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  #16  
Old 04-04-2008, 11:58 AM
High River Alberta Canada
 
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interested to see what you come up with
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1983 300CD ('Stinky')155k miles, 2.47 diff, EGR removed, AAZ injectors with 265 nozzles from Sean,and vogtland lowering springs.
1984 300SD ('Old Blue')150k Klicks from Japan originally, came with rear head rests, no sunroof and never had an EGR
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  #17  
Old 04-04-2008, 12:20 PM
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Don't put the sending unit behind the dash. While they don't leak extremely often, some of them will leak and ruin an interior or two.

How about canceling the alarm if the glow plugs are powered on? That would seem ideal for those of us with an afterglow feature.
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  #18  
Old 04-04-2008, 02:54 PM
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Quote:
Originally Posted by funola View Post
The way I'd do it is add a set of gold plated contacts from a miniature relay to the oem oil pressure gauge, actuated by the needle
the Opel I used to have probably worked the same way. It had a VDO oil pressure gauge with a light that would come on below a certain pressure. The bearings were getting worn, so the light would come on at idle
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  #19  
Old 04-04-2008, 03:16 PM
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I like the idea of a low oil level alarm. Wouldn't have to worry about the alarm being active when the glow plugs are warming up like with a pressure alarm. In many situations you would catch the problem before it became a low pressure situation. The only thing I wonder is how well on of these oil level sensors work with our black oil...

Hobbs makes pressure switches that are both normally open and normally closed, and adjustable. Do a search for Hobbs on Ebay.

Maybe the thing to do is pressure and level. No buzzer for the pressure, just a red LED. Heck, just a flashing LED for both, who needs a buzzer with a flashing bright red LED.
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Selling 1985 300TD parts again to generate $$ for Suburban conversion. Picture of parts here http://asnowsquall.smugmug.com/gallery/4411815_v9DER#P-1-20
1985 300TD engine/auto tranny, crossbars for sale!

Last edited by asnowsquall; 04-04-2008 at 03:22 PM.
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  #20  
Old 04-04-2008, 04:07 PM
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I'd buy two of them. There was a thread some years ago where someone installed one in the oil pressure gauge line. I think the problem is finding the right metric fittings to T into the original fitting.
There will have to be two designs, one for the 126 electric sender and one for the mechanical gauge.

It might even be possible to use the seatbelt buzzer. Just disconnect it from the seatbelts and wire it into the pressure sensor.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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  #21  
Old 04-04-2008, 05:00 PM
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mmmmmm Diesel...
 
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What about fitting a "t" to the turbo oil supply? That way you are not drilling into the oil filter canister.
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06 VW Jetta TDI 210K miles

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RIP--Lost in fire...82 300D 322K was My Daily Driver-On the search for a w126 now...

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  #22  
Old 04-04-2008, 05:58 PM
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Quote:
Originally Posted by rrgrassi View Post
What about fitting a "t" to the turbo oil supply? That way you are not drilling into the oil filter canister.
I drilled into the top of the oil filter canister partly because I wanted to test the oil pressure in that area. I tapped 2 holes one out side of the filter and 1 directly down the center of the cap. I eventually used the central hole for oil to set up a bypass oil filter system and the outer hole for the low oil presssure sending unit. So I had more than just installing the low oil pressure alarm going on.
In order to utilze the exisisting oil pressure gauge line hole I would have had to make a special fitting to thread into the hole and allow the origional Oil pressure line to be hooked up to it.
The other way would have been to cut the plastic oil pressure guage line tubing in two and put som sort of T there. (If you do this I would use a new oil pressure line as the old platic ones must be hard and brital by now.)
Since I already have a bunch of taps and drills and so on it was easier for me to drill the top of the oil filter cover.
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  #23  
Old 04-04-2008, 07:38 PM
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I like the idea of using the glow plug light power with a relay to keep the buzzer off while the glow plug light is on.That would allow you to hear the buzzer when you first turn the key as assurance that the system is working ,yet not have to listen to it all the time while waiting for the glow light to go out. Simple to do with any of the Bosch 5 pin relays.If you didnt want the buzz at all while starting,you can get pressure switches that have both normally open and normally closed circuits in one switch. Personally i would want the test buzz to be sure the system is functional. Most all the stock o/p switches are closed until the pressure reaches the pressure the switch is rated for which is usually too low (4 to 7lbs) for me to be comfortable with.I believe if the pressure drops to 4psi while at highway speeds damage would likely be done before the switch would activate the light/buzzer,so probably not a good idea to get the switch at the local pick-n-pull. My $.02 Don
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  #24  
Old 04-04-2008, 08:25 PM
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Okay. I will roll this around in my mind a little more for the next couple of days and report back. At this point the most likely operational trigger was going to employ the alternator. Better and simpler plus lower in cost will be to use the neutral safety switch on the automatic transmission instead. Thats how subjective changes in initial design for cost effectiveness will be. In neutral or park the system is off. With the ignition key on or off. Move the shifter to any gear with the engine off it should screech. If after starting the engine you move it to any gear it will stay quiet if operational. Absolute test if you feel the need.

I will keep it as simple as possible with a check button for testing that the system is functional. Or eliminate the check button. Instead just slide the transmission selector into a gear with the key on and engine not running. Saves the cost of another part A side benifit is you will never turn your engine off if not in neutral or park with the key on. Once will be more than enough. Again an operational test method as well.

I also think the alarm should activate at anything less than five to ten pounds of oil pressure. As already suggested say 12 pounds would be even better on the 123. It is almost certain in my mind that a tee will have to be installed in the present oil pressure fitting on the filter. That will be a custom fitting as room is low and provision will have to be made to protect it. Say a motor mount let go for example.

