D-Jetronic Testing (1973 450SL)
 

I'm currently troubleshooting my D-Jetronic injection to determine the reason for rough running.

According to the shop manual the fuel pressure should hold at least 1.5 bar after shutting down the engine for 10 minutes. It actually holds close to 2.0 bar 10 minutes after shutdown. It does however drop to 0 bar overnight. The book doesn't say if it should hold 1.5 bar indefinitely. Should it or is it ok to eventually drop to zero?

THanks.

JP

Residual fuel pressure is only important for hot starts. The D-jet v8s had some problems with vapor locking but this problem when existant cleared within seconds of the engine starting.

It will leak down overnight. This isn't your problem.

I do seem to have a problem with the fuel pressure fluctating between 27 and 29 psi while running. The pressure regulator and damper are both new.

Thanks.

JP

Thats probably not enough to cause any problems. Try adjusting it a few pounds higher to say 31-32psi and see if its more stable. This seems to improve injector irregularities sometimes.

Thanks, I'll give it a ry.

JP

Steve, Once I do get it running correctly, I'd like to help my gas mileage (about 11-13 mpg) a bit.

I've set the timing at TDC instead of 5 ATDC and had the distributor recurved to european specs. I've also replaced the cold start valve which appeared to have a slight leak. The car still seems to run too rich; full throttle acceleration leaves a black smoke cloud and the car runs best with the adjustment wheel on the ECU set to full lean.

I've told to set the fuel pressure to 34 psi and adjust it to get a CO of 2.5-3.0, both with and without the throttle switch connected. I've also been told that the MAP sensor should be adjusted instead to get the proper CO.

What would you suggest?

THanks,
John