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1986 MBZ 300SDL Fuel Injection Pump Problem

Have the mechanics checked everywhere that debris from the bad injector pump could have gone?

I’m no diesel expert, so I don’t know what the black smoke at high altitude is about. I don’t think a diesel can run rich without taking off, since there’s no throttle.

Is it possible that something is throwing the injector timing off even though it seems OK according to the standard procedure?

I’m still curious about what the compression figures are. The fact that someone has stated that it’s new, good, or whatever doesn’t mean that much to me.
People post on this forum all of the time and refer to figures given them by a mechanic who states that those figures are good when they’re not anywhere near even average.
In my humble opinion no mechanic on Earth should tell a customer anything about compression readings unless it’s down in black and white.
With the VWs, we used a Motometer gauge that scribed a line in red pencil on a graphed card. This would give a series of lines showing the actual compression figures.

Black smoke often points to (again, based on VW expeience) pump timing being off or faulty injectors, etc.

Something else for consideration. During all of this engine work is it possible that the timing chain was installed a tooth or two off? This could drastically affect the way the engine runs and possible the pump timing too.

I don’t even know what to say about 6600 bucks on this except that I would have dropped a Ford 5.0 SEFI engine and Ford AOD transmission in it long ago and been done with it. A couple or three grand at most would have accomplished this.

Have you checked the AIR pathway into the engine from end to end to be SURE there are no obstructions blocking the intake air??? After that checks out, do the same for the exhaust system…

I’m curious as to how the injector pump was tested. Was it shipped back to the manufacturer/rebuilder? Does the new pump have a different firing order on the injector lines? Is everyone just following up everyone else on the injector line order?
I also think that the timing on the pump could be off . It is driven by the timing chain,right? Once you pull the pump off, the chain goes slack.Worn gears and chain should be replaced at some point
I hope the fuel tank has been drained. Some deisels develop a "jelly "in the fuel tank that obstucts fuel flow.
How about the fuel return line?

Yeah, I’m worried about how things work ON the car, sounds like a lot of parts have been tested OFF the car. Any way to plumb in a fuel pressure gauge as close to the injectors as possible and drive it, watching the pressure?

Is the turbo charger working properly? I’ve seen malfunctioning turbos produce greatly reduced power and lots of black smoke, especially at altitude. Since diesels are compression ignition engines, the reduced pressures in the cylinders when the turbo malfunctions would result in incomplete combustion, hence reduced power, black smoke and increased fuel consumption. As the car went to higher altitudes, less air would be available for the turbo to force into the engine, exacerbating the problem.

I am not a mechanic, I’ve got far less experience than most people in this thread, but if 20+ mechanics can’t solve the problem then it can’t hurt for me to take a guess. If you get the car fixed, please let us know what the problem was.

I was thinking of the return line also, but for another reason. We had an old Ford in the shop awhile back with an exploded inj.pump. Replaced pump and the thing ran almost like the OP’s. After several days of troubleshooting, we found a small piece of metal in the return line, blocking it almost complete. Got it out and the thing ran perfect. Maybe worth checking.
Good luck.

Better late than never, have they adjusted the ALDA to the new pump? While the pumps have “hard” timings the ALDA unit is more by feel. Running shaky and no power at altitude are common symptoms for it being off in relation to the pump.

Similar but more painful to fix, if the pump failed that spectacularly, has every single part downstream of the pump been checked for an obstruction? Every line, fitting, valve, injector, etc? At higher altitudes your fuel pressure may be low and that “minor” obstruction that makes it shake suddenly becomes a massive blockage.

Hello John,
Did you ever resolve the issue with your SDL? I own one as well and had been considering replacing the injection pump as my car is sluggish and only gets 22-23 mpg.

Thanks for your input,
David