Home Technical Discussions Mercedes-Benz 240D/300D 1977-1985 (W123)

Mercedes-Benz 240D/300D 1977-1985 (W123) Mercedes Benz 240D injection timing


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Last Post: Sep 27, 2013 12:21 AM Last Post By: wajaka
Knightrider9

Posts: 25
Registered: 08/06/06
Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 1:04 PM
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I've got 2 service manuals for my 1982 mercedes benz and both offer conflictin procedures for setting the fuel injection timing! How do you know when you have it right? How can you tell when it is set correctly at 26 degrees BTDC?
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 2:14 PM   in response to: Knightrider9 in response to: Knightrider9
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What model mercedes do you have...?...The best method is the drip method...easy to do and very accurate...you remove the #1 line and take the little spring and valve out of the #1 element on the IP....and attach the drip tube to it....If you need more detailed info ...post back.....Do Not!....remove anything else on the IP element other than the fuel line to get to the parts in the element as the two nuts holding the element in place are actually part of an adjustment and are set on a test bench.........kevin
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 2:46 PM   in response to: Spiritburner in response to: Spiritburner
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I have a Mercedes Benz 240D. I haven't tried the drip method because my manual says to turn the crankshaft until the timing marks are aligned to specs. Simple enough, but nowhere in specs can i find out what these specs are!! According to my book, the true specs are 26 degrees BTDC when it is set properly and the photo shows the timing mark at OT. But the disclaimer says this photo is only to show where the timing marks are! Is the drip supposed to be as specified when the motor is at OT?
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 2:47 PM   in response to: Knightrider9 in response to: Knightrider9
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1982 240D
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 3:35 PM   in response to: Knightrider9 in response to: Knightrider9
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Do you have the drip tube...?...I can show you the easy way to do this....you are going to need to wire the IP lever in the full load position and remove the vacuum line from the shut-off device located on the back of the pump.....and have something to turn the crankshaft with...I use the power steering pulley nut if you can turn it with that...also a good idea to disconnect the glow plug relay......kev
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 3:47 PM   in response to: Spiritburner in response to: Spiritburner
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I don't have the "specified part, drip tube" but I do have a broken injection line I cut the end off of. Looks to be the same thing to me! Why disconnect the glow plug relay? Duane
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 3:51 PM   in response to: Spiritburner in response to: Spiritburner
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Also, where should the timing marks on the vibration damper be at? 26?
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 3:54 PM   in response to: Knightrider9 in response to: Knightrider9
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I'm really dissapointed with the Haynes and Chiltons manuals! Large gaps in info and neither agrees with the other! references made to procedures are often wrong and not in the books where the index says to look if at all!
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 4:23 PM   in response to: Knightrider9 in response to: Knightrider9
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Glow plug disconnect for safety...it just unplugs after you slide cover off....Timing marks are on pulley....clean real good all the way around as you will start gently pumping the hand pump at about 50 degrees before TDC....your cuttoff line will work fine ...I know what you are talking about with the lack of info...I have done this several times and it is not as bad as they make it out to be...tell me what you have done so far and we will go from there...kev
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 4:36 PM   in response to: Knightrider9 in response to: Knightrider9
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Timing marks on my 240D are 24 degrees before TDC ...yours may be 26 degrees if that is what it calls for mine is a 1980 model....Best just to check yours before loosening the 4 IP nuts and bolts...3 on the IP flange and one on the bottom rear of the IP.... kind of tricky to get to that one....that is why I say just check timing before trying to adjust...It may be Ok....
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 4:47 PM   in response to: Spiritburner in response to: Spiritburner
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Mine calls for 26 BTDC. I've replaced my timing chain after having my head redone at a machine shop. 120,000 original miles as far as I can tell, odometer works! replaced the chain just as required in the book, Haynes, using the old chain to pull through the new one. got the piston and valve timing correct, but fuel pump timing was off 180 degrees! removed fuel pump and rotated it to the pump shaft alignment marks as specified and pictured on pump. Here's where it gets sketchy, Chilton says to stop the crankshaft at 45 BTDC and make the fuel pump follower jump 2 teeth install and set at 26, weird. Haynes is even less specific. Has the drip method, but application is sketchy. there is a point where the fuel pump will spurt out fuel when primed with the hand pump like a gusher at almost 90 degrees of rotation.
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 4:55 PM   in response to: Spiritburner in response to: Spiritburner
