On social media recently, there has been a lot of discussion about footage of diesel trucks that are emitting white smoke and then suddenly die. The vehicle isn’t performing a massive burnout. You’re probably looking at a rogue diesel engine. No, it isn’t solely a problem with Power Strokes, Duramaxes, or Cummins, so stop slamming brands. It can happen to any diesel engine in any vehicle, but turbo-diesel applications are more common.
So, before you go commenting on that video in your newsfeed about how much better your Chevy is than the Ford, take a moment to learn more about what a runaway is and, more importantly, how to stop one if it ever occurs to you. You must either cut off the air supply or the fuel supply to halt a runaway diesel engine. The easiest alternative is to turn off the air supply because it is getting fuel from an unknown source. Finding something to block the intake can lower the RPM and cause the engine to shut down.
How common is a runaway diesel?
Diesel engine runaway is a rare event in which a diesel engine absorbs extra fuel from an unanticipated source and overspeeds at higher and higher RPMs, producing up to 10 times the engine’s rated output until it is destroyed by mechanical failure or bearing seize owing to a lack of lubrication.
How do you stop a runaway engine?
To bring a diesel engine to a complete halt, the air or fuel supply must be cut off. Because the fuel in a runaway engine is uncontrollable, the only effective technique to halt a diesel engine is to cut off the air supply. To accomplish this, the vehicle’s air inlet must be closed or sealed in some way. To do this, a positive air shutoff is used.
A positive air shutdown (PAS) is a throttle value (buttery fly or guillotine) that is often put in a diesel engine’s intake tubing. The valve is set to open by default and does not operate unless directed to. The user can activate the ‘PAS’ in the event of a diesel engine runaway by pressing a button that slams the throttle blade shut, starving the engine of air and causes it to stall.
Why won’t my diesel engine shut off?
Stop Lever on 671 Diesel Engine: For those who are unfamiliar with the diesel engine, there is an emergency shutoff lever that allows you to manually shut it down. Look under your hood for a little lever with a red sticker that says “STOP.” Place your thumb on this lever and press firmly against the engine until it stops. If the linkage is old or misaligned, you may have to use a lot of force to get the engine to shut down. The label on certain engines may have worn off. Look for this lever near the linkages on the top drivers side of the valve cover on older 4 and 5 cylinder diesels. Look under the drivers side of the intake manifold, immediately above the injection pump, on modern engines built after 1985.
To fix a diesel engine that won’t shut off, you’ll need to first have a basic understanding of how it operates. With a Mercedes gasoline engine, this problem nearly never occurs. That type of engine is powered by a 12 volt electrical spark from your car’s battery. When you turn your key off, the electrical power is cut off, and the engine promptly shuts down. Because a diesel engine does not use electric spark to start, it must be turned off in some other way. You may have observed that your Mercedes diesel engine does not turn off quickly when you turn the key off. It may even continue to operate for a second or two after you have turned the key to the off position before ultimately shutting down. That should be enough to indicate that a diesel engine shuts down in a different way. From the first 300D in 1975 to the mid-1990s, vacuum (suction) is utilized to turn off Mercedes diesel engines not electricity!
In simple terms, the diesel fuel injection pump has a valve positioned on the back or side. This valve is linked to an arm that extends down into the pump. The lever moves and shuts off the fuel flow inside the pump when vacuum (suction) is applied to this valve. The engine will not be able to continue to run without fuel. The engine will shut down immediately if the valve reacts rapidly. The engine may take a few seconds to shut off if the valve is sluggish. The engine will not shut off if this valve does not get vacuum or is broken. A mechanical vacuum pump placed on the front of the engine provides the vacuum for this valve. This pump pumps vacuum (suction) into the system using either a rubber diaphram or an aluminum piston. The vacuum then returns to your ignition key assembly under the dash before exiting out the back of your injection pump’s shut-off valve. Vacuum is fed through the back of the switch and on to the shutoff valve when you turn your key off. Your engine should shut off fast if the valve is working properly and the vacuum is not being drained out by a leak anywhere in the system.
The loss of suction to the fuel injection pump shut-off valve is the most common cause of your diesel engine failing to switch off. A leak anywhere in the lines is the most common cause of unexpected loss of vacuum. This leak might be the result of one of the rubber fittings becoming loose or being knocked off by mistake, or it could be the result of a leak elsewhere in your vacuum system (the most common on the 123 chassis is leaks in your door lock system). You’ll know the two are connected if your door locks cease working at the same time the engine shuts off. To solve your problem, think vacuum!
Mercedes Diesel Engine Won’t Shut Off When Turning the Key Off: Probable Cause is another video worth seeing.
Additional information is available at: If our quick repair tip doesn’t work, you’ll have to perform more debugging and work to address the problem. The first stage entails thoroughly testing your vehicle’s vacuum system. Check for dangling vacuum lines in and around the oil filter housing when you open the hood. Check the top of the valve cover for any loose lines. Examine the rubber connector fittings to ensure that all hard lines are securely connected. Those connectors should be replaced if the hard lines are loose in the rubber connections. A vacuum service kit with an array of those connectors is provided. Locate the vacuum lines for your door locks on a 123 chassis diesel and plug them off to see what happens (they are the two large yellow plastic lines going into the firewall just inboard of your brake booster). If you find that all of your vacuum lines are in good working order, you may have additional work ahead of you. It’s possible that it won’t be a quick cure after all!
