450 SL in Denmark

Hi Peter,
did you check the ignition timing following the instruction given by DB and noticed by Volker before?
It is really important especially in the lower engine rev's range.

I don't remember you reported having checked this in full.


Regards
Norbert 

Hi all,

I have now had the intake manifold and the valley cleaned which is nice in itself. In addition, all the lower rubber donuts have been renewed and so has the actual gaskets between the head and the manifold. 

Did it solve my running problem? Well, sort of. The car is indeed drivable and drives notably better. Smoother acceleration and a different shift pattern in the gearbox. Before, it would shift much sooner from 2nd to 3rd and now it goes naturally higher up the rev range before it shifts. It pulls evenly and steadily from 2000 upwards. From around 2000 rpm it runs beautifully. What is then the problem?

The problem is (still) that from 0 km/h and until the engine reaches 2000 rpm (no matter the gear), the engine stutters and there is intermediate "puffing" from the exhaust. It also smells of fuel. The idle is still rough and it smells of fuel. The idle screw on the ECU is turned all the way counter clockwise (i.e. lean). If I attempt to enrich the idle mixture, the engine reacts immediately and almost stalls.

So I have performed yet a new smoke test both with cold and warm engine and the conclusion is that it is tight (with a bellow on the throttle housing and opened flap). Only a slight trace of smoke from the throttle shaft and from two of the bolts for the cam covers. Hardly anything. I also measured engine vacuum which shows 680 mBar with hot engine. Prior to the renewal of intake gaskets and rubber, the vacuum was around 560 mBar. So clearly an improvement.

Any idea where to look? Can I still have a vacuum leak with 680 mBar idle vaccum?

Iginition timing is still on the mark and so is the fuel pressure (2 Bar). Dwell is smack on 30 degrees. 

Can the ECU be sending faulty signals to the injectors? Can something have happened with the MAP sensor? 

 





Best, Peter 

Hi Volker,

I have cleaned and lubricated the moving parts of the distributor and verified again that the vacuum can is doing its job (reacting to and holding vacuum) and cetrifugal elements are working. Static and absolute timing has been verified and is within spec for a US spec car. Dwell is steady at 30°. 

Upon testing today, there is no notable difference. It still stutters from standstill, but once it has gained some speed and rpm the engine smoothens out. Above 2000-2500 rpm it runs good. At slow speed from 10-60 km/h and when cruising 60-70 km/h it really struggles. At hard acceleration it really pulls and at 90 km/h there is nothing wrong. At idle it is running rough and smells of gas. Idle potentiometer all the way lean and still the CO is 4%.

Upon start-up and during warm-up it runs beautifully. Once it reached operating temp. things begin to go wrong.

When the engine is really hot - just around 100° the symptoms become even more apparent and the engine almost stalls when in gear and idling. Hot starting (after having sat for 20 min) after a good run, the engine starts but dies when put into drive. Only by applying extreme gentle throttle, I can manage to make it move. It seems to be temperature sensitive and not ignition related. I have tested and verified ignition timing and fuel pressure over and over again and it is absolutely fine. Valves adjusted and all sensor values measured at ECU plug are fine. Compression is = or >10 Bar on all cylinders and wiring harness is new. I really cannot figure out what is wrong. I have a known good spare cooling temp sensor that I will put in and test, but I doubt that is the solve.

I am pretty sure that it is getting too much fuel and much more than it can drink at light throttle and at cruising. I’d really like to get the ECU and MAP sensor tested to make sure and give me peace of mind that these are not the culprits. Everything else has been tested and shows no odd results.

best, Peter

Hi Peter my friend,

of course I will check that for the flower man ! You might also consider to join our D-Jetronic workshop in Frankfurt where we would run your engine on Mercedes-Benz engine and exhaust tester.