I just replaced my defective fuel shutoff valve on my wife's 87 300SDL. Now the engine delivers NO power.

I removed the Int manifold to gain access. I tried to remove the ALDA using two crescent wrenches but it would not break loose. I then turned the ALDA WITH the fitting that nurmally remains in the Injector pump (the lower, larger nut). It unscrewed 5-6 turns and then would continue to turn but it would not release from the injector pump. Obviously something in the pump captures the pin at the bottom end. However, with the ALDA unscrewed 4-5 turns, there was enough clearance to get a wrench on the fuel shutoff and remove/replace it.

I then screwed the ALDA back in, replaced everything else, checked the fuel shutoff for proper operation with a Mitey Vac, and started the engine. It started fine but now has NO power at all. With tranny in neutral and accelerator floored, it will rev to around 3500-4000 but do so quite slowly. In gear, on level ground, the car will accelerate VERY SLOWLY to around 20 MPH. It will not go up a hill at all. It will not shift out of 1st gear (autimatic tranny).

The car was running fine before I did this work.

I sure would appreciate some advice from the diesel folks - I'm totally stumped.

When I replaced the manifold I also plugged the vac lines to the EGR and ARV.

The usual suspect is the line from the intake manifold to the ALDA, but you say that it doesn't even rev in neutral. You don't need boost or a boost signal to the ALDA to rev in neutral.

I take it you didn't alter IP timing. No reason to touch the IP when removing the intake manifold.

You didn't mention undue noises, vibration or smoke so I assume the fuel system is bled. It's self priming so it should sort itself out by the time the engine catches.

If you would indulge me, remove the crossover pipe and see it revs more freely in neutral. Your sucking unfiltered air into the engine at this point so pay attention to what you;'re doing.

Then pull the ELR connector from the back of the IP and see if that changes anything. Expect the idle to drop but it should stay running on its own.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Are you getting the full range of motion through the throttle linkage? I seem to remember some part of the throttle linkage is bolted to the intake manifold.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

Sixto,

Thanks for your suggestions!

I did as you asked; there was no change with the crossover pipe removed. I unplugged the ELR connector and, as you suggested, the idle dropped fairly dramatically but it kept running.

I did nothing to the IP but I keep wondering if the fact that I partially unscrewed the ALDA using the bottom fitting has created the problem by causing some internal IP linkage to jam in the wrong position. Obviously, since the ALDA would not pull out of the IP, whatever is attached to the IP end of the rod that bears upon the ALDA moved upward as I unscrewed the ALDA. I have the MB shop manual for the engine but it doesn't really show a picture of the internals of the IP and the precise linkage of the ALDA. There is a diagram but it is not as useful as a picture would be. I guess I'm thinking that some internal linkage was pulled up and is now out of position. But I don't know if that's possible.

And, of course, the problem may be totally unrelated to the ALDA but since I didn't fool with anything else, it seems a likely suspect to me.

I checked the vacuum lines and other than the EGR and ARV lines that I plugged, I'm pretty sure I haven't left any disconnected.

The car starts quickly and idles fine.

I'm a very experienced gas engine mechanic/engine builder but Diesels are new to me and I'm quite discouraged at the moment...

I have a vague recollection of having the ALDA off and I had it off to replace the engine stop vacuum switch so I didn't pay attention to the ALDA. I think the working end of the ALDA has a cup that fits over a rod in the IP. If for some reason the cup wasn't centerd on the rod as the ALDA was installed, the rod would be pushed further in that it should be. Maybe that's what's causing your problems.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD

And that was it exactly! The socket of the alda was not seated upon the rod, causing the rod to be pressed down too far. ALL FIXED - Thanks!!