Setting Inj Pump timing with a multimeter

[Michael Fowler]

There is a long thread over on the Mercedes Shop Diesel forum about setting the injection pump timing using a multimeter to read millivolts. It seems that anything made with dissimilar metals will generate electricity when subjected to hear. Glow plugs are such a device.
It is said that by reading the voltages generated by the glowplugs, you have an effective thermocouple into the combustion chamber. There is some debate over which point is the preferred "correct" timing point--with some saying at the point where the highest voltages ( temps) are seen, while others say it is just to the retarded side of that point.
I don't know. But wouldn't it be great if we could time our engines that way? One guy claims 1/10 of a degree precision.

I could post a link, if its allowed, but if not you could find it yourselves.

What do you guys think?

 

[Mr_Roboto]

I say post the link. This isn't TDS!!

 

[highest_vision]

You may be able to find a voltage for your engine the first time you do it, but it won't likely be the same next time or for anyone else. There is also the potential for stray voltage to affect your reading (ever tested coolant voltage?). You could probably make your own deal to use with a timing light with a photo-electric diode or a knock sensor and assorted electrical components.
James

 

[94f450sd]

post the link.linking to other sites is allowed here

 

[Michael Fowler]

Here is the link, its a looonng one
http://www.mercedesshop.com/shopforum/showthread.php?t=152389

Yes, the link discusses how the readings will vary from GP to GP. The thread starter recommeds tying all GPs together to get a better average.
He also describes a simple capacitor/resisypt circut to stabilze the readings.

 

[Agnem]

I agree with James. Heck, the multimeter leads themselves could induce a sufficient problem when trying to measure such a small amount.

 

[tuckerd1]

Get your O'scope out guys!