603 ponderings - PeachParts Mercedes-Benz Forum

Johnhef · #1 02-19-2005, 03:50 PM

I'm still learning after graduating to a 603 last year. put a boost gauge on it this week and noticed im only getting 6psi. Although when The car is still in its warming up phase it gets 10psi. what gives? what controlls it on this thing? anything to do with that air sensor under the filter housing?

#2 02-19-2005, 06:48 PM

Quote:

Originally Posted by Johnhef

I'm still learning after graduating to a 603 last year. put a boost gauge on it this week and noticed im only getting 6psi. Although when The car is still in its warming up phase it gets 10psi. what gives? what controlls it on this thing? anything to do with that air sensor under the filter housing?

I would check and see if the waste gate is opening and closing properly. Also you should check your Alda and switchover. A clogged vacuum hose from intake manifold to switchover can be blocked. Stick a pin in the hose barb that go's into the intake manifold and make sure it's open too.

There are numerous threads and posts on this very subject with far more info than I've just briefly mentioned. Having more pressure when cold, and less after warm up, I've never tried to measure boost on a cold engine to witness this change! Maybe it's normal to do that, and then again maybe not! But it doesn't nessessarily mean something is wrong. But 6 psi is off for sure and should be around 12. Could be the Alda too! If it is not enrichening fuel, boost will not be made. BB

Brian Carlton · #3 02-19-2005, 07:48 PM

Quote:

Originally Posted by Johnhef

I'm still learning after graduating to a 603 last year. put a boost gauge on it this week and noticed im only getting 6psi. Although when The car is still in its warming up phase it gets 10psi. what gives? what controlls it on this thing? anything to do with that air sensor under the filter housing?

Can you please state where you measured the boost? In which line did you place the T to measure it?

Can you please advise the conditions whereby you observed the 6 psi? Vehicle speed, engine speed, and placement of right foot?

Then we can assist more.

Johnhef · #4 02-19-2005, 09:32 PM

Quote:

Originally Posted by Brian Carlton

Can you please state where you measured the boost? In which line did you place the T to measure it?

Can you please advise the conditions whereby you observed the 6 psi? Vehicle speed, engine speed, and placement of right foot?

Then we can assist more.

well give me a little credit

Car is a 1987 300D-T 235,000 mi, about 65k since engine rebuild.

Gauge was teed off the switchover valve line, in place of it incase the valve itself was bad (pretty sure its close to getting clogged). Had already pulled the pressure switch and "hose barb" from the intake and cleaned them out, as well as the the vacuum lines, which I had previously replaced due to rotted connections. Intake is already scheduled to be coming off when i find free time to be cleaned, and replace leaking seals and gaskets.

Conditions observed: 30's outside today, 2.5 mile drive to McDonalds, all the way there 10 psi, temp gauge was at about 60 C when I got there. Shut it off, went inside, picked up food, got back in and drove home, temp gauge at 80 C. 6psi all the way back. Not the first time I've noticed this, does it every time it starts when its cold.

Vehicle Speed: 60mph~
Engine Speed: ~3,000 - 4,600rpm
Right Foot: Pedal on Floor

Brian Carlton · #5 02-19-2005, 09:50 PM

Yep, you have it covered. Sorry for the previous detailed questions. Sometimes members fail to do the most basic of things.

I've got about the same skills you have with it, so, take my suggestions in context:

1) Disconnect the wastegate and see if you can get additional boost without it. It's a longshot, but, easy to test.

2) Apply pressure to the ALDA, directly, using a Mityvac and see if it holds pressure. If it does not, see how fast it loses pressure. If it loses all pressure in less than 2 seconds, then it's possible that you are not getting the enrichment you need from it. Then, the exhaust volume is down and the boost is down.

3) Make sure that the wastegate is fully closing. Any leak at the valve itself will drop the boost for sure.

4) Give the turbo a spin with your hand to see if it is rotating very freely. If it does not want to easily rotate on its own, then the boost will be low because it cannot spin up to sufficient speed.

It's an interesting case. Let us know how you make out.

Johnhef · #6 02-20-2005, 12:51 AM

Thanks, I'll try those ideas out in the morning (provided its a little warmer and not snowing

)

I haven't adjusted the alda on this one yet, or checked to see if its been done, keeps slipping my mind.

but still, whats the sensor/ flap? under the airbox for? I think It was in a post or PM from Mauri where he said to jam it open.

Brian Carlton · #7 02-20-2005, 09:09 AM

Quote:

Originally Posted by Johnhef

but still, whats the sensor/ flap? under the airbox for? I think It was in a post or PM from Mauri where he said to jam it open.

