Rough idle on 87 300D solved!
 

I fixed the rough idle on the 87 300D by replacing the pressure valve holder seals on the IP. Probably didn't really have to replace them, as the majority of the holders weren't properly torqued down (#4 was only finger tight!).

Pretty easy job -- just remove the injection lines at both ends, remove the lock rings (the hardest part for me since one was siezed!) unscrew the holders one at a time and lift off the copper ring, put the spring back on, and screw the holder back down to approx. 30 ft/lbs.

Had to bleed the injection lines to start, but that's normal.

Car runs wonderfully now -- just a hint of vibration and diesel noise at idle, gone as soon as I touch the throttle. Big improvement over the dead cylinder thump I had before.

Now, if I can just be sure that the oil in the coolant tank is left over from a previous repair.....!

Peter

I am glad to see that you were able to fix the problem. Did you use a special wrench to remove the delivery valve holder, how did you diagnose the problem?

Thanks!!

CJ:

These particular holders have a multi-spline rather than a hex nut. Older ones have a hex nut below the injector line cap nut. I borrowed the tool from my indy mechanic, but I think it is available for about $20.

Diagnosis:

Engine misses on one or more cylinders at idle, runs much better above 1500 rpm. Usually worse warm. VERY rough idle -- shakes car hard.

Hard knock on affected cylinder, goes away when line bled. No or little change in idle when line bled.

Fuel spill normal when line open!

Injectors OK.

Oil consumption is normal.

Fuel consumption normal.

Compression OK (not necessarily better than that!),

Valve adjustment OK or hydrualic tappets OK.

No unusual smoke at idle (hard to tell on cars with trap oxidizer or catalyst).

Think of it this way -- what would make the pump deliver fuel but not delelop enough pressure to open the nozzle and actually inject it?

What is going on is that the fuel is leaking back into the pump body rather than pressurizing the delivery line. At higher speeds, the leak is small enough that some fuel is delivered and burns more or less normally. At idle, the leak is large enough that the pintle in the nozzle won't lift on time, leading to very late injection and knock, low power, and hard shaking.

Naturally, a bad IP set will do the same things but it won't recover nearly so much at speed.

And it just seemed very likely to me that it was the problem. First thought I had when I saw the car and listened to it, in fact!

Peter

psfred

I'm currently working on an 83 300D with 132 kmiles that I recently purchased. The body and interior are nearly perfect, but the PO only did the bare minimum on maintanance. He told me the valve were adjusted right before he bought it , IN 1989 at 70kmiles !!!!!

The car idles roughly (and seems to have what I think is called "nailing"), has poor power at low RPM (slower off the line than my 240D), but jumps to life at higher RPMs, even before the turbo comes on.

If you remember, I discovered the injector element on #1 leaking, and have received the washer and oring after ordering them from fastlane. I was able to remove the element with better tools and your help, and now I have to finish the valve adjustment before I can start her up to see how she runs.

I'm a bit concerned about the quality of the fuel in this car, as the PO didn't put hardly any mileage on the car in the last year. I smelled the fuel at the tank, and it doesn't really smell like diesel. I put some power service conditioner in it, but that may be part of the poor power. I also have to change out the main and in line fuel filter.

I plan to replace only the #1 element washer and oring, but I have an extra. I'm wondering if you think I should change them all.

I found a place that will check all of the injectors for $25 total (Diesel injection service in St. Louis on South Broadway) I think I'm going to do that if I still have the poor power after the valves and the element seals are changed.

I can't wait to get some time at Thanksgiving to wrench on her. I appreciate any additional advice. I would do a compression test but don't I need special tools for that?

thanks

Joe

Joe:

I figured that the IP seals were a good bet since the compression was OK (marginal in #4), the injectors were clean and set properly, and a leakdown test showed ring leakage but no valve leakage. All work performed for previous owner while I was discussing purchase, all done by Hans (my indy mechanic and source of MB knowledge). Much cheaper than an engine overhaul, although that may still be in the works.

There are several causes of injection knock at idle -- low compression, late fuel delivery, and sticky injectors being the most likely.

Before I dived into the IP I'd get the valves right -- you might want to set them a little loose for a week or so, then recheck in case they are carboned up. As the compression comes up, the carbon will burn off, and the valves will go tight again. 60,000 miles without an adjustment is a LONG time for this car! Get some known good fuel in it and drive a bit before making any more changes. Find some RedLine or similar fuel treatment and run that through -- if it cures the knock, it's just nozzle carbon.

