glow plug replacement...help
 

Hi members. I am the owner of a 1979 300d andn i love it. however, as a very uncommon girl that thinks she is a little bit more mechanically inclined than i really am, i sometimes end up in a bind.such is the case.

I have replaced 3 of my 5 glow plugs which would be 5 of 5 but there is a problem...I broke the brass nipple that is on the end of the temperature control switch which is locasted right above the glow plugs. i have one ordered that will be here tomorrow.

also, i had opened a couple of the fuels lines in order to get them out of the way and i returned them to their proper placement.

my car won't start.it does not sound like it is pickiong up fuel. i pumped the manual injector pump until it was tight. I am wondering if the fact that their is no connection between this temperature module and the rest of the car is the reason it won't start. also, the glow plug light is not coming on...
help!!!!!!!

Not sure what the temp control switch is that you refer to, if its electrical it can prob be disregarded at this point, if vacuum, plug both ends for now.

Concerning the GP's, go to dieselgiant.com and follow the tutorial there for testing the GP's and the Relay. That will help you get to the bottom of no idiot light on the dash. Pretty basic stuff using a multimeter; scale of 1-10 its a 2.

After you've got the GP's straightened out if it still wont start you'll need to crack the inj fuel lines one at a time in order and manually prime and/or crank until fuel leaks, hten tighten that line and crack the next one.

ps: welcome to the forum and next time post on the Diesel Forum where you'll be inundated with expert help.

bear with me
 

which end of the fuel lines do i crack open. also, i may have used the wrong part name but it is located near glow plugs,there are 2 of them, and one end is like a copper sted that screws into the block,if removed water comes out.i9t is electrical as you said. sometimes i forget how basic a diesel engine is...thanks

I suspect you are correct and that is a temp sender. Shouldn't affect starting; once running, if you have no temp gauge you'll know.

Is usually best to crack the fuel lines at the pump. You only need to break them loose a turn or two, not remove them. When fuel leaks out, tighten them to retain prime.

You've got air in the lines. I crack the last injector line and the middle banjo bolt on the filter head, one at a time (filter bolt first is my preference), and really prime like crazy; not just till I see fuel, but until the fuel is solid. Makes a mess, and gets the air out!

I would for sure diagnose the entire system too, find out why that light is not on. It is simple stuff, and empowering too. http://www.dieselgiant.com/glowplugrepair.htm

On some models, a coolant temp sensor is part of the glow plug circuit. Given the symptoms, it sounds like that might be the case here.

And would the temp sensor being disconnected also interrupt the GP circut from receiving electricty??? If so, that is prob the sole issue.

Trying to use the dieselgiant tutorial on a '79 might be more confusing than it is empowering!!!

I am not sure what model and year of Mercedes you have. If it has one of these engines click on the enigine. It will lead to alot of informaion.
http://www.pauldrayton.com/uploadfiles/merc/Service/Library.html
Also there are several Women who fix there cars on this forum.

If you have the loop style glow plugs the info can be found at the above site if you click on the engine you have in your car. The glow plug relay for some of the loop style glow plug using engines is behind your instrument cluster; but I have not see a good way to trouble shoot the relay posted anywhere.
It might be the members of the Vintage Mercedes forum would have more experience with this type of system.

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I suppose it might if the car in question does not have the pencil style glow plugs. Is '80 the transitional year? Also, wisest not to assume that the gp's have not been upgraded...

My '80 does have pencil style glow plugs (from the factory) and the dieselgiant tutorial was just what I needed !

Glow plug light not coming on may be the key to this issue. I don't have the info in front of me right now but does this car have the sqiggly wires inbetween the glow plugs?

Glow light not working usually means the glows are not working.

Tom W