Making an adapter for GPs

[ORCoaster]

In my efforts to use an older Luminosity adapter MT 161 in the VW block I have come up against a problem that I am hoping you machinists can answer for me.

The threads of the adapter are 10 mm 1.25 pitch and the glow plugs are 12 mm with the same pitch.  I have tried to us an old glow plug for the in-between metal I need.  So I knocked out the heater part of the GP. then I tried to drill out the center hole enough to get a tap in there.  I do not own a drill press so it was slightly off to one side.  Not a problem until I started to tap into the hole.  The amount of metal left is not enough to keep it all together.  That may be due to the narrowing of the glow plug as it goes from threaded portion to the nut portion.   

So my question it two fold; 1. would the use of a 12 mm bolt be a better choice of material for this purpose?  2. Can I even get enough metal between the two threads to make this work?  1 mm with threads on inside and out is awful thin isn't it?

DAS

[vanbcguy]

You should be able to find a reducer out there in the wild... The problem will be sealing though with anything but a glow plug, as they have a tapered seat at the bottom. Most Metric fittings expect a sealing washer at the top instead.

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[745 turbogreasel]

Look in a harbor freight  compression test kit?

[ORCoaster]

Great ideas guys but sad to say I already combed through the Harbor Fright set and came up empty and I noticed the taper on the GP. 
That is why I used an old one,  It was still good until I cut and hammered out the ceramic part. 

I was thinking of using a brass flare fitting to simulate the taper thinking it would tap easier than the GP metal.  Kind of what I hoping for with a lower grade bolt as well. 

It is just a tough conversion and metric anything is like not even out there in case you are looking.  Grainer and what's that other place?  McMasters! came away dry there as well. 

I really think my only shot is to destroy another GP.  Well convert might be the better term as I will still be using it in some way.  Just not to start the car. 

[TylerDurden]

Those GPs can be tough... I tried punching one out with poor results.

The question regarding thickness after tapping is a good one. I'm not sure enough metal will be left to do the job reliably. I wonder if a fiber-optic insert could carry the light through the GP shell to your optical pickup.

[Rabbit79]

I came across a place a few years back called 'Speedy Cables' in Great Britain. They had a fair selection of metric bushings. I needed a M22 x 1/8 NPT (IIRC) for a gauge sensor, and they had it. Only place I could find it. Might give them a look.

[bajacalal]

A google search revealed a luminosity probe for our glow plug size is available... Is there a critical minimum distance the probe has to be from the combustion chamber? Here's what I would do- bore out the center of a glow plug, and then, instead of tapping it for 10 mm threads, attach a 10 mm fastener (you might even be able to find or make a 10 mm mild steel round bung with no hex sides) to the end of it, by tig-welding it on or maybe brazing it.

[RobertMcC]

I only paid like 50$ for my 20+ piece diesel compression tester. Comes with all the adapters for most diesel injection engines.

[ORCoaster]

Baja!  Brilliant?   I was so focused on getting the adapter inside the body of the GP that I didn't stop to think run it on the outside.  Going to work on that angle.  I think that may actually be a good thing for me.  Why?  Because the adapter I have that allows the light to come through the center is really not the correct one for the VW engine.  As RobertMcC says they make one for the VW/Audi but find one for me.  I nearly had my hands on one for roughly 30 bucks off ebay.  Got outbid so I am watching for them now.  The exact model is the MT 162 and I have the 164 that is for the Isuzu pup diesel engine.  

These things are like hens teeth.  Not many around when they were around.  Now all of these timing light converters use the Pulse adapter that clamps on the injection line.  I am borrowing one of them from a forum member and I want to make the compare and contrast chart available to all members here.  But I need to be able to get the optical one in the block and not have it blow out when the engine is running.  They are crazy special glued glass inside the tube to keep that compression in the cylinder.  Not sure how or what they use for keeping it in there.  The tube is not crimped in any visible way.

So I will fab as I can on that GP bored and welded idea.  The adapter is too long in the first place so the nut on top the GP is perfect way to deal with the extra distance.

More to come if I get it done.  DAS

[RobertMcC]

I assume this is for 1.9/1.6 NA?

Kit I bought.Then again I work on things other then VW.

http://www.ebay.ca/itm/Professional-Diesel-Direct-and-Indirect-Engine-Compression-Pressure-Tester-Gauge-/351035474585?hash=item51bb584299

Yeah the kit I got comes with a M10x1.25, a M10x1.00, M12x1.25. Plus a threaded mock injector.

http://www.ebay.ca/itm/Star-Products-TU-15-3A-Diesel-Adapter-M10-1-25-Glow-Plug-tu153a-/331180370639?pt=LH_DefaultDomain_0&hash=item4d1be36acf

[ORCoaster]

RobertMcC,  My need is to have the engine running whilst timing it so I can not use the injector body adapter in the compression kit.  I have GP adapters that came with my HF kit but they go in the GP hole and have a useful fitting on them.  What I have to do is adapt a Snap-on MT 164 Luminosity Probe tool that normally goes into an Isuzu GP hole.  Those are longer and have a 10 mm sized GP.  They are also filled with glass so that they keep the compression in the cylinder but let the optical pic up see the flash without blowing it off the end of the adapter. 

