...and that rev limiter would have worked too if Larry had reassembled the IP shutoff correctlly.

If you use the existing tach pickup for a tachometer, you will have to disconnect it from the cruise control, if you have working cruise control.

Squid - just try driving the car as is for a while. With the dots on the speedometer to remind you where the redline is, a tach really isn't necessary.

I used to be a "tach fanatic", too, until I figured out those dots (the top end should be in the owner's manual). The dots won't lie as long as you keep the tire size original and keep the clutch from slipping - then you've got other issues to deal with. I actually went as far as setting a throttle stop with an adjustable strobe light and then test driving to the dots, and found that the dots work. The only time a tach would be usefull on these engines, in my opinion, is when setting the idle or high rpm limit. But then again you set the idle on these little engines by sound and how the engine pulls from a start, and the high rpm in the shop, where those adjustable strobe lights are nice.

yea i know what you mean about the dots but i still like to know what the engine is doing exactly. not just on acceleration but at cruzing speeds. but thanks for the info

"With the dots on the speedometer"

I have revaluated my desire for a tach after looking at whats involved :eek: in getting one, the dots will work for me in my 240Ds. I have spent lots of time running marine engines where you need a tack but I think I will pass on the tach for my cars.:)

Another observation regarding the dots. They also serve as a very good guide to the lowest engine speed per gear as well. Single dot is lowest speed in 3rd, 2 dots is lowest speed in 4th. Happy shifting!

Dredged up from the deep
 

Hey guys, yeah, this thread is from last year, but I think I'm putting something together that a search did not reveal.

I have an '82 240D, it HAS a sensor of some sort on the front of the engine for the EGR "computer" (not sure if its a computer, but its a black box w/ electronics in it)

Could someone find out if the sensor for the EGR (it is an rpm sesor) and the 'reference sensor' on the 617's (w/ factory tach) have the same part number ? If they are (or are even electrically similar) maybe all us 240D owners ('82 and '83...) could just hook that sensor up to a junkyard tach amp and then place a 300D tach in where the clock is and be set.

Can anyone help here ? I can't find the part numbers myself (I have the factory repair manual CD's, but I'm not seeing the part numbers...)

Angel,

Get the whole kit and kaboodle from a junked 300D turbo and try that. I believe the place to hook up is the same at the front of the block. Never looked into the change but would begin by stealing the parts, including the dash instruments, from a similar vintage 300D. I believe the "sensor" you are referring to is probably a cruise control item. I could be wrong on all accounts, but the tach was a factory option on the German model and it is very unlike MB to have a different instrument for the 300D and the 240D. Jim

Jim's right. If you can find all the parts off of a 300D in a wrecking yard you're home free.

Just an observation - Why did my manual shift 240D NOT have a tach while my automatic 300D has one? Don't make sense to me...

Wes

Ever had the speedo check on that 240D? ;) My 240D is really buzzing at 75 mph, can't imagine it doing 95 mph unless pushed over cliff. :eek: Seems like we had the discussion before. :p :D MB says redline is 85.7 mph approx. for automatic and 88.8 mph approx for 4spd manual trans. :rolleyes:

Old navy: I think those dudes that go 100mph in thier 240s are ***seriously*** exceeding the redline

...and providing a testament to the solidity of the OM616 =) =)


Tach seekers- Thats the thing- the sensor on my 240 (looks exactly like the one on the 300 I owned for 3 months, not sure about the connector) and is mounted properly, same place and everything, but sends an RPM signal to the EGR computer (at certain rpms and engine temperatures the 240D's of this vintage (1982 and 83) have a computer that tells the egr valve when to open..., the black box is in the passenger side footwell IIRC.
The 300D tach signal goes from the pulley, through the sensor, to a wire to the tach amp (the cigarette fix thing), then from the tach amp to the tachometer.

If the sensors are the same part number (which I cant find out, not sure how to save going and looking for a p/n on both, and they are tough to see/get at in the first place on an OM617) then the amp and tachometer should bolt/power right up. Thats why I'm asking if someone can look up those part numbers for me.

This could be another 240D easter egg (appl to '82 and '83 models only =)

-John

Us boy's and our toy's. :cool:

this might be of interest to some
 

I was going to buy or build one of these but found 300SD instead. Some of the guys over at one of the Powerstroke web sites spoke highly of them. The only downside is that the display only updates once per second. But, it is easy and cheep.

www.tinytach.com

Also, I was looking into this option.

http://www.4crawler.com/Diesel/CheapTricks/Tachometer/index.shtml#Kits

This one is on a VW and is optical but one could be built (for you engineers and techs out there) one using a hall effect pickup mounted somewhere. Most tachs just measure the RMS voltage. The faster the pulses occur the closer the needle moves to full scale. With the correct design and calibration any of the older tachs should work. But I am not an expert, this is just some of the diggin' I've done.

The dots are even better than the tachometer because they show when you can downshift too -- important in a 240D!

As for rpm in fourth, divide the mph by 2 and you have a very good estimate of rpm; e.g. 80 mph is 4,000 rpm. The goverened maximum engine speed of about 5,000 rpm then works out to a bit more than 100 mph indicated.