Super Slow 1987 300D - Page 2 - PeachParts Mercedes-Benz Forum

Maxbumpo · #16 07-13-2019, 08:02 AM

Quote:

Originally Posted by noquarter1

At idle, it registered flatly at 0. The needle didn't move.

I then did a 0-60 run with the accelerator firmly against the floor. The highest psi it registered was 3.

So, this would suggest there's no boost at all, is that correct? I wasn't able to get to the turbo tonight to see if it spins or if the wastegate opens. Could a clogged cat converter also be a culprit?

Thanks so much.

Yes, boost is not nearly sufficient. Minimum of 12 psi at peak pressure is what you are targeting.

So, either airflow is restricted (check the air filter yet? No mouse nest somewhere in the intake?) or exhaust is restricted, or the waste gate is failed open so all the boost is dumped, or your turbo has failed.

I'd pull the intake accordion plenum from the front of the turbo, and check out the impeller. Should look good, spin relatively easy by hand, have zero play going in/out, and just detectable play going up/down.

Next pull the air filter and check underneath. There is some kind of MAF device between air filter box and turbo, if you can check that to make sure it has not frozen up in closed position and is starving the intake of air.

After that, I'd try the exhaust removal step, just make an opening somewhere after the turbo and before the catalytic converter / filter.

Your car doesn't still have the oxidative cat under the hood, does it?

If all these things don't help, then you probably need to pull the turbo and fix the waste gate. You can try to fix it on the car, but that may not be possible. Somehow it is jammed open, hard to say if that is external to the turbo or internal.

R.Diesel · #17 07-13-2019, 08:06 AM

This came up as a 1987 300D diagram. If you know which diagram is applicable to OP's car perhaps you could post it. Checking the ALDA is important in my opinion since insufficient fueling will cause insufficient boost in a Bootstrap like process. Besides, its a 5 minute check.

Diseasel300 · #18 07-13-2019, 09:26 AM

Quote:

Originally Posted by noquarter1

Thanks for the help. Please excuse my ignorance, I'm clearly new to this, despite having tried to do my research, which is why I confused the intake manifold to ALDA as being a vacuum, when it is pressure line.

I attached a pic that I drew on to show what I did. I ran a line (red in the pic) from the intake manifold nipple directly to the 'Y' connector which is also connected to the ALDA and goes on to something else (transmission related, I think). In that line from the intake manifold nipple to the 'Y' connector, I inserted a 'T' connector, with that line running to the Harbor Freight pressure gauge (represented in green). I then ran it inside the car, and, once warmed up, floored it to see how much pressure I'm getting (measured clockwise on the gauge).

At idle, it registered flatly at 0. The needle didn't move.

I then did a 0-60 run with the accelerator firmly against the floor. The highest psi it registered was 3.

So, this would suggest there's no boost at all, is that correct? I wasn't able to get to the turbo tonight to see if it spins or if the wastegate opens. Could a clogged cat converter also be a culprit?

The turbo produces no boost at idle. It requires waste heat in the exhaust to function (meaning the engine is doing work). You should have no boost at idle and very little boost when cruising steady-state (maybe 3-5PSI). Foot to the floor should get you up 12-14PSI if everything is working.

The "mystery" hose on your ALDA goes to the blue "UFO" vacuum amplifier on the fender. For testing purposes, make sure your manifold line connects ONLY to the ALDA. If the line to the blue UFO is broken, or if the blue UFO itself is leaking internally, guess what.....your boost to the ALDA isn't pumping up the ALDA.

Speaking of the ALDA, they have rubber seals in them that fail over time. The result is that boost comes on late. Once you find and fix the issues with your car, consider opening it up and replacing them. There's a thread on this forum somewhere that gives sizing (do a search for ALDA reseal). It makes a HUGE difference in how the car drives. Leaky ALDAs will make the boost come on late and very suddenly.

Quote:

Originally Posted by Maxbumpo

This diagram appears to be for the vacuum-operated waste gate? I think it is wrong for the OP's car.

Wrong. The '87 diagram shows the ARV (which is vacuum operated). Many if not most '87 124 cars had the ARV on the turbo. A vacuum operated wastegate would show a second vacuum connection to the turbo.

Quote:

Originally Posted by R.Diesel

This came up as a 1987 300D diagram. If you know which diagram is applicable to OP's car perhaps you could post it. Checking the ALDA is important in my opinion since insufficient fueling will cause insufficient boost in a Bootstrap like process. Besides, its a 5 minute check.