Many people mistakenly believe that if their lines are correctly connected and the diesel engine would not shut off, all they need to do is buy and install a new shutoff valve. You should have figured out by now that the problem might be caused by a variety of system problems. It might be something as basic as a broken vacuum hose or something as complex as a vacuum pump rebuild. “Don’t just throw pieces at a problem,” I’ve always stated. Be warned: you can waste a lot of money and never have it fixed! To identify which parts, if any, need to be replaced, first diagnose the problem. We strongly advise you to get Kent’s “Diesel Vacuum Source Troubleshooting and Repair” guidebook. This guidebook will guide you through the process of diagnosing your diesel’s vacuum system step by step. Most 240D 300D 300CD 300TD 300SD 190D 300SDL 350SD 350SDL and S350 with vacuum controlled engine shutoff are covered by this manual. We have a convenient kit if you don’t have a vacuum hand pump tester. We have everything you’ll need to fix the problem, but we strongly advise you to troubleshoot it first!
Why does my diesel take so long to start?
It’s the middle of the summer, and your diesel engine refuses to start. Cold-weather issues are well-known and quite common, such as utilizing summer-grade fuel in the winter, a poor glow plug system, difficulty cranking, or thick, cold oil.
Summer, on the other hand, brings with it a whole new set of issues. If your diesel refuses to start, there are a few things to examine.
If you suspect a problem with gasoline distribution, there are a number of things to look for.
- Make sure the gasoline isn’t contaminated with air. If the engine dies soon after starting and is difficult to restart, this is the most likely cause. Air might enter the system through leaks in the fuel lines or pump.
- Fuel filters that are clogged. Fuel filters should be changed every 20,000-40,000 miles, so if you haven’t done it recently, this is a good place to start.
- If a new fuel filter doesn’t fix the problem, and the problem is getting worse on a vehicle with a higher mileage, it’s time to replace the pump. When you turn the ignition switch on, listen for a clicking sounds if the vehicle won’t start at all. If the click is missing, the solenoid is most likely to blame. If you hear a click but no fuel is being pushed through the injector lines and nothing is obstructing the lines, the pump needs to be replaced.
In comparison to gasoline engines, the pressure in a diesel injector is normally relatively high, however it can decrease over time. You can check the injectors’ opening pressure to see whether it’s too low or too high, as either could be troublesome.
Your injectors may be dirty if you notice a rough idle, a decrease of power, or white smoke in the exhaust on occasion. If you observe black smoke coming from the exhaust, it’s most likely due to a leaking injector. To see if your injectors are bad, check the temperatures of the cylinders or the resistance of the glow plugs (which increases as the temperature rises).
Diesel fuel, unlike gasoline, can provide an excellent home for certain microorganisms. The bacteria grows better and faster as the temperature outdoors rises. This is the most likely cause of a clogged fuel system if you notice a sulfuric odor or a black or green coating in the fuel tank. You’ll need to drain and clean the fuel tank with a biocide to get rid of it. If other elements of the system are dirty, such as the fuel lines or injection pump, you’ll have to clean those as well. To prevent the germs from returning, add a little extra biocide to the gasoline tank when you refill it.
The replacement of filters, for example, is an inexpensive and simple repair for some causes of hard starts. Others can take a long time and cost a lot of money. Ask the specialists at All in the Wrist Auto and Diesel Repair if you’re sure you’ve located the problem and that it’s rectified properly. All of your diesel maintenance and repair needs can be handled by their trained diesel specialists.
What happens when a diesel engine runs out of oil?
Your vehicle’s lifeblood is engine oil. It is required for the proper operation of your engine. Any lack of engine oil, or even unclean oil, will result in extreme engine wear, and running a car low on oil can result in some fairly disastrous circumstances.
Your engine will break down if you run out of oil. Fast moving elements with a lot of potential friction can be found inside the engine. The engine oil is the lubricant that keeps parts sliding smoothly against each other rather than grinding them down. When the engine runs out of oil, it begins to grind and ultimately seizes, causing the car to stall. Your engine will be harmed, if not completely destroyed. Many drivers will not be aware that their engine oil is low until it is too late. More diagnostic instruments, such as an engine oil pressure sensor unit and dashboard tools, are available in newer vehicles, which may assist in identifying low oil issues. Drivers in older vehicles may often have to manually check the oil because the “check oil” dash light will not alert them to a low oil problem.
Will a CO2 fire extinguisher stop a runaway diesel?
Diesel engines are capable of running on nearly any fuel. This is a huge advantage, but it also has a deadly weakness. When a turbocharged diesel’s oil-feed line or seal fails, oil is pumped directly into the combustion chamber. That’s a diesel engine on the verge of exploding. Unless the air intake is blocked or the air is displaced with CO2, the operator cannot stop the engine because it is now operating on motor oil and will be destroyed by mechanical failure or bearing seizing. Directing a CO2 fire extinguisher into the air intake is the safest approach to halt a runaway diesel engine. Take away one part of the fire triangle, and the flames will go out, just like we learnt in fire school.
How do you stop a Duramax runaway?
Registered. Defueling will not stop a diesel engine that is running away owing to gas or oil in the intake. The only way to turn it off is to turn off the air supply.
How do you warm up a diesel engine?
If the temperature is below zero degrees Fahrenheit, you should allow your engine to warm up for up to seven minutes. Warm-up time should be three to five minutes if the temperature is between zero and fifty degrees. Warming up to above fifty degrees takes only one or two minutes.