Egr bypass on 85 TDT w/CA emissions

[squaredealz]

Searched the previous posts to no avail other than to install an old style boost control valve. 1985 TD with trap oxidizer. This AM I started car and drove off and huge clouds of smoke billowed out behind me and no power. Pulled off vacuum line to EGR. No smoke. Also no turbo boost. Seems there is electrical input to boost control. Other than replacing with non-electrical boost module, can I trick the existing boost module with voltage? The EGR diaphram does not move when I pull vacuum to it. The valve is much harder to access than a non-CA or I would just pull it and clean it out.

[Brian Carlton]

Originally Posted by squaredealz

Pulled off vacuum line to EGR.

Did you happen to plug this line after you pulled it?

[squaredealz]

Originally Posted by Brian Carlton

Did you happen to plug this line after you pulled it?

Sorry about that. Should have given more details. Prior to EGR failure, normal turbo boost. I ran engine at highway speed to get engine to normal ops temp then tested vacuum to EGR from vacuum converter. 8 Hg. Plugged vacuum line with golf tee. Engine runs normal except no turbo boost. Double checked all vacuum connections and all are good. Unplugged electrical connector at boost pressure aneroid but it has no effect.

[Brian Carlton]

Originally Posted by squaredealz

Sorry about that. Should have given more details. Prior to EGR failure, normal turbo boost. I ran engine at highway speed to get engine to normal ops temp then tested vacuum to EGR from vacuum converter. 8 Hg. Plugged vacuum line with golf tee. Engine runs normal except no turbo boost. Double checked all vacuum connections and all are good. Unplugged electrical connector at boost pressure aneroid but it has no effect.

Something is amiss. That's not a computer controlled engine and it has no clue that you disconnected and plugged the EGR. Are you sure you don't have a leak somewhere in the system?

[squaredealz]

Thanks for the info. I will just have to start isolating each section of vacuum back to the boost valve. Without a computer controlling the boost, it will probably be something simple I have overlooked. All part of the learning curve with these old 617's. If I learn anything I will repost the results.

Ok, checked entire ALDA circuit for clean lines & even bypassed boost control for temporary test run. Nothing. Not even a hint of boost. Engine starts perfect but acts like fuel starvation or potato in muffler. The only change has been the EGR failure. Could that cause the trap oxider to plug from the unburned fuel & back-pressure? I'm just guessing The odds of the ALDA failing are pretty slim. If the ALDA is good, would it be able to compensate for a plugged oxidizer? This has been my first 617 with all the emission stuff and seems that most of you benz diesel guys think that was not a very good design. Any thoughts or theories on this puzzler?

[Maroon 300D]

My EGR line is plugged, for off-road testing purposes of course, and I have boost. Are you sure your EGR just failed recently? Maybe it hasn't been working for some time.

Try plugging the line to the air recirculating valve as well. It's not doing any good anyway without the EGR, and I think it does slow you down a bit when it's not plugged and the EGR is. I doubt plugging this line will fix your problem, though.

I would think the liklihood of your trap ox being plugged is slim unless you only drive your car for a few miles at a time. Theoretically it should clear out on long highway drives, especially if your going over hills and such. Basically when it gets hot, the crap is supposed to burn off.

Do you know if MB has performed the recall work on your trap ox?

You wrote that you had 8 hg going to the EGR. I think this is low; my memory is that when I tested it on mine it was 22.5 hg at idle. I'm not sure if you were testing it at idle, but I'll test that today when I get home and report back tomorrow. This lack of boost doesn't seem to be a vacuum issue, though.

If the problem is fuel starvation, maybe you have clogged filters or a clogged tank screen. A lack of fuel could explain why you have no benefit from the turbo.

Also, have you checked your turbo? You mention boost but I'm not sure whether you're measuring the boost or just seeing whether the turbo kicks in or not. Maybe the turbo failed.

I'm also pretty sure there's a boost sensor of some sort on the intake manifold. I'm not sure how that relates to what is going on with your car, but you might want to do a search for that.

Well, that's all I can think of. Good luck!

[Maroon 300D]

Well I was way off on my recollection of the EGR vacuum. It is 0 at idle, 22.5 when revving the engine at any rpm. I tested it in my driveway when the car was warm; I would guess the electronic gizmo the vac to the EGR goes through might regulate it while you're driving.

22.5 is the strength of my vac pump.

So if you tested it the same way I did, 8 hg is probably indicitive of a massive leak somewhere.

[my123ca]

are you sure you pulled the vacuum line and not the hose to the wastegate? Maybe your EGR is stuck open?