Economy Gauge 300TD w124

chastrain

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Hi, i have a problem with my Economy gauge, it doesn't move, with engine on or off.... it just sits in the red, the motor's new to me :) (just learning) but from what i can ascertain it's perhaps a vacuum leak/disconected or faulty gauge?

should my first move be to pull the instrument panel and check connection ?




300TD w124 lhd
 

Number_Cruncher

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1995 W124 E300D TE
It sounds like someone has fitted the gauges out of a petrol engined W124.

It would be unfair of me to speculate on possible reasons for this.
 

television

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The economy gauge is operated from the vacuum system,,and your car does not have one, well not on the engine
 

brianbrian

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w124 250D, SL129-deisel
Sorry malc but the 300TD has a vacuum pump on the front of the deisel engine as I had to T off of it to make all the vacuum parts work when I fitted the deisel into dizzy lizzy's 129sl. Hope this helps
 

Number_Cruncher

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Yes, although the diesel engine does have a vacuum pump, it doesn't have any manifold vacuum like a petrol engine would use to drive an economy gauge.

There is, of course, the system of restrictors and the valve on the injector pump which mimics the manifold pressure variations of a petrol engine. You could tee off from the vacuum pipe which goes to the transmission's modulator valve and connect that to the gauge - the gauge would then (roughly!) mimic the gauge as fitted to petrol models.

The diesel engined cars were not usually** fitted with economy gauges - which raises the question of where your instruments are originally from, and why they were fitted.

** I say usually, because there are doubtlessly some exceptions during the production run
 

Alex Crow

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It sounds like someone has fitted the gauges out of a petrol engined W124.

It would be unfair of me to speculate on possible reasons for this.

i am happy to though, number cruncher thinks it's had a hircut! :D
 
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chastrain

chastrain

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thanks, well the German owners handbook that came with the car has the gauge, not unusual being that it covers T/TE as well as TD version, though the thin pamphlet that i have covering interior buttons dials and other gadgets doesn't show the Economy Gauge as having, the pamphlet covers 200-300 TD versions. confusing :)

I have history/bills running to 10 years previous, the majority being a local Merc dealership.
All numbers fit, including VIN and the guy the merc came from is known to me, worse case being there was a dial change, but then nothing needs to be fixed so perhaps i'd prefer it that way...if it is that way ?
 

Number_Cruncher

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If there was already such a tee off from the vac pipe to the gearbox which would be leaking air in, your gearchanges would be hammer hard, as the gearbox would respond as if on wide open throttle in terms of shift firmness.
 

brianbrian

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w124 250D, SL129-deisel
Yes I agree with every thing Number Cruncher has said, also you don't need the economy gauge it will do 30to35mpg allday.Hope this helps
 
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chastrain

chastrain

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If there was already such a tee off from the vac pipe to the gearbox which would be leaking air in, your gearchanges would be hammer hard, as the gearbox would respond as if on wide open throttle in terms of shift firmness.


yes,as of earlier thread , Auto change is jerky, could be a connection...or lack of :)
as mentioned quote: 'definitely check the vacuum level at the modulator', checked the pipes/connections, all were good, visually at least, as of pipe to gearbox, are you saying to check Vacuum to gearbox (connection *at* gearbox end) and/or that this perhaps Economy gauge connection could be to blame ?

careful i'm a novice, thanks.
 
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Number_Cruncher

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yes,as of earlier thread , Auto change is jerky, could be a connection...or lack of :)
as mentioned quote: 'definitely check the vacuum level at the modulator', checked the pipes/connections, all were good, visually at least, as of pipe to gearbox, are you saying to check Vacuum to gearbox (connection *at* gearbox end) and/or that this perhaps Economy gauge connection could be to blame ?

careful i'm a novice, thanks.

Yes, this signal only really exists between the vacuum valve on the injector pump and the modulator valve on the transmission.

However, leaks and problems upstream of here can also cause problems, and affect the level of vacuum in this line - as can blockages in the injector pump mounted valve as you'll have already read.

I use a mityvac tool to check around vacuum systems, but, a recent post has suggested that the Beta / Sykes vacuum pump and gauges are, well, better!
 
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chastrain

chastrain

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This is the gearbox vacuum system

Many thanks for the link, i believe i need to put some decent time out to dig deep/become properly acquainted, the mysterious dial would be best sorted (i think) by looking behind, nothing to connect...never existed, then the jerky gear change, a couple of bulbs and she's good, also unfair on you guys for me to post question without me having done the basics beforehand.

Regards C
 
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chastrain

chastrain

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I use a mityvac tool to check around vacuum systems, but, a recent post has suggested that the Beta / Sykes vacuum pump and gauges are, well, better!

thanks , have been looking at pressure gauge's, think that would be a good start, thanks for the tip :) and explanation .
 
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chastrain

chastrain

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Let us all know how you get on.

will do :) ....and better so, when in the West Country (nr exeter) for anything other than liquidchange took the car's to the bro-in -law's garage , made me lazy . Cheers.
 


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