Congratulations Jim. Harry
----- Original Message ----- From: "Jim Cathey" <[EMAIL PROTECTED]> To: "Mercedes Discussion List" <[EMAIL PROTECTED]> Sent: Monday, March 27, 2006 4:31 PM Subject: Re: [MBZ] Project 240D in Oregon > (The cruise is fixed. What a nightmare!) > > -- Jim > > March 25, 2006 > > Removed the test contacts in the amplifier and put it back in its > case. Put together the bench vacuum pump again now that its glue has > had a chance to dry. When stuffed inside its foam 'football' it's > really quite quiet. It ought to come in very handy from time to time, > and it's nice to finally have a use for that wretched pump I got stuck > with. > > March 26, 2006 > > Reinstalled the cruise amplifier. Installed the auxiliary fan support > brackets. No auxiliary fan, but this is the best place to store the > brackets! Glued torn right-side door weatherstrip. Checked brown and > green vacuum lines (again) for leaks, nothing. I don't know what to > think. While driving it today it seems to me that the throttle pedal > gyrations (which you can feel with your foot if you try) must be > abnormal, and reflect an excessive consumption of vacuum by the > actuator. But _why_ does it do this? It doesn't on the bench. > > I thought I'd better cover some bases, something I believe to be true > is not. So I tried a different stalk switch. A long shot, but in > theory it is possible for a contact that doesn't open-circuit all the > way to disrupt the amplifier. No dice, the car drove the same. Maybe > I need to swap actuators too to be sure of it. > > I also started the resoldering process on the two dead amplifiers I > have in the box. If I can get them to work on the bench I'll try them > both in the car to see what happens. > > ...Got one running well on the bench and took it for a drive. Exactly > the same results. Definitely pointing away from the amplifier. > > The other spare amplifier, after resoldering, goes into immediate > deceleration. Probing reveals a climbing FET output voltage, for no > apparent cause. Looks like a leaky FET, probably gate punch-through > damage induced during the resoldering resulting in leakage from the > Drain. Be careful with those! > > This exercise leaves me with two spare vacuum amplifiers that seem to > work, one from before and the one I just fixed. That's enough! > > March 27, 2006 > > Removed the cruise actuator and brought it in to the bench. Seems to > act exactly like the one I use for testing. No abnormal appetite for > vacuum in other words. > > Removed vacuum pump. What a PITA! Disassembling it I find no torn > diaphragms, and the valves work. There was oil in one of the valves, > the intake, but I suspect that this car had an oil leak into the > vacuum system at a prior date that was not completely cleaned out. I > suppose it could be that the puddled oil was preventing the valve from > working fully? Let us hope. The cam and bearing are perfect. The > rubber bits all look good. > > Reassembling the pump looks to be even harder than disassembling it. > I put the valve cover back together and sucking and blowing on the two > ports results in good behavior. No backwards leaking that I can > detect. The pump requires 1" of preload on the main spring for > reassembly, I used a block of wood on the floor as a spacer while > standing on the pump. Awkward, but do-able. > > The reassembled pump went back on the engine easily enough and > 'squawked' as it pumped when the engine was turned by hand. Sounded > normal enough. With the engine started the brake booster pumped down > in a normal amount of time. Went for a test drive. > > Same. Crap. That was the last major piece to look at and it looks > good. > > Y'know, as I mentioned before when weird things happen that you can't > explain then something you believe to be true is not, one of your > basic assumptions is wrong. So I started a round of > divide-and-conquer diagnosis. First I unhooked the brake booster and > used duct tape to secure the vacuum check valve (which feeds the > reservoir/doors/cruise systems) to its end, taped shut the usual tap > for the accessories, and went for a drive. Perfect cruise operation, > other than the lack of power brakes! The vacuum level never dropped > much at all. The pump has got plenty of 'oomph'. I then hooked up > all the vacuum taps to this point and tried again. Still good. I > then taped off the brake fitting and moved the check valve to the > usual tap, though bypassing the splitter and much of the hose and > tried again. Better than usual, but not good. So that eliminates the > brake booster as a leak (not that I suspected it but we are in full > science mode now). At least this lets me hook up the power brakes > again! I then removed the usual vacuum hose from the tap and used a > section of 1/4" fuel line as a vacuum tap. This fits over a stepped > portion of the body of the vacuum fitting, and should eliminate any > chance of restrictions in the usual hosing causing problems. The > check valve was taped into the end of the fuel line. Still not good. > That leaves the vacuum tap as the only remaining potential culprit. I > removed the brake vacuum line from the car and heated the plastic tap > fitting with a heat gun and drove a nail down it to stretch it out. I > couldn't get it in all the way. With it stretched a bit I then ran a > drill down it to finish opening it up. Then I blew out the shavings > and put it back on the car, using the fuel line tap system. I used a > section of cruise actuator bleed line (extra large) as the thing to go > between the fuel line and the 4-way splitter. Duct tape was used to > seal it all up as an extra precaution. > > Success! On a test drive the cruise worked well, and the vacuum gauge > never fell very far. Either something was caught in this vacuum tap, > it was defective all along, or somebody replaced this tap (or the > entire line) with one that was for a non-cruise-control car. > > As a bonus, when the car is shut off it shuts off much faster now, > more like every other diesel we have. Something was definitely wrong, > and I wasted a _lot_ of time chasing what turned out to be a very > simple problem. > > > _______________________________________ > http://www.striplin.net > For new parts see official list sponsor: http://www.buymbparts.com/ > For used parts email [EMAIL PROTECTED] > > To Unsubscribe or change delivery options go to: > http://striplin.net/mailman/listinfo/mercedes_striplin.net >
