240D help, loss of power
#1
09-17-2008, 02:00 PM
240D help, loss of power
I have recently converted my '82 240D, though I haven't used any oil yet. While going up a steep hill that I am usually able to take in 2nd gear I started to lose power and roll backwardstowards the top. I had to finish off the hill in 1st. Since then while taking any grade my car will start to jerk or stutter in 3rd at around 33 mph, shifting up will simply worsen this. All of this has been city driving. Finally, while trying to get on the freeway it of course started to happen again. With many cars behind me I tried to get up to speed though once I reached around 44 mph the car would not go any more. After a few minutes she started to accelerate but trying to be safe I got off at the first exit. In town with no grades I seem to be fine as long is I don't go over 40 mph. I'm hoping this is a goof-up from the install and not my car about to die. Please help.
#3
11-26-2010, 05:23 PM
Sounds like a fuel supply problem I had recently with my 1981 240D showing up as semi-random loss of power.
Locate the primary and the secondary fuel filters. They are on the left side of the engine compartment (as viewed from the drivers position).
The secondary filter is attached to its bracket near the left front of the engine. There are numerous pipes attached to the bracket and a central bolt secures the actual filter tightly under the bracket. The filter looks just like a spin-on oil filter but it is NOT, it is secured by the central bolt. Near this central bolt is another bolt that
secures three tubes. This bolt is the bleeding bolt, the highest point in the system, that is loosened to let air out of the fuel lines and filters whilst operating the manual priming pump.
The primary filter (the fuel goes through this one first) is a small white translucent plastic filter
with rubber hoses connecting one end to a metal supply line from the fuel tank and the other end to the lift pump on the engine side which pumps fuel from the fuel tank to the injector pump. This lift pump has a white plastic **** which is unscrewed then pushed/pulled to operate the manual priming pump used to manually pump fuel from the tank and drive air from the system out the loosened bleeding bolt.
If you have significant resistance pumping fuel from the tank using this manual priming pump (with the bleeding bolt loosened and new filters installed) then it is the strainer inside the tank that is plugged. The fuel should pump easily. If you see bubbles coming into the plastic primary filter while pumping, these are likely fuel vapor bubbles produced by the low pressure of you pulling on the manual priming pump. At this point switch the rubber hoses on the fuel tank pipes: connect the hose from the plastic primary filter to the return pipe and connect the return hose to the supply (suction) pipe. Try the priming pump again. It is very likely that fuel will flow easily. Tighten the bleeding bolt when the air stops coming out and you are ready to go.
When starting the engine after doing any fuel work keep the rpm's up for a minute or two to flush all the air out because you will always have some bubbles you must get through the system.
Personally, I would be reluctant to put the hoses back the way they were, at least for a while. I
would much rather change the plastic primary filter a couple of times than pull the tank strainer to clean it. The car will give you plenty of warning of fuel starvation so you can change the primary filter at a safe location.
However, if you feel confident that operation of the engine has sufficently flushed the tank strainer, by all means put the hoses back. Now that you understand the situation and how to remedy the clogged tank strainer problem you could actually do it blindfolded!
Don't forget to flush the air out whenever you open the fuel system.
Always carry a set of filters (primary and secondary) and associated tools (screwdriver and 8" adjustable wrench or proper mm wrenches).
95% of diesel problems are caused by an insufficent supply of clean fuel.
Hard starting, especially in cold weather, is often due to bad glow plugs. To test the glow plugs, remove their wires, then check continuity from the place the wires were attached to ground with a ohm meter. They should read low ohms. High ohms means they are open and must be replaced.
Alternatively, after removing the glow plugs' wires, hold one end of a test wire on the battery hot terminal and touch the other end to each glow plug's electrical connection. You will get sparks if the glow plug is good, none if it is dead.
Note to Mercedes engineers: Next time fit a slide-out, easily removable, strainer in the fuel fill pipe to catch trash and NO strainer inside the tank. This strainer is only to protect the supply pipe from becoming plugged by large trash. A larger supply pipe and primary filter would be nice too.
I sincerely hope it keeps someone from going through the grief I had on on I-10 last week.
Locate the primary and the secondary fuel filters. They are on the left side of the engine compartment (as viewed from the drivers position).
The secondary filter is attached to its bracket near the left front of the engine. There are numerous pipes attached to the bracket and a central bolt secures the actual filter tightly under the bracket. The filter looks just like a spin-on oil filter but it is NOT, it is secured by the central bolt. Near this central bolt is another bolt that
secures three tubes. This bolt is the bleeding bolt, the highest point in the system, that is loosened to let air out of the fuel lines and filters whilst operating the manual priming pump.
