1990 300D 2.5 Running Rich - PeachParts Mercedes-Benz Forum

mcguirjf · #1 09-04-2007, 03:51 PM

Greetings,
I'm currently finishing the engine installation in my 1990 300D and have one problem left. Black smoke!

The car runs very very very rich. So much that I'll make your eyes water.

I even ran a separate container of fresh diesel just to make sure that I don't have bad fuel in the tank.

I replaced the timing chain. Cam marks align with TDC indicator. I've installed the IP with the locking tool at 15 deg ATDC. I used the allen key to adjust the timing within a certain range with no change.

I cracked each injector line individually with the same loss of cylinder affect and no change in smoke content.

The air filter is a K/N and is clean and not over oiled! I have also run the car with the air box disconnected from the air filter. There is no appearance of air restrictions.

Also when giving the car gas, if I don't let off the gas pedal slowly the car stalls. Example - Rev to 4000 rpms and let the rpms fall and the car stalls. If I hold the pedal a little the car's idle will fall slower and then regain idle.

From other posts... the vaccum controlled valve located after the turbo is suppose to move with actuation of the throttle this does not happen.

I'm going to perform a compression test later this week. I should have codes pulled this week. Any other suggestions on how I should trouble shoot this problem? Can the EDS alone cause a rich condition or does it just control idle?

sailor15015 · #2 09-04-2007, 05:09 PM

I don't know much about your model year but if the computer is holding the wastegate open, you won't get any boost and there won't be enough air to burn the supplied fuel, resulting in black smoke. A stuck open wastegate shouldn't cause stalling though, just a lack of power.

2.5Turbo · #3 09-04-2007, 07:53 PM

Quote:

Originally Posted by sailor15015

I don't know much about your model year but if the computer is holding the wastegate open, you won't get any boost and there won't be enough air to burn the supplied fuel, resulting in black smoke. A stuck open wastegate shouldn't cause stalling though, just a lack of power.

Yeah, but the ALDA keeps the fuel down when there isn't any boost. If the wastegate was open, the ALDA wouldn't get any pressure, so it wouldn't enrich the fuel to the point of black smoke. That is if the ALDA is unmolested, working and installed properly.

Make sure your EGR and flapper valve on the intake are both working and not stuck open or closed. Also check the two transducers that control these just behind the airbox. If you need to test them, there are three on this car and they're all the same part number and are interchangeable. This is how I pinned down a bad turbo wastegate transducer; I replaced it with the flapper valve one which was known to work.

You're also absolutely sure your intake isn't gunked up with that evil mix of EGR soot and oil from the breather?

mcguirjf · #4 09-05-2007, 11:10 AM

The ALDA is unmolested with the original black cap on top.

I will check to see if the egr is stuck. The intake runners only have 90K miles on them with very little sludge inside.

What is the part number on those transducers?

If there are error codes, could that result in car running in safe mode (shutting down the transducers) resulting in this rich condition?

I'm hoping my compression values are good and this is nothing more than a computer issue!

777funk · #5 09-05-2007, 11:33 AM

As far as stalling when you let off the pedal. That could be your linkage/bowden cable not being tight enough.

Unplug the electronic idle (ELR) plug on the back of the pump. If your engine kills at idle then you have a mechanical adjustment problem. The ELR maintains your idle electronically. So if it kills without it, you've got linkage etc. to tighten. Most likely it's the bowden cable needs to be tightened. Try that first.

Simple test. Just start the car and unplug that ELR. If it kills you have the mentioned things to adjust.

mcguirjf · #6 09-05-2007, 12:02 PM

Which is the bowden cable?

The cable to the accelerator pedal or the cable to the transmission?

Are you refering to the solid adjustable linkages on the injector pump?

iceman805 · #7 09-05-2007, 01:46 PM

I have to say it is a privilege to watch how some members on this board work through issues...amazing. I hope I can learn half of what some of you have forgotten.

I saw this post and figured I could contribute from my service CD.

mcguirjf · #8 09-05-2007, 03:18 PM

OK! So the bowden cable referred to is the one connected to the accelerator pedal.

I found 07.1-2006 Testing Electronic Idle Speed Control in the FSM.

I also see listed 07-2053 as listed for Preceding work: Testing and Adjusting Idle Speed (07-2053).

There is enough slack in the cable so the spring stop is fully seated. I don't want to pull in the slack in the gas (diesel) pedal to raise the idle.

I see that there is a screw with a lock nut located to the side of the EDS on the injector pump.

I think I should solve the "rich" condition first before adjusting the idle.

Keep the Suggestions Coming!

2.5Turbo · #9 09-05-2007, 05:36 PM

Quote:

Originally Posted by mcguirjf

The ALDA is unmolested with the original black cap on top.

I will check to see if the egr is stuck. The intake runners only have 90K miles on them with very little sludge inside.

What is the part number on those transducers?

If there are error codes, could that result in car running in safe mode (shutting down the transducers) resulting in this rich condition?

I'm hoping my compression values are good and this is nothing more than a computer issue!

The transducers have gone through revisions over the years. The one I got had a totally different part number and was smaller, but it works just fine and mounts up to the bracket perfectly. Don't know the PN off the top of my head, but you might have some luck discussing it with Phil on fastlane.

You can test the vacuum operated gadgets with straight vacuum. If you hold the wastegate closed with straight vacuum, be careful not to drive it too hard or you'll risk damage from overboosting. It would be good to have a boost gauge hooked up while doing this testing so you know you're not boosting to dangerous levels.

