Alda

[oldsouth]

I checked my alda unit on the injector pump today by putting a guage inline and applying pressure and then vacuum. It would slowly leak off both ways. Car is running fine except at high altitude as I have already posted. Does this mean the alda is bad? Could this cause problems at high altitude?

[h2odiesel]

No, it doesn't indicate the unit is bad. some leakage of boost is normal. Failure occurs when the the disc shaped bladders inside the housing rupture allowing pressure to equalize. The units are more robust than commonly believed. When functioning correctly high boost pressure in the ALDA housing collapses the bladders allowing the linkage in the pump to move upward and enrich the fuel at a particular speed. Have you tried adjusting the ALDA? Are your boost sensing lines and switch over solinoid clear?

Bob D.

[oldsouth]

Next to impossible to adjust unless the intake manifold is removed. Only about .5" clearance between top of alda and intake runner. Glad to hear some leakage is normal. About a $350 item and a pump shop has to have the pump off to calibrate it. I guess I will just forget about my high altitude problem. Talked with Marshall Booth and he seems to think it is normal to smoke at altitude. Said if I lived up there he would recommend recalibrating the pump.

[gsxr]

It may be possible to remove the ALDA with the intake in place, although I haven't tried yet. It unscrews while you hold the brass nut underneath (or vice versa). To adjust you break/twist off the little "coffee can" on top. Once that's off, you can adjust it externally with the intake in place, using a 10mm (?) wrench to loosen the locknut, then use a "right angle" flat blade screwdriver to turn the shaft. It's a PITA but possible. The "correct" method to adjust it is actually inside the pump. Yes you need to yank the pump off and bring it to a Bosch shop for that. I did that with mine, it cost $150 plus ~$25 in gaskets (I removed it and brought it to the shop myself). I agree with Marshall, btw.

Photos of the ALDA & I/P are here:

http://www.meimann.com/images/mercedes/OM603_intake/


I snagged an ALDA off a car in the junkyard last week, I want to take it apart and snap some photos, and post those too. The OM603 engine manual has no useful description of the internal operation. The older OM617 (5-cyl iron head diesel) engine manual had a GREAT description of the operation, with nifty diagrams too!


HTH,