The most of dash lights in my recently acquired 240 D did not work, so today I replaced the bulbs in the speedometer cluster/instrument panel. It seemed like an easy repair, and did not take long to finish.

However, when I put everything back together, the glowplug light did not come on. When I started the car, it ran fine, but when I tried to kill the engine, it kept running. I could even remove the key, but the engine idled perfectly.

When I took the instrument panel back out, there seemed to be the odor of burnt electrical wires from the general vicinity of the clock, but I can see no evidence of shorting.

I’m reading my Haynes book, and it mentions the fuel cut-off solenoid is a likely suspect. Is this likely, and could its failure be caused by something I did while removing / replacing the speedometer cluster/instrument panel?

Can anyone tell me what I did wrong, and better yet, how to solve this problem?

You have probably disconnected the vacuum line either to or from the vac switch that is mounted on the steering lock/ignition switch.

The diesel uses no electrical circuits for running OR shutting off. The shut-off is done by connecting vacuum to the fuel shut-off servo on the back of the injection pump (you didn't say but I assume you have a 77 or newer 240D with vacuum shut-off; not the manual cable shut-off of the 74-76 240D). The fuel shut-off servo uses a diaphram and vacuum to pull the pump rack to the zero delivery position; no more fuel, no more run.

The lines going to and from the switch are brown. One of them might have a second color tracer.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

Thanks with your assistance on my 1980 240 D.

You were correct; both vacuum lines on the steering lock/ignition switch were off. In fact, the rubber nipples that connect the two lines were so loose that, coupled with the film of oil that covered the switch, they came off at the slightest touch.

However, I got them back on and kept them there while I re-installed the instrument cluster. Now my car dies when it's turned off.

On a less positive note, my dash light problem is even worse than when I started. This morning there was, at best, one bulb lighting the instruments.

However, all the warning lights worked, as did the high beam, brake warning, and parking brake light. The turn indicator lights also worked, as did the lights for the air conditioner fan. The rheostat didn't really dim the lights, it instead seemed to have an on-off function.

After my morning efforts, there are no illumination lights working, neither the glowplug light nor the seatbelt light works, and the brake warning light now glows constantly. The rheostat now dims the lights for the air conditioner fan, but seems to have no effect on the instrument lights.

I also checked the bulbs that I replaced with an ohm meter, and all seem to have been good, so there is, I think, a bigger problem than just blown bulbs. I suspected the rheostat, but it now working, at least on some of the lights.

Can you offer any advice about what I might check next.

Thanks again.

Ken Mitchell

[This message has been edited by Ken (edited 04-01-2000).]

[This message has been edited by Ken (edited 04-02-2000).]

The lighting is so low on the 123 dash that we usually solder a wire across the reostat taking it out of the system giving full voltage to the bulbs and fixing any bad reostat.

Another thing, the bulb ground circuit passes from sector to sector by the contact that occurs from the overlap of the gauge sections. You should unscrew and retighten the philips head screws where the sections overlap.

One other point; that oil has probably come through the diaphram of the shut-off servo. This can become a real mess. You probably should be sure there isn't more oil in that line and maybe a new servo is in order.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician

[This message has been edited by stevebfl (edited 04-01-2000).]

Thanks. Now I know what I'll be doing tomorrow.

Is there a diagnostic test to
check the valve's condition? Is it difficult to replace?

Take a section of vacuum hose and connect to the servo, then suck on it. Be carefull you may get a mouth full of oil. With a suction applied see if it leaks down. It should hold a vacuum indefinitely.

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Steve Brotherton
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician