beeman

I drove my 300sd sixty miles freeway, the car ran like a bird , I returned running on four cylinders, what a let down. Now which is the offending pot? It is not as tho' a person can short out a spark plug as in gas etc. I am guessing I have a faulty injector but there must be other possibilities. I need help on this one anybody please.

TMAllison

Assuming that it will start.....fire it up and crack the fuel lines at the IP ~1/8 turn, one at a time, then retighten. Idle should deterioate if that cyl is firing. If no change, you found the bad one(s).

beeman

Thank you TMAllison, the engine does start and I will do the procedure to-day.

beeman

#5 cylinder was found to be dead and we removed the injector and found at the very bottom a thin curl of metal hair thin and 3/4 of an inch long. How, why? We reassembled but that cylinder remains non-functional and so I will replace the injector.

TMAllison

Don't know what that would be; some sort of fuel contamination?

Teh next step is to swap that inj with another and see if the miss moves with the inj that came form the bad hole. That confrims the inj is the issuse and not compression or the IP.

EACH time an inj is torqued it OUGHT to receive a new crush washer. This protects the inj nozzle by sealing it from excessive heat exposure.

Bad inj's can be pesky. They can squirt a stream of fuel and burn a hole in a piston; have a bad spray pattern so the fuel doesnt ignite properly which sounds like Grumpy (one of the Seven Dwarfs) is in there with a big hammer trying to get out, AND he's realy realy mad; or can pop at the wrong time causing the engine to act like a missfire on a gasser. They can usually be repaired by pop testing, cleaning and/or replacing nozzles to restore a proper spray pattern and pop pressures.

240D 3.0T

This is right.

beeman

Thanks for the advice. I need to know more about injectors. The crush washer will be replaced. It sure would be great to have the MB special tool to remove inj with two flat sides on a round nut. Thanks again.

240D 3.0T

What are you talking about?

beeman

The inj has a round nut with two flat sides for a special MB socket tool. We removed the cam cover and removed the nut and the springs, needle and two washers. The bottom washer with a relief machined into it is very badly worn and the curl of metal came from this part. Swapping inj showed that the inj works fine in another cylinder so we are looking for another fault. The glow plug works fine tho' it was caked in black soot. I would like to remove the nozzle but this is difficult since I do not know the procedure. Does it simply pull out as there is a threaded sleeve that holds it in place or does it unscrew? We are thinking that the worn inj is allowing fuel into the cylinder on an unregulated basis. I am looking for an exploded drawing of an inj.

240D 3.0T

That is the precombustion chamber collar.

I strongly suggest you figure out what you're doing instead of guessing and randomly tanking things apart! If you keep this up you are going to be in FAR worse shape than a simple misfire.

beeman

Yes I appreciate your comment and this has occurred to me also. So far we have proved the injector is very badly worn. I have swapped inj with 5 and 4 finding that the inj is faulty but that is the inj from the PCC up only. We would like to remove this also and inspect. I was trying for a reasoned elimination of faults until I find it. I did not think I was randomly approaching this problem but I am surely looking for advice and your point is well taken.

beeman

I did not think I was randomly looking at this problem. I thought I was going thru' the order of finding the fault. If you have a better suggestion I am all ears. I plan to use special tool to remove nozzle and inspect. Meanwhile I have bought an '85 300 sd, same colour and in great condition. It drives fine with 376000 K. but I must get to the bottom of missing cyl on my '82.

TMAllison

No special tools required other than a vise and a wrench.

Short of pop testing the inj to see if it pops and sprays correctly you are not going to accomplish much by taking it apart and looking at it. If you do open it up you need to do so in a VERY clean environment. If you want to see how clean your garage is put a couple drops of diesel in a pyrex bowl, rub it around and leave it on the work bench for 30 minutes and see how much dust you collect. Each of those particles will foul your inj when put back together.

You also should not touch the inj nozzle with using gloves, the oils from your fingers will damage it.

beeman

Thank you for your constructive commentary and instructions. I have assured a clean environment and am now aware of the need to wear gloves if and when handling inj nozzles. I have found that the offending cyl has a working inj on a swap with number four. Could the nozzle of number five be at fault? I am only trying to work thru' the system step by step so far I am at square one

TMAllison

Checking the spray pattern, pop testing and then adjusting as needed using different sized shims (precisely machined washers) is the next step. One or the other aspect is bad. More than likely the former.

For ~$60 your best bet is prob to purchase a rebuilt inj and new heat sheild. Some big rig shops can test/balance them for $10-20 each. A new nozzle prob goes for $30. Its less time consuming for one only to just get a new one.

beeman

To that end I have tried a new inj but with no change. It seems to start with five and drop to four immediately. Could it be the nozzle? and if so how to check. Thanks again for your interest and time.





































can it be the nozzle?

TMAllison

The nozzle is inside the inj. If you installed a new/rebuilt one that should not be the problem. (You do know you can't use an old inj from a non-turbo in a turbo engine, right?)

Probably time to check compression, then a leak down test if that hole is low to try to determine if it is valves or rings.

240D can give you better advice going forward.

beeman

Yes TMA I know the difference in injectors. I tried a rebuilt inj but no change alas. Can there be a problem below the crush ring? A special tool is needed to lift out the pre combustion chamber and I am curious to know how that features in the mix. Does the nozzle determine the spray pattern? Can this be the fault?

TMAllison

The nozzle and pintle on its end, combined with the spring and shim establish the spray pattern and pop off pressures.

The part below that which the inj screws into is the pre-chamber. It is removable with a special tool and slide hammer. There is a small ball on the end of it that can break off with a really bad inj that is popping early, popping late, dribbling or squirting (rather than spraying) causing missfires. Not that common and if it did occur it ought to be rattling around in there getting smacked around by the piston making a racket such that you wouldn't fire it up again.......

You might crack that inj fuel line again while cranking or running and make sure it has fuel. If that doesnt make a difference, its time to check compression next. If it does make a difference, do it again as it is remotely possible that line has air in it.

beeman

Thanks for your patience. When we cracked the fuel line to the bad cyl there was no difference in the running of the engine however that line when cracked showed air, frothy small bubbles, where the others did not. The glow plug was heavily coated with black gummy soot that burned off when I put current thru' it on the bench. I will do a leak down test next this coming Monday when I get back from the Island and before I tamper with any thing else. The heat shield was badly worn with a curl of metal like a machine turning having separated from it. That inj was however functioning in cyl #4 damaged or not when swapped over. There are no unusual sounds coming from the engine.

TMAllison

Was there any fuel staining on top of the IP prior to cracking fuel lines?

If uncertain, spray it clean with brake cleaner so it is good and dry, run it and look for any leaks. Is possible the Delivery Valve and/or metal fuel line is leaking (fuel or air) and preventing pressurized fuel being delivered to the inj.

Ask for help advice before playing with the DV's.

beeman

Thanks TMA I shall check for staining/evidence at connection row on top of the IP. I will not tamper with DV until advised.

beeman

I need the MB number for the special tool required to remove pre-combustion chamber and crush ring. Anybody? Thanks again.

TMAllison

Much easier to check compression first.

Yours is a 617. http://www.peachparts.com/diy/mb_too...ls.php?page=56

The crush washer/heat sheild is beneath the inj tip. No special tool needed.

beeman

Thanks for the advice again and I shall check compression first. The glow plug was so sooted up with a heavy coating of black carbon that I thought (randomly) perhaps the PCC was fouled also.