You posted the correct diagram. Checking/Fixing the ALDA sense line is absolutely the first step in all of this. If the ALDA doesn't enrich fuel, the boost doesn't build. If the boost doesn't build, the ALDA can't enrich the fuel. The two functions are intrinsically related to each other.

noquarter1 · #19 07-14-2019, 08:28 PM

Thanks all for the help.

Maxbumpo, the trap was replaced with a catalytic converter years ago. Based on a growing suspicion, (based on this thread and others that I read) I took a sawzall to the catalytic converter (started with an exhaust pipe chain cutter, quickly realized that would take all day, hence the sawzall) and removed it altogether. I put a flex pipe and clamps in its place, and took it for a spin. Don't remember if I mentioned this, but I also removed and cleaned the IM nipple and replaced the rubber hoses/connectors to/from the ALDA in case those were leaking.

Remembering that my original 0-60 was somewhere in the mid 20's, today's was around 16 seconds. Pretty good improvement. I didn't check the turbo's PSI, but when I do, I'll post the new results. It is shifting much better as well. Still a bit late and a bit of a kick, but much better than it was. Additionally, the oil pressure was lower than it's been previously.

To try to regain the last 4-5 seconds, I'm going to:

-replace the air filter, and make sure there aren't any blockages
-replace fuel filters
-put a can of seafoam in the tank
-adjust/reseal the ALDA
-make sure the wastegate is functioning
-remove EGR and other smog
-start replacing the various rubber hoses as an easy and simple way to make sure they aren't leaking

I'll keep updating the thread for the new PSI, and I'll post improvements/results after each step.

dlssmith · #20 07-15-2019, 10:46 AM

16 sec to 60mph is not normal. Not sure what is optimal but mine is around 6 sec - and I think everything is right with mine - and I have no egr or catalytic converter. Remove the rubber boot off the front of the turbo and reach in and spin it with your fingers - it should spin freely and have just the tiniest amount of fore/aft play - I'm not sure of the spec, but its a small fraction of a mm. My suggestion is to remove the air cleaner box and heat shield before fiddling around on that side of the engine. It saves a lot of time unless you have very small hands. And watch the waste gate actuator. It is easy to test - should move freely when pressure is applied. The replacement hose installed by lesser mechanics on the wastegate actuator is often rubber - it is supposed to be silicone. Lots of heat there and the rubber fails early. I've attached an image of the turbo fan taken with the accordion boot removed, just to give you a reference. This turbo is in good condition. Fans intact, spins freely.

Maxbumpo · #21 07-15-2019, 11:03 AM

Quote:

Originally Posted by R.Diesel

This came up as a 1987 300D diagram. If you know which diagram is applicable to OP's car perhaps you could post it. Checking the ALDA is important in my opinion since insufficient fueling will cause insufficient boost in a Bootstrap like process. Besides, its a 5 minute check.

I stand corrected!

Re-reading your post with the diagram, were you recommending a check of the intake manifold itself? That may be worth a look to make sure the EGR valve has not let a bunch of junk flow into the intake and plug it up and lead to reduced airflow. Not a fun job, best to take the intake manifold to a machine shop with a hot dip tank so they can clean it out for you.

Maxbumpo · #22 07-15-2019, 11:15 AM

noquarter - good progress! I've got a complete exhaust system for your car, if you want a put it all correct again. Came off a sedan with 143k miles, totaled after a major collision.

Replace the air filter, and then check the boost again. You may need to adjust the waste gate to get up to 12-13 psi. No need to go any higher, you'll just be making the intake charge hotter than needed at that point, and will start loosing power without more fuel or some type of cooling of the compressed air. Check the ALDA to see if it is holding pressure or leaking.

After that, fine tuning until you can get back to 12 sec or less.

noquarter1 · #23 07-15-2019, 01:30 PM

Quote:

Originally Posted by dlssmith

16 sec to 60mph is not normal. Not sure what is optimal but mine is around 6 sec -

Being the noob here I hate to disagree, but every source I've seen shows around 11 seconds 0-60.

1987 300D 12 seconds 0-60 -- what else to check?

87 300d 0-60 time

If you've got a way to get it to 6 sec please let me know!

Regardless, thanks for the tip on removing the heat shield and the like, I'll make sure to do that before I start fiddling.

Diseasel300 · #24 07-15-2019, 02:18 PM

Quote:

Originally Posted by noquarter1

Being the noob here I hate to disagree, but every source I've seen shows around 11 seconds 0-60.

1987 300D 12 seconds 0-60 -- what else to check?

87 300d 0-60 time

If you've got a way to get it to 6 sec please let me know!

Regardless, thanks for the tip on removing the heat shield and the like, I'll make sure to do that before I start fiddling.

