Just changed my IP delivery valve seals which had been leaking a bit on this `87 w126/300sdl. There doesn't seem to be any more fuel leaks in the engine bay, which is great, yaay! When I crank over, smoke comes out the back pretty quickly, whereas before it'd take quite some time to re-prime first. But I'm still not getting combustion unless I keep cranking for a good bit of time.

My glow plug light doesn't engage on the dash when I turn the key on. I suspect that might indicate the underlying problem, but I don't know where to look. I didn't disconnect anything, but tried testing plug by plug and each plug registers 0.4 ohms. I assume for that to mean anything I'd have to disconnect each plug to test them individually, not connected? Can I do that without removing the intake header? I sampled two and there seems to be 12V across them when I insert the key & warm them, but again- my dash doesn't show the glow plug light coming on. What should I check for problems?

I understand there's a precombustion chamber? What are good ways to check whether it's clogged up, and what kind of routine is there for cleaning it if not?

Thanks for the advice. I'd really like to get back to being able to start without much trouble. I was rather expecting that the lack of fuel from the delivery valve seals failing was the problem, but it seems I have more issues to chase down. Let me know what other information I should post, what else I should check out. Thanks.
-r

Can we assume the engine was running properly before you worked on the delivery valve seals?

Is the fuel system primed? Does the engine start? If you can start the engine and have it idle normally, the fuel system has to be primed. If that remains a problem, try this method:

- loosen all six injector lines
- crank the engine for 10 seconds
- check for fuel leaking from the loose injector line fittings
- tighten the fittings that leak fuel
- crank the engine for 10 seconds
- check for fuel leaking from the loose injector line fittings
- tighten the fittings that leak fuel
- after a couple of three cycles, the engine should catch and run on its own

If any loose injector lines still don't dribble fuel, you made a mistake with the delivery valves.

It also sounds like the glow plugs aren't glowing. There's an 80-amp strip fuse under the glow relay cover. Is that fuse intact? Disconnect the battery and remove the strip to be sure there isn't a hairline crack. Replace the fuse and reconnect the battery to check for voltage at the downstream end of the fuse. For the glow plugs, 0.4-ohms at the relay connector seems low for good plugs. I hear that good plugs measure 0.7-1.0 ohms at the connector. You don't need to take anything apart to test the glow plugs alone. Disconnect the relay connector then touch one probe to the electrode tip of the glow plug and the other to ground.

The precombustion chambers are installed in the head. They're what the injectors screw into. They can accumulate soot over time through city driving and hypermiling. Driving the car above 4000 rpm (in second or third gear unless you can safely and prudently drive 100 mph) for a few minutes from time to time should keep the prechambers (nickname) clean. It's not a practical matter to remove prechambers for cleaning. You can use a reamer to clean the prechamber when replacing glow plugs but even that only goes so far. At any rate, prechambers don't gunk up just sitting there and they didn't get gunked up while you were replacing delivery valve seals.

Sixto
87 300D

I had to crank for quite a long while before doing the delivery valve seals. It seems to be a little bit less cranking now (less priming before exhaust starts up), but it's hard to estimate.

I'll re-bleed the injectors and make sure they're all bleeding. I think everyone was squirting pretty well, but I was mainly thinking about bleeding air not checking for fuel when I cracked them previously. #4 was in particular bubbling quite a lot, there may still be some air in the system worth trying to bleed.

Thanks for the words on glow plug testing. I think there'll be much more interesting results coming back tomorrow.