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I know mine will be off as much as I've had the engine apart! The fuel pump has been out of the car too. I bought this thing for $900 as an Arizona rust free car and it has had a $1300.00 paint and refinish job. Intend to go biodiesel since my Dodge Ram Cummins runs so well on it! The engine surges ans mokes more now and I would suspect the timing is too far advanced. Also at low RPM it performs poorly and will not run in drive while the AC is on!
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:08 PM   in response to: Knightrider9 in response to: Knightrider9
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Ok...Sounds like you know about these engines enough....Do not worry about the fuel coming out before the timing point of 26 degrees...that is what it is supposed to do...this is what had me confused....what is happening is the fuel is flowing through the pump as you are gently putting pressure on it with the hand pump....this is occurring right up to the (beginning of delivery)...As you rotate the crank very slowly while hand pumping....you will reach the point when the fuel will just stop flowing out of your drip tube if you have removed the spring and valve in the #1 element.....what has happened here is the #1 IP plunger that pushes the fuel out of the drip tube is beginning its upward travel so it has blocked the inlet and outlet ports down in the guts of the IP...this is the point you are looking for....then read your pulley and pointer to see where they are....the fuel is flowing out of the drip tube and through the IP back to the filter before the delivery piston has closed the ports...this is why the spring and valve need to be out of the #1 element... The fuel is still flowing through the IP and back to the filter as the timing point is reached as you are hand pumping....It just stops coming out of the drip tube because the IP piston has picked up all the fuel it needs and has shut off the fill and spill ports until it is through the delivery cycle after it pushes the fuel column to the injector......I can explain more if needed....it took me a while to catch on to this.....kev
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:12 PM   in response to: Spiritburner in response to: Spiritburner
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It seems as if my timing is too far advanced. The fuel begins to stop flowing at 45 degrees and comes to a complete stop at 40 degrees! I take it should come to a stop at 26 if that is what my specs are?
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:15 PM   in response to: Knightrider9 in response to: Knightrider9
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Make sure all 3 of your fuel filters are new....that can sure rob the power..... same with air filter...I run 100% of my own home brew biodiesel...these cars love the stuff...made about 30 gallons this weekend....I will check my email frequently till we get your timing right...I was an automotive machinist for years... about to do the head on mine also......your 240D should run like a top after all this...kev
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:23 PM   in response to: Knightrider9 in response to: Knightrider9
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That is correct....26 degrees Before top dead center.....are you reading the leading edge of the pointer and not the cut out circle ?...This is where you should get complete drip tube fuel stop...you do have the parts out of the element...?...some people try a (well up ) test with the parts still in there....that is misleading....I have a friend here that owns a Bosch IP shop so I know this info is correct....sounds like you are on the right track...and will need to adjust the IP timing device to the chain about 25 degrees....what is that..? about 3 links...? keep me posted....kev
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:29 PM   in response to: Spiritburner in response to: Spiritburner
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I'd love to make my own fuel, but working as a truck driver here in the valley, I don't have the free time like I used to! This area is growing so fast and I do have access to Western States petroleum where I can buy Biodiesel at $2.99 per gallon in any quantity I want. The National biodiesel board has listings for Bio in every state and I don't have to spend much free time processing used cooking oil! It's also federally ASTM compliant and has consistent quality and quantity for further study! The city of Phoenix will run all city vehicles including busses on B100 in a 2 year emission test to study the smog effects and pollution compliance on our evironment here in the desert! If you are interested in becoming a member of the National Biodiesel Board, membership is free and we all get to voice our opinion and keep up on the latest details of the National Biodiesel movement through the National Bio Board, which was started by US farmers!
Spiritburner

Posts: 513
Registered: 03/01/04
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:32 PM   in response to: Knightrider9 in response to: Knightrider9
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Just checking to see if the IP lever is wired in the full throttle position and the vacuum line is disconnected from the shut off valve.....
Also important to make sure you are coming up on the power compression stroke by looking at your intake/exhaust cam lobes as you approach the 26 degree mark....
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:34 PM   in response to: Spiritburner in response to: Spiritburner
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Oh no! Timing device???? I was pulling the pump out of the mount long enough to turn the spline shaft to line up the timing marks on the fron of the pump to the No 1 position! Does access to this "timing device" require removing the Vaccuum pump installed in fron of it to gain access?
Knightrider9

Posts: 25
Registered: 08/06/06
Re: Mercedes Benz 240D injection timing
Posted: Aug 6, 2006 5:36 PM   in response to: Spiritburner in response to: Spiritburner
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I found my compression stroke by pulling out a glow plug and feeling compression beginning to build while watching the timing marks. This also made it easier to turn the engine, not having to push against compression!

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