It would be easiest of all to insert a tee in the plastic oil line itself but there are unknowns due to many viarables. . I feel it is the wrong thing for universal application. Just too many potential issues. We are trying to protect the engine with as little additional risk being added as possible.

This plastic line if used would also have to be examined for vibration issues as we are then increasing the mass and inertia of that plastic line. The oil gauge pressure lines are old and brittle to boot. I would not like people to have to change that line out either. It overly complicates the installation. These engines also like to vibrate a little. The function of no false on alarms is the challenge while keeping it as simple as possible. But as close to 100 percent reliable at the same time as possible.

Adding an optional overheat of the coolant function might be so cheap it could be incorporated if an individual desired. I would want a two tone buzzer or something like an intermitent beep for it to differentiate the two functions. Although it seems rational at any buzzer noise you would immediatly check your gauges. Just human nature.

One way or another we can do this in a cost effective manner. For the gentleman that considered the tachometer output. On a normal car with no tach problems in general it would have been ok. It's just to keep this as simple as practical I am trying to keep away from electronics. I do have 25 years active electronic experience but made a decision to try to keep away for this particular item. On some things it is unavoidable.
An additional consideration is if the tach failed after the installation I would get the blame. Guilt by asocciation I think. Deserved or not.I have just started to think seriously about this so as mentioned earlier give me a few days. A variation has to be designed for those speedy 240ds with manual transmissions as well.

Okay the critical issue how much for a kit? I would target a price at less than you could source the parts yourself. Almost irrespective of your ability to scrounge. One piece already has to be custom manufactured I think. . We could even sell that self standing if it makes sense to you.

The intent here is not to make a lot of money but to payback for allowing me to have been a member of this site. Unfortunatly I had no ideas on how to double your fuel milage.

Including myself some of the owners of 123s are by nature conservative. If I thought I could make a quarter by squeezing a nickle I might go for it. Tragically it does not work. Don't ask me.

Again buying in volume at my end and passing along with no greed component should do it. Everything would be well thought out so the installation is very neat and quick. The addition for high coolant temperature is just a cheap add on if desired I suspect at this point. Basically you already have most the parts with the oil pressure kit.

Complete comprehensive instructions would be included for all but really pertain to newcomers to mechanical things. Am I on track? Any suggestions? I always try to keep an open mind.

This is not rocket science. Just well thought out applications of common sense I hope. At this point I see no insoluable difficulties. Does anybody?

Parts counts are about as minimal as I can think of while still retaining desired functions including quick operational tests if desired. I think it is down to three plus a wiring harness but will again have to consider it. Perhaps to five parts if the overheat condition is included. This kit should be pretty cheap.

Last edited by barry123400; 04-04-2008 at 09:11 PM.
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  #25  
Old 04-04-2008, 09:33 PM
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"I will keep it as simple as possible with a check button for testing that the system is functional."--Barry,

If your sensor is 'on' when not under pressure and you have to press a normally 'on' switch to disable the noise while you are starting the car ( after you have turned on the key ) then you have a system which is tested each time you start the car.. most aircraft have ' press to test' type switches... this sounds like the simplest and most reliable setup...
if you add stuff like the glowplugs circuit activating the 'noise off' system you will never know if that has failed without you being aware of it.. until too late...stay direct and simple.
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  #26  
Old 04-04-2008, 09:40 PM
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Kiss
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Selling 1985 300TD parts again to generate $$ for Suburban conversion. Picture of parts here http://asnowsquall.smugmug.com/gallery/4411815_v9DER#P-1-20
1985 300TD engine/auto tranny, crossbars for sale!
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  #27  
Old 04-04-2008, 11:11 PM
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There are warning systems available for trucks and boats. Perhaps some of the components can be looke into for use on Mercedes.
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  #28  
Old 04-05-2008, 10:26 AM
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First, there are chimes or beeper alarms used in cars today that are more pleasant than the raucous buzzers that most carmakers dispensed with many years ago.
Perhaps one of these newer noisemakers could be adapted to this low-pressure warning system and simplify the circuit, while retaining an automatic-check function whenever the ignition is turned on.

Second - A buddy that competes in vintage sportscar racing installed a large low oil-pressure warning light on his steering column to supplement the guage. I think he found his low-pressure warning kit through a racing supplier. With the prevailing engine noise during a race, and with a helmet on, a buzzer would have been worthless. Downside of this setup is you would be have to mount an obtrusive light housing on the dash or steering column, however, as someone else mentioned, there are spots in the cluster where an extra warning light could be added.

Third - I'm not crazy about having the warning triggered only by low oil level, as there can be situations where low oil-pressure wouldn't be automatically accompanied by low oil level.
The solution would be to fit a suitable tee to the oil-filter pressure port - tricky but probably the best arrangement as I certainly wouldn't want an oil switch dangling from a makeshift splice in a plastic oil line or fastened at the cluster where it might dribble black goo on my pants or carpet someday.

Happy Motoring, Mark
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  #29  
Old 04-05-2008, 10:56 AM
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Many years ago some cars had low pressure oil senders which disabled the ignition circuit.
I think Pinto was one of them...
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  #30  
Old 04-05-2008, 11:11 AM
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Quote:
Originally Posted by leathermang View Post
Many years ago some cars had low pressure oil senders which disabled the ignition circuit.
I think Pinto was one of them...
Generators typically have them. The Perkins 108 in my Wanderlodge has both a high temperature and low oil pressure automatic shut off.

As a truly failsafe system, it'd be designed to pull a vacuum on the shut-off when low pressure activated it but then it would need to be disabled during starting.
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1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13
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