So yesterdays fabrication du jour!

Starting with the basic parts.  See the size differences?  Lumy adapter is longer and narrower.  But yet it needs to be in the GP hole in the running engine to see the flash of the ignition and send that signal to the box that fires the timing light. 

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The Proper depth of the GP when installed in a head is like this.  Less the metal shavings

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The adapter is way long and doesn't bite to the threads anyway but this is the distance I am over. 

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So I sacrificed that GP for the sake of the body by cutting off the end and filed it smooth.

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Then I put it into a spare/bad head I have and punched the sucker out with about 5 good sharp raps of ole greenie!

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With that done you can see the way I want to go here.  Drill the GP and mount it on the 10 mm nut and then have the secured adapter inside the GP body inside the head at the correct location. 

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I used a couple of drills to get me close to the adapter diameter.  A 5/16ths inch drill was so close!  Rather than bump up to the 11/32nds I just pulled out the round file and enlarged the hole that way.  It took a bit but I didn't give up any extra that I think I need to keep the body doing the work it has to do. 

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Once I had all the pieces completed I tested for proper depth in the head and sad to say I missed it by 1.5 mm.  Not going to futz with that.

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I had to use JB Weld on the nut to GP body as I was not able to get any kind of good solder or braze to hold.  different metals maybe?  Overnight it cured to this and I only hope it holds up to the 500 PSI in the compression stroke.  Time will tell there.

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The final glued and drilled GP body for the holding of the MT 164 Lumy adapter. 

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Photo Folder Slideshow with titles on top, for other pics not viewed here.   http://s1087.photobucket.com/user/Orcoaster/slideshow/Adapting%20adapter

[RustyCaddy]

Just saw this...that is so cool, nice work.  How did the setup handle the compression pressure? Where is the magnetic pickup holder on one of these engines...i have never noticed one but wasn't looking either.

[libbydiesel]

Just make sure you aren't in line with it in case (when?) the JB fails and it gets shot out like a bullet. 

[ORCoaster]

UPDATE Needed.  Like Libby says when it fails, I didn't have any trouble with it until one time I lost focus and put adapter in the GP hole and snugged it up with a 17 mm wrench but not too snug.  Then followed up with the actual glass and metal adapter that allows the flash of the compression stroke to send a light signal to the end of the tube.  I tightened it with the 12 mm and cracked the JB Weld.  The light of the flash is changed to a signal by way of an optical pick up and that is where the signal to the next part of the system comes into play.  The SnapOn MT 254 signal generator dohicky is what fires off the timing light.  So it is sort of an optical to electrical to second electrical system way to get the timing light to flash on the Flywheel mark. 

The timing is all whacko for those of us that grew up on distributors and gas engines.  We normally think of timing at before TDC but this one being Diesel shows the combustion of the diesel after it has been injected so timing is ATDC.  To hit the mark of TDC on the flywheel you need one of those timing lights that adjust the advance and read it from when you line up the pointer and the mark.  Yeah, could it be more complicated?  Is it even correct?  My engine loves the light timing over the mechanical.  I do it both ways just to know what the dial gauge is reading when all is on TDC.

I have since taken the parts to a guy and he put them together with a good braze job.  I am hoping one day to get an actual VW/Audi adapter and have a spare I can loan around I just saw one of the Snap On tools on Ebay a bit back.  So they are still around.  The newer stuff uses a mechanical sensor that you clamp on to the injection line.  That system uses a 12 degree BTDC measure if I remember right. 

Maybe if time allows tomorrow I will pop a picture of the new more securely joined adapter.  Libby can stop fretting now.  It never did shoot out at me. But yeah, I was leery of it for sure at first.

[ORCoaster]

I found the time to snap the new solidly connected adapter and the rest of the system as it lays out. 

Hope you can follow the sequence.  Adapter sees the flash and allows it to pass through to the silver plug thing that goes on over the o rings.  In there is a photocell that switches on and off.  That signals the MT 254 device to produce a signal in the loop like wire that is much like the signal of a spark plug.  That trips the timing light which you point to the flywheel.  Turning on the dial of the timing light till it gets to TDC tells you what the timing is.  You adjust the pump position to get to the number of degrees you want it to be. 

This is done with the engine running.  You pull a glow plug and insert the adapter.  You can adjust on the fly to get to the place you want the engine timing to be.  Sometimes this is a faster method for me as I loan out the dial indicator and going to another state to get it is a little long at times. 

So these are all the parts and pieces you need, well wrenches too.


Libby approved now?


Need to have this type of light to adjust the time of fire


The closer look of the way it goes together.