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ben.martins
- Pico Staff Member
- Posts: 544
- Joined: Tue May 16, 2017 1:02 pm
Diagnosing Unit Injectors
Hello all,
Trust we're keeping safe and well?
Thought I'd start up another topic on the fueling systems, more accurately injectors. These seem to vary between truck manufacturer's with combinations of Common Rail, EUI and HEUI.
One of my go to setups when looking for a possible fuel related fault is to have the Crankshaft sensor, cylinder ID (camshaft or injector current) and the rail pressure sensor. By including a frequency math channel on the crankshaft sensor we can then see the relationship between crankshaft speed and the rail pressure and if there are any obvious, repeating, patterns we can then determine if it's related to a particular cylinder. This is something you can see in more detail in the following link https://www.picoauto.com/library/case-s ... ic-process.
A while ago Sharpy posted a great case study featuring a Volvo FMX - viewtopic.php?p=99562#p99562, which had a fuel pressure fault. Carl then kindly chipped in with a capture showing a rail pressure drop which I hope he doesn't mind me adding here.
This will hopefully show that a scan tool can get you some of the way but the scope has the potential to show you more.
I'm not going to go into too much detail as I thought this might be a good for other to share any other tips and tricks or questions relating to diagnosing fuel systems.
Kind regards
Ben
Trust we're keeping safe and well?
Thought I'd start up another topic on the fueling systems, more accurately injectors. These seem to vary between truck manufacturer's with combinations of Common Rail, EUI and HEUI.
One of my go to setups when looking for a possible fuel related fault is to have the Crankshaft sensor, cylinder ID (camshaft or injector current) and the rail pressure sensor. By including a frequency math channel on the crankshaft sensor we can then see the relationship between crankshaft speed and the rail pressure and if there are any obvious, repeating, patterns we can then determine if it's related to a particular cylinder. This is something you can see in more detail in the following link https://www.picoauto.com/library/case-s ... ic-process.
I'm not going to go into too much detail as I thought this might be a good for other to share any other tips and tricks or questions relating to diagnosing fuel systems.
Kind regards
Ben
Re: Diagnosing Unit Injectors
In regards to this post:
https://www.picoauto.com/library/case-s ... ic-process
You mention the math formula, crank(A,60) or freq(A), would you please elaborate on what that formula is doing and what the significance of the (60) is in the equation.
https://www.picoauto.com/library/case-s ... ic-process
You mention the math formula, crank(A,60) or freq(A), would you please elaborate on what that formula is doing and what the significance of the (60) is in the equation.
Re: Diagnosing Unit Injectors
He is creating a Math Channel to convert the Crank Sensor Pulse to a RPM Graph.
60 will be the number of teeth on the Crank Phaser / Relucter Wheel.
More accurately 60 -1. 1 being the missing tooth
60 will be the number of teeth on the Crank Phaser / Relucter Wheel.
More accurately 60 -1. 1 being the missing tooth
Re: Diagnosing Unit Injectors
Thanks, I had been racking the brain trying to figure out what the 60 represented and that never crossed my mind.