91 300D 2.5. Wont Go Over 2,000 rpms! - PeachParts Mercedes-Benz Forum

JamesDean · #1 09-01-2012, 01:43 PM

Hey everyone,

I'm sure some of you have seen my previous posts regarding my 300D..

I've just recently repaired a broken governor gear. I was out for a test drive yesterday. I took it on the freeway and all was well. I left the freeway and encountered a red light and discovered that the 300D became slow as a turd.

It felt as if there was no boost. I'm not 100% sure if this is the problem or its something transmission related. The transmission shifts through all its gears normally and seems to operate normally.

I grabbed the vacuum gauge and ran some tests.

The EGR (or ARF?) valve holds no vacuum.
The flap actuator opposite the EGR/ARF holds no vacuum.
The wastegate on the turbo holds no vacuum, but unlike the EGR and flap with enough pumping I was able to get the gauge to get up into 10+ inches and it would leak out slowly.

I tested the vacuum supply to the three transducers and the reservoir. It provided (i think) 15 inches of vacuum.

I tested the reservoir, it held vacuum.

I disconnected one of the VAC IN lines to the egr and flap transducers and connected my gauge to them. The egr unit was receiving 7 inches. The flap was getting 5 inches. Not sure if these numbers are low or what.

I read the vac supply to the wastegate transducers and it read nothing.

I connected the wastegate actuator to the vacuum supply and drove the car. I heard the turbo whine but the engine would still not advance past 2k rpm unless I dropped down to the lowest gear.

I'm not sure but I think the EDS might be doing something at this point? Maybe?

Hopefully someone more knowledgeable can say chime in.

One step forward. Two steps backwards.

sixto · #2 09-01-2012, 03:36 PM

Some opinions until that knowledgeable person comes along:

1) 15" from the small fitting at the pump is way low. 22-24" is what you should see.

2) The 2000 rpm limit is strange. Even without turbo assistance a 602 will rev to the governor limit under load, it just takes longer.

3) EDS's main point of influence is the wastegate actuator. I suppose it can use the flap as a secondary inhibitor but I doubt the Germans are that petty. EDS influence over the IP is limited to idle control.

4) Are you sure your MityVac is in good shape? Does it hold a vacuum indefinitely if you cap the line with your fingertip?

How easily does the engine rev in neutral?

Sixto
87 300D

JamesDean · #3 09-01-2012, 03:59 PM

Sixto,

1) Correction at the supply line, it held 20+ inches of vacuum.

2) I agree this is strange. I am curious if its somehow related to transmission.

3) I checked codes at the X11/4 port and retrieved:

14 - EDS pressure sensor faulty
2 - control rod travel sensor
3 - airflow potentiometer.

I cleared 14 by connecting the supply line directly up to the wastegate. 14 fault meant the pressure sensor was not seeing the boost pressures it was supposed to.

I checked 2 and verified the resistances as listed in the FSM.

I have not checked 3. I'm moving onto the 190E for the time being.

4) Vacuum gauge is in good shape. I tested it at a vac line that branch off direct from the brake booster, 23-24 inches of vacuum no problem.

The engine revs through its entire range in neutral. There is no restriction/limit. I cannot tell or hear if the turbocharger is running though. It is only when the engine is under load does it get to the 2k wall.

The transmission shifts through all its gears normally. I drained the pan and refilled it with about 5-6 quarts of fluid. It has a slight leak that I've not investigated. Perhaps it is low? I dont know if that will explain much or anything.

If I dont find decent answers by Monday. I'm going drop it off at the mechanics shop and see what they have to say.

sixto · #4 09-01-2012, 04:07 PM

Do you hit the 2000 rpm limit if you start out with the shift lever in 2 and floor it? It should rev to the governor in first before shifting to second.

Time to go back to basics and check fuel filters and supply.

Sixto
87 300D

Hit Man X · #5 09-01-2012, 04:08 PM

Check the basics...does the linkage allow for full rack travel from inside the car??

