Questions involving I.P. timing.
 

Hey guys,

1979 240d....
I had a post on here about a rough idle when warm, Ive done almost everything I can do myself with no improvement. I've decided to check the Injection pump timing, but am having a strange problem...

I have the mercedes factory service manual for my engine, and it lays down pretty clearly the procedure for timing the ip. I have the special drip tool and I checked the timing EXACTLY as outlined in the manual. The only problem is, it doesnt start dripping untill about 10 AFTER top dead center! Its supposed to be 24 before. I even pulled the valve cover off to make sure I was on the compression stroke for number one (had both cam lobes up on #uno while lined up with the marks on the crank pulley and the notch on the cam) I had the regulator on the ip set to WOT, as outlined in the manual, as well as removed the spring and that other little piece from the i.p. before putting the tool on.

Am I looking at the marks on my crank pulley correctly? It seems like I should be looking to time it at the marks to the LEFT of the zero mark, because thats 'before' that piston hits the top. The car idles rough, but it doesnt run THAT rough, i'd think 30 degrees off would make it pretty much undriveable. Is there something wrong with the I.P.?

I am officially stumped, and I dont want to muddle with my car any further until I have a little more insight..

P.S. there appears to be NO cam chain stretch. There shouldn't be any need to mess with the pump, but its free and i had the tool. Also the engine sat for a very long time without being run, and i wasnt certain if that would have some effect on the pump.

Thanks a mil

Seth

Well Seth, be sure you know what you are doing when messing with that IP. Personally, I will never ever touch mine, but some of the guys will go for it. Anyway, go back to the Factory SM and check it out and verify the cam shaft timing by the way they set it. I have seen it on my CD manual and it is pretty straight forward

If the timing is that far off, you are going to need to remove and re-index the IP. You won't have enough adjustment range to set the timing correctly.

If I were you, I would remove the IP and re-index it. That way, you can be sure of your starting point in the process. (This assumes that you are 100% sure that you have followed the FSM directions completely.)

I wish there was a class i could take on JUST this engine...theres no shop in town i'd trust with this, except the dealership and thats 120 bucks an hour.
I've never heard of re-indexing the pump, is there a thread on this website?

What would cause it to be that far off? I'm confident i followed the procedure in the manual. Is there a thread with pictures on this website for checking the IP timing? If not we need to make one, after i figure out how to do it, ha ha. I guess i need to talk with someone whos done this procedure before.. theres no one in town that i know. Any tucsonans out there? If something caused the pump to need to be re-indexed, would i be looking for mechanical failure in the pump? is it possible it slipped on the timing chain, from being started after sitting a long time and being cranked for a little while with probably little oil in the pump? Wouldnt it run alot worse if it where really this far out of time? Could a bad hand pump not be pushing enough pressure through the ip during the procedure?

Thanks again!

Seth

There might be another possible for you. Fast lane (the pictures are from Fast Lane special Tools for Diesel page 58).

The timing tools in the pictures go into a Plug that you remove from the side of the Governor Housing.

On my 84 I used the one in the left picture. (Note: The timing is done 15 degrees After Top Dead Center.)

You most likely need the one in the right hand picture.

It would be best if you could post a pic of your Fuel Injection Pump so I could see what type of Plug you have on the side of your Governor Housing.

So you have the 615,616,na 617 paper manual ?
Hold what you have until you are sure of what you have/ are doing..
Whatever you do do not pull the IP out of the engine...we had someone do that lately without marking stuff first... sent chills through many of us who feel like Junkueyardjim..... rather does most anything else than touch the IP...

i dont have a digital camera, but if you do an image search of an engine in a 1979 240d, youll most likely see what injection pump i have. yeah im not pulling that bad boy out any time soon.... I do have an extra engine in my driveway with known good parts, though... As far as a shaky idle when warm, what do you guys think about the lift pump? how often would one of these go bad, and what are the symptoms? This definitely feels like a fuel delivery problem. For those just tuning in, ive already done:

fuel filters
motor mounts
injector nozzles
fuel tank cleaned out
fuel hose
primer pump
valve adjustment
cracked each fuel line, not one cylinder stands out as culprit
compression test, all good
diesel purge

not just shotgunning this, all this stuff was in bad shape.

thanks for suggestions!

seth

There is no need to mark anything. The drive on the IP has its own marks. It's really a piece of cake. And it's going to be unavoidable if the timing is actually as retarded as stated.

