300SD won't turn over - PeachParts Mercedes-Benz Forum

viqx · #1 12-01-2005, 03:55 PM

Last night my orange brake light sensor came on dimly and intermittently, and then this morning my car wouldn't start. When I could get it to turn over, it would die after 3-5 seconds. I can't figure out how brake pad sensor and not turning over could possibly be related, but it's too much a coincidence for me not to ask, since it's only been 12 hours since the brake light first came on. Are there any possible problems that could cause both of these?

My friend asked about temperature, but it's been 3-6C every time I've started for the past week or so without a problem.

boneheaddoctor · #2 12-01-2005, 04:00 PM

I say they are two seperate issues........

you check your battery voltage right now? above or below 12 volts? car turned off doors closed. I am curious of its state of charge before we start chasing posible casues.

MonsieurBon · #3 12-01-2005, 06:16 PM

Luke (viqx) is a friend of mine, and we talked about this earlier. To add on to his post, when he says it doesn't start, he means that it turns over, and after about 3-5 seconds of running the starter, will stumble a bit and then die.

Don't know if that helps any, but it sounds like the starter is at least engaging and turning over the engine.

If it's turning over, what else could be wrong? He says the glow plug light always comes on. Could summer-weight oil be congealing too much all of a sudden? I suppose it could also be a sudden fuel clog, yes?

I may head over to his house later this evening, so anything to try within reason would be helpful, otherwise he'll probably take it to the local indie in the morning.

Also, it's a 1984 300SD with 170k or so on the clock. The car is clean as a whistle inside and out, and in the engine compartment, but he hasn't taken it to a mechanic since purchasing it a few months ago.

Ramblin · #4 12-01-2005, 07:09 PM

Sounds like battery and or charging system connections problem...Clean battery terminals and charge the battery complete...How old is battery...If it is over 3-4 years old have it load tested when fully charged...I have seen a fully charged battery drop like a stone on a load tester..........

pawoSD · #5 12-01-2005, 07:13 PM

Boy do I love my voltage gauge I installed in the dash, tells me exactly what the system is at at any time the key is in position 1 or further... I get about 13V in "accesory" mode, then it falls to around 10.3V when I go to glow, then it "hops" between 8 and 11ish when cranking (very breifly, never takes more than 1 crank when warm out or with block heater, or 3-5 cranks in -5 and up w/out a heater.) 1 year old DieHard International. its held up like a beast so far....I even left my dome light on for 13 hours by accident before, voltage when I put the key in? 13V! Big batteries rock!

System voltage without defroster on and blower on high etc.. is around 14.2V, with blower at level 5 its 13.7ish, and with the rear defroster+headlights etc all on it will fall to around 12 at idle and manages 13ish when above 1300rpm or so.

Someday when my alternator bites the dust (its been humming great and problem free the last 26k...) I want to go to an 80 or 90amp one....then I will always have 14V, even with the afterglow and all other things on....

Fisherman · #6 12-01-2005, 07:21 PM

If it stumbles but won't start it sounds like you may have one or two cylinders not helping to start the engine. When it's cold if all 5 GPs aren't doing their job you get a very rough start, no start or as my old 1980 did it would stumble and act like it was going to start until it kicked the starter out then it died.

I could be wrong but how long has it been since you changed out the GPs? Actually your not that cold right now but this is an easy fix. Also as noted above the battery must be in good charge to spin the motor up.

boneheaddoctor · #7 12-01-2005, 07:51 PM

Quote:

Originally Posted by MonsieurBon

Luke (viqx) is a friend of mine, and we talked about this earlier. To add on to his post, when he says it doesn't start, he means that it turns over, and after about 3-5 seconds of running the starter, will stumble a bit and then die.

Don't know if that helps any, but it sounds like the starter is at least engaging and turning over the engine.

If it's turning over, what else could be wrong? He says the glow plug light always comes on. Could summer-weight oil be congealing too much all of a sudden? I suppose it could also be a sudden fuel clog, yes?

I may head over to his house later this evening, so anything to try within reason would be helpful, otherwise he'll probably take it to the local indie in the morning.

Also, it's a 1984 300SD with 170k or so on the clock. The car is clean as a whistle inside and out, and in the engine compartment, but he hasn't taken it to a mechanic since purchasing it a few months ago.

with the additional info it sounds like one of four things is happening....

#1 the battery is not holding sufficient charge...(are you sure its the right battery for the car?)

#2 the alternator is not sufficiently charging the battery....

#3 you have a weak starter thats not up to the cold weather load..

#4 you have corroded connections somewhere between battery and starter.

you should get far , far more the 5-10 seconds cranking before it gives up....even in -20 F weather.

However if I missread that and it will crank far more you likely have multiple glowplugs burned out...

MonsieurBon · #8 12-01-2005, 08:04 PM

Quote:

Originally Posted by boneheaddoctor

with the additional info it sounds like one of four things is happening....

