try using an amp meter thats what I do and it works great. I can power each glow plug individually and measure it's current. I think they start out using about 25 amps and within a couple of seconds when the filiment heats up they drop to about 5 amps. I can check the the amp readings for sure if you would like.

What's the specification for the amperage? Is it 5 amps.......or 6 amps......or 7 amps after 5 seconds?

What's acceptable........what's not?

You don't know.........because there is no specification for this.

After months of frustration, my 300SD gave up. With everything seeming normal, the car still just wouldn't start. The local old MB shop checked it out and made a very expensive prognosis. The engine would not start without a two person process involving the injection pump. The compression on one cylinder was about 300, and on the other four it was between 210 and 250. The valve lash was checked, and only two valves were too tight, and one of them was on the cylinder with good compression. There was a lot of blowby, you could see gases puffing out the broken crankcase vent hose. Injectors 1-4 looked fine, but injector 5 looked bone dry and had a white powder on the nozzle. The coolant system was pressurizing before the engine was running, leading them to believe that either the head gasket had failed or the head was cracked near that injector. I was surprised since I never saw any coolant loss and never smelled any coolant burning. Staring at repair bills that could now escalate to $5,000 (new head + labor + previous work) I cut my losses and sold the shop the car but still had to pay them $250 in labor since they had done more in work than the car was worth. If I would have kept the car I would have ended up financing the towing company owners next Jamaican vacation.

Thank you guys for all your help. Its time to go shopping for another I guess...

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73 450SL AMG "Millennium Falcon"
88 Volvo 740GLE B230F/M47
84 300SD Turbo (Sold, looking for new one)
86 300E (FOR SALE)
78 450SL (totalled by girl on drugs in SUV)
87 Volvo 740GLE wagon (totalled by Ford Expedition)