If the above doesn't fix the problem -- and you will know pretty soon when you do the valves -- if any of the exhaust valves have less that 0.010" clearance cold, your compression will be low -- loosen the cap nut at the injector one cylinder at a time and locate the offender, then try just snugging up the pressure valve holder.

If everything seems fine, then replace the pressure valve holder seals. I spent $7.56 for the entire set!

Compression check isn't too hard, just don't squirt oil in to check the rings for leakage -- it can ignite, or worse, if you get too much in there, bend a rod! You will need a gauge good for at least 500 psi and the appropriate adapter. Otherwise, same as for gas engines.

Peter

Re: Rough idle on 87 300D solved!
 

Peter,

I think the torque is 30 Nm (22 ft/lb)during the initial torque down. As I was told, retorque it two more times and the final torque is 35 NM (25.7 ft/lb). This is for the 602 and 603 engines only. The 601 engine may be the same. Others engines may have different requirements.

David

Psfred

Am I doing something wrong? I could only find the brass washer under the valve after I removed the element in the injection pump. I bought the o ring but can't find where to put it. Maybe the o ring goes under the plate that everyone says not to remove.

I put the new brass washer in and tried it, and it seems to have a very very minor leak, only enough to see it in the tread area. I have it torqued properly.

I got the valves adjusted, and two intakes had zero clearance. The exhausts were all about 0.004 inch too tight. I changed both fuel filters.

The car seems to run a little better but not up to standard yet. I have to work on the thermostat as the car never gets above 60 degrees C, and I have to find an oil leak.

Thanks for the help.

Joe

Joe:

The copper seal goes under the pressure valve seat on the older IP -- the o-ring goes on the holder just above the threads and seals the fuel in the pump.

Peter

I still don't understand where the o-ring goes. I never took the two nuts off of the pump. Is the o ring under that plate?

I removed the element in the second slot and I can see no o ring, only the brass washer that goes under the valve. Am I still missing something?

Joe

Joe:

It's on the part you unscrew -- at the top of the threads. Fits into a shallow slot against a flange, and goes down into the top of the part you don't remove!

They tend to cut on the egdes, and this is where the fuel leak is coming from.

Peter

I still don't know what's going on. The part I removed screws into the injection pump and it had no oring on it, and I took 2 off just to be sure.

Could the orings have fallen off of all of them over the years.

Maybe mine is different then yours.

Joe

Joe:

Hmmmm. Now you got me thinking. I'll have to ask my brother tomorrow when he gets home from T-day in Detroit where his were.

They may be in the recess where the fitting screws in, and it is possible that there is no o-ring on these particluar pumps. Did you get some from you supplier? If so, they belong there on the pressure valve holder up above the threads, although it is possible they go under the bottom end or sit in the sleeve instead.

The copper seal is for the high pressure part of the pump. The o-ring seals the low-pressure part. However, the early 300D pumps are different than the earlier and later pumps, so there may be a difference in o-rings, too.

Anybody else know about this?

Peter

I replaced the copper o-rings on my 1985 300D within the past week. Once I removed the part that the "spider" screws (this is called the "pipe connection" ) onto at the injection pump and pull the spring out I took a magnet and pulled the part out that the spring holds down (this is called the "delivery valve" and the part underneath it came out too (this is called the "delivery valve holder". Look underneath the "delivery valve holder" and you should see the copper gasket. The MB part number for the copper gasket on my 300D was 000-074-17-59 and is called "gasket, injector" on the bag label. It goes on to say slightly lubricate the threads of the pipe connection and tighten ot 40-50 Nm in ONE STEP. I used Marvel Mystery Oil to lube the threads because that is what is in my squirt can :).

Good...there isn't an o ring in my car...I was starting to question my sanity. I did replace the copper washer. I failed to oil the threads before I put mind back together, and it leaked slightly for awhile, but it seems to have stopped.

thanks everyone for the help...Now back to the oil leaks...

Joe

Hi All
I was delighted to see this topic as it seemed the answer to my 87 300D problems too! However on corresponding with psfred am going for a compression test tomorrow.
Unfortunately my car produces a good bit of smoke(as well as the other symptoms described by psfred) at low rpm and recently runs mainly on 5 cyls. If it does go on 6 a loud knock/clack is heard. I notice a few tiny globules of oil in the coolant too so maybe a head gasket is at fault. Will let you know how I get on with the mechanic.
Gerard