0-60 on a W124 should be around 10.5-11 seconds. 12.5-13 seconds for a W126 (bigger/heavier car). 6 seconds is faster than many sports cars, there's no way a stock 145ish HP diesel from the 80s is gonna do a 6 second 0-60 without some serious modifications.

noquarter1 · #25 07-16-2019, 10:49 PM

Quick update:

I had a new straight pipe welded in place of the flex pipe, and finally put in fresh fuel (it near empty and still on the diesel from a few years ago).

I downloaded an app called "Drag Racer" to try and get more accurate results (versus looking at a stopwatch when I see the speedo at 60). I measured 15.9 seconds 0-60.

I then put in a new air filter, and made sure all the ducting to the turbo is clear and that the air valve wasn't stuck. I then measured the 0-60 again: 15.2 seconds.

Tough to say if it's due entirely to the air filter, maybe to the seafoam doing its job, or maybe one of a thousand other variables but regardless, I'm happy with the progress.

On to the ALDA and fuel filters...

dlssmith · #26 07-17-2019, 12:04 PM

I wrote earlier that I got 6 sec 0-60 from mine. Not true. Never true. I was typing a bit fast but old 87 will do about 12-13 most of the time. She's fast for an 87d, at least in my opinion. Taking the cat out made a big difference. Fixing all vacuum leaks made another big difference. Sorry for the appearance of fantasy in this thread.

noquarter1 · #27 07-20-2019, 03:12 PM

Update: I changed both fuel filters. The primary one was pretty easy, I just wrapped the hose on both ends in a rag and used a vice grip on each side, disconnected the hoses from the filter, and swapped the new one in.

The secondary was a bit trickier due to my ignorance, as I kept trying to get it off by hand, not realizing that the loosening the bolt on top would drop the filter with no problem. I kept trying to figure out the access issue, even disconnecting the coolant hose (spilling plenty of coolant in the process) before my better half pointed it out and suggested I try it, and voila, the filter came out super easy. I filled the new one with Seafoam and reconnected it. I kept reading about having to crank the engine for 20-ish seconds to get it to turn over after replacing the filters, but mine started right as if I hadn't replaced anything at all.

New 0-60: 14.2 seconds.

If I can get to a sub 12 seconds 0-60, I'll be happy. I'm actually okay with the acceleration as is (and even before I started this process, not realizing how quick this car is), but now that I know what it should be, I feel compelled to get it there.

Next will be removing/resealing/adjusting the Alda and removing the EGR.

R.Diesel · #28 07-22-2019, 06:13 PM

Quote:

Originally Posted by noquarter1

Update: I changed both fuel filters. The primary one was pretty easy, I just wrapped the hose on both ends in a rag and used a vice grip on each side, disconnected the hoses from the filter, and swapped the new one in.

The secondary was a bit trickier due to my ignorance, as I kept trying to get it off by hand, not realizing that the loosening the bolt on top would drop the filter with no problem. I kept trying to figure out the access issue, even disconnecting the coolant hose (spilling plenty of coolant in the process) before my better half pointed it out and suggested I try it, and voila, the filter came out super easy. I filled the new one with Seafoam and reconnected it. I kept reading about having to crank the engine for 20-ish seconds to get it to turn over after replacing the filters, but mine started right as if I hadn't replaced anything at all.

New 0-60: 14.2 seconds.

If I can get to a sub 12 seconds 0-60, I'll be happy. I'm actually okay with the acceleration as is (and even before I started this process, not realizing how quick this car is), but now that I know what it should be, I feel compelled to get it there.

Next will be removing/resealing/adjusting the Alda and removing the EGR.

I wouldn’t adjust the Alda, I’d simply check for leaks, disassemble, and replace the o rings if necessary...

dieselworks · #29 07-23-2019, 11:31 PM

The guy who suggested you check the alda and see if it holds a vacuum. Spot on.
The other thing he noted was to verify the boost pressure. I couldn't find where the boost pressure finding is but if it's less than 12 psi then a manual boost control is in order.
These 2 issues could get you into the 12 second zone.
How about going to a straight pipe exhaust. They aren't very loud.

Sent from my SM-G900I using Tapatalk

noquarter1 · #30 08-19-2019, 11:54 AM

Sorry for the delayed response, everyone.

I finally found the right size O ring for the Alda and determined that I would take it off/apart over the weekend and then see whre I was, but the teenage driver texting behind me had other plans, and he rammed my car into the one in front of me. Needless to say, the car is totaled, so unfortunately all the work I put into it was for naught.

Thanks for everyone's help, this forum is a great resource. Not sure if I'll seek out another W124, as I've always lusted after a W140, but we'll see what's out there on the market. If anyone is local and needs parts, let me know.