W124 93 300D 2.5 Boost Problems (I too am stumped!) - Page 2 - PeachParts Mercedes-Benz Forum

2.5Turbo · #16 04-30-2007, 10:22 AM

These cars never came with cats...it's straight out the muffler from the turbo. I think adding the EDS with full control over the wastegate and EGR reduced the emissions enough at the time to allow the elimination of the cat.

James L · #17 05-23-2007, 03:57 PM

This EDS is whoopin' my ass!!!

I am so sick of reading so many W124 boost searches!

Update on what I have done so far; I removed the intake charge pipe (both) they were so caked with crud and soot. The flap and intake ports on the head also. I took a butterknife and scrapped it out, then used shop vac/shop air, cleaned with rag. For air pipes, I pressure sprayed with hose, soaked in a bucket of degresser, ect. Also removed and cleaned the EGR valve. (checked with mityvac-it works) Installed new gaskets on all along with 5 new glow plugs since I was there. Before installing charge air crossover pipe, I ran engine, noticed that the flap always stayed open no matter what RPM.(when is it supposed to close?)

Still the same symptoms although a little better boost and a little more air comming out of the center vents, slightly better shifts. Same LED fault codes 5, 15.

Using a multimeter, did the ohm (beep test). I got beeps on all 3 control valves and 2 transducers. Checking volts with engine running, I am getting voltage and voltage drop with increased rpm on all 3 control valves (as in manual). Using boost/vac gauge, am getting a good vacuum from the pump. When I checked vacuum on side connections of the control switchover valves (as in manual) I am only getting vacuum out of the boost pressure control switchover valve (Y27/4). Am I supposed to get vacuum at the other two valve side connections? (Y27 and Y27/5). Do they work in a series?

I hate to just start buying parts I don't need (control valves and transducers)

Also is there supposed to be a little filter (62) at the vacuum line connection at the vacuum pump, as in manual? (mine does not have one). I am trying to make sure I have all the right connecters with restrictions and without as called for. (cleaning the mesh filter fixed somebodys boost problem)

Suggestions?

Thanks!

gsxr · #18 05-23-2007, 04:31 PM

The flapper valve stays open all the time, until the EDS wants to turn on the EGR. Then the flapper starts flapping, to adjust boost pressure so it can dump sooty exhaust into the intake (yuck).

I would seriously consider just converting the wastegate from the reverse Polish vacuum type, to the good old pressure type and remove the EDS from the boost system entirely. I picked up a pressure-type wastegate for my 602 and I'm going to install that eventually.

It sounds to me like you have a serious vacuum issue that needs to be diagnosed - the vac signal to the tranny and climate control should be a solid 20-25", if not, you've either got a bad leak or a failing vac pump.

James L · #19 05-23-2007, 04:43 PM

Thanks, I will check vacuum for 20-25" at the cc and transmission. Where do I plug into? the line going from alda to firewall? line going to the right of the 4-way tee at front of engine.

2 months ago it was runing fine until I got the bright idea to clean the boost sensor and alda line, then the stuff around the air filter box. I must of burped up something.

Lesson learned, if it works, damnit....leave it alone!!!

gsxr · #20 05-23-2007, 04:50 PM

Whoa, hold on there... the tranny sees a modified signal from the VCV on the side of the IP. You want to check for 20-25" at the input to the VCV, and at the ACC system. Start with the vac pump itself, should get 20-25" there, then check each branch line... everything should hold vacuum. Any line that doesn't has a leak.

The ALDA line has pressure, not vacuum. Don't get pressure and vacuum confused, they are opposite. Some tubes & hoses carry pressure, others carry vacuum. Totally different functions.

BigBen · #21 05-23-2007, 05:20 PM

gsxr,

Any specs on the pressure type wastegate you're going to fit on your car?

Will you have to remove turbo and exhaust manifold to do that? Because if it can be changed in place, I'm certainly in for this modification as well.

And then bye bye MAF, EDS, EGR, intake flap... I even think there is no Check Engine Light that can come on in the dash!