JamesDean · #6 09-01-2012, 06:32 PM

Update: I guess my title is inaccurate. It does go over 2k rpm. It just is slow as **** doing so.

I took the car, put the shifter in to "2" and floored it on a long stretch of road. After about 15+ seconds the car achieved 50-60MPH. Right where the double dots are on the speedometer. It did not shift out of gear but I assume it was already in second gear. I didnt feel a distinct shift from 1-2, perhaps its starts out in second gear? I'm not entirely sure. Once I put the shift up into "3" it up shifted like normal.

So this does not sound like a transmission related issue as we get up to speed (eventually) and shifts through its gears (as best as I could tell).

This makes me lean back towards the turbocharger system. When I drove this car home from Columbus, it had this interesting sound as the engine got to the higher rpm's. I believe it was the turbo's normal operation. That sound is now absent.

sixto · #7 09-01-2012, 07:00 PM

IIRC your transmission should always start in first gear. In case it has second gear start, the devil's own creation, you should feel 1st gear engage when you pull the shift lever back to 2 at a full stop. First gear is only good for about 35 mph so you definitely weren't in first if you got to 50 mph without a shift.

15 seconds to 60 mph in second gear is commendable. If you disconnect the ALDA signal on a supposedly quicker '87 300D, you don't see 60 mph for closer to 20 seconds even starting in first gear.

Sixto
87 300D

JamesDean · #8 09-01-2012, 07:15 PM

Sixto: that was my guess, 15 seconds. It was probably more like 20+. I'll make another run and get a better number.

Here is what I know:

EDS controls (among other things):
-EGR
-Wastegate
-Some flap thing opposite the EGR

If any of these are not working, EDS shuts down wastegate operations. Correct?

So either:
A) My EGR and/or Flap are not working correctly thus, shutting down wastegate ops
B) Wastegate actuator or transducer is not working.
C) I have some linkage not performing fully.

I'll also have to make another pass at reading codes. I kind of winged the last read. I put the positive of my LED to the battery...Had a Y on the negative side of the LED, put one into pin 4 and tapped the other to a ground source for a few seconds and let it blink off things. I did this with the car running and wasn't sure how it would read it.. As in, would it read out high numbered codes first, then pause, then read the next..

-Kris

JamesDean · #9 09-01-2012, 08:25 PM

Another Update:

Went for another drive and took some videos and got better times.

I am still not confident that the car is starting in first gear. I also noticed that my kickdown does not seem to work. I might have damaged the cable working on the transmission.

The shifter interlocks seem angered as well. I can not shift from D to anything above N without having to turn off the car first. I am not sure if that is normal behavior or not..seems odd to me.

Here is a video of the car in neutral, revving through the full range:
WP_20120902_000015Z.mp4 video by MafiaNicky - Photobucket

Here is a video of the car in "2" at full throttle. Quality of the video is poor, but 0-60 was about 25-27 seconds.
WP_20120902_000356Z.mp4 video by MafiaNicky - Photobucket

benmack1 · #10 09-01-2012, 09:38 PM

You have a fuel delivery problem of some kind. At least from casually reading this that is what it sure seems like to my untrained eye. Apologies if I am missing details (I didn't re-read carefully) but your dilemma sounds just like mine over this past summer (a non-functional ALDA due to the line being plugged up solid). Here are the things I would suggest in the following order.

1) Do the wastegate swap if you haven't already and take the EDS, EGR and associated crap out of the discussion once and for all. Even if this doesn't solve your issue (I doubt it will) you can rest easy the the passenger side of your motor isn't the problem. Just consider it cost of entry for continued enjoyment of this automobile. Every one of these W124 90-93 300D's should have this done. It's a $100 swap and takes an hour conservatively to do as a one man job requiring using standard tools and some band aids.

p.s. on point 1. All the EGR and crossover tube flapper hardware can just sit there for now. EGR should be closed and not causing issues and the flapper default is held open. Both become spectators once you pull the vac tubing line off going to the passenger side of the car after the wastegate swap.

