Cold Stazrting Season Begins - PeachParts Mercedes-Benz Forum

pdxman · #1 09-07-2003, 06:11 PM

Last spring, I fought the cold start battle and wasn't sure if I won...I tested GPs and they seemed fine. I replaced the battery with a good heavy duty one. I removed the starter and took it to two places for a bench test and neither one wanted to sell me a new one because mine was good. The last hing I can think of is my compression. I haven't checked it yet because I don't have a tester. I will though but will check with some neighbors first to see if they own one that I can use.

My questions...

1. If the compression is the issue, wouldn't it start hard in warm weather also?

2. Are there other probable causes I haven't looked at yet?

3. What corrective action can I take short of new rings to address the compression starting? Does synthetic oil help? What about a heavier viscosity oil...will that increase or impede compression?

Car is a '79 240D.
Has some gray smoke (not a little but not a lot) visable when idling.
240k miles.
Engine vibrates when idling but shakes when in DRIVE and the brake applied.
Uses a quart of oil about every 1000 miles.
Runs well in both city and hwy speeds with what I believe to be normal accelaration speeds for a 240D.
Gets 25-28 mpg.
I notice some exhaust in engine compartment from under air cleaner and is probably from exhaust manifold gasket leak.

Any ideas?

#2 09-07-2003, 06:23 PM

What kind of shape are the battery cables in? You can replace them with home made cables made out of 0 guage welding cable. This is very popular in the VW diesel crowd with notable increases in starter speeds.

With what you state on oil consumption, I would want to get a compression test done. Have a diesel shop do this since you don't have the tools. It's not an expensive test ($35 for the Datsun diesel pickup that I used to own).

kerry · #3 09-07-2003, 07:59 PM

There is a later starter that spins the motor at higher speeds. My 85 spins much faster than my wife's 77. I know this causes hard start problems for her 300d below 5 degrees. I have bought the newer starter and plan to install it before the cold sets in.
Even at warm temperatures, I can tell the difference in the rpm's of the motor when starting.

pdxman · #4 09-07-2003, 11:11 PM

I called one local shop to do a compression test and couldn't believe they wanted $80!!! For that, I could buy myself a really nice gauge set...haven't pulled the trigger on that though.

When I say the vehicle starts harder when cooler..I'm just talking about 50 degrees so far.

I'll check the condition on the battery cables though.

What about my question on low compression...Wouldn't car still be hard to start in warmer temps?

JimSmith · #5 09-07-2003, 11:36 PM

pdxman,

Try the later starter - I put a 1985 300D or SD "heavy duty" starter from FastLane in the 1982 240D and it worked wonders. Started last Winter in Troy, NY where the temps went below zero Fahrenheit for weeks. I also found the engine mount on the driver's side completely broken in half. This allowed the starter to roll the engine over, lifting it up as the next compression stroke was being exercised, then slam it back down as the engine attempted to start. This beat the starter up good, made the engine vibrate a lot, and eventually loosened the exhaust manifold bolts and cracked the EGR tube between the intake and exhaust manifold. So the exhaust noise got louder along with the hard starting and higher vibration. Except for the fact that once started the car ran fine, I was nearly ready to give up on it. It had about 250,000 miles at the time and owed me nothing.

The smoking, shaking and the hard starting may or may not be related although the causes may be "complimentary" in that they all reinforce each mode of failure. Check the valves, making sure they are adjusted "loose" rather than tight, check the spray pattern and pressure set point for each injector, the condition of the prechamber and so on. I would also have the injection timing checked, as with a lot of miles it is feasible the timing may be a little off, leading poorer combustion at idle. Then, have the glow plugs and relay checked too. Good luck, and I hope this helps. Jim

pdxman · #6 09-08-2003, 09:23 PM

The smoking, shaking and the hard starting may or may not be related although the causes may be "complimentary" in that they all reinforce each mode of failure. Check the valves, making sure they are adjusted "loose" rather than tight, check the spray pattern and pressure set point for each injector, the condition of the prechamber and so on. I would also have the injection timing checked, as with a lot of miles it is feasible the timing may be a little off, leading poorer combustion at idle. Then, have the glow plugs and relay checked too.

I had the valves adjusted about 1000 miles ago.
Last winter I took the injectors out and had tested...spray pattern was good.
Haven't had the injection timing checked.

I did though order the HD starter from FASTLANE (good price too!) and while the delivery person is out had them bring a new engine shock also. I am going to make the assumption that since the battery is new, GP's/relay tests fine, that the starter is the culprit even though it tested fine last spring. I did find a receipt for the previous starter and it is about 10 years old...probably past due. I hope this works as my luck never does.

Did I mention that I was selling this car and was doing this as a matter of not selling someone something with problems? It's been in the local classifieds for a couple weeks now and only 2 people have looked at it.

300SDog · #7 09-08-2003, 09:41 PM

Regarding recommended oils..... Heavier viscosity will actually slow down the starting considerably - with much greater drag on the engine while cranking it over. What you think you can gain with piston ring sealing for higher compression is lost in rpm's the starter can no longer achieve.

Converted to synthetic on my '79 240D several oil changes ago.... am glad to have made the change.

angst · #8 09-10-2003, 01:07 AM

The McGyver compression test is free. Park on a hill and turn the ignition off and put the car in gear and slowly realease the brake. If it goes screaming into the kids at the bottom of the hill then you probably have compression (and a few Legal) problems. Comarison to same model car with no known compression problems would give you a baseline comparison but then it wouldnt be McGyver testing would it.

I can speak to the effectivness of full synthetic oil in my gasser one winter in the mountains. Definatley a very tangible amount of difference in effort to spin the engine at wicked cold temps.

Eric Z
Chatt. TN

pdxman · #9 09-12-2003, 08:45 AM

Update: I changed the oil to synthetic and did notice an easier time of turning over (but it has been warmer lately).

The new starter came and I installed last night. Much faster spinning and quicker start! I think that in itself will help considerably.

On the downside, I also replaced the motor shock (mounts were done recently also) and it did not fix the shaking. Maybe a lttle, but not to where I would like it. I may try a diesel purge next.