W115 240D slow, and eating glow plugs - Page 3 - PeachParts Mercedes-Benz Forum

Hawk8789 · #31 03-23-2018, 03:39 PM

What about the fuel filters? I replaced them along with the priming handle when I took delivery of the car, before we got it running. I ran it with two(maybe three, I can't remember) bad injection pumps. My only experience with a bad fuel filter was with my 81. It went from running fine to not passing 30 mph. That was a terrifying on-ramp experience!

Shortsguy1 · #32 03-23-2018, 04:50 PM

Quote:

Originally Posted by Diseasel300

... This is a diesel engine, not a gas engine. Every time the cylinder goes through an intake cycle, it pulls in a full volume of air, regardless of RPM or load. ....

This is unfortunately wrong for the OM616 in the OP's car. There is a butterfly valve before the intake manifold, so the air volume in the cylinders is constantly changing. The early MB diesels are quite different from the later ones and from most diesel engines.

Maxbumpo · #33 03-26-2018, 12:14 PM

Fuel filters that are plugging up can definitely cause a lack of power.

Maxbumpo · #34 03-26-2018, 12:23 PM

Quote:

Originally Posted by Shortsguy1

This is unfortunately wrong for the OM616 in the OP's car. There is a butterfly valve before the intake manifold, so the air volume in the cylinders is constantly changing. The early MB diesels are quite different from the later ones and from most diesel engines.

If that butterfly valve is not working correctly, can it cause such a power loss that the car struggles to exceed 30 mph?

Hawk8789 · #35 03-26-2018, 12:38 PM

If I understand correctly, the butterfly valve controls the air to the pneumatic governor on the injection pump. I’m not sure if that could be my issue.

Father Of Giants · #36 03-26-2018, 12:45 PM

I'd say diesel purge it and see what happens, get your engine at operating temperature, and go through two cans of diesel purge. While parked in Neutral, snap your throttle and go HIGH in the rpms, rev it hard. Replace both fuel filters and see if there's a difference.

My 300SDL was SLOW, foot to the floor it wouldn't go past 35mph when cold, Diesel purge brought it back, now it can do 100mph+.

Diseasel300 · #37 03-26-2018, 12:45 PM

The butterfly valve does control the pneumatic governor. Check for oil in the line to the governor to determine if the diaphragm is leaking.

That would likely only be related to power loss though, not rapidly failing glow plugs.

NZScott · #38 03-26-2018, 10:11 PM

Quote:

Originally Posted by Shortsguy1

This is unfortunately wrong for the OM616 in the OP's car. There is a butterfly valve before the intake manifold, so the air volume in the cylinders is constantly changing. The early MB diesels are quite different from the later ones and from most diesel engines.

It's not to that full extent however. Remember there cannot be a strong vacuum in a diesel engine, otherwise it will have nothing/too little air to compress to ignite the fuel. I don't know the details, but it would be a very slight vacuum.

sgnimj96 · #39 03-26-2018, 10:44 PM

I test for sticking brakes when driving by coming to a very gradual stop in neutral. It should keep rolling down to a very, very slow speed before stopping - and you won't feel it stop.

As far as speed though, a normal running diesel engine will drag brakes no problem at highway speeds. Your wheels will get so hot it'll ruin the bearings.

Hawk8789 · #40 03-29-2018, 12:07 AM

So I had my shop install my prechambers and check my brakes. I hope to have a chance this weekend for the stem seals, but we’ll see.

They said the brakes are fine but I didn’t get a chance to talk to them. I work out of state so I usually pick the car up after hours. On the drive home I was paying more attention and the car feels like it’s braking when I let off the accelerator. Not too badly unless I’m coasting in 1st, then it almost comes to a complete stop when I let off the pedal. I just don’t have any experience with a W115. I never got to drive this one when it was running right. The previous owner never had a problem driving it up the hill to work, but I do.

How does the acceleration actually differ from the W123? What should I really expect from this car?

barry12345 · #41 03-29-2018, 03:46 PM

Many clues in your posts. First since you can contact the past owner. Ask him if the car was also eating glow plugs before he removed the injection pump? Also what was the issue that caused him to remove the injection pump in the first place? Get as much information as you can and post it.

You also mentioned some of the glow plugs had physical damage. Plus continue to fail. The causes of this are known and limited. Either an injector is squirting a direct stream of fuel on them. Or the pre chamber is running really much hotter than by design. One known cause of this is an injector pump being out of time enough.

Constantly on glow plugs just burns them electrically out. Causing no physical damage to my knowledge. Plus I would suspect you would have been dealing with battery charge issues. If they were.

I also wonder what effect if the holes in the pre chamber had too much carbon built up and this obstructed the amount of fuel getting out. To me that should be cleanable. Perhaps get the ones the mechanic removed and examine them.