#1 the battery is not holding sufficient charge...(are you sure its the right battery for the car?)

#2 the alternator is not sufficiently charging the battery....

#3 you have a weak starter thats not up to the cold weather load..

#4 you have corroded connections somewhere between battery and starter.

you should get far , far more the 5-10 seconds cranking before it gives up....even in -20 F weather.

However if I missread that and it will crank far more you likely have multiple glowplugs burned out...

Luke told me that he releases the starter after 3-5 seconds to let the engine run, then it stumbles and dies. Should he be turning it longer than that?

What is an OK duty cycle on a starter? As in should we not try turning it over for more than X seconds every X minutes?

Thanks!

boneheaddoctor · #9 12-01-2005, 08:10 PM

Quote:

Originally Posted by MonsieurBon

Luke told me that he releases the starter after 3-5 seconds to let the engine run, then it stumbles and dies. Should he be turning it longer than that?

What is an OK duty cycle on a starter? As in should we not try turning it over for more than X seconds every X minutes?

Thanks!

ok I got a clear picture now....no he shouldn't need to be cranking it longer....I say he has a couple glow plugs not working. How cold is it now with it hard starting.....less than 3-5 C? Thats not cold enough for fuel to gell.

MonsieurBon · #10 12-01-2005, 08:15 PM

Quote:

Originally Posted by boneheaddoctor

ok I got a clear picture now....no he shouldn't need to be cranking it longer....I say he has a couple glow plugs not working. How cold is it now with it hard starting.....less than 3-5 C? Thats not cold enough for fuel to gell.

Mid 30F's at night and 40F's during the day. So due to the fact that the GPs seem to fail on a gradient (various wrong resistances and infinite resistance, etc), that could account for his GP light coming on anyway? Does that light only not come on if all GPs are bad, or if one or more are bad only in a specific way? Or should we just not trust an idiot light?

Thanks for the help, folks. We'll test the GPs tonight.

whunter · #11 12-01-2005, 08:21 PM

Quote:

Originally Posted by boneheaddoctor

How cold is it now with it hard starting.....less than 3-5 C? Thats not cold enough for fuel to gell.

http://www.google.com/search?hl=en&q=weather%2CPortland%2C+OR&btnG=Google+Search

whunter · #12 12-01-2005, 08:25 PM

Quote:

Originally Posted by MonsieurBon

Mid 30F's at night and 40F's during the day. So due to the fact that the GPs seem to fail on a gradient (various wrong resistances and infinite resistance, etc), that could account for his GP light coming on anyway? Does that light only not come on if all GPs are bad, or if one or more are bad only in a specific way? Or should we just not trust an idiot light?

Thanks for the help, folks. We'll test the GPs tonight.

Glo Plug Testing?
http://www.peachparts.com/shopforum/showthread.php?t=104547&page=1&pp=15

Don't always trust your glow plug indicator light!
http://www.peachparts.com/shopforum/showthread.php?t=138347

84300DT · #13 12-01-2005, 08:43 PM

Quote:

Originally Posted by MonsieurBon

Luke told me that he releases the starter after 3-5 seconds to let the engine run, then it stumbles and dies. Should he be turning it longer than that?

What is an OK duty cycle on a starter? As in should we not try turning it over for more than X seconds every X minutes?

Thanks!

yes you can turn the starter longer than 3-5 seconds. just don't run it more than 30 seconds before shutting down and waiting a minute or two for the iter to cool down (even in ambient temp just above freezing!)
try run the starter until you feel more than one or two cylinders are firing and the engine should then start. you will not grind the starter if you keep cranking even if a cylinder is already firing.

MonsieurBon · #14 12-02-2005, 01:18 AM

We tested the resistance on most of the glow plugs. The stupid non-autoranging analog multimeter made it difficult at best. Some of them may be bad. Some are definitely good. Some read a little under 1 ohm, and others read possibly 0, but bouncing all over the place too.

All are getting 12v.

None feel warm even after multiple glow cycles.

We tried giving it a little throttle when it stumbled after starting and it evened out. It sounded like one cylinder wasn't firing properly though. After about 3 minutes at idle it went away. Luke/viqx drove it around and said it worked just fine.

We're gonna test the GPs with my digital multimeter this weekend and replace any bad ones before taking it in to the mechanic on Monday to do the brake pads.

Thanks again!

#15 12-02-2005, 01:31 AM

Definitely sounds like GP issues. Mine will stumble a bit with one bad GP, but it's a real PITA to start with two bad GPs. It will try to start while the starter is spinning but die as soon as you release the starter. When it does start it feels like there's a bunch of unburned fuel that takes quite a few seconds to clear out. I would do a good test on the GPs before getting into anything else. If in doubt, pull them out and bench test them (carefully).