Cold starting problems
 

Hi i have a '79 300sd,.. and recently it has gone down to about 20 degrees. and i have no luck at all starting in the morning. i am sure my glow plugs, and relays are fine. (i think) it starts at pretty cold temps. but i can't start when i leave it over night.. i try cranking it over til the battery goes dead. the other day i noticed the inline fuel filter had a vegetable oil like consistency, so i assume it was the diesel fuel. so then i bought some diesel fuel additive to put in the tank. work fine for that day. now it doesn't work anymore. so here are my questions:

1. is there a way to check if any of my components are bad? i.e relays?

2. i heard people put some petro in the tank does that work good? (they have no.2 diesel over here)

3. any advices?

thank u ahead..

ned

The first thing to make sure is that you have a fully charged and good battery. Give it an overnight trickle charge and try it again in the morning.

Recently I found my battery was really low on water (added half gallon to bring it to full). After a full charge, the car starts much easier and smokes much less (the glow plugs are also getting more power).

Ned, 20 degrees C or F?

it is farenhieht,. well and about the battery i made sure i hade the most crakig amp one. i got one with 900CA, and about 790 CCA.. i will try to get and charger and try that out.. (because battery sucsk when its cold right?).. well i took out the fuel filter (inline) and theres a bunch a black stuff in it. it may be clogged.. but i have ran out of battery to try it again.. well keep the advices comming.. and thxs a lot for the help guys

yes. i was thinking of that too. thxs.. the only problem is i live in an apartment. so they might complain about a cord coming down over there patio. but oh well scr*w them..,and also what kind of diesel should i use. over here they sell no.2 and i add in a additive (cetane) that saids it will be equivilent to "mixture of no.1 and no.2" my dad told me to find just no.1 is there any way to know where they sell it? like do trucks use no.2 or no.1

I had the same problem for the last two weeks when the morning temperature was down to 25F. After my mechanic adjusted the valve clearance, the car started right up. The valves were too tight.

Few things has to be done on diesel for winter weather:
1. Valves adjusted every 15,000 miles
2. Thinner engine oil (Synthetic oil)
3. Good Battery
4. Good Glow plugs
5. Block heater
6. Wait 40 seconds after glow plug light goes off before starting the car

Hopes it help!

DieselBenz

85 300SD, 81 & 83 300D, 68 220D

ps. Tight valves mean low compression, the fuel won't ignite

thxs, i'll looking into the valve adjustment, but why do u have to wait 40 secs after the light goes off? i thought u can only glow your plus for 15seconds or so. so my dad told me to glow it for 15 secs, then turn the key back and go for another 15 seconds. etc.. anyways thxs a lot i'll try to get it started again tomorrow

cycling glow plugs
 

No way on waiting 40 secs to start after cycling glow plugs. The whole concept is to heat up the prechamber to the highest possible temp to aid starting. 40 seconds is quite a bit of time for that huge heat sink called a cylinder head to dissipate the vast majority of the heat generated by the glow plugs. Turn the key as soon as the light shuts off.

Not sure about the '79 300SD, but on my '84 300D, the glow plugs stay on for a full minute after the light goes out. I wait about 20-30 seconds in the cold weather, and starting is never a problem...as long as everything else is in order.

Diesel power:

By you theory of using the GP for only 15 seconds so that the head would not act as a heat sink, then you should use GP for only a fraction of a second so no heat would be sunk.

This is of course ridiculous because the longer the GP are on the warmer it gets inside the pre chamber where the combustion starts. That's why the GP relay stays on for more than a minute.

P E H

okay here are some of the updates of the problems i had,, well i cheaked all my glow plugs with a multimeter, they all seem fine and the wires going to them are fine when key turned (they get 12 volt).. still no luck, i got it started the other day with a jump start and about half an hour of cranking.. starter works fine.. i charge my battery with a charger everyday doesn't seem to help..

okay the day i got it started i drove it for the whole day with out any problem, the problem seems to be leaving it over night. so i came to a conclusion i need a block heater.. now i went to check out my friends 300d (78) and he said he has a factory cord for a heater, the plug comes out of a corner of the grill and traces back to the back of the engine somewhere, went to check another 300d and it had the one too, now i don't have one on my 79 300sd.. so what kind of block heater should i get? my dad is getting me one for the upper and lower radiator hose, and i am getting a battery pad.. hope it works out so..

1. anything i might have over looked?

driving around in a 93 grand caravan for a few weeks now and it is no benz, oh and a story to share.. a 2001 dodge neon going 65 mph hit my friends 300d, the neon was wrecked! the 300d? just a new grill, a piece of a bumper, and the rubber that goes around the bumper, these benz are built tough!!! anyways thxs for any advices

You may have a block heater on the engine. I think the heaters were installed on all the Diesels at the factory, but not the cords. I think I read here that putting on the cord was a free dealer option, so maybe a southern car might not have the cord attached.
You might be able to just attach a cord to get the heater to work. Find where the block heater is on your friends car and yours should be in a similar place.

P E H

Couple of thots:

1. Had to put a block heater in my 84 because the first owner lived in Georgia and opted not to get the freebie from the dealer.

2. Do a thorough search for block heater installment. Tons of help here but it requires a long breaker bar and a strong back. We did two of them two months ago.

3. Have Aaron Bonger send you the tool he welded. It worked great for me.

4. Of my 3 diesels, one starts horrible in the winter even with a block heater. Very low compression. So its imperative that you burn the best fuel and that is Amoco "Premier". As Amoco sells different grades of diesel (sometimes at the same station), make sure it says "Premier". That stuff is liquid gold and cost about as much. But my cars love it.


Don

Ned:

Check engine cranking speed, and get an oil change to Mobil 1 or some other synthetic -- the lower viscosity of the oil cold will help tremendously. Engine MUST turn at at least 100 rpm when starting -- if it doesn't, you need a new starter.

Change your main fuel filter, and check the suction hoses for leaks. If you are drawing in air from leaking hoses, you will have terrible trouble starting. My 220D had leaky hoses when I bought it. Still doesn't start well below freezing, but that is low compression.

Adjust the valves. I cannot overstate the importance of this! If they are tight, you will have cold start problems, and nothing else will fix them.

Peter

Maybe these cars act differently. I'm new to MB cars. My experience is as follows:

99 Dodge Ram Cummins Turbodiesel. Preheat system consist of heating grid in intake. When the light shuts off, the grid shuts off. Grid cycles on and off during the first few minutes of warmup. You can watch this cycling at night as the lights dim when the grid comes on.

81 Datsun 720 pickup with the SD22 diesel. When the light shuts off, the glow plugs shut off. You can hear the relay cut off. Glow plugs cycle back on after engine started for a minute or two.

83 VW Rabbit turbodiesel. I had injectors out of engine to have them tested. Checked glow plugs for proper operation right then. When the light shut off, the glow plugs cooled off.

I would have expected MB cars to behave similarly. Shutting down prevents unecessary wear to the GP's, and unecessary drain on the battery. I will verify this with a voltmeter later on my 240D and post the results.