280SLeuro

I have a 1976 280SL EURO. It has electronic fuel injection. I know that it did not come this way new. Everything is mercedes original components on the fuel injection system. I have been trying to find out more about this system as I have a problem with the engine cutting out under a load. The ignition checks out good on the scope and has new spark plugs,wires,distributor cap, rotor and points. I am pretty sure it is not getting the proper fuel under loads or higher RPM. the fuel pressure was 25 psi on the rail. It runs better when I raise the rail pressure up to 40 psi. The system has no air flow meter, but has a rheostat type throttle position sensor. I have three Chilton shop manuals from early 70's to 85, on Mercedes, but can not find this particular system. I am sure this engine has been modified.
Any help I can get would be greatly appreciated.
here are the specs that I have on this car.
vin # 107 042 12 001040
Eng.# 110 982 12 001584
Fuel injection ECU unit # 0 280 001 015
Dose anyone know when this ECU unit was used on the 110 DOHC engines. Help, Boyd


[Edited by Beals on 06-02-2001 at 07:44 AM]

[mbdoc]

Sounds like a 1975 or earlier car! & that is a factory set-up as far as the fuel system goes!! HAVE seen & worked on several of that exact set-up! The fuel pressure is supposed to be at 2 BAR(30psi), & the system has a MAP sensor that does 75% of fuel adjustments. The 1976 & later cars had CIS fuel systems. The MAP sensor is the key to this engine running correctly. Follow large Vacuum from the rear of the engine to the MAP sensor around the brake booster area. THE 1971 to 1976 V-8's used a very simular system, specs would be very close.

[cth350]

The 280SL was a euro-only car. The early euro M110 motors were electronically fuel injected (the D-jetronic system), as were ALL the M116 & M117 motors (the 3.5 & 4.5 v8s) and period volvo's, saabs & VWs.

Benz never shipped the M110 versions to the US, so the available doc is pretty scant. BUT, the v8 service manual has most everything you want to know, as do some of the books on older fuel injection systems. Lastly, the M110 service fiche has section 7.4 that specifically covers the system.

According to my 1974 TDM, the 280SL was built as-of Aug 1974, so having the D-jet system is perfectly OK, if you car is old enough.

Some people consider the system a real pain, others less so. You can spend a great deal of money swapping out parts to figure out what's wrong. DON'T do that. There are published diagnostics to follow. If you email me (I've already sent you a mail via this site), I can reply with what doc I have already scanned magnetically.

Read the docs and then use them and be patient. The system's biggest failures are:

- poor electrical connections (look for and clean the ground point from the harness).
- vacuum leaks (check VERY carefully. REPLACE the hose to the manifold pressure sensor)
- ignition system & valve clearance problems (get things to SPEC).

Lastly, anybody that suggests that you REPLACE your "trigger points" should be smacked. Rarely if ever do they need to be replaced. However, they probably haven't been cleaned. They do get dirty. Use a little contact cleaner spray, once you find them and figure out how to remove them. Then put them back.

Also, check this site, in both this forum and the vintage one for other postings related to the D-jet system and the woes various folk have had with the 280se 4.5's & 250CE's.

-CTH

[stevebfl]

And the Map sensor is adjustable.

To verify the condition of the Map sensor, take your scope and hook it to the injector. Read the pulse width, while Key-on, Engine Off. To do this move the throttle by hand. You should get 20 injection pulses. Read the pulse width. Now get a hand held vacuum pump and pull 15 inches of vacuum on the Map sensor. You should get a pulse width less than half of the no vacuum test. Normal range of injection pulse width would be from around 3.0ms at idle vacuum to around 10ms at no vacuum.

The Map sensor works off an evacuated bellows that swells and contracts due to different vacuum placed on it. It moves an armature through to coils one an input and the other the output. If the evacuated chamber is corrupt then no motion comes and no enrichment gained.

I found the problem with the 280SL, cutting out on accelerartion. You put me on the right track. I checked the MAP sensor and found a cold solder conection inside the unit. The car runs great now, nice and smooth, no misses.
Thanks for your help, M.C.Doc, cth350, Stevebfl. Some day I guess I well have to tell you the story about how I aguired my $2500. 280SL and grasped it out of the distructive hands of fate. Boyd

Originally posted by stevebfl
And the Map sensor is adjustable.

To verify the condition of the Map sensor, take your scope and hook it to the injector. Read the pulse width, while Key-on, Engine Off. To do this move the throttle by hand. You should get 20 injection pulses. Read the pulse width. Now get a hand held vacuum pump and pull 15 inches of vacuum on the Map sensor. You should get a pulse width less than half of the no vacuum test. Normal range of injection pulse width would be from around 3.0ms at idle vacuum to around 10ms at no vacuum.

The Map sensor works off an evacuated bellows that swells and contracts due to different vacuum placed on it. It moves an armature through to coils one an input and the other the output. If the evacuated chamber is corrupt then no motion comes and no enrichment gained.