hi,
i would like to buy a 79 240d that has been sitting for about 2 years. it's a 4 speed car that came from florida with a 100,000 miles and has no rust.
upon trying to start it, the engine turns over but doesn't even try to start.
i replaced the inline filter only because it didn't have a small enough oil filter wrench to fit on the spin-on filter.
i disconnected the fuel lines at the injectors and pumped the manual pump until fuel came out of the fuel lines.
i then tried to start it again with the same result.
any advice would be appreciated.
thanks,
steve

 

If you have a Spin-on Fuel Filter you do not need an Oil Filter Wrench to Change it. There is a Bolt in the center of the Fuel Filter Housing you can turn to remove and install the Filter.
When the Filter is out pull out the central Bolt and you will see an O-ring at the bottom and there is an Aluminum or Copper Crush Washer/Seal Ring that goes on the Top under the Bolt Head.
If you pull out that Bolt and it has 2 O-rings on it someone has changed the Fuel Filter Housing to a later date of housing and there is no Metal Crush Washer that will go under the Bolt Head.

Before you install the Spin-On Fuel Filter fill it with Clean Diesel Fuel.
The other alternative is to install the empty Spin-on Fuel Filter and locate the Fuel Hand Primer on the side of the Fuel Injection pump.

If the Hand Primer has a hard round White or Black Plastic **** on it you need to unscrew it before you pull it up.

Pulling it up and pushing it down pumps the Fuel. When all the air has been pumped out you will hear a soft buzzing or squishing sound coming from the Fuel Injection Pump. When you hear that continue to pump some more and hope all the Air is out. (This bleeds the Air From the Fuel Supply System.)
When you stop shove the Pump Plunger down to the bottom and screw it in snug.
If that Pump Plunger was leaking while you were pumping the Fuel it is time for a new Hand Primer.

If the Hand Primer on the Fuel Injection Pump is black and covered with Rubber that is the new style Hand Primer and all you have to do is push down on it and release it to pump. (This bleeds the Air from the Fuel Injection Part of the system. If Air gets trapped in the Fuel Injection Tubing it compresses a lot and moves only a little bit because the Injectors take a lot of pressure to open. You can easily kill a used Battery and over heat a Starter trying to crank the Engine and get the Air out.)

If you replace the Old Style Hand Primer you should replace it with this new rubber covered one made by Bosch. Don't use one of the copies of that pump.

If you think you got Air in the Fuel Injection Steel Tubing you need to loosen the Tubing Nuts at the Injectors and crank the Engine till Fuel comes out of them. That allows the Air to get out fast.

For hard starting besides the Glow Plug issue; when a Car has sat that long a lot of the Fuel in the Fuel lines has likely gone back towards the Fuel Tank. If you did not start pumping on the Hand Primer before you started the Mechanical Lift/Fuel Supply Pump that the Hand Primer is attached to has to pull that Fuel up to it and that takes time and a lot of cranking of the Engine.

 

I am not entirely sure if the 1979 240D has a Glow Plug light or not.

If it does have one you should watch your Instrument Cluster and turn your Key and see the Light go on. You want to keep your Key in that position at least until the light goes out and then turn the Key more to start the Car.

If the Light does not go on or the light flashes intermittently is an indication you have some issue with the Glow Plug System.

There will be a Fuse on the Fire Wall or the Fuse will be in the Glow Plug Relay itself. The Fuse in this case is just a strip of Metal screwed down.

Another note on starting. The Glow Plug Light sort of indicates the minimum time for you to have the Glow Plugs on. If you keep the Key in that Preglow position the Glow Plugs will remain on until the Timer in the Relay shuts off.
On My year and model that is close to 30 seconds.

 

hi guys,
thanks for all the info.
i removed the buss bars and checked the glow plugs with a dvm and found between 1/2 and 1 ohm.
i again loosened the fuel lines and cranked the engine and saw fuel shooting out about 2-3". i tightened them back up, waited for the glow plug light to go out (about 10 seconds) and cranked it about 10 seconds 6 times waiting about a minuet in between.
it still doesn't try to start.
isn't there an electric fuel lift pump in the tank or inline to bring the fuel to the injection pump? i turned on ignition with the inline filter disconnected and nothing came out.
i will change the spin on filter next but since the fuel is getting to the injectors, i don't thing it is the problem.
thanks for help.
steve

 

No Electric Fuel Pump on the these old Diesels unless someone added one.

And in fact the original Fuel Supply/Lift Pumps will function reliably beyond 20 years and are entirely adequate for the job.