That flap measures airflow and provides same to the "Electronic Diesel System". The more the flap opens, the greater the airflow. You might check to see that this flap is not stuck closed. But, I doubt it, because there would be clouds of black smoke.

I cannot imagine what the system does with it. AFAIK, it cannot be fuel related because the IP is strictly mechanical.

Johnhef · #8 02-20-2005, 11:49 AM

I pulled out the airbox and flap mechanism, checked all the lines for leaks, I did find that the lines into and out of the valve that goes to the egr had ball bearings stick in the lines. switched them out, but no difference. When you said disconnect the wastegate, you mean undo the 12mm bolt and let it hang and drive it? or pull that vacuum line off and plug it?

man stuff is so cramped on this engine I cant get to anything. how do I adjust the alda without pulling the GD intake manifold! grrr give me a 617 any day.

Brian Carlton · #9 02-20-2005, 12:08 PM

The line to the wastegate is a pressurized line from the intake side of the turbo. Disconnect this line and plug it (you probably will need a clamp).

Without this line to the wastegate, the wastegate valve cannot open. If you then have additional boost, it's the valve that needs to be adjusted.

Yeah, I know the feeling. I've been reluctant to try and get around in there.

You don't need to adjust the ALDA just yet. Just try and see if it will hold pressure (don't exceed 15 psig). Some Mityvac's can provide pressure for this test, otherwise you need a small regulator on a compressed air line and a needle valve to shut off the air supply so you can test the leakdown.

Johnhef · #10 02-21-2005, 07:57 PM

Well, finally was able to use a *working* pressure/vacuum tester... alda leaks down, replaced a handful of semi rotted rubber vacuum lines, got the flex metal tubing for the exhaust between cyls 2 and 3 coming tomorrow morning, since its leaking.

I saw a picture procedure somewhere for removing the alda (in under two minutes??), was that on this site? I need to pull the intake anyways, should I just do it all at once? once i get the alda off, what am i replacing and is it a dealer item?

Brian Carlton · #11 02-21-2005, 08:23 PM

Run a search on "ALDA" and use the username "Gsxr"

I'm sure it's here.

H2O2 · #12 02-21-2005, 08:53 PM

I'm able to remove the ALDA on my '87 603 without removing the intake. I use a 24mm(?) wrench and a medium sized pair of channel locks (to hold the ALDA). It's not too hard.

The seal at the bottom of the ALDA is more than likely shot and won't hold pressure--it should be able to hold ~10 psi for a period of time. I purchased a spare seal from a guy over on the MBZ.org diesel list serv, but I don't know if he has any others, or where he got them.

You could use a fuel line clamp to choke the wastegate pressure line, unless you've got a KKK turbo, which uses a steel line. Does the turbo have any excessive sideplay or chipped vanes?

I removed the air flow meter altogether with 4" ABS electrical conduit. The meter is only used to signal the computer for EGR function, so its removal eliminates ~6 lbs of dead restrictive weight.

Johnhef · #13 02-21-2005, 10:50 PM

Quote:

Originally Posted by H2O2

You could use a fuel line clamp to choke the wastegate pressure line, unless you've got a KKK turbo, which uses a steel line. Does the turbo have any excessive sideplay or chipped vanes?

I removed the air flow meter altogether with 4" ABS electrical conduit. The meter is only used to signal the computer for EGR function, so its removal eliminates ~6 lbs of dead restrictive weight.

It has the KKK turbo. I had that black intake pipe to it off a long time ago, but I dont remember anything insignificantly wrong with the impeller blades.

So if I take out the air flow meter completly, what ill effects if any, by not having that little sensor mounted at the front of the flow meter will there be?

H2O2 · #14 02-21-2005, 11:10 PM

Are you referring to the air intake temp sensor? If you've disabled the EGR already, then you'll experience a slight tingling sensation, but no lasting side effects whatsoever. I pulled the entire EGR system, complete with vacuum transducers, plumbing and the works. It just cleans up the engine compartment a bit, but other than that, it's not critical. Again, the airflow meter and its attendent hardware are simply signal generators for the computer to control the EGR system--remove that, and there's nothing for the computer to control anymore.

Johnhef · #15 02-21-2005, 11:28 PM

Thats the one.

I checked out that link, nice work on the intercooler, anymore progress lately?

I'm going to try and adapt a conical filter in place of the airbox- the one I got is slightly bigger than the opening, so i'm going to need to find some kind of adapter, hittin the hardware stores this weekend.

One of the valves behind the right headlamp controls the egr, i dont remember what the other one does, did you remove that one too? As soon as I hear from brian, my ex-egr kits should be on the way.

have any photos of your 603 setup? i like visual aids

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