The primary filter (the fuel goes through this one first) is a small white translucent plastic filter
with rubber hoses connecting one end to a metal supply line from the fuel tank and the other end to the lift pump on the engine side which pumps fuel from the fuel tank to the injector pump. This lift pump has a white plastic **** which is unscrewed then pushed/pulled to operate the manual priming pump used to manually pump fuel from the tank and drive air from the system out the loosened bleeding bolt.
If you have significant resistance pumping fuel from the tank using this manual priming pump (with the bleeding bolt loosened and new filters installed) then it is the strainer inside the tank that is plugged. The fuel should pump easily. If you see bubbles coming into the plastic primary filter while pumping, these are likely fuel vapor bubbles produced by the low pressure of you pulling on the manual priming pump. At this point switch the rubber hoses on the fuel tank pipes: connect the hose from the plastic primary filter to the return pipe and connect the return hose to the supply (suction) pipe. Try the priming pump again. It is very likely that fuel will flow easily. Tighten the bleeding bolt when the air stops coming out and you are ready to go.
When starting the engine after doing any fuel work keep the rpm's up for a minute or two to flush all the air out because you will always have some bubbles you must get through the system.
Personally, I would be reluctant to put the hoses back the way they were, at least for a while. I
would much rather change the plastic primary filter a couple of times than pull the tank strainer to clean it. The car will give you plenty of warning of fuel starvation so you can change the primary filter at a safe location.
However, if you feel confident that operation of the engine has sufficently flushed the tank strainer, by all means put the hoses back. Now that you understand the situation and how to remedy the clogged tank strainer problem you could actually do it blindfolded!
Don't forget to flush the air out whenever you open the fuel system.
Always carry a set of filters (primary and secondary) and associated tools (screwdriver and 8" adjustable wrench or proper mm wrenches).
95% of diesel problems are caused by an insufficent supply of clean fuel.
Hard starting, especially in cold weather, is often due to bad glow plugs. To test the glow plugs, remove their wires, then check continuity from the place the wires were attached to ground with a ohm meter. They should read low ohms. High ohms means they are open and must be replaced.
Alternatively, after removing the glow plugs' wires, hold one end of a test wire on the battery hot terminal and touch the other end to each glow plug's electrical connection. You will get sparks if the glow plug is good, none if it is dead.
Note to Mercedes engineers: Next time fit a slide-out, easily removable, strainer in the fuel fill pipe to catch trash and NO strainer inside the tank. This strainer is only to protect the supply pipe from becoming plugged by large trash. A larger supply pipe and primary filter would be nice too.
I sincerely hope it keeps someone from going through the grief I had on on I-10 last week.
Last edited by Bandership; 11-26-2010 at 05:47 PM. Reason: spacing, readability, clarity
#4
11-28-2010, 11:49 AM
There is also a Filter Screen in the bottom of the Fuel tank that can get Plugged. You can test for this by having at least 1/2 tank of Fuel and swapping the positions of the under the hood Fuel Inlet Hose with the Fuel outlet Hose.
This will bypass the Fuel Tank Screen and draw fuel from a higher position in the Fuel Tank.
Another thing that can make the Car slow is if the Throttle Linkages adjustment is sloppy (sometimes due to the Bell Crank on the Fire Walls bushing being worn). This keeps the Throttle lever on the Fuel Injection Pump from moving far enough.
If you have the Old style Hand Primer with the shiny Aluminum body it is often the source of an Air leak.
This will bypass the Fuel Tank Screen and draw fuel from a higher position in the Fuel Tank.
Another thing that can make the Car slow is if the Throttle Linkages adjustment is sloppy (sometimes due to the Bell Crank on the Fire Walls bushing being worn). This keeps the Throttle lever on the Fuel Injection Pump from moving far enough.
If you have the Old style Hand Primer with the shiny Aluminum body it is often the source of an Air leak.
#5
12-01-2010, 09:18 AM
As crazy as this sounds, check the primary (plastic) fuel filter for a hole or air leak. I have always run MANN filters until this last change cycle I had to settle for a WIX. It had a pinhole in it causing the same issue that you are having.
#6
12-17-2010, 03:23 PM
I had the same issue in my 79 300cd. The fuel tank had all kinds of issues with gummed up fuel. Drained the tank, new filter and wvuala - problem solved. I probably need a new fuel tank next summer but should be fine til then.
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