'72 280SE New Owner - PeachParts Mercedes-Benz Forum

MerkeyTerkey · #1 07-30-2012, 05:10 PM

Hey guys

Someone at Benzworld told me to come here. I just recently became an owner of a 1972 280SE. I don't know a damn thing about the car, it was actually a gift. The car is in pretty decent shape, it only has 115k on the clock. I dont think it has been driven lately though. The car runs, it idles pretty good but as soon as you try and get on the gas it wants to stall. The guy I got it from said the previous owner had someone come and look at the car and he started tweaking some knob that's in the engine bay on the front passengers side? He said after the guy messed with that knob it started to run pretty badly...?

Well anyways, I'm looking forward to the help you guys are going to give me when I need it

Pics of said car:

Tomguy · #2 07-30-2012, 08:10 PM

Congrats! I assume the 4.5 badge isn't upbadging, so the knob was probably the ECU for the fuel injection - which only affects idle mixture. Unless he was on the firewall, in which case he was messing with the MAP sensor. Which could be bad! Before spending time chasing your tail on adjustments, replace every vacuum hose - especially the one to the MAP itself. Use some carb cleaner (preferably on a colder engine) around the injectors and manifold plenum seals while it's idling to see if the idle speed changes - if so, those seals are bad. Once you have the vacuum leaks sorted out, THEN clean the EFI trigger points, adjust the timing, and THEN adjust the mixture if needed.

MerkeyTerkey · #3 07-30-2012, 11:22 PM

It is the 4.5 V8 so he was changing the mixture eh. What happens when I start turning that knob? Although you say dont mess with this until after replacing all the vacuum hoses...

So my list so far is:

Change fluids
Replace all vacuum hoses

wbain5280 · #4 07-31-2012, 01:12 AM

The front suspension needs to be greased, as does the front of the driveshaft and there are two in the rear swing axle. Use a rag to clean the nipples and then grease them.

The front suspension has a nipple for every joint including the back side of the kingpin housing.

alabbasi · #5 07-31-2012, 02:36 AM

You mess with the adjustment to richen (clockwise) or lean the mixture but as Tomguy said, don't mess with it until you sort out the vacuum system. Also put some fresh gas in the tank.

tram · #6 07-31-2012, 03:24 AM

NICE!!! White on burgundy. Mmmmm.

Tomguy · #7 07-31-2012, 08:17 AM

Also make sure to replace every rubber hose that carries fuel under the hood. The lines from the fuel rail on the firewall to the engine feed rail, from the feed rail to both left & right rails, the 8 injector hoses, and the lines behind the rails to the return. Use EFI-rated higher pressure hose, 7mm IIRC. Ensure the flex disc that attaches the trans to the driveshaft is in good shape before driving as well.

MerkeyTerkey · #8 07-31-2012, 09:57 AM

Stop adding stuff to my list, geeze guys.

Change fluids
Replace all vacuum hoses
Replace all fuel line hoses
Check the flex disk from tranny to the drive shaft (looking for leaks/tears?)
Grease front/rear suspension.
Fresh gas ✓

It also sounds like it has an exhaust leak, but the muffler/tail pipe/exhaust piping under the car looks fine. And what looks to be the coolant reservoir has a hole in the cap, and now that I think about it I think there's supposed to be a hose going up there...

Graham · #9 07-31-2012, 11:28 AM

Quote:

Originally Posted by MerkeyTerkey

Stop adding stuff to my list, geeze guys.

Change fluids
Replace all vacuum hoses
Replace all fuel line hoses
Check the flex disk from tranny to the drive shaft (looking for leaks/tears?)
Grease front/rear suspension.
Fresh gas ✓

It also sounds like it has an exhaust leak, but the muffler/tail pipe/exhaust piping under the car looks fine. And what looks to be the coolant reservoir has a hole in the cap, and now that I think about it I think there's supposed to be a hose going up there...

I was thinking same thing! But do check fuel line hoses that connect to injectors. They do leak and can cause fires. And flex disk failure can make a big mess. The engine injection system uses vacuum for control, so if it doesn't run well, finding the leaks will become important. A bad Auxilliary Air Valve (AAV) will sometimes make you think you have a vacuum leak - something we have all found out!

By the way, what you have is a D-Jetronic (Early Bosch electronic fuel in jection, D-Jet for short)). If you search here and on Benzworld (mainly in SL forum), you will find a ton of stuff on D-Jets. same system was used on all MB V-8s of that era as well as on Porsche, VW, Jaguar and a number of other Euro cars.

Re the knob on the ECU - You can't do any harm adjusting that. It only affects the IDLE mixture (foot off pedal). Try setting the knob at middle of it's range (11clicks from either extreme) then adjust slowly a click at a time each way until it idles better (do it with car warm).

You might also adjust the idle speed so it is at about 700rpm with engine well warmed up. You can find the idle screw in the first post here a few pics down. (BTW, that link has most of what you will need to get car running smooth!)

MerkeyTerkey · #10 07-31-2012, 12:14 PM

Awesome! Thanks Graham...

gingerkid · #11 07-31-2012, 12:35 PM

if you do the fuel lines, might as well send the injectors off to get refurbished. These are a blast to work on... Unbelievably sophisticated for an early '70s car!

MerkeyTerkey · #12 07-31-2012, 01:10 PM

Quote:

Originally Posted by gingerkid

if you do the fuel lines, might as well send the injectors off to get refurbished. These are a blast to work on... Unbelievably sophisticated for an early '70s car!

Anywhere in particular or just somewhere offline?

gingerkid · #13 07-31-2012, 02:01 PM

WitchHunter Performance - Injector Cleaning & Flow Testing Services these guys seem to have a great reputation. I was going to use them until i discovered someone put the wrong injectors in my car at some point in the past... so i ended up getting new ones.

meltedpanda · #14 07-31-2012, 04:02 PM

thats who I use, great group. Search my name for Djet issues and resolve, been there done that on many !!!

PS - nice car

Graham · #15 07-31-2012, 07:06 PM

A couple of more things:

There is another owner on this forum parting out what seems the same car. Maybe you could pick up teh following parts from him:

- MPS (Manifold Pressure sensor)
- AAV (Aux Air Valve)
- Distributor (including trigger points)
- Throttle Position Switch (TPS)
- ECU
- Injectors
and maybe a few other parts too.

Regarding having injectors cleaned, some on line stores had new Bosch injectors on sale for just over $50 recently. I was tempted, but already have a spare used set that I checked & cleaned myself.