Note: If you disconnected the Plastic Primary Filter from the Hose you have allowed the Fuel to migrate back towards the Fuel Tank and let in a lug of Air.
If the Engine has not been cranked I would reconnect the filter and I would get on that Hand Primer and until I could hear that squishing buzzing sound I spoke of before. And, as I said pump some more to try to get the Air out of the Fuel Supply System and hopefully out of the Fuel Injection System.

If you have no Diesel Experience there it is going to take time to develop some knowledge about them.

Just as a side note. In the US Electric Fuel Pumps were not common on Gasoline Engines until Gasoline Fuel Injection was used on them. Mainly because the Electric Fuel Pump also provided the Fuel Injection Pressure.

On your Mercedes the Fuel Supply System pules the Fuel from the Fuel Tank and pushes the Fuel Through the upper part of the Fuel Injection Pump; past a Fuel Pressure Relief/Over Flow Valve and returns most of the Fuel Back to the Fuel tank (that Fuel is used to cool the Fuel Injection Pump).

In side of the upper portion of the Fuel Injection Pump are Elements (Plungers and Barrels) that create the High Pressure to the Injectors and the Injector controls the pressure of Injection by way of a Spring Loaded Pintel (somewhat like a Needle Valve) in the Injector Nozzle.

So the lower pressure Fuel Supply System only has to supply enough pressure to fill the Elements properly. I don't recall the specific figure from the Manual but at the highest pressure at about 3000 rpm is 18 psi. I don't recall the idle pressure.
The Fuel Pressure Relief/Over Flow Valve controls the Fuel Supply System Pressure.

Since starting a Diesel Engine is all about having enough Heat in the Cylinders; If this year and model already has a Block Heater (normally for Winter use) You might consider plugging that in and getting the Coolant nice and hot.

 

One advantage you have is a manual transmission. In that case it's possible to tow the car (with another car) up to 10-15 miles per hour with the car in second gear, clutch pedal depressed, and then engage the clutch. This will spin the engine without wearing down the battery, and you can actually spin the engine long enough to warm it up (heat of compression in the cylinders). If it's injecting fuel it should start even if the glow plugs are kaput.
If the engine doesn't start within a couple hundred yards of towing like that, it's very likely that the fuel injection system isn't getting fuel to the cylinders. First thing to check is that the injection shut-off (a manual lever on top of the injection pump that should have a sticker that says "engine stop" on it. If that lever isn't in "run" position the injection won't work. Otherwise, it may be air bound, or the pump defective. Two ways to check this: 1) With someone cranking the engine, touch one of the steel fuel injection high pressure lines (that run from the pump to the injectors) Touch it lightly with the tips of your fingers. There should be a "ping" feeling as the injector valve opens and then slams shut. If you're not sure, loosen the nut that secures the high pressure line to the injector. Use a bit of paper towel to catch spraying fuel. With the line cracked, the "ping" should go away, and then return when you tighten the nut back up. 2) Remove one of the injectors and then connect it back to its high pressure pipe. Crank the engine, and watch for a fine spray of fuel from the injector every fourth revolution of the engine. CAUTION!! The injector spray is under very high pressure. DO NOT GET YOUR SKIN IN THE SPRAY! because the spray can blow right through your skin, and cause serious injury, like infection, removal of affected skin, skin grafts, etc.
On the subject of towing cars, I use nylon rope, at least 1/2" in diameter. Nylon is stretchy, and makes a nice shock absorber. If you only have chain or non-stretchy polyester rope, I use an old tire as a shock absorber. The tire is not mounted on a rim, and has a short loop of rope or chain through the center hole in the tire. The loop goes over the ball hitch of the towing vehicle (or gets tied through the towing point under the rear bumper). The tow rope also gets tied around the tire, and the business end gets tied around the towing point under the FRONT bumper. If you tie those knots with a bowline, you'll be able to untie them. Any other knot, you'll end up using a knife.
The longer the towrope, the better, up to about fifty feet. More tow rope absorbs shocks, and the greater the distance between tow and towed vehicles the less chance that a failure in timing will lead to a bumper crash. The best place to do this is on an untraveled dirt or gravel road, or an empty parking lot, or a deserted street. If another car appears, stop and wait for them to clear your area. Towing a car like this is illegal in most places, but in 45 years of doing it occasionally I've never gotten a ticket. Once even had a sympathetic policeman turn on his bubble gum machine and provide an escort! But I wouldn't count on that. Hope this is helpful.

 

I've had two 123's with Ottomatics, and had heard that they could be pulled to turn the engine. Neither one did that, either when towed or when rolling down a hill at highway speed. Is there a trick to getting the torque converter to lock up and roll the engine?