I've done hours of reaseach before posting this thread, but I still need some advice.

Here's the symptoms...

turn key to on
no glow plug indicator light
auxillary fan in front of radiator comes on (does not normally come on but always coincides with this problem)

turn key to start
starter engages normally but no engine fire

I can get the car to fire normally after turning the key on/off for several times. I know the engine will fire even before I turn the key to start because the glow plug light will come on/off normally and the aux. fan will not be on while the ignition switch is in the on position. No additional problems after car has started.

The first time I had this problem was after I let the car sit for a week while I was out of town. The problem was intermittant for the first two days and then then the car started fine from that point on. Then I went out of town for two weeks. Got back yesterday and the same problem again when I tried starting for the first time. Now the car seems to be doing ok.
I can have the symptoms when the car is cold or hot.

I have a few theories I would like to run by you...

Bad temperature switch or sender causing the aux. fan to come on and the glow plug light not to illuminate and the car not to start?

Bad iginition switch?

Is there an OVP relay on a diesel that may be bad?

Bad fuel shutoff valve? Where is it located? How to check its operation? Why would that make the aux. fan come on when the key is on (car not running) and the car is cold.

I don't think it's a bad neutral switch because the engine always turns over ok. It's just an intermittant starting/firing problem.

Hope you guys can shed some light on this. I'm taking a gamble in the morning and driving to my mom's for T'giving.

Neil Eaton

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

neil, when you are cranking the engine, does the red and green lights on the inside rear mirror alternately flash?
Ray
mercedessd@cox.net

I have not noticed the lights blinking so I don't think they are. I'll try to specifically look for this in the future.

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

if they do it is an indication of no drive authorization being sent. please let me know your findings. i agree with the previous post.
Ray
mercedessd@cox.net

Interesting.

I have two infrared keys and couple of keys w/out the infrared contraption. But the infrared only operates door locks (right?).

Are you saying that I should lock / unlock my door w/a key that does not have the infrared contraption and then try starting the car?

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

Car is giving the same non-starting symptoms tonight.

I tried another infrared door opener, but still had the same problems. Locked / unlocked several times.

I did notice the following:

1) The red and green lights did not flash while I was cranking.


2) It takes about 5-seconds before the aux. fan comes on after turning the key to the on position (I'm going to double-check whether this is normal next time the car starts normally)

Thanks for your ideas.

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Neil
1997 E300D - naturally aspirated
280,000 miles (as of November 2015)

Did you try another key? I had some problems with start up and it turned out to be a dying infrared key.

In the 97 you can use the spare, non infrared key if you need to and want to avoid the $200!!!!!!!!!!! replacement.