Cheers,

pmckechnie · #22 05-23-2007, 07:42 PM

I have hesitated telling what I did to my 91 300D 2.5 Turbo. I had the same problem as others of no power. I bought a small cheap 0 - 15 lb guage and found I had very little or no boost. I had error codes which couldn't seem to be fixed. Found several bad components that were going to cost more than I paid for the car (well not quite). I tried several things like puting vacuum to the turbo all the time but the boost went way to high. Other people drive this car at times so I couldn't leave it that way. I removed the EGR and made a plate that was held on with 2 bolts that had springs on them. When the boost got high enough to compress the springs the plate would push open and regulate the boost. This worked fine but since the air out of the turbo also has the blowby gases in it and it would make a big mess. This worked but was not an option as I try to keep my engine clean.
Last and final fix was as follows and has been this way for over a year and has worked great.
I blocked the EGR with a metal plate.
I removed the air flow sensor, held it open and put a sheet metal screw in the top to hold it open.
Now comes the trickey part. I converted the air flap vacuum actuator to a pressure operated actuator . I added a spring to hold the plate open until the pressure (boost) gets up to 14 lbs.
Converting the air flap vacuum actuator was not hard. I used an old steel injector line. Cut it to the correct length for my needs. I drilled a hole the same size as the injector line in the opisite end of the vacuum actuator (there is a vent hole that I just enlarged verrrrrry carfull drilled out. I inserted the injector line into this hole and put JB Weld around it. This line got boost pressure. I don't know if the pictures will make it on this message but if not I will try again

pmckechnie · #23 05-23-2007, 07:55 PM

Trying again with pictures.

James L · #24 05-23-2007, 10:11 PM

I appreciate some of these suggestions. But here is a thought, why not just find the true problem (like a technician) and fix it to OE specs? These cars ran good at one time with the OE EDS.

I checked the vacuum pump output it seems ok. I will continue on with the 07.1 1120 5 and 15 pulse readout maual troubleshooting. I am thinking I did not check "vacuum at ARF valve with Y distributor"". Going to re-check vacuum at all components again.

I am using this harbour freight us general fuel pressure tester (red box), the needle flunctuates, I wonder if I need a new gauge?

Thanks for the help

pmckechnie · #25 05-24-2007, 07:25 AM

James L,
I totally agree that the car should be fixed correctly. I am a professional Tech and never do this to a customers car, however this car needed so many things ( i believe it was used as a parts car for a while and then put back on the road). I gave $1000 for the car. It needs painting, has 306K miles on it now, the valve cover is broken (you can see the JB Weld in some of the pictures), all three of the vacuum control valves (air flap, EGR, and waste gate) leaked, boost pressure sensor bad, and EDS output for boost control, and the list goes on and on. I don't know how all this was bad at one time unless parts had been used for another car. Yes this car was a mess. I said to myself, I am not putting this kind of money in this car and was tempted to just pass it on to someone else. I desided to work around some of these problems in my spare time and see what shape the rest of the car was in. Well for almost nothing except some spare time I made this car run GREAT, uses no oil, gets 34 mpg on the highway at 70 to 80 mph. Now the car is NOT for sale. It is my daily driver.
This information was just for the people who are tired of messing with the EDS system on these cars and want to just do away with it. When you get ready let me know and I will try to answer any questions you may have about what I did.

James L · #26 05-24-2007, 10:25 AM

pmckechnie, I think that is very resourcefull what you did on a car that sounds like it needed it.

I found a spliced hard vacuum line going to the vacuum control amp. Going to replace it with a full line. Can I clean with shop air and brake cleaner the in/out of the vacuum control amp without damaging a diaphram or the like?

I have found a good source for the vacuum transducer (pressure converter) $46.00 and the control valves $36.00.

gsxr · #27 05-24-2007, 11:28 AM

Quote:

Originally Posted by BigBen

Any specs on the pressure type wastegate you're going to fit on your car?

Will you have to remove turbo and exhaust manifold to do that? Because if it can be changed in place, I'm certainly in for this modification as well.

And then bye bye MAF, EDS, EGR, intake flap... I even think there is no Check Engine Light that can come on in the dash!

I got it off eBay, claims to fit most Garretts like we have on the 602/603. I have no idea what will need to be removed to install this. The main benefit is the ability to remove the EGR. The MAF is only there for the EDS, which controls the EGR.

babymog · #28 05-24-2007, 12:58 PM

The air flow sensor only controls the EGR? I've been wondering what its function is. So, ... I can un-plug it (from an '87) with no ill effects, or remove it?

BTW, technically it is not a MAF, it doesn't detect mass air flow, only air flow, old technology. Many a BMW et al would damage this item on the L-Jetronic system from a backfire, ... I've dropped many in the dumpster with a cracked flap.

gsxr · #29 05-24-2007, 01:04 PM

Correct - on a 1987 with the EGR disabled, you can ditch the AFS. Euro models without EGR have an open pipe in the same place. You can also jam the flapper door open although I don't think it's causing any real airflow restriction. We could ditch the EDS entirely, except I still like it for idle speed control. But that's about all it does now on my car, lol.

James L · #30 06-19-2007, 03:49 PM

Update; I removed the air filter box and switched the vacuum transducers Y31/1 and Y31/5. Now I only have fault code 15 instead of 5 and 15!!! A/C is comming strong through a/c center vent and not defrost!. Transmission shifts better.

Still slow boost until 30 mph or so, but better. I think I found the problem, a bad transducer. Will do some more FSM test to be sure.