Error codes will hold your wastegate open. What is the power like? Is your 0-60 18-20 seconds? If so, your wastegate is not closing. If the EGR isn't working (transducer or valve itself) you may have an EGR transducer code. If something is wrong with the EGR system you may also get the airflow meter code. If you haven't built one already, build a code flasher/clearer. I've posted the link numerous times on here, so a quick search should turn it up. Costs about $20 in parts from Radioshack and a bit of time to solder it all together.

Also, the only thing the EDS does on the IP is control idle speed. The rack is controlled through the cable and linkage by your right foot. I don't see how the ELR actuator could create an over rich condition.

One more thought...if the ALDA went bad somehow and allowed full enrichment all the time and the turbo wasn't building boost because of error codes, you would have one hell of a smoke show. Are we sure the IP and ALDA on this new engine is good? Check and see if there are any extra shims under the ALDA as well...simply looking for the protective cap on top does not guarantee that it hasn't been tampered with underneath.

Hope you can get this sorted out without too much trouble...I have pretty much memorized the systems of the 602.962 by troubleshooting and working on mine. Currently my 300D is at home 2500 miles away

mcguirjf · #10 09-07-2007, 11:22 AM

Well I couldn't get her started last night as the battery has finally died. I was able to check for codes with the new scanner I built. Only had a code 7 which is ok since the car wasn't running.

Just to clarify for others #4 is where the signal output is located, and #1 is where the Ground connects. It took me an hour to figure out why the damn light would stay on because I had them reversed!

I checked the ERG Valve and it opens when vacuum is applied. And is closed with vacuum off.

I'm going to do a compression test when I get home today. Pending the results, I either have a compression problem or a fuel problem.

Stay Tuned!

2.5Turbo · #11 09-07-2007, 05:17 PM

I have also found that on the '90 the light will stay on when there are codes stored in the EDS. I've heard that the computer in later models is slightly different, so YMMV.

Now that you know your emissions systems are functioning, it's time to look into compression and the IP. Hope it's the IP because it's cheaper than an engine

pmckechnie · #12 09-07-2007, 07:22 PM

I have been busy the last couple of weeks and am just now getting cought up with my thread reading. I have a 91 300D which is almost the same as yours. As for your problem, First, the only way a diesel can run rich is not getting enough air. If you are getting too much fuel, the engine will just run faster. First, what you need to do is unhook the vacuum lines from EGR, Wastgate and the air flap in the intake. In fact, you could just remove the part of the intake system that runs over the valve cover. If it is still acting like it is rich (black smoke) then make sure the exhaust is not pluged. You could unhook the exhaust pipe from the turbo and again check for the black smoke. If it is still there, then the only other possibility is a timing issue. Ususally if the cam is too far out of time the compression will be low and it won't start at all. However if the injection pump is out of time you could have black smoke due to the fuel getting into the cyl at the wrong time and geting incomplete combustion. I know for a fact that these cars will run OK, not great but OK with no boost. After you get it running smooth, then you can worry about all the other things.
Gook luck

mcguirjf · #13 09-10-2007, 11:56 AM

Greetings!

Well this was a very busy weekend. My compression gauge came in on Friday and pulled some numbers.
Cylinder/Pressure
1/425
2/425
3/400
4/400
5/400

I cranked for a ten count per cylinder, and I think the new battery started to lose juice. So compression is Good! Thank god because I bought this engine from a salvage yard months ago and I'd be "very mad" if I had to ship it back.

So yesterday I paid a visit to Tom at Yankee Diesel in CT to see if I had a fuel issue. Tom is very knowledgable in MB diesels and his shop is awesome. After talking with him the possible causes of my problems are...
-Engine Timing
-TDC Location
-Timing Chain Off a Tooth

Well I shifted the chain one tooth and the cam and harmonic balancer would not align and be off by 20 degrees. Next I swapped in the injectors that were in the original engine. I noticed a better idle and less knocking, but still same amount of smoke and ran the same.

I pulled the connector off the idle control on the IP and the car stalls. According to the manual the idle is suppose to increase???

I also pulled the intake manifold and found very little black slug inside.

I have to believe that my problem is either or both injectors and injector pump. I'm going to have all (10) of my injectors pop tested and have the IP bench tested. I am thinking of running some diesel purge and rebuilding the delivery valves, but I feel that I'm just waisting my time.

One thing to also note is the IP is off the engine that originally came with the car. That engine died because the oil pump drive sprocket was rounded smooth and as a resultant had no oil pressure. What affects of no oil pressure have on the IP???

I also noticed some damage on the IP where it interfaces with the engine. A copper or brass colored "thimble" is dented in. I don't know its function, but it could be related to the problem. See Picture.

Please keep the help coming.
Thank you!

mcguirjf · #14 09-11-2007, 09:54 AM

Well this morning on my way to work I dropped off two sets of injectors and my IP to Steve at H&L Diesel in Deep River, CT. I should have it back by the end of the week. This job has definately been mind racking. I'll keep everyone posted on the results.

mcguirjf · #15 09-14-2007, 12:58 PM

Just spoke with the shop and the diagnosis is mixed. The "golden thimble" is a protective cap for the rack. The shop is going to disassemble to verify that no damage has occurred. There has been an observation that the govener is tight. I don't know what the exact function of the governer is, but please chime in if you know!

I should get it back with injectors tested by middle of next week.

What does the governer in the IP do?