Diesel timing question

[GeneratorGus]

I just recieved an Alltest diesel timing light I purchased from Ebay, like new and it seems to work perfect, but I'm a tad confused. My diesels are all antique and the recommended injection timing is by the port opened or port closed method, which usually corresponds with a mark on the flywheel. All well and good, but sometimes I don't trust the results plus an old diesel injection guy advised me that wear and tear in the timing gears and injection equipment would'nt give accurate results, he always used a timing light, which prompted me to buy the timing setup.
Question:The instructions show a typical injection pressure curve which should occur at port opening through port closing. The machine has a 30 percent and 70 percent pressure settings and recommends the 30 percent setting. According to the pressure curve, 30 percent doesn't occur at the start of injection, but an unknown amount of time or flywheel degrees into the cycle. Should I allow for this and set the timing a few degrees late or should I set it at port opening. For example my FM 45B manual calls for 32 derees BTDC for opening, which is where I set it, but the light reads it at 21 BTDC. Is my timing late or is the 30 percent setting somewhat negligable.
ALL comments , advice and criticisms are welcome.

[John Schwiebert]

HAve you every "flow timed" your pump(s)?

[KidDynamo]

I'm not clear on some of your info as per instructions are for which and for what and which is the machine- the light or the engine, so that aside, I've never used a diesel timing light but I have timed a number of different old time diesels and then run them successfully in serious business operations, for years.

What does the timing light use for a transducer or trigger mechanism? Is the 30% and 70% some setting on the timing light, I presume ?

One thing that gets overlooked commonly is the idea of "zeroing" your flywheel pointer, particularly on the bigger stuff. Sometimes it get knocked around a little and it is a good idea to check your pointer and your marks. I'm guessing that you are still using the flywheel marks and pointer when using your light, no? This might not be a big deal for your's, but it is on some Fairbanks engines.

Most of the old engines were timed by using the pointer, flywheel marks, and then some sort of measurement, be it dial indication, feeler gauges, or maybe like some Atlas engines, you watched the fuel pressure for the start of injection.

You might need to get your engine mechanically timed spot on and then see what the timing light reads and use that as a benchmark for future reference. Of course, if this is a seldom used engine, that kind of defeats the need for the light, except if you can use it on a multicylinder engine to make a comparison of the cylinders to see that they are the same.

What model engine and number of cylinders are we talking about here?

[ListerDiesel]

Originally Posted by GeneratorGus

I just recieved an Alltest diesel timing light I purchased from Ebay, like new and it seems to work perfect, but I'm a tad confused.

Most electronic diesel timing devices are for much higher/faster pressure buildups than you will find on the older stuff such as we play with. I don't know how effective this gear would be on, say, an old Lister or Witte engine injection system.

Spill timing is the old-fashioned way but works with virtually every kind of diesel except perhaps rotary pumps which are 'modern' anyway. As most single pumps had adjustments on the pump plunger, it is always best to check the timing after reassembly to make sure that you didn't change anything when stripping down. Spill timing instructions are on our web pages in the restoration and rebuild article on the Lister 10/2:

http://www.oldengine.org/members/die...s/rrchapt6.htm

The settings you make on the device will affect what results you get, and while it is useful to see the advance/retard working correctly on your car or truck engine, these were never used on the old diesels so have little relevance.

Peter

[ronm]

I think the Diesel timing light was pioneered by Caterpillar, for the 1150/3150/3208 series V8's which are, as Listerdiesel noted, high-speed engines. The early ones were not that great as I remember Cat guys saying, but they have undoubtedly improved since then...(70's). My feeling is to agree that the light would be of limited use in slow-speed engines. Spill timing is pretty accurate once you get the hang of it, & as KidDynamo said, I would be more concerned w/the accuracy of the TDC mark than anything else.
Just 2c as usual, Ron in CO...

[GeneratorGus]

Hey Fellas, sorry for the delayed reply, every once in a while I have to go out and earn some $ to supply my iron habit. And thanks for the replies. Although I'm an amature diesel mechanic, I'm pretty familiar with what you guys call the spill method, I've only seen reference to port opening/closing used to describe spill. At any rate that's how I time my diesels, I just figured a timing light might be easier and possibly be a convienient way to check and see if everything is honky-dorry. I have 7 diesels, all water cooled. The singles are: Stover DSL 5 hp, Witte AD genset 4hp, Lister 6/1 ,6 hp, Petter AV1 5 hp, Fairbanks 45B 5 1/4 hp. Also Fairbanks mod 45A V-twin 10hp, and Fairbanks 36A 3 cyl. 30 hp genset (my favorite). The ones with Bosch pumps are fairly easy to time because of the timing window, and the spill method seems to work good on the others, except that you have to reprime the system every time, which can be fairly easy to kind of difficult especially if your hand cranking. Not that I re-time them a lot.
I was hoping to get a reasonably simple aswer to my question about the light, but it doesn't seem to be all that simple. I played with it more yesterday and it seems to be consistantly off, that can probably be the 30 percent thing. I'm going to mess with it more and try to figure it out, but I may just be better off to stick with the spill thing.

[ronm]

Once you've established reference points for your engines, it might be useful as a way to check things quickly w/o disassembly & mess. If the error is consistent, you could apply it to other engines of like make & model. Sounds like a fun toy, anyhow...
Ron in CO...

[r scarf]

Gus, I been a performance engineer for some years and I have had so much trouble with devices trying to pickup the timing of the injection event on the injector line. See the dead volume and pressure rise rate in the line will mess up the true injection event on the meter. I have completed a study years ago that showed that the timing the sensor read varied with fuel delivery and engine speed. See the injection pulse rate varies for a given line set,injection pressure or injection rate, and the sensor was calibrated to one line and injection rate. ( I hope that makes sense, I never been good about wording)

The best way to truely measure the timing is with a injector that is instrumented with needle lift sensor. I know this does not help you because they are hard to make and you would have to modify perhaps a one of a kind injector.
For older low speed diesel it would be best to remove the injector an hook up the injection line up to the injector and using the mark on the flywheel you should beable to see when the injection event is occuring by rotating the engine.
One thing that make this hard is if you have an leaking injector. If its an weeper, the timing will change from event to event. You need to get the injector to pop properly.

I hope this is helpfull, and what a nice day it is here(20S,but better than -9F). I think I will go out and run some engines.

God be with you, and your family