How does a Mercedes diesel engine shut off?

Proper diagnosis is a must! On older Mercedes diesel engines models: 1975 to 1976 115 chassis 300D, all 123, 126, 201 and 124 chassis diesels from 1977 to 1993 the engine shutoff is controlled by vacuum (not electrical). An engine driven pump supplies vacuum to the system and a vacuum operated shutoff valve shuts fuel off inside the injection pump.

What should I do if my Mercedes Benz won’t start?

Start the car and you should be able to get around 60 psi. When the engine is running and when you turn off the engine the pressure should stay steady. Always perform this test on a cold engine. Next, make sure that the fuel injector connections are secure and not loose. Check the fuel pump and the fuel pump relay.

Where does the vacuum go on a Mercedes 300D?

In all Mercedes diesel engines from the first 300D in 1975 up to the mid 1990’s, vacuum (suction) is used to turn the engine off – not electricity! In simple terms – there is a valve mounted on the rear or side of the diesel fuel injection pump. This valve has an arm attached to it that goes down inside the pump.

What are the problems with a Mercedes Benz?

Top 5 Mercedes-Benz no start problems 1 Engine Click, No Start 2 Engine Dies Right After It Starts 3 Car turns over, but it won’t start 4 The car makes a clicking noise but won’t start. Hint: Starter Problem or Low Battery 5 Key will not turn the ignition More …

What happens when catalytic converter is clogged in Mercedes?

If your catalytic converter is clogged you will notice a drastic drop in fuel efficiency and real struggle getting your Mercedes to accelerate. If the cat is completely clogged your car won’t even start.

Why does my Mercedes Benz engine misfire so often?

Engine misfires are one of the most common problems we see in many Mercedes-Benz cars. To be honest, it is not because MB cars are weak in this area, but because most owners forget that spark plugs are wear items and need to be replaced at the recommended intervals.

Where is the vacuum valve on a Mercedes 300D?

How does a diesel fuel pump shut off?

In simple terms – there is a valve mounted on the rear or side of the diesel fuel injection pump. This valve has an arm attached to it that goes down inside the pump. When vacuum (suction) is applied to this valve, the lever moves and shuts the fuel flow off inside the pump.

Why does my car keep running at idle?

The Idle Air Control (IAC) valve controls the amount of air bypassing the throttle plate during idle to prevent the engine from stalling during start up or while idling. In most modern vehicles, the amount of air that bypasses the throttle bore is preset from the factory and controlled by the car computer, so it can’t be adjusted.

Why does my diesel engine keep running after I Turn Off the key?

When you turn the key off on your Mercedes diesel, you may have noticed that the engine will not quit immediately. In some cases it may even keep running a second or two after you have turned the key to the off position before it finally quits. That alone should give you a clue that a diesel engine uses a different approach to shutting down.

What happens when you turn off the engine on a Mercedes diesel?

When you turn your key off, electrical power is interrupted and the engine quits immediately. Since a diesel engine does not run on electric spark, the engine has to be shut off by some other means. When you turn the key off on your Mercedes diesel, you may have noticed that the engine will not quit immediately.

Why does my diesel engine not shut off?

Since a diesel engine does not run on electric spark, the engine has to be shut off by some other means. When you turn the key off on your Mercedes diesel, you may have noticed that the engine will not quit immediately. In some cases it may even keep running a second or two after you have turned the key to the off position before it finally quits.

What causes the throttle body on a Mercedes to fail?

When there are throttle body malfunctions the wrong amount of air enters into the engine causing problems with air/fuel mixture ratio. Here is a close up picture of a Mercedes throttle body. Mercedes throttle bodies made by Bosch and VDO may fail. Luckily these units are repairable.

What to do when your diesel engine won’t shut off?

Open your hood and look for a small lever with a red label marked ” STOP.” Put your thumb on this lever and push hard towards the engine until the engine stops. If the linkage is worn or maladjusted you may have to push really hard to get the engine to quit.

What to do if your Mercedes W123 is bouncing?

Engine having a hard time shutting off? Make sure to check and or replace your injector pump shut off valve. Overload protection relays are located in different places on different chassis, so check for the location of yours and follow these instructions. Car bouncing down the road?

What should I do if my engine is having a hard time shutting off?

This is the first thing you should try Engine having a hard time shutting off? Make sure to check and or replace your injector pump shut off valve. Overload protection relays are located in different places on different chassis, so check for the location of yours and follow these instructions.

Why does my car shut down while driving?

The car is automatic (not manual). I’m driving in my car just like a normal person and all of a sudden the RPM starts dropping to zero then going back up to 9 a couple of times afterwards it shuts down. It doesn’t matter what the speed I’m driving at.

