Picking up injection pulse on #1 injector line for timing

[Steveddd]

Hello:
I have seen a tool at Snap-on (p/n MT257A) that wraps around the #1 high pressure injection line. This sensor will pick-up the timing of the firing of injector #1 so that the user may time the vehicle.

Does anyone know how this device works? I would like to build one instead of paying $500 for a tool that I will use once or twice in my life.

 

[GregLocock]

I used to use one on diesels, I think it was a strain gauge. Why not hire one? The downstream electronics are probably rather important.

Cheers

Greg Locock

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[Steveddd]

Thanks for the input.

I am unsure of the type of sensor used but once this is figured out the downstream electronics will be quite easy to make.

Chances are it will be a simple voltage follower with some gain and perhaps a schmitt trigger to square off the wave depending on what the timing light requires.

 

[icrman]

I would think a piezoelectric transducer could work too.

 

[magnograil]

Are you trying to find the injector timing or ignition? Electronic injection systems are either single batch, dual batch or sequential. Some sequential will revert to batch injection at higher RPM since there is not enough time to inject all the fuel during the intake stroke.
In any case it would be simpler to get a set of connectors to pick off the signal.
If it is a mechanical system you might look at a piezo pickup (perhaps a crystal microphone) and listen for the injection pulse. Then you have to determine at what level signal the injector is considered open.

 

[Steveddd]

Thanks for the replies.

Yes I am trying to find injector timing off of a mechanical system. The crystal microphone sounds like an interesting way of picking up that signal.

I will scope one out. I am guessing that that signal will contain quite a bit of ambient noise as well, hopefully the injector pulse will be obvious.

I would also guess that the waveform would indicate the when the injector opens. Perhaps I will be doing some DSP work as well.