2) Since the above really isn't your problem (my guess) then move over to the drivers side and pull off the ALDA and see what happens. Again sorry if I missed this in your post somewhere. My problem and my guess at yours is you aren't getting any fuel when you need it. I personally would throw the ALDA in the landfill and live your life but others will be upset by this. Make your own decision of course. Eitherway, it's another 15 minutes of your time to pull the thing off (maybe another band aid) and do a test drive. You can put it back on if it makes you nervous. My guess would be the line to it is plugged with all the wonderful crap that the EGR system introduces into your intake. The caveat I feel I need to mention here is the 91 model W124 has an even worse vac system set up on the drivers side of the motor where it has a switchover valve between the manifold and ALDA if I am not mistaken. This was eliminated in at least some of the 92's and beyond. I think you should be able to just disconnect nonetheless at least to test. Shifting may not be great and you will need to revisit this plumbing but at least you will be able to make RPM's and have power if this is the problem (ALDA line being full of crud). Sorry if that is confusing, look up some W124 vac diagrams and how the 90-91 differ from the 93 for example and this might make more sense and not seem like endless rambling. Sorry.

3) If that doesn't solve your problem, leave the ALDA off until you find the problem. Step 3 is to make sure you are getting fuel from the tank. Make an aux fuel tank with a gatorade bottle and run the car off of this (just like doing a diesel purge). Run a line to the primary and put the return in the bottle, strap it down and give it a whirl. If this solves it, then you have some crap in the fuel strainer at the tank or along the supply line restricting your fuel before you even get to the engine well. Not fun, but at least you'll know.

4) If that doesn't do it, check fuel pressure from the 2ndary over to the IP. (of course all of this assumes you have change the two fuel filters recently.) Just making sure the lift pump that pushes the fuel into the 2ndary is doing it's work.

If you pass all of the above tests then you can go from there at least knowing you have fuel and air moving where they need to and start asking about the IP I guess. Others are probably much wiser than I am and this advice is worth exactly what you paid for it!

I could be dead wrong of course, but if any of the above fuel issues are your problem, once fixed I would guess your shifting woes will miraculously disappear also, mine did anyway. The best of luck!!

pawoSD · #11 09-02-2012, 12:05 AM

The later cars all start out in second...both gas and diesel. It will only go to first if manually shifted there or if the pedal is mashed (kickdown switch).

Weak power levels could also be a dying lift pump.

JamesDean · #12 09-02-2012, 11:34 AM

Another Update:

I was checking rod linkage and all travel seemed OK. I watched everything and poked some with a screw driver none seemed to have any problems.

I did notice that the prefilter to lift pump connection was loose. So I replaced the prefilter and tightened the connection. There was no change in performance. The lift pump does not have a primer pump like the 617 does so I just started the car. There is an air bubble in the prefilter. I'm not sure how to tell if the lift pump is weak or not. This performance loss all happened rather quickly too. We'd left the house, all was normal, drove on the freeway, got off the freeway stopping at a stop sign (still normal) then went to a red light and that was when it seemed to lose.

I checked for vacuum leaks. The vacuum pump was outputting 23 inches of vacuum measured at the first connection off the brake booster line.

I then noticed that there were two ports on the vacuum pump, one for brake booster one for other stuff. I also measured 23 inches at the secondary connector. The secondary connector supplies three circuits. One goes to the transducers, one goes to the interior (I think) and another goes to the vacuum control valve for the transmission (I think thats what it is, is on the driverside of the IP).

I pulled vacuumed on these the two connections:
-The VCV held vacuum
-The line that went inside the car did, but leaked slowly.

I then plugged the line that leaked slowly to see if had any change on performance. It did not.

