Glow plugs
05-23-2004, 04:35 AM
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300 TDT and 350 SD
Glow plugs
I have a 1985 300 TDT wagon. Recently the yellow glow plug light did not illuminate, I was told by my local mechanic the glow plug relay and 2 of 5 glow plugs were bad. I ordered the Bosch glow plug relay kit + 1 plug and replaced all 5 plugs and the relay myself. Now the car starts great, the yellow light works again, but the power seems to be down maybe 20%. I checked all the plugs and they are all tight, any suggestions?
05-23-2004, 10:34 AM
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02 W163, 84 W123, 03 E39, 98 E39
Strange...
I have/had three W123s with 700,000 accumulated milage. I have replaced many glow plugs, but no relays. The glow plug circuit is only operational when the key is in the start cycle. As you note, short of a leak around the glow plug, changing the plugs should not affect your power.
Suggestions & thoughts:
Is your MPG down? if you have an actual loss of power, your MPG should drop also.
Have you changed where you get fuel? Mabe you have bad fuel or got a tank of Kerosene. Kerosene has much lower amount of energy than Diesel fuel or #2 heating fuel. It does not jell during the winter and some people in very cold areas use a 50/50 mix to avoid fuel jell problems. They exerience a signifigant loss of power and fuel economy when they do this. There is no highway taxes on Kerosene so it can be obtained and sold less expensive than Diesel Fuel.
Have you changed your fuel filter and pre-filter lately? It may just be a coincidence, but a clogged fuel filter or pre-filter can cause the symptoms you describe. An old MB mecanic suggested when you change your fuel filter, that you fill it with ATF. He said the small amount of ATF was good for the injectors. I have done it every fuel filter change with no problems.
Did you run your tank down low just before you changed your plugs? I had a problem with a clogged fuel screen in the fuel tank once. Black crud grew in my tank and clogged the fuel screen in the tank when I let the fuel get low. I temporarily solved the problem by blowing air back into the fuel tank from the fuel outlet pipe to unclog the screen, but I eventually had to replace the screen.
Let us know what you discover.
Suggestions & thoughts:
Is your MPG down? if you have an actual loss of power, your MPG should drop also.
Have you changed where you get fuel? Mabe you have bad fuel or got a tank of Kerosene. Kerosene has much lower amount of energy than Diesel fuel or #2 heating fuel. It does not jell during the winter and some people in very cold areas use a 50/50 mix to avoid fuel jell problems. They exerience a signifigant loss of power and fuel economy when they do this. There is no highway taxes on Kerosene so it can be obtained and sold less expensive than Diesel Fuel.
Have you changed your fuel filter and pre-filter lately? It may just be a coincidence, but a clogged fuel filter or pre-filter can cause the symptoms you describe. An old MB mecanic suggested when you change your fuel filter, that you fill it with ATF. He said the small amount of ATF was good for the injectors. I have done it every fuel filter change with no problems.
Did you run your tank down low just before you changed your plugs? I had a problem with a clogged fuel screen in the fuel tank once. Black crud grew in my tank and clogged the fuel screen in the tank when I let the fuel get low. I temporarily solved the problem by blowing air back into the fuel tank from the fuel outlet pipe to unclog the screen, but I eventually had to replace the screen.
Let us know what you discover.
