my 83 SD... very slow from light... - PeachParts Mercedes-Benz Forum

vstech · #1 08-26-2009, 11:43 AM

once the turbo kicks in, it's fine.
I timed the 0-60 and got around 18, so not far off the standard SD, but it's nearly dangerous from a light... especially if there is a hill... the turbo will not kick in until rpm come up, and it is SOOOO SLOOOOW from the line...
what do you think I should check first?
I am new to this SD, my 82 was MUCHHHH faster, nearly 10 seconds to 60, and very fast turbo spool... alas, it will not start. this 83 is nearly pristine, everything works well, such a change from the myriad of issues the 82 had, but I am at a loss of the take off weakness in this car.

Mad_Matt · #2 08-26-2009, 11:53 AM

Based on what you are saying it sounds like your waist gate is stuck open not allowing your turbo to spool until you over come the opening in the gate. Seeing as I'm new to the MD world myself I'm not sure what to look for but that's what it sounds like.

I find it odd that no one on these forums recommends the installation of a boost gauge and a Pyro to monitor EGTs. EGT's as well as charge air temps not boost will melt your pistons.

blackestate · #3 08-26-2009, 04:00 PM

count the shifts, may be starting in 2nd

vstech · #4 08-26-2009, 04:20 PM

nope, 4 gears... that was my first thought...
pulls sloooooooowly, then pulls strong into about 20ish... then bangs into 2nd, and pulls hard all the way up to 40ish, then goes to third and pulls strong into the 70's and slides solid into 4th.

cmbdiesel · #5 08-26-2009, 05:00 PM

Possibly your throttle linkage is not adjusted properly? Not delivering full movement to the IP? Kind of like only HALF flooring it?

Brian Carlton · #6 08-26-2009, 10:19 PM

Quote:

Originally Posted by vstech

nope, 4 gears... that was my first thought...
pulls sloooooooowly, then pulls strong into about 20ish... then bangs into 2nd, and pulls hard all the way up to 40ish, then goes to third and pulls strong into the 70's and slides solid into 4th.

If it has the fuel, the camshaft timing or IP timing is off.

If those are correct, then it's got an exhaust restriction in some fashion.

If no exhaust restriction, remove the ALDA and see what it does.

If that provides no benefits, it's time to dial up the fuel.

p.s.: I'm in a similar situation with the '87............not very slow at 12.5 seconds..........but much slower than the '86...........with a brand new cylinder head...........makes no sense.

babyjames · #7 08-27-2009, 12:21 AM

Has the ALDA adjuster screw been monkeyed with, or does it still have the cover on it? My friend's '85 behaved exactly the same way. I backed the screw out a couple turns and it runs like a different car.

Jay.

toomany MBZ · #8 08-27-2009, 09:25 AM

Quote:

Originally Posted by babyjames

Has the ALDA adjuster screw been monkeyed with, or does it still have the cover on it? My friend's '85 behaved exactly the same way. I backed the screw out a couple turns and it runs like a different car.

Jay.

Mine also, it used to start in second tho.

MercFan · #9 08-27-2009, 09:36 AM

My '85 was acting exactly the same way... here's what I did:

1) Adjusted the valves (not much improvement)
2) Changed filters (not much different)
3) Cleaned out the banjo bolt and the hose in the back of the intake manifold - made a difference already but not enough
4) Turned the ALDA adjustment screw 3/4 CCW and the car came to life

Later I discovered that I have about 4deg timing chain stretch - which I need to replace eventually.

Those made a difference on mine - good luck.

James

vstech · #10 08-27-2009, 10:54 AM

arrrrgh.
I really didn't wanna mess with the alda.
I was under the impression that the alda did nothing but limit fuel under boost... I am having problems well before the boost kicks in. and TONS of power above 2000RPM... doesn't sound like alda to me, but I'll investigate further, thanks!
the car has low miles, and starts instantly cold, no blowby, slight oil leaks around the VC... no smoke. I will get a new VC gasket, and adjust the valves, and investigate the timing chain. I gotta change the oil, and give the motor a good bath anyway.
did the original motors have white stencils denoting their OM#? mine has right above the VP is .951 on it... in HUGE white letters. ya think it's got a replacement motor in it? or is that just a sign of a low mileage vehicle?
hmmm
turbo is filthy, much oil on the blades, I gotta clean out the air cleaner/oil collector... I'll investigate the throttle linkage, but it feels like it's getting full travel. I'll totally clean out the banjo bolt and the OB lines....
plenty of power on highway, so the filters are fine, I wish I had a clear primary, it's white plastic... but it looks ok. I'll change it soon. I've got a full tank of B20 in there at the moment, that ought to loosen up anything in the system, it seems slightly perkier this morning...

Brian Carlton · #11 08-27-2009, 11:06 AM

Quote:

Originally Posted by vstech

arrrrgh.
I really didn't wanna mess with the alda.
I was under the impression that the alda did nothing but limit fuel under boost... I am having problems well before the boost kicks in. and TONS of power above 2000RPM... doesn't sound like alda to me, but I'll investigate further, thanks!

My assumptions were invalid.

I presumed that you would have adjusted the ALDA as the outset...........given your experience.

The reason you don't want to mess with the ALDA is the risk of snapping off the screw...........so, just remove the damn thing as a test. Two wrenches and five minutes and you are done. Plug the pressure line.

Report back with results.

vstech · #12 08-27-2009, 11:25 AM

Brian, you are the man. thanks again and again.
my experience falls FARR short of the intricacies of these cars. I am a blunt tool, you are a precision weapon.

vstech · #13 09-04-2009, 11:36 AM

While I may tinker with the alda, I found the problem...
throttle linkage. at full pedal (which is broken too...) the IP only makes it about 1/2" from the stop. I dissassembled and cleaned all the links, lubed them with atf, and reassembled, then adjusted for full travel. I noticed that the little roller on the VC that rides in the groove is VERY worn. that must have eaten much of the travel. I'll have to replace that part I guess. anyway, I'm back to 14ish seconds to 60 now. not quite the barn burner of the 82, but acceptable. I'll tinker with other things to get all the power I expect later in the fall.
Thanks everyone!