If that shop actually owned the pre chamber puller. Chances are better than average they know these engines better than would be common today. If they just borrowed the puller that bet is off.

Your description does not really indicate the injection pump is on the wrong stroke. Yet I have been wondering a little at the same time. It should be running worse than you say. With smoking out the tailpipe and hard to start. The pumps time the same if on or off the right stroke.

Normally if you remove your foot from the pedal without pushing the clutch down. It normally will feel like you applied brakes. Where it is the engines back pressure doing the rapid slowdown.

To test the brakes in your case. When the car is driven for a few miles. coast to a stop. Get your posterior off the seat and outside the car. Check the wheels individually for temperature. None should be hot.

I mean of course feel the metal part of the wheels. Wet the tip of your finger to eliminate any chance of a burn. Also you should not smell hot brakes. The problem is unless the garage is doing things for free now in this case.

You may need to do a lot of tests yet yourself to be described to verify what is good or bad. They are fairly easy. The alternative could be a very depleted wallet otherwise. Plus a mechanic with a reasonable knowledge is not going to be very accepting of being told what to test and how.

All I am really certain of at this time. The rapid loss of glow plugs and physical damage to them is not very common to the point of being almost very rare on these engines. Also for the time it takes remove the fuel cap. It should not smell like gas.

I see almost no reason a new set of pre chambers have really helped much if any. Other than if the output holes where obstructed.

No more expensive guessing otherwise. Time to do some detective work starting with the past owner. Plus a series of reasonable simple tests if his answers do not help. Unless you favor an open wallet approach.

Also this gives you time to see if the exhaust stings your eyes. Plus describe if it is too smoky or anything unusual about it.

I am also basing the car is just not up to your expected power level. On the past owner telling you that the car would climb a certain hill far better than it does now.

Hawk8789 · #42 03-29-2018, 08:22 PM

Thanks for that Barry. The car is too slow I think. My wife learned to drive a stick in my W123 240D, but I’m not comfortable with her or anyone else driving this one. The mechanic I go to collects these and he’s got a whole yard of parts cars. He’s very knowledgeable and given me free advice and cheap parts. I kept thinking the injection timing must be off and he looked offended when I asked him to double check it. When the glow plugs are good, the car fires right up and it’s smooth as silk, even when shifting, just so slow as to be undrivable. I’m in Las Vegas, and I don’t think I would ever make it out of the valley if I wanted to take it out of town.

barry12345 · #43 03-30-2018, 12:10 PM

Sounds like you have a reasonable relationship with that mechanic. Plus he knows these cars. At least to some extent. That is good.

Does he also think it is abnormally slow? I think with your car having a manual transmission. 0-60 mph should be about 19 seconds. I assume the new pre chambers did not do much.

It sounds like you owned one of these before. So you are somewhat familiar with them yourself. From that I assume it is quite slow in comparison to the first one in your opinion.

There is a pretty extensive list for you to check. Simply because something could have been missed.First talk to the last owner in a friendly way though. Any usable clues may help shorten it.

It is more than possible your mechanic has missed something. This does and can happen. At this time some tests done by you might indicate what it is.

Possibly the best source of what was going on with this car. As for their general usage they are not really a suitable car to put a wife into fast moving heavy urban traffic today. Entering ramps to get into the fast moving traffic streams can be too tricky. In my opinion.Still safely usable otherwise.

There are fewer than two million people in all the combined Canadian maritime provinces and this explains the low overall traffic volume. To me this is the ideal 240d area of this country. .

Hawk8789 · #44 03-30-2018, 06:25 PM

I haven’t driven it more than 2 miles home from the shop with the new prechambers. Still smoking, but that’s no surprise. I want to see what the stem seals do. They are over 40 years old and my mechanic had mentioned them. He told me $250 to do it and I laughed at him. He laughed too. I’ve done it before. If I put my hand in the exhaust, I don’t get oil on myself. I don’t smell diesel, and it doesn’t smell sweet. I just don’t know.

barry12345 · #45 04-01-2018, 12:51 PM

I would forget the stem seals for now and pull and check those injectors. This is why I suggested you talk to the last owner. Maybe he did. Or maybe your mechanic did. If nobody did somebody almost has to.

They could be the originals with some leaking down for example. This would act the same as seriously retarding the injection pump timing. Smoking would go along with that as well.

If this has not been covered it is something that should be seriously considered. Tired valve stem seals will not kill off the engine power. No problem at all for a set of really poor injectors to accomplish that or even just two of them leaking down. Having them just tested is not a big thing. This could also account for the glow plug issues. The valve seals certainly cannot. A person has to stay focused on any clues when they present.

Now if the injectors have been properly checked out already. Back to basic troubleshooting.