Where is the shut down button on a Mercedes Benz?

This is located behind your ignition tumbler. Remove the instrument cluster and remove the switch’s connector by wiggling it out very slowly and carefully. Remove the three screws, replace the unit, reinstall the three screws and reinstall the connector.

What causes a car to shut down while driving?

If the fuel filter is clogged, the fuel entering the system will be insufficient and the engine will shut down. Fortunately, it is pretty easy for you to replace a fuel filter. The third and final thing that could go wrong with your fuel system is a leaking fuel supply line.

Where are the overload protection relays located on a Mercedes Benz?

Overload protection relays are located in different places on different chassis, so check for the location of yours and follow these instructions. Car bouncing down the road? Fix it by replacing your worn out front shocks

What does it mean when your brake pedal is hard?

Brake Pedal feels hard when pushing on the brakes – This indicates that your brake booster is not working properly or is leaking. There is a seal between the booster and the master cylinder that often goes bad. If the seal is ok it could be a faulty brake booster but not always.

How to diagnose common brake troubles before replacing parts?

How to Diagnose Common Brake Troubles. Shake, side pull, binding, grabbing, grinding, squealing, overheating and soft / hard pedal issues. When it comes to brakes, you need to find out the problem BEFORE replacing parts. Sometimes this is harder than it sounds.

What causes brake pedals to jump when replacing a booster?

Be sure to test your vacuum system before replacing an expensive brake booster. Brake pedal jumpy (ABS systems) – This means your ABS system is trying to come on even when not needed. Usually caused by dirty or faulty wheel sensors, air in the system, or an ABS controller going bad. See Kents YouTube video on ABS brakes. UPS GROUND SHIP ONLY!

What causes a car to pull to one side when braking?

Master cylinder would be the last thing to suspect. Car pulls to one side during braking – This can also be caused by a sticking brake caliper or plugged rubber brake hose. Try to determined which brakes are dragging and check for sticking caliper first.

What should I know about my Mercedes 300D?

Good compression is paramount on a diesel engine. These cars use vacuum extensively. The vacuum lines become old and brittle with age and can cause all sorts of gremlins from door locks to engine shut off. Fortunately the vacuum system is (relatively) easy to diagnose and repair.

How can I tell if my Mercedes 300d is rust free?

Start with a vehicle that has a rust free body and under carriage. Next, run a compression test on all five cylinders. Good compression is paramount on a diesel engine. These cars use vacuum extensively. The vacuum lines become old and brittle with age and can cause all sorts of gremlins from door locks to engine shut off.

How do you change the shutoff valve on a Mercedes?

So out of the car you go and lift the hood to depress the stop lever. That whole operation is a pain, but Mercedes foresaw the valve failing, so they gave you a stop lever to use in a pinch. Replacing the shutoff valve is not hard, but if done wrong can destroy your engine.

Are there any problems with a Mercedes vacuum pump?

Typical Mercedes diesel vacuum pump. They are very reliable and easy to rebuild if need be. The most common failure is the check valve and internal diaphragm. The very first thing I do is make sure we have a constant supply of vacuum.

Where is the leak on a Mercedes vacuum?

Another area of great leakage is the metering valves on the main supply line. There is a 3 way and 4 way connector on the valve. Be very careful removing the 2 connectors from the supply line metering valve. The nipples are small and very fragile and prone to cracking.

Where is the check valve on a Mercedes?

Well different year cars have some differences but these are the main ones. The 2 yellow lines going to the check valve is for the door lock system. The solid brown line is the ignition switch supply line. The brown with blue stripe is to the fuel shut off valve. The green with yellow stripe goes to the HVAC system.

Why does my engine not shut off when the key is turned off?

This leak can be caused by one of the rubber fittings getting loose or accidently knocked off, or it can be caused by a leak somewhere else in your vacuum system (the most common on the 123 chassis is leaks in your door lock system). If your door locks stopped working at the same time the engine shut-off failed you will know the two are related.

Why does my vacuum not shut off when the key is turned off?

And the number one reason for sudden loss of vacuum is a leak somewhere in the lines. This leak can be caused by one of the rubber fittings getting loose or accidently knocked off, or it can be caused by a leak somewhere else in your vacuum system (the most common on the 123 chassis is leaks in your door lock system).

Where does the vacuum go when the key is turned off?

The vacuum then goes back to your ignition key assembly under the dash and back out to the shut-off valve on the back of your injection pump. When you turn your key OFF vacuum is routed through the back of the switch and on to the shutoff valve.

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