Looks like you are following a plan.... you are way ahead of the game ...
Now, as far as I can figure.... you checked the fuel delivery by the book... found it was way off... and are wondering if that could be true before taking a chance on moving your ip to make it fit what the book says it should be ?
You did the 2mm movement of the number one cylinder intake valve already ? with regards to the chain ? and factored in the ' constant' before declaring ' the elongation ' ? based on which cam you have ?

If your timing was really 10 degrees late then it would most likely run very poor if at all, and you would have gray smoke, that smelled strongly of fuel.

If a lift pump is going bad fuel pressure will be low. I think your next step should be to put a fuel pressure gauge on it, and check both idle and running fuel pressures. If weak then look up "spring stretch" for the relief valve, this often gives low fuel pressure. You may also want to look at the hand/primer pump, it could be leaking air into the system. The lift pump itself rarely goes bad, not to say it can't just kind of rare.

As for rough idle it may also be idling to slow, do you have a tach to measure it?

this is a live action thread, since i'm working on it while talking to you guys...

why did they make these damn mac books white...

so even though I had new nozzles put in, i went ahead and put the fuel injectors in from my old engine, just to see if anything changed. Presto, about 80% of the shake went away! So evidently the injectors werent rebuilt properly. Unfortunately, ive already re-time my injection pump. Yes, i will accept all ridicule for this. But it's still confusing me on why it didnt start dripping untill so late.. So what im going to do while im having these injectors re-rebuilt, is put away the beer and get out the manual and get real about this timing thing. An yes, i turned the crank forward then back to make up for the slack in the hydraulic tensioner not being filled with the engine off while checking for stretch in the cam chain. not sure what you meant about the moving the intake valve 2 mm though...

So if anybody here has timed a pump before, my first question is: am i looking at the marks to the left or to the right of zero on the crank pulley?
And my second question thus far is: why is it that im able to get it to drip at the right place with the throttle down as opposed to WOT, despite the manual stating to have it at WOT?

You claimed no chain stretch...
how did you determine that ?
' live action thread '...LOL

I have not read anyplace in the Manual where ith has that you should turn the Engine Backwards. (In fact there are cautions not to do that at all.)

To the best of my knowlege you always turn the Engint Clockwise; viewed from the front of the Engine.

As you turn the Engine Clockwise the Before Top Dead Center degrees are going to show up first and the higher numbers will count down to OT which is Top Dead Center.
If you go past OT you are After Top Dead Center.

Ok, just for the record..... and I hesitate to mention this.. because I TOTALLY AGREE with your warning about NOT turning the engine backwards..
But....
on page 03.8-345/6 f2

"14 Reverse crankshaft for approx 10 degrees by means of combination tool .
15 Screw dial gauge holder with threaded sleeve to stud in the cylinder head.
16 Insert dial gauge and screw measuring extension to dial gauge.
17 Place measuring arm on valve stem with 2 mm preload.
18 Slowly rotate crankshaft with tool combination in direction of rotation of engine until the large needle of the dial gauge stops (TDC position)"

This is under the directions for replacing the TDC transmitter..
for the 617 Turbo engine... and page 03.4-345/6 in the 616,na617 manual.

10 degrees ATDC is a lot more than 10 degrees late.

Engines with start-of-injection only 10 degrees retarded run great. In fact, I would bet that the majority of W123's on the road today have timing that is in that ballpark.