Mercedes incredibly hard to start - PeachParts Mercedes-Benz Forum

#1 12-10-2002, 09:57 PM

Hello all,

First let me introduce myself. My name is Ron, and i'm from Brunswick, Maine. I just got my first mercedes over the weekend, a 1983 300d. It's deep green and looks awesome. My problem is, if i don't literally leave it plugged in for hours, it positively despises starting. I replaced both the primary and secondary fuel filters and glow plugs when i got it because the guy couldn't remember the last time they were changed. This didn't do anything to help the problem. I was thinking of trying a new battery, mine only usually reads 12.3 volts. Other than that can anyone offer any advice? I'd like to start driving the car everywhere, but i work third shift and i'm afraid if i let it sit in the parking lot for 8 hours while i'm at work (not plugged in of course) that it will leave me sitting. it runs great once it does get started, i had it on the heater for probably 5 hours and it started with minimal trouble. Then it sat for five hours and then woldn't start again. any and all help is greatly appreciated.

Lonny · #2 12-10-2002, 10:22 PM

you might try adjusting the valves. Adjusted mine over the weekend. Made a world of difference.

joe p · #3 12-11-2002, 08:52 AM

Ok, mileage?

As suggested, adjust the valves, also test the glow system, one or more dead plugs makes these no fun at all to fire up. As will tight valves. (617 engines tend to tighten the exhaust's in the winter and intakes in the summer for some reason)

If you determine the glow system is ok, valve lash is right and fuel filters and fuel quality is good, run a compression test.

Joe

keithed · #4 12-11-2002, 01:31 PM

And don't forget the oil. In really cold Maine winters it will crank over much easier with Syntheic oil, than petro base oil.

I've found that to be true working alot in NH next door in those cold winters. One reason I switched years ago to syntheic oil in crankcase, transmission and rear-end diff.

K

ctaylor738 · #5 12-11-2002, 10:54 PM

There is a guy who advertises starters for hard-to-start diesels in Hemmings. Are you getting a lot of blow-by when the engine is warm?

A tip-off to low compression.

riske · #6 12-11-2002, 11:37 PM

If all else fails,just leave the car running for the 8 hours while your at work.At an idle, these cars burn very little fuel, plus the car will be nice and warm for the ride home!
Bill

neileg · #7 12-12-2002, 09:24 AM

What does it do?
- Not turn over
- Not turn over very fast
- Turns over fine but won't fire
- Fires but stalls
etc, etc

rdanz · #8 12-12-2002, 12:05 PM

How many miles on the car? It may be a low compression problem.
Should take it to a mechanic!

#9 02-04-2003, 01:07 AM

Just for the sake of continuity of the forum, what did end up fixing my problem was a good valve adjustment, they were way too tight.

furthermore, the following things also helped mildly improve my cold starts:

-commercial grade 5w50 synthetic oil.
-new glow plugs (helped very little, the old ones were fine)
-getting the battery fully charged (it was only .5 v low)

NC240D76 · #10 02-04-2003, 07:49 AM

I thought the new battery helped alot in mine until I had the starter reworked (we really had to overuse the starter to get the car running after it had been sitting for 3 years), now it really spins. Starts very well until temps are in the teen's and then I have to roll it off the starter.
Valves are next.

You might do a search on this problem, there is a lot of info already on this site.
One thing I read here that seemed to help me was when it is very cold compress the pedal three times and hold it part way down before trying to start.
The other suggestion I see a lot is to cycle the glow plugs a time or two and leave them on an extra 30-45 seconds before trying to start. I don't know how this works since mine is setup differently. (1976 240d)