I checked vacuum at the supply line to the transducers, it was achieving slightly less than 20 inches. I connected up at the Y at the vacuum pump and it was 23". There were reducers and other connectors so that might account for the difference.

So best I can tell right now is:
1) Control Rods are proper
2) Fuel Hoses are proper
3) Vacuum seems OK.

pmckechnie · #13 09-02-2012, 12:52 PM

Have you checked for codes in the EDS. Most codes will disable the turbo. Either way, Put full vacuum on the wastgate actuator. Plug the disconnected hose. Remove the hose on the intake flap (I don't know what it's called). Plug the line disconnected. Run a vacuum line from the intake port directly to the ALDA. Plug any hoses disconnected. Test drive. If it runs good, you have an ESD system problem. Dont drive the car too much in this condition as the boost will go to almost 30 psi.Best to just change the wastgate actuator to the pressure type. If it doesn't help then start looking at fuel problems.
I think you mentioned that you couldn't shift past neutral unless you turn the engine off. That is caused by the governor in the transmission. It is sticking. Probably a piece of trash got in it while it was out. It may work itself out. Mine didn't and I had to remove the governor and clean it.
Your car should start in first gear in normal driving. If you pull the stick all the way back it will lock the trans in first gear. Push the stick forward 1 notch and the pull it right back and it will shift into second. Push it forward again and leave it there will be third gear. One more notch forward will be fourth gear.

Good luck

Paul

JamesDean · #14 09-02-2012, 01:08 PM

I did pull codes.. I'll re-do it because it was a half-ass attempt.

Code 14 was one of the first. Which was the EDS pressure sensor, I was able to get this to clear once I opened up the wastegate manually,
Code 2 was the next one I got, it is control rod postition sensor I think...I checked the resistances listed in the FSM and got the same numbers when measured.
...

Quote:

Originally Posted by pmckechnie

Have you checked for codes in the EDS. Most codes will disable the turbo. Either way, Put full vacuum on the wastgate actuator. Plug the disconnected hose. Remove the hose on the intake flap (I don't know what it's called). Plug the line disconnected. Run a vacuum line from the intake port directly to the ALDA. Plug any hoses disconnected. Test drive. If it runs good, you have an ESD system problem. Dont drive the car too much in this condition as the boost will go to almost 30 psi.Best to just change the wastgate actuator to the pressure type. If it doesn't help then start looking at fuel problems.

I will try this today and post up the results.

Quote:

I think you mentioned that you couldn't shift past neutral unless you turn the engine off. That is caused by the governor in the transmission. It is sticking. Probably a piece of trash got in it while it was out. It may work itself out. Mine didn't and I had to remove the governor and clean it.

Sigh..... Not Again

JamesDean · #15 09-02-2012, 02:02 PM

Alright so I altered the vacuum routing as pmc indicated.

Wastegate hooked directly to vacuum.
Alda hooked directly to the manifold.

The car was still a dog when left in "D" and full throttled.

I put the shifter into "2" and was able to hear the turbo whistling from ~2500 rpm+. This seemed to help my acceleration greatly.

I am curious as to how closely all this ties to the "cannot shift from N->R/P + governor sticking" issue. I really loathe the idea of dropping all that BS to get to the governor again.

I think I need to get a boost gauge and see what the turbo is doing. It might be operating normally. The transmission's governor might be the issue.

I found a bit in the ATSG manual about "poor acceleration when starting." It says to:
1) Check Stall Speed
2) If stall speed drops by 400-700/min below specified value, one way roller clutch in torque converter will slip. Exchange Torque Converter.

I dont think this is my issue. I'm not sure what the specified value but my torque converter appears to stall at about 1800-1900 rpms. Perhaps my governor is sticking something hardcore and being more of a drag on the transmssion....

Another bit in the ATSG manual about "Selector Level Position "R" and "P" cannot be engaged"
a) with engine running -> 1a) Clean centrifugal governor and make operable.