My fuel economy gauge became stuck the other day. What drives that gauge anyhow? It's not that I feel it's important, but I would like to have it work if there''s a simple way to fix it. Anybody else had that happen? If so, what did you do to get it unstuck?

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" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

You must have lost vacuum at the back of the cluster. Is it stuck in the red(right)? Or a vacuum leak in the engine bay. Thats how I know I have a vacuum leak somewhere, when my gauge quits working. If its stuck half way, then who knows.

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1984 300SD Orient Red/ Palomino
1989 560SEC
2016 Mazda 6 6 speed manual
1995 Ford F-150 reg cab 4.9 5speed manual

The plastic vac line plugs into a rubber hose that plugs into the back of the instrument cluster. If you or a PO had the instrument cluster off it the line may have disengaged. Otherwise look in the engine compartment for a vac line leading from the firewall that has worn through or disengaged.

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Selling used Mercedes parts on Ebay...always changing...
cdplayer51 take a look!
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How is the car running? Do you have high idle, rough running at slow speed? If so, you have a big vacuum leak and your econ gtauge is trying to tell you something. The gauge has value as a vacuum fault detector.

If it is truly just stuck that is another issue but they are so simple it is not likely. Previous poster pointed out the possibility of a leak at the main vacuum source. That source is at the rear of the intake manifold near the firewall. It is hard to see and difficult to reach unless you have tiny little fingers (maybe call on Mistress for help). The rubber connector at that source lives in an environment of high heat and an oily atmosphere. It is usually the first to go. I used a simple piece of plastic tubing until I found the correct connector. Happy Hunting.

On my 1987 300e the vacuum gauge is stuck on the left, in the black. When I had the cluster out a while ago, I did feel vacuum suction on the black rubber hose. Does that suggest my gauge is toast?

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87 300e (white/black; amg body kit)
88 300ce (red/cream; amg body kit)
93 300ce cabrio (white/blue/blue top)
93 300ce cabrio (black/grey/black top)
98 ml 320 (totaled @ 137,000 miles)
99 clk320 (black/grey/black top)

If your gauge is pegged into the black, even when accelerating and you have vacuum at the hose, I believe your gauge is indeed toast. The black range indicates increasing intake manifold vacuum whereas the red range indicates intake manifold pressures approaching atmospheric.

The normal reading when engine is off is pegged in the red. A vacuum leak problem will also be seen as needle tending toward red.

Yeah, it's stuck all the way in the red. I wondered if that was run off of vacuum.

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

My engine runs and idles fine. Other than the gauge not moving, I haven't noticed any other things out of the ordinary.

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

If it is stuck in the red you must have a vacuum leak or a break in the vacuum line that runs to the cluster.

__________________
1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine

I'll check that today if I have a chance. What is there to the gauge to break? If the gauge isn't working, is it possible that a little oil on the moving parts would get it working again?

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles

Have you checked the vacuum attachment in the engine compartment?
On my sons 300TE, it is located near the fuse box. Should be yellow.

__________________
2009 Mercedes ML320 Bluetec

I'll go look. I got caught up in all the excitement of doing my income taxes and haven't been out to the garage yet.

__________________
" We have nothing to fear but the main stream media itself . . . ."- Adapted from Franklin D Roosevelt for the 21st century

OBK #55

1998 Lincoln Continental - Sold
Max 1984 300TD 285,000 miles - Sold
The Dee8gonator 1987 560SEC 196,000 miles - Sold
Orgasmatron - 2006 CLS500 90,000 miles
2002 C320 Wagon 122,000 miles
2016 AMG GTS 12,000 miles