Wierd sound when starting engine
 

Hi,

First let me introduce myself, my name is Jorn, bought a 1978 300CD with 145k last summer. Drives like a dream, two owners, one MB mechanic who did everything from installing a broken dome light to engine work.
I replaced all the filters, the trans. flushed, two cans of diesel purge to clean the engine, etc.

Now my problem; last week the car would not start, the pre-glow light didn't come on. Replacing the glow-plugs resolved the problem. Car would start up all weekend fine.
This morning it took me three turns to start up, first two times engine would start but die after 3 or 4 sec. the third time engine started making a "clonking" sound and producing a lot of white smoke. I let the engine run for a minute and restarted with out a problem, started right up and no white smoke.

Car is running fine now, smooth lots of power but I'm a little worried that this is the start of a bigger problem to come.

This is the first week that it's getting cold at night, I'm living in LA. Could this be the problem?

Thanks Jorn

It's going to run a little rough and smoke a little when it's cold...but it doesn't get THAT cold in Los Angeles, does it?

Might need new glow plugs...does the glow light blink after you start it? Try glowing it a little longer before starting...20-40 seconds AFTER the light goes out. If that doesn't help enough, do it TWICE before starting.

Mike

Jorn .....welcome


Allot of the time a "clonking" sound" is heard when the engine shakes more then normal upon starting or stopping. Its usually the exhaust system banging some place. Did she shake more than normal? The smoke could mean you have a bad GP and if a motor mount was not up to par, you got the shakes then a clonking and some smoke. Anyway thats the way it went with my car. Next time you hear the clonking pay attention to how much she shakes. Mine was LOUD and deffently got my attention.

i think you have a bad glow plug relay, as you said you replaced glow plugs. check the fuse in the relay first. could be the smoke at startup is because the glow plugs were not energized at all. after the engine is warm it would be no problem to start w/out glowing.

I just replaced the motor mounts and the
trans. mount. This was a different sound, I know the sound you are talking about, used to have it. This sound came from the engine itself, almost if the engine was running without oil.

If a fuse is bad that means it would always have a problem to start, during the entire day it started right up, even after three hours of not driving.

I know it doesn't get that cold here, but it all started after the first night of rain here.

Thanks

84300DT, do you know where I can find the glow plug relay in my 1978 300CD.

There is a fuse on the firewall just behind the engine. But I can't find the relay. And how do I know if it's bad, they are not cheap?!

not sure on your model but might be on the firewall.
i believe the fuse is a strip fuse 50amps.

you can test the glow plugs and relay with an ohmmeter. do a search on the subject here.