Diesel injection systems

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Technician
TwoWaves
TwoWaves
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Joined: Thu Apr 24, 2014 8:32 pm

Diesel injection systems

Post by Technician »

Although most diesel vehicles seen in a workshop today are electronic control, there are still a few oldies with mechanical injection systems about. I have one in at the moment and I was wondering about adapting some old test equipment to the PicoScope to analyse vibration pulses through the mechanical high pressure injection system. I know I could use the NVH kit but I have the snap on MT257 diesel pulse adaptor with a vibration sensor that clamps around the injection pipes from the 1990's. Looking back at the design it was used in conjunction with a timing strobe light, but if I could modify one of my old timing light pickups to connect the PicoScope I could effectively scope the secondary injection pulses from mechanical injection systems. I suppose all I'd need really is some BNC lead connectors to connect the pickup lead to the scope! Then again, I know I could just use the NVH kit.
Attachments
Diesel_Timing_Adapter.jpg

Iver
TwoWaves
TwoWaves
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Re: Diesel injection systems

Post by Iver »

Delete 1.JPG
I'm guessing that Snap on thing is similar to this ?
I suppose all I'd need really is some BNC lead connectors to connect the pickup lead to the scope!
What about using an amp clamp as the pick up. It creates a magnetic field is my best guess ?

Technician
TwoWaves
TwoWaves
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Re: Diesel injection systems

Post by Technician »

Thanks Ivor, sometimes I can't see the wood for the trees. I'd never thought about using the amp clamp.

Dzltec
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Re: Diesel injection systems

Post by Dzltec »

Or a secodary pick up lead for a petrol ignition system.

ben.martins
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Re: Diesel injection systems

Post by ben.martins »

Hello Technician,

Thank you for your post and having been spending more and more time with construction equipment, these engines are still going to be around for a while.

The clamp that comes with the timing light you mention and also present in the kit Iver posted is made out of Piezo. As we know when a force acts on Piezo crystal, changing it's shape, a small voltage is generated. With the timing light kits, this needs to be amplified in order to trigger the strobe light but for Pico we can just measure the voltage. The same principle applies to a knock sensor.

If you have one of these devices, or even an old knock sensor, it's worth giving them a go. It's a good idea to remove any supporting clamps that are present on the injector pipes as this can introduce vibrations from neighboring cylinders.
Crank Maths slow down 6 cylinder.png
The above capture had Channel B with the Piezo clamp around the injector pipe for cylinder 1. It's not always this clear but by adjusting filtering, scaling and coupling it is a way of identifying cylinders when you have nothing else.

Kind regards

Ben

Technician
TwoWaves
TwoWaves
Posts: 621
Joined: Thu Apr 24, 2014 8:32 pm

Re: Diesel injection systems

Post by Technician »

Thanks Ben,

I've done a trial run here with an amps clamp as Ivor advised. See here;/support/topic22110.html. Sorry if I've misunderstood Ivor with the Piezo as I thought he was referring to piezo injectors, which this engine has not got fitted. I never thought about the pickup connected to the injector pipes being piezo material? Thanks for pointing that out Ben. Is there a way of improving upon this test to gain better results?

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